Philippa Kaur

Here, we examine infection dynamics in the four regions of focus to learn more about how various control interventions performed in each region. Since the first documented cases emerged in these regions, the virus was able to spread freely across much of the first and second phases with a gradual increase in the control interventions. In the four regions of Makkah, Madinah, Eastern, and Riyadh, cases peaked on 12th May (6397 cases; 95% CI 5960–9697), 15th May (1967 cases; 95% CI 1625–2308), 23rd June (10367; 95% CI 8948–11785) and 11th June (11273 cases; 95% CI 11068–12491) respectively according to the fitted model shown in Fig. 2. As the epidemic progressed, more measures were adopted to contain the disease, and the disease’s infectiousness sharply decreased after the third period. There are a few factors responsible for the sudden declining trend: first our model is dependent on official data on cases that have been documented, and these data will only ever reflect a portion of the overall number of cases. Second, different regions developed different testing strategies, and some locations altered their approach to testing during the course of the time period that was investigated. It is possible that the beginning of the Hajj term (period 4) was a contributing factor in the decrease in the number of documented cases. Additionally, previous to this time period, the government indicated that it would be increasing the size of its local testing in order to detect new cases. It is possible that the efficacy of interventions would be reduced if increases are found to be occurring during the falling phase of an epidemic. This may result in measures being kept in place for a longer period of time than they would have been had more accurate data been provided.Figure 2With the use of the Delay Rejection Adaptive Metropolis method, the relevant parameters were estimated for each of the four areas of interest by fitting the data from 13th March until 25th September.Full size imageWe estimate the effective reproduction number (R_t) as an indicator of SARS-CoV-2 transmission before and after the interventions. Figure 3 depicts the dramatic shift in the rate of SARS-CoV-2 transmission as a result of decreased social contact and other control measures. At the beginning of the pandemic, (R_t) for SARS-CoV-2 in Saudi regions was between 4 and 6 as illustrated in Tables 6 and 7. In other words, on average each case spread to between four and six others. Considering that each new generation of SARS-CoV-2 cases occurs every five days, it is evident that this pandemic was rapidly expanding out of control. Moreover, we assumed that the transmission rate and the documented infection rate did not change during the first two periods since interventions were carried out gradually until a complete lockdown took place. As more measures were introduced, the spread of the disease began to decrease. Therefore, our data were based on the weekly reported number of documented SARS-CoV-2 cases broken down by region. As a result, it became clear that the reliability of the (R_t) value was relatively high for transmission.Figure 3Distribution of Rt estimates derived from 10000 MCMC samples for Makkah, Madinah, Eastern, and Riyadh, respectively. The black dot in the centre of each violin plot denotes the median, the thick bar in the plot denotes the interquartile range, and the thin bar in the plot denotes the lowest and maximum values. The mean and the credible interval for 95%, which is shown in parentheses, are labelled below or above, respectively.Full size imageThe effects of the events and interventions on the dynamics of SARS-CoV-2 in the regions of interest are considered. First, if the controls remained in phase four in Makkah, our model projects that the total number of documented cases would increase to 81047 (95% CI 79421–82672). In Al-Madinah, the cumulative number of documented cases would have increased to 22997 (95% CI 19578–26415). The number of cumulative documented cases may have reached 80520 (95% CI 78335–82704) if controls stayed steady in the Eastern region at the level they were at in phase four. If the pattern shown during the fourth period is taken into account, we estimate that there would have been 67150 (95% CI 63731–70568) documented infections in the Riyadh region. Figure 4 illustrates these findings.Figure 4The relevant parameters were estimated for each of the four regions of interest by first fitting the data of each region, and then predicting using the parameters from period 4. This was done with each of the four regions of interest separately.Full size imageWe now explore the impact of controls remaining in place at the same level as that implemented in phase three. In that case, the number of documented cases in Makkah would have increased to 116641 (95% CI 105015–128266). Similarly, the total number of documented cases in Al-Madinah would have increased to 53877 (95% CI 50458-57295) if the outbreak had been allowed to continue at the same level. If the controls had remained unchanged from how they were in phase three in the Eastern region, the total number of documented cases would have been 310459 (95% CI 298362–334981). Finally, in Riyadh this would have resulted in 665241 documented cases (95% CI 651822 to 678659). Figure 5 highlights these findings.Figure 5For each of the four areas of interest, the relevant parameters were estimated by first fitting the data of each region and then predicting using the parameters from period 3. This was carried out for each of the four areas of interest independently.Full size imageWe now investigate the impact of second-period controls remaining in place. In that case, the number of documented cases would increase to 1236642 (95% 1218314–1251626), 442865 (95% CI 439446–456283), 454031 (95% CI 441846–466215), and 2322624 (95% CI 1919206-3026042) in the regions of Makkah, Madinah, Eastern, and Riyadh, respectively (see Fig. 6).Figure 6For each of the four regions of interest, the relevant variables were identified by first fitting the data from each area and then making predictions using the parameters from period 2. Each of the four regions of interest was done separately.Full size imageThe efficacy of NPIs is dependent on when they are adopted, with earlier adoption resulting in greater success in lowering transmission rates of infectious diseases. In the early stages of COVID-19, Saudi regions made the decision to gradually implement measures in order to understand the severity of the disease and reduce the economic and social costs of lockdowns, as well as the political costs. In Fig. 6, if the government were to rely on the interventions of the second phase, then the number of cases of infection would considerably rise owing to the ineffectiveness of the measures. In the third period as in Fig. 5, the government made it possible to relax some of the control measures, but it is ultimately up to each area to decide whether they will maintain the same level of control or whether they will increase or decrease it. In comparison to the control measures carried out during the third and fourth periods, this led to significantly improved outcomes. The reason that these time periods were chosen is that there was no stiffening of the NPI response in most Saudi regions during the first two periods and control interventions were improved later on.Significant undetected infections resulted in the fast spread of new coronaviruses (SARS-CoV-2) which is illustrated in Fig. 7. The proportion of undocumented infections, including asymptomatic cases and undocumented symptomatic individuals who did not seek medical treatment or be tested for mild symptoms, was greater than that of Wuhan at the onset of the pandemic26, which may be a result of the following factors: first, the medical configuration was not optimal and public awareness was limited during the onset of the pandemic while the undocumented rate progressively increased; Second, contact tracing procedures employed in Saudi regions may have become overwhelmed if the number of early-stage cases in Saudi regions rises substantially. The discrepancy between the predicted proportions of asymptomatic (undocumented) cases may be attributable to the difficulty in the un-identifiability of parameters in epidemiological models. There were a substantial number of asymptomatic infected individuals with high infectivity in Saudi regions, where the epidemic situation escalated rapidly. Our research emphasises the frequency of asymptomatic SARS-CoV-2 cases and their role in transmission in order to increase people’s knowledge of asymptomatic cases and to serve as a guide for the prevention and control of SARS-CoV-2.Table 3 Estimated transmission rate in Saudi Regions.Full size tableTable 4 Estimated ascertainable infection rate.Full size tableIn this model, we fitted dynamic transmission rates because of varied preventable measures by the Saudi government at the level of the country or region. After a series of actions taken by the government, regions and cities went into lockdown, resulting in a decrease in the transmission rate as in Table 3. Before the interventions were introduced, in the first two periods of our study, we assumed the transmission rate did not change since individual and community responses had not effectively taken place. After severe interventions were implemented, the transmission rates were allowed to vary in later periods and reduced gradually due to the control measures that reduced the spread of disease27. Estimates of documented infection rates are presented in Table 4. Our model estimates show the documented infection rate has continued to decrease in the last two periods. Thus, the parameters we fit across periods are a measure of how effective the lockdown was in bringing down the documented infection rate28.Risk of resurgenceThe risk of resurgence in Saudi Arabia’s four regions has been examined in this section after the relaxation of intervention measures. There will be a rise in disease activity if control measures are relaxed without taking into account increases in the number of cases being detected, isolated, and/or traced. We predict the first week of no new cases of infection and the week when all current infections in Saudi Arabia will be eradicated.In the Makkah region, had the trend continued into the fourth period, the number of documented infections would have dropped to zero on average by the 6th September (23rd August to 27th September), and all infections would have been eradicated by the 26th of October (7th October to 14th November). On the 28th June, the number of weekly active infections (including presymptomatic, symptomatic, and asymptomatic cases) reached its highest point of 230,230 (95% CI 226811–234364), and on 8th September, that number dropped to 44023 (95% CI 40604–47441).Therefore, the number of documented infections would have reached zero in Al-Madinah region on average on 6th November (23rd October to 22nd November), and all infections would have been eliminated by 1st December (27th November to 14th December). On 23rd June, weekly active infections (including presymptomatic, symptomatic, and asymptomatic cases) peaked at 130,134 (95% CI 126715–133552) and then declined to 60023 (95% CI 58604–63441) on 25th September.If the trend had continued as it did in the fourth period in the Eastern region, the average number of documented infections would have reached zero on 2nd November (from 23rd October to 18th November), and the total eradication of infections would have happened on 1st December (26th November to 22nd December). The number of weekly active infections (including presymptomatic, symptomatic, and asymptomatic cases) peaked at 65000 (95% CI 61581–68418) during the week of July 23rd and subsequently decreased to 800 (95% CI 765–834) on 8th of September.Lastly, the model predicted that the number of weekly active infections in the Riyadh region (including presymptomatic, symptomatic, and asymptomatic infections) peaked on 28th June at 562332 (95% CI 513379–619542) and then decreased to 188215 (95% CI 174796–191633) on 18th September. On average, we expected that the number of documented infections would have decreased to zero on 18th October (7th October to 14th November) and that the total number of infections would have been eliminated on 1st December if the trend continued as it did in the fourth period (20th November to 23rd December). Figure 7 illustrates these findings. We found that if control measures were lifted 30 days following the first day of zero documented cases.Figure 7The estimated number of infected cases that were active (presymptomatic, symptomatic, and asymptomatic) during the research period in the areas of Makkah, Madinah, Eastern, and Riyadh respectively.Full size imageThe probability of resurgence, which we define as the number of active documented cases greater than 100 could be as high as 0.96 in Eastern, 0.95 in Madinah, 0.97 in Makkah, and 0.96 in Riyadh. If we adopt more stringent conditions of lifting controls after observing no confirmed cases for a continuous period of 30 days, the probability of resurgence decreases to 0.31, 0.28, 0.30, and 0.30, with probable resurgence occurring on 13th February, 7th February, 2nd January, and 8th January for Eastern, Makkah, Madinah and Riyadh, respectively (Fig. 8). Despite the use of a simplified model, these results emphasize the hazards of ignoring undetermined occurrences when modifying intervention techniques.Figure 8Figure demonstrating the effect of relaxing all control measures in all four regions 30 days following the first day without confirmed cases.Full size imageSensitivity analysisFor the purpose of testing the robustness of our research results, we conducted a series of sensitivity analyses by varying the durations of the latent and infectious periods, the ratio of transmissibility in asymptomatic (undocumented) cases to symptomatic (documented) cases, and the initial documented infection rate. We conduct eight sensitivity analyses (S1 to S8) within each model for each region of Saudi Arabia to assess the robustness of our model results. For instance, the sensitivity analysis performed for S1 was based on the changes of the latent period and pre-symptomatic infectious period, respectively, and other parameters remain the same. These modifications were carried out with the help of reference15,29, and the same approaches were used for the other parts of the sensitivity analysis, which is summarised in Table 5.Table 5 Description of essential model parameters that were not fitted in the MCMC, where (D_e) refers to the latent period, (D_p) refers to the pre-symptomatic infectious period, (D_i) refers to the symptomatic infectious period, (gamma _0) refers to the initial ascertain rate and (alpha) refers to the ratio of the transmission rate for P and A to I.Full size tableIn particular, for (S1), we raised the incubation period to 7 days (upper 95% CI based on ref15) and the pre-symptomatic infectious period to 3 days (upper 95% CI based on ref29). Therefore we set (D_e = 4) and (D_p=3), and modified (E_0) and (P_0) as needed. The transmissibility of the undocumented cases was assumed to be 0.46 (lower 95 % CI according to ref.31) of the infection cases for (S2); for (S3), the transmissibility of the asymptomatic (undocumented) cases was assumed to be 0.62 (upper 95 % CI according to ref31). We assumed that in (S4), the initial documented infection rate was (gamma _0) = 0.14 (lower 95 % CI according to ref13) and adjusted (A_0), (P_0) and E(0) accordingly. Similarly for (S5) we assumed the initial documented infection rate was (gamma _0) = 0.42 (upper 95 % CI according to ref13) and adjusted (P_0), (A_0), and (E_0) accordingly. In (S6) we set the variables (D_ e=3) and (D_p=1.1), and altered the values of (P_0) and (E_ 0) as necessary in accordance with13. In (S7) we assumed that the transmission rate of asymptomatic (undocumented) cases was half that of documented cases by setting 0.5. Finally, in (S8) we assumed that the infectious period ((D_i)) was double that of symptomatic cases by setting 6 days. Both (S7) and (S8) were based on30. The results of our sensitivity analysis are summarised in Tables 6 and 7. We note that the variation in the model predictions of (R_t) varies from setting to setting. However, these variations appear to be fairly small, proposing the robustness of the results to the specification of associated values in fairly realistic ranges13,13. Our sensitivity analysis provides information about the importance of each parameter to the model representing the transmission of SARS-CoV-2. An increase (or decrease) in parameter values, while other parameters’ values remain the same, contributes to an increase (or decrease) in effective reproduction numbers. For example, an increase in infectious period would result in a higher effective reproduction number at the beginning of the epidemic and a longer time required to clear all infections in Saudi regions32. Our sensitivity analysis indicates that almost all model parameters may have an important role in spreading this virus among susceptible people. In particular, the contact rate from person-to-person and the transition rate of asymptomatic (undetected) individuals play a significant role in disease spread. Our important findings, of a significant decrease in (R_t) after interventions and the existence of a substantial number of presymptomatic and asymptomatic cases, were found to be robust. This highlights that Saudi authorities should pay attention to intervention strategies in the event of a resurgence of cases and quarantining those who were in contact with active cases can effectively reduce the disease33. In Tables 6 and 7 we show the estimated effective reproduction number (R_t) associated with 95% CIs obtained from those eight sensitivity analyses for all four regions and all five time periods.Table 6 Sensitivity analysis of the effective reproduction number (R_t) for Eastern and Madinah.Full size tableTable 7 Sensitivity analysis of estimated effective reproduction number (R_t) for Makkah and Riyadh.Full size table More

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Morphometric measurements are subjective and used to assess the carcass development and quantitatively measure the muscular distribution in the carcass with estimates of its conformation. In the present study there were not significative differences observed for these parameters or for carcass compactness index (CCI), inferring that the use of cactus pear silage as well as intermittent water supply combined or alone did not alter animal growth and/or carcass conformation, maintaining the muscle pattern achieved by the control diet (usual) and demonstrating body and carcass uniformity. Since animals used in this study were homogeneous and had similar age and body performance, as indicated by the carcass morphometric measurements and by the difference between the empty carcass and hot carcass weights, which resulted in the sum of head + limb with an average of 8.2 ± 0.13 kg between treatments, giving an idea that the animals were similar in chronological age, since the allometric growth of the body occurs from the extremities to the interior of the body.The significant difference between treatments with inclusion of cactus pear silage for hot carcass yield (HCY) and cold carcass yield (CCY) may be related to the weight of the full gastrointestinal tract, which showed higher values for animals fed with a higher proportion of Tifton 85 grass hay in the diet (0% CPS). Increasing the NDF content of the diet reduces the passage rate of digesta, and the emptying of the gastrointestinal tract (GT) that cause a distension of the rumen-reticulum and increase the weight of the gastrointestinal tract, resulting in lower HCY and consequently lower CCY. While the diets with inclusion of CPS increase NFC content, such as pectin, which have higher rates of rumen degradability and, higher rates of passage7,8,9.Measurements and evaluations carried out on the carcass, such as the carcass compactness index and loin eye area (LEA), are parameters that quantitatively measure the muscle distribution in the carcass, an edible part of greater financial return, which indicates the conformation of these animals3, while the body condition score (BCS) and the measure C, which are highly correlated, measure the distribution of fat on the carcass, giving an idea of the carcass finish, in which the higher these variables, the greater the proportion of fat that allows for less water loss due to carcass cooling10. These variables in the present study were also not influenced by the levels of cactus pear silage and water restrictions, presenting an overall mean of 0.17 kg/cm, 7.68 cm, 2.42 points and 0.7 mm respectively, and consequently did not influence the losses due to cooling, which presented an average loss of 1.48%.The main cuts of the goat carcass are the neck, leg, shoulder, loin, and rib. Their economic values differ, and their proportions become an important index to evaluate the carcass quality9. The cuts of greatest importance and commercial values are the leg and the loin, called noble cuts because they present greater yield and muscle tenderness, being interesting that they present a good proportion in the carcass, for providing greater edible tissue content, mainly muscle.Carcasses with similar weight tend to have equivalent proportions of cuts, as they exhibit isogonic growth. As the cold carcass weight (CCW) and the conformation of the animals were similar, with similar morphometric measurements, they had a direct relationship in the absence of an effect on commercial cuts.The commercial value of the carcass, whether through carcass yield and/or the proportions of the cuts, is also linked to tissue composition, thus the dissection of the leg represents an estimate of measuring the tissue composition of the carcass, in which is sought a greater proportion of muscle, intermediate proportion of fat and less bone in carcasses11. In this way, diets with cactus pear silage and the different levels of intermittent water supply resulted in the constancy in the amount of muscle, fat, and bone in legs of goats. The similarity in muscle proportion is related to the lack of effects on slaughter weight and CCW, as the weight of muscles is highly correlated to carcass weight. The average muscle yield was above 60% in all treatments, confirming that the animals showed good efficiency to the diets and adapted well to the water supply levels. Although the diets with cactus silage had high amounts of metabolizable energy (ME) and no difference in DM intake, the energy input was similar that not influencing carcass weights and carcass compactness index. That is, it did not influence muscle deposition in the carcass, probably due to synchronicity of energy and protein.As for the weight and proportion of bone tissue, it is believed that because this is a tissue with early development in relation to muscle and fat2, diets in the final stages of growth (average of 8 months) would hardly change their participation in the tissue composition, where the relationship of this tissue with the others is usually only increased when there are changes in the proportion of muscle and/or fat.Water restriction, as long as it is moderate and acute, mainly affects the loss of body water and not tissues, which does not cause deleterious effects on animal productivity and growth.The muscle:fat ratio indicates the state of leg fattening, while the muscle:bone ratio estimates the carcass muscularity, both being attributes of quality3. The similarity previously reported in the weight of fat, bone and muscle corroborates that these relationships also do not have differences. The same occurs for the leg muscularity index (LMI), due to the weight of the five muscles used to determine the index and the length of the femur which had been similar between the animals.Nevertheless, when considering fat as a percentage of participation in leg weight, it is possible to observe that the intermittency in water supply in both intervals (24 and 48 h) reduced the proportion of fat in the leg. Although in this research, the water supply levels did not affect the daily intake of dry matter from animals, with average intake of 650.67 g/kg DM, ranging from 599 to 682 g/kg DM between treatments7, during days of water deprivation, fat mobilization for energy availability may occur, possibly offsetting water stress and influencing not only feed intake, on these days of deprivation but also affecting energy metabolism, which results in the mobilization of energy reserves2.When the physicochemical composition of the meat was evaluated, it was observed that the diets and water supply levels probably did not affect the reserves of muscle glycogen during the pre-slaughter management as can be seen through pHinitial and pHfinal. The pHinitial right after slaughter should be close to neutrality, as well as in the live animal, indicating that the animal did not suffer from stress during the pre-slaughter period. The pHfinal, on the other hand, is expected to show a considerable variation, between 5.55 and 6.2 for goat meat; and due be inversely proportional to the concentration of muscle glycogen at the time of slaughter, that is, a more intense expenditure of glycogen stores results in less lactic acid production and higher pHfinal10,12,13. In this research, the pHfinal had an average of 5.74, a pH higher than the isoelectric point of muscle proteins (5.2–5.3). This result is favorable, since it is above the neutral charge and presenting an excessive negative charge that provides the repulsion of filaments, which allows water molecules to bind and improve the organoleptic characteristics of the meat, through succulence and texture of meat13 evaluated by cooking loss, moisture, and shear force, principally. The cooking loss (CL), moisture and shear force (SF) were within the values recommended (20–35% CL, moisture above 70% and SF up to 44.13 Newton (N) for goat meat) to classify the meat as soft and tender14. Statistically, interactions were found between the supply of silage and intermittent water supply, in which goats on a diet without cactus pear silage and without intermittent water supply showed higher values of cooking losses and shear force.Higher concentrations of collagen content and/or greater activities of calpastatin (which inhibit the action of calpains), as well as larger fascicles and greater number of fibers present in each muscle fascicle, as was visually observed in the meat of the animals in this research, can lead to reductions in meat tenderness15. Because goat carcasses are generally small, with low marbling degree and a thin layer of subcutaneous fat, there is rapid heat dissipation at the beginning of the post-mortem period, which can lead to cold shortening, muscle hardening, and less tender meats16.pHfinal of the meat has a high correlation with color parameters (L*—lightness, a*—redness, b*—yellowness and Chroma), as the pHfinal can affect the reaction of myoglobin to oxymyoglobin. The b* index in meat, on the other hand, may be related to the concentration of fat and/or the presence of carotenoids in the diet which can be affected by forage preservation processes, such as silage and hay, which significantly reduces by up to 80% carotenoids levels13. It is believed that the carotenoid concentrations in the diet of this study were similar between treatments and consequently in values of b* of meat. Values of a* and Chroma directly depend on the content and state of the heme pigments in the muscle, due to the chemical state of iron (Fe), playing an important role in meat color10. These parameters showed no significant difference between treatments, however, higher values of a* and Chroma in meat are desired, as a result of the increase in oxymyoglobin and decrease in metmyoglobin that provides the meat’s “bloom”. According to Dawson et al.17, the minimum critical value for meat luminosity (L*) is 34. Lower values of L are related to elevating pHfinal, which results in the high concentration of metmyoglobin, making the meat darker, which causes rejection by consumers for associating dark meat to as old meat.The meat’s presentation and more precisely its color is an important factor that can influence a consumer’s purchase decision, as it gives us the idea of freshness and meat’ quality. The L* and a* color parameters are the most representative for these characteristics18. Although in our research it did not have a significant effect on the color parameters, we can indicate that the meat obtained in this research would be well accepted by consumers, because Hopkins19 suggests that consumers will consider meat color acceptable when the L* value is equal to or exceeds 34, and a* value below 19 or equal to or exceeds 9.5 according to Khliji et al.18. In the present study, all values for L* remained above this aforementioned threshold and the values of a* remained within these values which suggests that meats from all diets and water supply levels had an acceptable color for consumers.When evaluating the chemical composition of meat, no significant differences were observed between treatments, except for the ash content, that remained above the average values found in the literature, which is 0.99–1.10%16. It is believed that because cactus pear is a rich source of Ca, Mg, K and with increasing level of cactus pear silage in the diet31, these minerals were consumed in larger amounts, which could have resulted in a higher proportion of minerals in the meat of animals that received 42% cactus pear silage.The lipid fatty acid profile in meat has a major impact on sensory properties and nutritional quality, influencing acceptance and health for consumers20,21. Intermittent water supply, cactus pear silage, and interaction between water supply and cactus pear silage did not influence most fatty acids present in the Longissimus lumborum muscle of the animals under study, except only a few saturated fatty acids e.g. docosanoic acid (C22:0), tricosanoic acid (C23:0), BCFA, anteiso-tridecanoic acid (C13:0 anteiso) and anteiso-pentadecanoic acid (C15:0 anteiso).Biohydrogenation of ruminal bacteria results in a circumstantial variety of fatty acids (FA), which will be absorbed in the intestine and later incorporated into the meat of goats. In addition to the diet and the biohydrogenation, the meat lipid profile can vary due to de novo synthesis, desaturation, duration of the feeding period and differences in pathways of various FA by the animal organism22.A high concentration of saturated fatty acids present in meat is not desirable, as there is evidence that saturated fatty acids, mainly C16:0, as well as myristic (C14:0) and lauric (C12:0) increase the blood cholesterol and low-density lipoproteins (LDL) concentration, due to interferences with hepatic LDL receptors23, however, in the studied treatments, there were no significant differences for these fatty acids. On the other hand, C18:0 has no impact on cholesterol levels, due to being poorly digested and easily desaturated to C18:1 by Δ9-desaturase24, present in the cell endoplasmic reticulum. This fatty acid is not harmful to health and is considered the only desirable SFA. As the levels of C18:0 in diets tend to be minimal, their main origin is the biohydrogenation of PUFA and de novo syntheses in diets with a high energy pattern25.In addition to carrying out the biohydrogenation process, ruminal bacteria synthesize a series of FA, mainly those of odd and branched chain, that comprise mainly the lipids of the bacterial membrane26,27, to maintain membrane fluidity. Linear odd-chains fatty acids are formed when propionyl-CoA, instead of acetyl-CoA, is used as a de novo synthesis initiator25. On the other hand, iso and anteiso FA are synthesized by the precursors branched-chain amino acids (valine, leucine, and isoleucine) and their corresponding branched- short-chain carboxylic acids (isobutyric, isovaleric and 2-methyl butyric acids)28.There is an increasing interest to study odd-and branched-chain fatty acids (OBCFAs) from animal products, mainly in milk due to its higher concentration compared to meat. Researchers reported that several OBCFAs have potential health benefits in humans29 as improved gut health30 and presenting anti-cancer activity31, as well as improve the sensory characteristics of the meat, providing a greater sensation of tenderness and juiciness, because BCFA content are associated with a less consistent fat in meat from lambs due to its lower melting point and its chain structure32.The FAs profile in the ruminal bacteria is largely composed by OBCFAs (C15:0; anteiso C15:0; iso C15:0; C17:0; iso C17:0; C17:1 and anteiso C17:0) in the bacteria membrane lipids24. Thus, the higher concentration of OBCFAs might be the result of the difference in the rumen bacterial populations induced by variation in the dietary carbohydrate, that is, a higher concentration of cellulolytic bacteria in relation to amylolytic bacteria, due to the high neutral detergent fiber (NDF) content in the diet with 0% cactus forage silage. It is also known that amylolytic bacteria produce more linear odd chain and anteiso FAs than iso FAs, whereas cellulolytic bacteria produce more iso FAs28,32. As the Tifton 85 grass hay-based diet had the highest neutral detergent fiber corrected for ash and protein (NDFap) and starch content (highest % of ground corn), the meat of those animals had higher concentrations of anteiso C15:0 and anteiso C13:0 compared to animals fed diets with the inclusion of cactus pear silage, also influencing the total sum of branched chain fatty acids.Although levels of intermittent water supply have generated punctual changes in tricosanoic acid (C23:0) SFA, the same was not observed for MUFA and PUFA, due to changes in the rumen environment, promoted by water restrictions, which were not sufficient to circumstantially modify biohydrogenation, resulting in similarities in concentrations of unsaturated fatty acids in goat meat.The animals subjected to 24 h of intermittent water supply (IWS) presented the highest concentration of C23:0 in relation to other treatments, which is interesting because it is involved in the synthesis of ceramide and reduces the risk of diabetes in humans33.The cactus pear has high non-fibrous carbohydrate (NFC) content (mainly pectin), having 59.5% high and medium rumen degradation carbohydrates which provide a higher production rate and removal of short-chain fatty acids and changes in rumen bacterial populations34. The inclusion of CPS resulted in a higher passage rate of digesta, affected biohydrogenation, and resulted in the escape of intermediate fatty acids isomers that are absorbed in the small intestine. Consequently, there was changing composition of fatty acids in the muscle of these animals, with a significant effect being observed only in the cis-13 C18:1. Furthermore, diets with high proportions of cactus pear silage (CPS), such as 42% CPS diet, can decrease ruminal pH and affect the final stages of biohydrogenation, resulting in the escape of intermediate fatty acids isomers, that are absorbed in the small intestine, which can explain the similarity of the C20:1 in 42% CPS diet from the Tifton hay-based diet, with differences between goat meat from 21% CPS diet and Tifton hay-based diet.Oleic acid (c9-C18:1) was the MUFA with the highest participation in the lipid profile of goat meat, which is interesting because it has a hypocholesterolemic effect, being a desirable fatty acid (DFA) for not reducing the serum high density lipoproteins (HDL) levels and thus prevent cardiovascular disease by reducing LDL levels35. The high concentrations of c9-C18:1 in ruminant meat come from the food intake, the effect of biohydrogenation, and mainly of the high activity of Δ9-desaturase, necessary for animal biosynthesis through desaturation of C18:0 to c9-C18:127. This fatty acid in the lipid profile of red meat varies between 30 and 43%36, confirming that the meat in the present study had a good concentration of this fatty acid.Much of unsaturated fatty acids, which have 18 carbons or 16 carbons, are largely converted to C18:0 and C16:0 through biohydrogenation, and when this process is not 100% completed, in addition to the PUFA that pass through this process intact, some product intermediates are formed, reaching the duodenum and are absorbed by the animal, in which significant amounts of cis and trans-monounsaturated, such as vaccenic fatty acid (t11-C18:1), reach the duodenum and are absorbed, later composing the muscle tissue22.The literature indicates that the precursor of conjugated linoleic acid (CLA) in the meat of animals is trans vaccenic acid (t11-C18:1), so the enzyme ∆9-desaturase, besides acting in the conversion of stearic into oleic fatty acid, also converts the trans-vaccenic acid to its corresponding CLA isomer, c9t11-C18:236. This pathway is more expressive in the mammary gland, and as the concentration of vaccenic acid (t11-C18:1) was not different, the concentration of CLA was not affected by the supply of silage and intermittent water supply, in the same way, that there are also no differences in the activity of ∆9-desaturase. Nevertheless, it is worth noting that in the human adipose tissue there is also the presence of ∆9-desaturase, and therefore, increased intake of vaccenic fatty acid could have the same beneficial effects associated with the intake of CLA, where the dietary vaccenic fatty acid shows 19–30% conversion rate37.Tifton hay is a natural source of n-3 fatty acids, mainly C18:3 n-3 with up to 20% participation in the lipid profile2, allowing a certain part of these PUFAs to be absorbed and increased in the tissue muscle, with 10 to 30% PUFAs in the diet generally escaping from biohydrogenation.Linoleic fatty acid (c9c12 C18:2) and α-linolenic acid (C18:3 n-3) are essential fatty acids for humans, that serve as precursors of the n-3 and n-6 pathways, distinct families, but synthesized by some of the same enzymes (∆4-desaturase, ∆5-desaturase, and ∆6-desaturase)25. Arachidonic fatty acid (C20:4 n-6) comes from elongation and desaturation of linoleic acid, where its concentrations, even close to that of its precursor, may indicate that there was a high activity of ∆6-desaturase (desaturation to γ-linolenic), elongase (elongation of γ-linolenic to dihomo-gamma-linolenic) and ∆5-desaturase. This fatty acid was influenced by the diets, presenting lower concentrations in the meat of animals fed the 42% cactus pear silage when compared to the Tifton hay diet (0% cactus pear silage).A higher concentration of long-chain PUFA n-3, docosahexaenoic (C22:6 n-3), was observed in the muscle of animals fed on Tifton hay. This was probably due to the high concentration of C18:3 n-3, precursor of C22:6 n-3, that the hay presents in relation to the cactus pear silage.The ratios and proportions of fatty acids are used to determine nutritional and nutraceutical values of the product or diet, and mainly, to indicate the cholesterolemic potential4. It is interesting that the n-6/n-3 ratio is low due to the pro-inflammatory properties of n-6; it is recommended to decrease its intake to assist in disease prevention38, while n-3 fatty acids are anti-inflammatory, antithrombotic, antiarrhythmic and reduce blood lipids, with vasodilating properties, being interesting that they present a higher proportion24. n-6 fatty acids tend to have a higher percentage in meat, and this directly influences the formation of n-3 isomers, since linoleic acid, when in excess, can reduce the synthesis of linolenic acid metabolites. The percentage of FA in one group can interfere with the metabolism of the other, reducing its incorporation into tissue lipids and altering its general biological effects38. Therefore, it is not recommended that the n-6/n-3 ratio be kept above 5 or 639, demonstrating that the averages of the current research remained acceptable.In relation to atherogenicity index (AI) and thrombogenicity index (TI), Ulbricht and Southgate39 proposed that sheep meat should have values of up to 1.0 and 1.58, respectively, and the lower the values for these indices in the lipid fraction, the greater the prevention of early stages of cardiovascular diseases. In the present study, the general averages observed were 0.29 for the AI, and 0.81 for the TI, although there were no significant differences, all treatments are within the recommended range, despite having been used as comparative standard to sheep, due to the absence of the proposed standard for goat meat.The h:H ratio did not differ for diets and water supply levels, but had an average of 1.90, below the reference value for meat products, which is 2.0. Values above 2.0 are recommended and favorable40, as it indicates a higher proportion of hypocholesterolemic fatty acids, that are beneficial to human health.The ∆9-desaturase enzyme that acts on both the mammary gland and adipose tissue, responsible for the transformation of SFA into unsaturated fatty acids (UFA), as well as in the endogenous conversion of CLA37 did not differ between treatments. On the other hand, the elongase showed less activity. Probably there was a greater “de novo” synthesis which resulted in a greater accumulation of palmitic fatty acid, and a reduction in the activity of the elongase enzyme.The crossbred goats demonstrated to present efficient mechanisms for adapting to water restrictions, especially when receiving feed with higher water content, such as cactus pear silage, being able to replace Tifton hay with 42% cactus pear silage in the diet for goats in confinement without negatively affecting the carcass traits and meat quality. Because, although these animals have shown some differences in the indices of tenderness and juiciness of their meats, however, all presented values of juiciness and tenderness compatible with meat extremely appreciated by the consumer market, and even goat meat showing some fatty acids with different concentrations induced by the supply of silage and water intermittence, the final lipid profile was appropriate to the health of consumers, observed by the absence of differences in the total concentrations of PUFA and in the main nutraceutical parameters (DFA, n-6/n-3; h:H; AI and TI).These results are relevant, indicating that goat feedlots in regions with low water availability may adopt strategies of lesser demand for drinking water and considerable concentrations of cactus pear silage in the diet, can reduce production costs without considerably affecting the product to be marketed, and therefore, provide higher profitability of the system. More

In 2008, I was investigating the methane bubbling up on the beaches and in shallow waters of Mocha Island, off the coast of central Chile. I became intrigued by how microorganisms could thrive in methane-rich areas and changed my research focus from marine biology to extreme environments. I wanted to understand how methane acts as a source of energy and carbon for microbes.Since then, I have explored a number of bizarre environments. In 2010, I went in a submarine down to 200 metres in the Black Sea, one of the world’s largest anoxic water bodies. There, I found mats of filamentous bacteria that survive on sulfur compounds.In 2017, I studied the microbes in Canada’s tailing ponds, artificial lakes of water, sand and clay waste that are left behind after petroleum extraction. And I sampled the microorganisms living in 100 °C Antarctic hot springs in 2022.I came home to Chile in 2018 and began collaborating with an international team researching the geomicrobiology of thermal features, including hot springs, geysers and volcanoes. After travelling with the group to Argentina’s active volcanic region, I got funding to explore the microbial communities that exist beneath hydrothermal vents in southern Chile, where the oceanic crust is subducting beneath the continental plate.In this image, I am in the Atacama Desert in South America, the driest non-polar desert on the planet. I am measuring 80–100 °C steam released from a fumarole containing yellow sulfur, which crystallizes at its opening as the vapour cools. I also sampled sub-surface microbes that are flushed out with the fluids. We’ll sequence their DNA to assess the microbial communities and their biological interactions.My goal is to learn more about subsurface microbes in extreme environments. I want to understand how microbial forces shaped the planet and how these communities might shift in the future with climate change. More

We acknowledge members of the EDGE lab at the University of Gothenburg for stimulating discussions that inspired this comment. Special thanks to A. Bjorkman and R. Bjork for their feedback on the manuscript and to K. Happonen for help with data collection. More

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Disturbance detectionWe used a well-established spectral-temporal segmentation method, Landsat-based Detection of Trends in Disturbance and Recovery (LandTrendr), to detect disturbances within the Google Earth Engine (GEE) cloud-computing platform57,58. The core of the LandTrendr is to extract a set of disturbance-related metrics by breaking pixel-level annual time-series spectral trajectories into linear features using Landsat observations. The LandTrendr has been widely used for change detection in various forest settings, and details about the algorithms can be found in previous publications57. Here we briefly described the key steps in generating the year and type of disturbances in China’s forests using the LandTrendr within the GEE platform. The overall analytic flow can be found in Supplementary Fig. 10.First, we generated annual spectrally consistent time-series data by using all available, good quality (cloud cover ≤ 20) Tier 1 Landsat 5 (Thematic Mapper), Landsat 7 (Enhanced Thematic Mapper Plus), and Landsat 8 (Operational Land Imager) images acquired during the peak growing seasons (June 1—September 30) from 1986 to 2020. The peak growing seasons were selected to exclude compounding influences from ice, snow, and soil, and to maximize the spectral changes after forest disturbances. To tackle the spectral inconsistency among Landsat sensors, we harmonized spectral values via linear transformations according to band-respective coefficients presented in59. Clouds, cloud shadows, snow, and water were masked out using the Fmask algorithm60. The annual band composites at 30-meter spatial resolution during 1986–2020 were computed using the Medoid method61.Secondly, we ran the LandTrendr using five spectral indices, including two spectral bands (shortwave infrared I and II that were B5 and B7), tasseled cap wetness (TCW), normalized burn ratio (NBR), and normalized difference vegetation index. These five indices were effective indictors to represent vegetation greenness and structures, and were commonly used for detecting changes in forest disturbance and recovery62. For each spectral index, the LandTrendr produced a set of parameters to describe a possible disturbance event at the pixel level, including spectral values at pre-disturbance level (preval), magnitude of change (mag), duration (dur) and rate of change (rate), and the signal-to-noise ratio (dsnr) (n = 5). Using these five spectral indices, we generated a stack of disturbance-related parameter layers (n = 25, 5 spectral indices × 5 parameters), which were later used to detect and classify disturbances using machine learning models derived from reference data (described below).Disturbance classificationReference dataHigh-quality consistent reference data is key to train and classify disturbance types. To do so, we generated a total of 31225 reference points using a hierarchical approach. We first generated a large number of potential disturbance points using forest loss data from 2001 to 20203. Then we separated fire disturbances from non-fire disturbances by overlaying MODIS burned area (BA) with potential disturbance points following the procedure used by63. Specifically, fire disturbances were determined if the MODIS BA data coincided with the Landsat-derived forest loss for the fire year and 2 years postfire (i.e., t + 0, t + 1, t + 2) to account for delayed post-fire tree mortality. Following this step, we derived points as potential disturbances that consisted of fires and non-fire disturbances (including forest conversion to other land use types and silvicultural practices at various intensities). We also generated roughly the same number of points that experienced no disturbances (e.g., persistent forests), which were determined by selecting pixels with very few changes in spectral indices. These reference points, including fire, non-fire disturbances, and persistent forests, were then used to sample the time-series spectral data from 1986 to 2020. Finally, time-series spectral data from each reference point were visually checked to make sure they accurately represented disturbance events. This process resulted into a total of 31225 reference data points, including 2356 fire disturbance points, 13,242 non-fire disturbance points, and 15,627 no disturbance points (persistent forests) (Supplementary Fig. 2).Random forest classificationWe used machine learning modeling to classify each pixel into fire disturbance, non-fire disturbance, or no disturbance. The reference data points were used to sample the LandTrendr-derived disturbance-related parameter layers described above, which resulted into a dataset consisting of disturbance types. We divided the dataset into 70% of training data, and 30% as validation data. Using the training data, a Random Forest (RF) model was trained to classify each reference point into fire, non-fire disturbance, or no disturbance. Our RF approach showed that short-wave infrared (SWIR)-based moisture indices (e.g., B7, TCW) were strong predictors for detecting forest disturbances (Supplementary Fig. 11) likely because of their sensitivity to vegetation water content and canopy structure64. Finally, we applied the trained RF model to the full classification stack to consistently map the disturbance types from 1986 to 2020 across China’s forests, assuming that the spectral trajectories derived from reference data period 2001–2020 can be extrapolated to the whole mapping period 1986–2020. However, note that our approach was meant to detect relatively acuate and discrete disturbances that caused canopy opening, rather than subtle changes of forest structure or composition resulted from low intensive silvicultural practices and chronic disturbances.Year of disturbanceWe used the LandTrendr to determine the year of disturbance as the onset of magnitude of spectral change. Since we ran LandTrendr on five spectral indices, there were five possible years of disturbance for each pixel. Thus, we determined the year of disturbance using the median value from at least three different indices (i.e., NDVI, NBR, TCW, B5, B7). In this way, we only kept pixels that were detected as disturbances using at least three indices, thus reducing commission errors. The year with the greatest spectral changes generated by the LandTrendr often had an accuracy within 3 years11. A confidence level was also assigned to each disturbed pixel based on numbers of indices which showed possible disturbance events. Specially, low, medium, and high confidence were assigned if the disturbance was detected by three, four, or five spectral indices, respectively.ValidationsWe validated the disturbance map at the pixel and national levels. At the pixel level, we validated the final map using the validation sub-sample described in the previous section. We derived a confusion matrix to report user’s and producer’s accuracy (Supplementary Table 1) as the main accuracy assessment metrics. At the national level, we compared forest disturbance detected in this study to available existing dataset. Specifically, we compared the area of forest fire disturbance between our study and the national fire records during 2003–2009 (Supplementary Fig. 5). We compared the disturbance rates between our study and Landsat-derived global forest cover changes from 2001 to 20193 (Supplementary Fig. 4).Post-processingWe applied a series of spatial filters to minimize the unrealistic outliers from two potential sources of uncertainty, including speckle in time-series spectral trajectories or misregistration among images. This may lead to individual pixel or small patches including only a few pixels, which were (a) detected as disturbances, thus increasing the commission errors, or (b) not detected as disturbances, while their surrounding pixels were mostly disturbed, thereby increasing the omission errors. To address the issue (a), we removed all single-pixel disturbance patches through setting the minimum mapping unit as two 30 × 30 m2 pixels (0.18 ha). To address the issue (b), we applied a 3 by 3 moving window to fill holes through assigning the year of disturbance based on the years in the surrounding pixels. Finally, we smoothed the year of disturbance by assigning the center pixel using majority rules from surrounding pixels within the 3 by 3 windows, thus accounting for artefacts associated with uncertainties in the correct identification of the disturbance year.Characterizing disturbance regimes and their trendsWe characterized the disturbance regime using five indicators within each 0.5° grid cell (n = 1946) across China’s forests based on annual forest disturbance maps generated from the previous step. Within each grid cell, we calculated (1) total annually disturbed forest area (km2 yr−1), (2) percentage of forest disturbed annually (% yr−1), as annual disturbed forest area divided by the total forested area, (3) disturbance size (ha), as the number of disturbed pixels for each individual patch using an eight-neighbor rule, (4) disturbance frequency (# of patches per 1000 km2 forested area each year), as the number of disturbance patches per year divided by the total forested area, (5) disturbance severity (ΔNDVI = NDVIt−1 − NDVIt+1), as magnitude of NDVI change 1 year before and 1 year after disturbance, obtained from the LandTrendr analysis. We used (1) and (2) to characterize the disturbance rate, and (3)–(5) to describe the patch characteristics. The (2) and (4) were normalized by forest area within each grid cell, thus making them comparable among grid cells. For (3)–(5), we only calculated the patch size >0.45 ha (five 30 × 30-m2 pixels), because patches  TC2000), and the expansion of forested area from 1986 to 2000 (e.g., TC1986  20% following Liu et al., (2019). We should note that our study area did not include the newly afforested area after 2000. All analyses were performed within the forest mask, thus excluding the potential confounding factors from other land cover types. The description of TC1986 and TC2000 can be found in3,32. More

Plant Ecology and Nature Conservation Group, Wageningen University, Wageningen, the NetherlandsFons van der Plas & Liesje MommerSystematic Botany and Functional Biodiversity, Life Science, Leipzig University, Leipzig, GermanyThomas Schröder-Georgi, Alexandra Weigelt, Kathryn Barry & Christian WirthGerman Centre for Integrative Biodiversity Research Halle-Jena-Leipzig, Leipzig, GermanyAlexandra Weigelt, Kathryn Barry, Adriana Alzate, Nico Eisenhauer, Anke Hildebrandt, Christiane Roscher & Christian WirthTerrestrial Ecology Research Group, School of Life Sciences Weihenstephan, Technical University of Munich, Munich, GermanySebastian Meyer & Wolfgang WeisserAquaculture and Fisheries Group, Wageningen University and Research Centre, Wageningen, the NetherlandsAdriana AlzateAgroécologie, AgroSup Dijon, Institut National de la Recherche Agronomique, Université de Bourgogne, Université de Bourgogne Franche-Comté, Dijon, FranceRomain L. BarnardEidgenössische Technische Hochschule Zürich, Zurich, SwitzerlandNina BuchmannDepartment of Experimental Plant Ecology, Institute for Water and Wetland Research, Radboud University Nijmegen, Nijmegen, the NetherlandsHans de KroonInstitute of Ecology and Evolution, University Jena, Jena, GermanyAnne Ebeling & Winfried VoigtInstitute of Biology, Leipzig University, Leipzig, GermanyNico EisenhauerHumboldt-Universität zu Berlin, Berlin, GermanyChristof EngelsInstitute of Plant Sciences, University of Bern, Bern, SwitzerlandMarkus FischerMax Planck Institute for Biogeochemistry, Jena, GermanyGerd Gleixner, Ernst-Detlef Schulze & Christian WirthHelmholtz Centre for Environmental Research, Leipzig, GermanyAnke HildebrandtFriedrich Schiller University Jena, Jena, GermanyAnke HildebrandtGeoecology, University of Tübingen, Tübingen, GermanyEva Koller-France & Yvonne OelmannInstitute of Geography and Geoecology, Karlsruhe Institute of Technology, Karlsruhe, GermanySophia Leimer & Wolfgang WilckeEcotron Européen de Montpellier, Centre National de la Recherche Scientifique, Montferrier-sur-Lez, FranceAlexandru MilcuCentre d’Ecologie Fonctionnelle et Evolutive, Unité Mixte de Recherche 5175 (Centre National de la Recherche Scientifique-Université de Montpellier-Université Paul-Valéry Montpellier-Ecole Pratique des Hautes Etudes), Montpellier, FranceAlexandru MilcuDepartment of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, SwitzerlandPascal A. NiklausUFZ, Helmholtz Centre for Environmental Research, Department Physiological Diversity, Leipzig, GermanyChristiane RoscherInstitute of Landscape Ecology, University of Münster, Münster, GermanyChristoph ScherberCentre for Biodiversity Monitoring, Zoological Research Museum Alexander Koenig, Bonn, GermanyChristoph ScherberGeobotany, Faculty of Biology, University of Freiburg, Freiburg, GermanyMichael Scherer-LorenzenCentre of Biodiversity and Sustainable Land Use, University of Göttingen, Göttingen, GermanyStefan ScheuJ.F. Blumenbach Institute of Zoology and Anthropology, Animal Ecology, University of Göttingen, Göttingen, GermanyStefan ScheuDepartment of Geography, University of Zurich, Zurich, SwitzerlandBernhard SchmidInstitute of Ecology, College of Urban and Environmental Sciences, Peking University, Beijing, ChinaBernhard SchmidLeuphana University Lüneburg, Institute of Ecology, Lüneburg, GermanyVicky TempertonAgroecology, Department of Crop Sciences, University of Göttingen, Göttingen, GermanyTeja TscharntkeF.v.d.P. wrote the initial draft of the manuscript. T.S.-G., A.W., K.B., S.M., A.A., R.L.B., N.B., H.d.K., A.E., N.E., C.E., M.F., G.G., A.H., E.K.-F., S.L., A.M., L.M., P.A.N., Y.O., C.R., C.S., M.S.-L., S.S., B.S., E.-D.S., V.T., T.T., W.V., W. Weisser, W. Wilcke and C.W. helped edit the manuscript. More