Review: Adaptation of ruminant livestock production systems to climate changes

Impact of heat waves on semen quality: A retrospective study in Argentina between 2005 and 2023

Heat waves, defined as periods with daily temperatures surpassing the historical average for a specific region, have become more frequent worldwide in recent years. Previous studies have reported a negative association between temperature and semen quality, but the focus has mainly been on Asian and European populations. The study included 54,926 men (18-60 years) undergoing routine semen analysis between 2005 and 2023 at CEUSA-LAEH andrology unit, in Buenos Aires, Argentina. Hourly temperature readings were provided by the Servicio Meteorológico Nacional. R programming (R Studio v2022.07.2) was used to define heat waves, calculate key characteristics, visualize results, and perform statistical tests at the IBYME laboratory. During the period studied, a total of 124 days had heat waves (defined after at least 3 consecutive days with 32.3 °C and 22 °C). Men exposed to heat waves during spermatogenesis exhibited lower sperm number (concentration and count; P < 0.0001) and decreased normal morphology (percentage of normal sperm and normal motile count; P < 0.05) compared to those not exposed. These differences were most pronounced between semen samples from years with several heat waves (2013, 2023) and none (2005, 2007, 2016), displaying 4-5 times higher fold changes (P < 0.05). Further analysis employing multiple regression revealed a significantly negative association between semen quality and heat wave length, suggesting that a prolonged exposure may be more detrimental than an acute exposure. Subsequent analysis focusing on prolonged exposure (≥6-days heat wave) during spermatogenesis revealed a negative (P < 0.05) association between early exposure (spermatocytogenesis: 64-90 days prior semen collection) and semen quality. This study underscores the negative association between early exposure to heat waves during sperm development and semen quality, raising concerns about its possible association with the worldwide declining male fertility. A comprehensive collaborative approach is crucial, involving global governmental policies, sustainable practices, and coordinated efforts across scientific, healthcare, and policy domains.

Uterine tone influences fertility of Merino ewes following laparoscopic artificial insemination

Artificial insemination (AI) plays a critical role in facilitating rapid genetic and production gains within the sheep industry. However, variable rates of AI success remain a concern for the industry and a barrier to adoption. Furthermore, the degree to which female factors influence the success of intrauterine laparoscopic AI rather than natural mating remains unknown. As such, this study investigates the effect of several factors collected during the time of AI, on the success of intrauterine laparoscopic AI. Data was generously donated by artificial breeding companies and stud breeders during routine commercial AI operations. AI data was collected over 3 breeding seasons during commercial AI programs (N = 24 programs) using Merino ewes (N = 24,700). Sire ID (N = 253), time of AI following progesterone removal (approx. 43-59 h post removal), uterine tone and intra-abdominal fat (both scored 1-5) as well as age of the ewe were all recorded at the time of AI. Transcutaneous ultrasound subsequently determined pregnancy rate approximately 55 days post-AI. A multivariate regression analysis was performed and revealed pregnancy success to increase when semen was inseminated into a ewe with a uterine tone score of 4 or 5 (P < 0.001). The remaining factors fell short of significance within the multivariate model. An interclass coefficient variation matrix was also used to determine the proportion of variation contributed to AI success by random factors allocated in the model; site, sire, AI date and breeding season (45.99 %, 29.94 %, 15.15 % and 8.92 %, respectively). These results highlight the influence of uterine tone on ewe fertility following laparoscopic AI, but also that program location and the sire used can further modify this influence on pregnancy rate. These factors must now be considered in combination with semen factors per individual sire used during AI to ascertain the contribution of several factors to the success of laparoscopic AI in Australia.

Genetic analysis of phenotypic indicators for heat tolerance in crossbred dairy cattle

Climate change-induced rise in global temperatures has intensified heat stress on dairy cattle and is contributing to the generally observed low milk productivity. Selective breeding aimed at enhancing animals' ability to withstand rising temperatures while maintaining optimal performance is crucial for ensuring future access to dairy products. However, phenotypic indicators of heat tolerance are yet to be effectively factored into the objectives of most selective breeding programs. This study investigated the response of milk production to changing heat load as an indication of heat tolerance and the influence of calving season on this response in multibreed dairy cattle performing in three agroecological zones Kenya. First-parity 7-day average milk yield (65 261 milk records) of 1 739 cows were analyzed. Based on routinely recorded weather data that were accessible online, the Temperature-Humidity Index (THI) was calculated and used as a measure of heat load. THI measurements used represented averages of the same 7-day periods corresponding to each 7-day average milk record. Random regression models, including reaction norm functions, were fitted to derive two resilience indicators: slope of the reaction norm (Slope) and its absolute value (Absolute), reflecting changes in milk yield in response to the varying heat loads (THI 50 and THI 80). The genetic parameters of these indicators were estimated, and their associations with average test-day milk yield were examined. There were no substantial differences in the pattern of milk yield response to heat load between cows calving in dry and wet seasons. Animals with ≤50% Bos taurus genes were the most thermotolerant at extremely high heat load levels. Animals performing in semi-arid environments exhibited the highest heat tolerance capacity. Heritability estimates for these indicators ranged from 0.06 to 0.33 and were mostly significantly different from zero (P < 0.05). Slope at THI 80 had high (0.64-0.71) negative correlations with average daily milk yield, revealing that high-producing cows are more vulnerable to heat stress and vice versa. A high (0.63-0.74) positive correlation was observed between Absolute and average milk yield at THI 80. This implied that low milk-producing cows have a more stable milk production under heat-stress conditions and vice versa. The study demonstrated that the slope of the reaction norms and its absolute value can effectively measure the resilience of crossbred dairy cattle to varying heat load conditions. The implications of these findings are valuable in improving the heat tolerance of livestock species through genetic selection.

Effects of heat stress on feed intake, milk yield, milk composition, and feed efficiency in dairy cows: A meta-analysis

Heat stress compromises dairy production by decreasing feed intake and milk yield, and it may also alter milk composition and feed efficiency. However, little information is available for evaluating such effects across different levels of heat stress and cows enrolled in heat stress studies. The objectives of this study were to evaluate the effects of heat stress on dry matter intake (DMI), energy-corrected milk (ECM), milk composition, and feed efficiency (kg ECM/kg DMI) and to investigate the relationship between such effects and heat stress intervention and animal characteristics by using meta-analytical approaches. Data from 31 studies (34 trials) fulfilled the inclusion criteria and were used for analysis. Results showed that heat stress decreased DMI, ECM, and milk protein concentration, but did not alter milk fat concentration or feed efficiency. Meta-regression confirmed that such reductions in DMI and ECM were significantly associated with increasing temperature-humidity index (THI). Over the period of heat stress, for each unit increase in THI, DMI and ECM decreased by 4.13% and 3.25%, respectively, in mid-lactation cows. Regression models further revealed the existence of a strong interaction between THI and lactation stage, which partially explained the large heterogeneity in effect sizes of DMI and ECM. The results indicated a need for more research on the relationship between the effect of heat stress and animal characteristics. This study calls for the implementation of mitigation strategies in heat-stressed herds due to the substantial decrease in productivity.

Improving Human Diets and Welfare through Using Herbivore-Based Foods: 1. Human and Animal Perspectives

Human health and diet are closely linked. The diversity of diets consumed by humans is remarkable, and most often incorporates both animal and plant-based foods. However, there has been a recent call for a reduced intake of animal-based foods due to concerns associated with human health in developed countries and perceived impacts on the environment. Yet, evidence for the superior nutritional quality of animal-sourced food such as meat, milk, and eggs, compared with plant-based foods, indicates that consumption of animal-sourced food should and will continue. This being the case, the aim here is to examine issues associated with animal-sourced foods in terms of both the quantification and mitigation of unintended consequences associated with environment, animal health, and herd management. Therefore, we examined the role of animal proteins in human societies with reference to the UN-FAO issues associated with animal-sourced foods. The emphasis is on dominant grazed pastoral-based systems, as used in New Zealand and Ireland, both with temperate moist climates and a similar reliance on global markets for generating net wealth from pastoral agricultural products. In conclusion, animal-sourced foods are shown to be an important part of the human diet. Production systems can result in unintended consequences associated with environment, animal health, and herd management, and there are technologies and systems to provide solutions to these that are available or under refinement.

An analysis of substantiated complaints made about incidents of poor livestock welfare, in Victoria, Australia

Incidents of poor welfare on farm in Victoria, Australia, are generally identified during an investigation that follows receipt of a complaint. Using deidentified records of complaints received by the Victoria State Government between 2011 and 2020, this study aimed to describe the source, number and the relationship between rainfall/stock prices and substantiated welfare complaints (SWC). Only incidents involving non-dairy cattle, sheep and goats in extensive farming systems will be considered. The main source of complaints received by the Victorian Government is the general public. Almost half of all complaints were made for cattle (48%), 39% for sheep, 11% for mixed species, and 2% for goats. The number of SWC varied between months, each year and across the different regions of Victoria. The ratio of the actual mean rainfall of the last three seasons to the long-term mean of the last three seasons of rainfall (RL3SR) and livestock prices together were the best predictors of the total number of SWC (adjusted R square value for heavy lamb-RL3SR was highest (0.590), followed by merino lamb-RL3SR (0.588), goat-RL3SR (0.545) and steer-RL3SR (0.478) all were significant (p ≤ 0.05)). The rainfall by region and town were not good predictors of the number of SWC. There was a correlation between rainfall and the number of SWC, possibly due to changes in pasture availability. Favorable seasonal conditions however, were not protective of livestock welfare and it is likely a number of factors may be implicated.

Influence of Heat Stress on Body Temperatures Measured by Infrared Thermography, Blood Metabolic Parameters and Its Correlation in Sheep

The aim of this research is to examine the influence of heat stress (HS) on body temperature (BT) measured rectally (RT) or by infrared thermography (IRT) of the nose (NT), eye (ET), leg (LT) and abdominal (AT) regions in intensively and extensively breed sheep and to detect a correlation between body temperature and metabolic response in sheep. A total of 33 Wurttemberg × Sjenica Pramenka sheep breeds were examined, 17 ewes were from outdoors and 16 were from indoor housing systems during three experimental periods (thermoneutral period, severe HS and moderate HS). Sheep under HS have a higher BT, and the magnitude of BT measured by infrared thermography (IRT) was higher than RT. LT and AT showed positive linear correlations with the temperature-humidity index (THI), while other ways of measuring BT did not give statistically significant correlations. Sheep under HS showed higher cortisol, insulin, total protein, albumin, urea, creatinine, bilirubin, aspartate aminotransferase, alanine aminotransferase, gamma-glutamyl transferase, alkaline phosphatase, lactate dehydrogenase, creatine kinase and index of insulin resistance, with lower values of triiodothyronine (T3), thyroxine (T4), non-esterified fatty acids, beta-hydroxybutyrate (BHB), glucose, calcium, inorganic phosphates, magnesium and cholesterol. BT and metabolic response were different in the function of the housing method of sheep. LT and AT showed a significant correlation with almost all blood parameters, and the strongest connections were made with T3, T4, BHB and the revised quantitative insulin sensitivity check index of insulin resistance. The abdomen and legs are good thermal windows because LT and AT are good summative responses to external ambient THI and internal metabolic changes in sheep under heat stress.

Blood Transcriptomic Analyses Reveal Functional Pathways Associated with Thermotolerance in Pregnant Ewes Exposed to Environmental Heat Stress

Environmental heat stress triggers a series of compensatory mechanisms in sheep that are dependent on their genetic regulation of thermotolerance. Our objective was to identify genes and regulatory pathways associated with thermotolerance in ewes exposed to heat stress. We performed next-generation RNA sequencing on blood collected from 16 pregnant ewes, which were grouped as tolerant and non-tolerant to heat stress according to a physiological indicator. Additional samples were collected to measure complete blood count. A total of 358 differentially expressed genes were identified after applying selection criteria. Gene expression analysis detected 46 GO terms and 52 KEGG functional pathways. The top-three signaling pathways were p53, RIG-I-like receptor and FoxO, which suggested gene participation in biological processes such as apoptosis, cell signaling and immune response to external stressors. Network analysis revealed ATM, ISG15, IRF7, MDM4, DHX58 and TGFβR1 as over-expressed genes with high regulatory potential. A co-expression network involving the immune-related genes ISG15, IRF7 and DXH58 was detected in lymphocytes and monocytes, which was consistent with hematological findings. In conclusion, transcriptomic analysis revealed a non-viral immune mechanism involving apoptosis, which is induced by external stressors and appears to play an important role in the molecular regulation of heat stress tolerance in ewes.

Impact of heat stress on dairy cattle and selection strategies for thermotolerance: a review

Climate change is a problem that causes many environmental issues that impact the productivity of livestock species. One of the major issues associated with climate change is an increase of the frequency of hot days and heat waves, which increases the risk of heat stress for livestock species. Dairy cattle have been identified as being susceptible to heat stress due to their high metabolic heat load. Studies have shown heat stress impacts several biological processes that can result in large economic consequences. When heat stress occurs, dairy cattle employ several physiological and cellular mechanisms in order to dissipate heat and protect cells from damage. These mechanisms require an increase and diversion in energy toward protection and away from other biological processes. Therefore, in turn heat stress in dairy cattle can lead numerous issues including reductions in milk production and reproduction as well as increased risk for disease and mortality. This indicates a need to select dairy cattle that would be thermotolerant. Various selection strategies to confer thermotolerance have been discussed in the literature, including selecting for reduced milk production, crossbreeding with thermotolerant breeds, selecting based on physiological traits and most recently selecting for enhanced immune response. This review discusses the various issues associated with heat stress in dairy cattle and the pros and cons to the various selection strategies that have been proposed to select for thermotolerance in dairy cattle.

Effects of cow reproductive status, parity and lactation stage on behaviour and heavy breathing indications of a commercial accelerometer during hot weather conditions

Heat stress presents one of the most urgent challenges to modern dairy farming, having major detrimental impacts on cow welfare, health, and production. Understanding the effect of cow factors (reproductive status, parity, and lactation stage) on the physiological and behavioural response to hot weather conditions is essential for the accurate detection and practical application of heat mitigation strategies. To study this, collars with commercial accelerometer-based sensors were fitted on 48 lactation dairy cows to record behaviour and heavy breathing from late spring to late summer. The temperature-humidity index (THI) was calculated from measurements of 8 barn sensors. We found that, above a THI of 84, cows in advanced pregnancy (>90 days) spent more time breathing heavily and less time eating and in low activity than other cows, while cows in early pregnancy (≤90 days) spent less time breathing heavily, more time eating and in low activity. Cows with 3+ lactations showed less time breathing heavily and in high activity and more time ruminating and in low activity than cows with fewer lactations. Although lactation stage interacted significantly with THI on time spent breathing heavily, ruminating, eating, and in low activity, there was no clear indication at which lactation stage cows were more sensitive to heat. These findings show that cow factors affect the cow's physiological and behavioural response to heat, which could be used to provide group-specific heat abatement strategies, thereby improving heat stress management.

Genetic Markers Associated with Milk Production and Thermotolerance in Holstein Dairy Cows Managed in a Heat-Stressed Environment

Dairy production in Holstein cows in a semiarid environment is challenging due to heat stress. Under such conditions, genetic selection for heat tolerance appears to be a useful strategy. The objective was to validate molecular markers associated with milk production and thermotolerance traits in Holstein cows managed in a hot and humid environment. Lactating cows (n = 300) exposed to a heat stress environment were genotyped using a medium-density array including 53,218 SNPs. A genome-wide association study (GWAS) detected six SNPs associated with total milk yield (MY305) that surpassed multiple testing (p < 1.14 × 10^-6). These SNPs were further validated in 216 Holstein cows from two independent populations that were genotyped using the TaqMan bi-allelic discrimination method and qPCR. In these cows, only the SNPs rs8193046, rs43410971, and rs382039214, within the genes TLR4, GRM8, and SMAD3, respectively, were associated (p < 0.05) with MY305, rectal temperature (RT), and respiratory rate. Interestingly, these variables improved as the number of favorable genotypes of the SNPs increased from 0 to 3. In addition, a regression analysis detected RT as a significant predictor (R² = 0.362) for MY305 in cows with >1 favorable genotype, suggesting this close relationship was influenced by genetic markers. In conclusion, SNPs in the genes TLR4, GRM8, and SMAD3 appear to be involved in the molecular mechanism that regulates milk production in cows under heat-stressed conditions. These SNPs are proposed as thermotolerance genetic markers for a selection program to improve the milk performance of lactating Holstein cows managed in a semiarid environment.

Beef cows' performance and metabolic response to short nutritional challenges in different months of lactation

Lactating cows can react to changes in nutrient availability with a range of behavioural and physiological mechanisms, which may differ among lactation stages. We investigated the effects of short feed restriction and refeeding periods on beef cows' performance and metabolic status in different months of lactation. For this, Parda de Montaña beef cows [n = 31; 626 ± 47.7 kg body weight (BW)] were subjected to short nutritional restriction and refeeding cycles, which were repeated in months 2, 3 and 4 of lactation. Each month, cows were consecutively fed a diet to meet 100% of their energy and protein requirements during a 4-day basal period, 55% during a 4-day restriction period, and again 100% during a 4-day refeeding period. The performance (energy balance, BW, milk yield and composition) and plasma metabolite concentrations (glucose, non-esterified fatty acids (NEFA), β-hydroxybutyrate (BHB), urea and malondialdehyde) were measured daily. Most of the traits were significantly affected by the interaction between feeding period and lactation month. Feed restriction induced milk yield loss, decreased milk protein and increased milk urea contents to different extents. The plasma NEFA concentrations rose with restriction in months 2, 3 and 4 but BHB and urea concentrations increased only in month 4. Most of these metabolites lowered to basal values during refeeding. These results suggest that beef cows use different adaptation strategies to cope with nutritional challenges as lactation advances, body fat mobilisation predominates in early lactation and protein catabolism prevails at later stages.

The role of feeds in the transmission of chicken pathogens in Dodoma Urban District, Tanzania

Chicken production is an important economic activity in Tanzania. Indigenous chickens are kept in rural areas, while exotic breeds are kept in urban areas. Due to their high productivity, exotic breeds are becoming important sources of protein in fast-growing cities. Dodoma is one of the cities growing very fast in Tanzania. As a result, production of layers and broilers has increased dramatically. However, diseases remain the major challenge to chicken production despite the efforts of livestock officers to educate people on good management practices. This has made farmers think that feeds may be the source of pathogens. The study's objectives were thus to identify the major diseases affecting broiler and layer chickens in the Dodoma urban district, as well as the potential role of feeds in pathogen transmission to chickens. A household survey was conducted to identify common diseases affecting chickens in the study area. Thereafter, locally prepared feed samples were collected from twenty shops available in the district to determine the presence of Salmonella and Eimeria parasites. The presence of Eimeria parasites in the feeds was determined by raising day-old chicks in a sterile environment for 3 wk while feeding them the feed samples collected. Fecal samples from the chicks were analyzed for the presence of Eimeria parasites. Salmonella contamination of the feed samples was determined in the laboratory through the culture method. The study found that coccidiosis, Newcastle disease, fowl typhoid, infectious bursal disease, and colibacillosis are the main diseases affecting chickens in the district. After 3 wk of rearing, 3 out of 15 chicks developed coccidiosis. In addition, about 31.1% of the feed samples showed the presence of Salmonella spp. The prevalence of Salmonella was highest in limestone (53.3%), followed by fishmeal (26.7%), and maize bran (13.3%). It has been concluded that feeds are potential carriers of pathogens. To reduce economic losses and the continuous use of drugs in chicken production, health authorities should assess the microbial quality of poultry feeds.

Molecular markers for thermo-tolerance are associated with reproductive and physiological traits in Pelibuey ewes raised in a semiarid environment

Pelibuey sheep exhibit reproductive activity through the year, but warm weather lowers their fertility and demonstrates physiological limitations of environmental heat stress. Single nucleotide polymorphisms (SNPs) associated with heat stress tolerance in sheep have been reported previously. The objective was to validate the association of seven thermo-tolerance SNP markers with reproductive and physiological traits in Pelibuey ewes raised in a semiarid region. Pelibuey ewes were assigned to a cool (January 1st^.- March 31st^.; n = 101) or warm (April 1st^.- August 31st^.; n = 104) experimental group. All ewes were exposed to fertile rams and assessed for pregnancy diagnosis 90 days later; lambing day was reported at birth. These data served to calculate the reproductive traits of services per conception, prolificacy, days to estrus, days to conception, conception rate and lambing rate. Rectal temperature, rump/leg skin temperature and respiratory rate were measured and reported as physiological traits. Blood samples were collected and processed to extract DNA, which was genotyped using the TaqMan allelic discrimination method and qPCR. A mixed effects statistical model was used to validate associations between SNP genotypes and phenotypic traits. The SNPs rs421873172, rs417581105 and rs407804467 were confirmed as markers associated with reproductive and physiological traits (P < 0.05), and these SNPs were in the genes PAM, STAT1 and FBXO11, respectively. Interestingly, these SNP markers resulted as predictors for the evaluated traits but only in ewes from the warm group, which indicated their association with heat-stress tolerance. An additive SNP effect was confirmed with the highest contribution (P < 0.01) of the SNP rs417581105 for the evaluated traits. Reproductive performance improved (P < 0.05) and physiological parameters decreased in ewes carrying favorable SNP genotypes. In conclusion, three thermo-tolerance SNP markers were associated with improved reproductive and physiological traits in a prospective population of heat-stressed ewes raised in a semiarid environment.

Tunisian camel casein gene characterization reveals similarities and differences with Sudanese and Nigerian populations

Milk is a primary protein source that has always played a role in mammalian health. Despite the intensification of research projects on dromedary and the knowledge of the genetic diversity at the casein loci, the genetic structure of the Tunisian camel population still needs exploration. This study sought to determine the genetic diversity of 3 casein gene variants in 5 Tunisian camel ecotypes: c.150G>T at CSN1S1 (α_S1-casein), g.2126A>G at CSN2 (β-casein), and g.1029T>C at CSN3 (κ-casein). The obtained results were compared with data published on Sudanese and Nigerian camels to establish the level of differentiation within and between populations. A total of 159 blood samples were collected from 5 Tunisian camel ecotypes and the extracted DNA was genotyped by PCR-RFLP. A streamlined genotyping protocol was also developed for CSN3. Results indicated that allele T was quite rare (0.06) at CSN1S1 for all ecotypes. Minor allele frequency was found for G (0.462) in CSN2 except for Ardhaoui Medenine ecotype who deviated from the average CSN2 allele frequency of the total population. Allele C showed minor allele frequency of 0.384 in CSN3. Among the Tunisian population, GAT (0.343) was the most represented haplotype in all ecotypes except for Ardhaoui Medenine, where GGC (0.322) was the most frequent one. Significant differences in heterozygosity and local inbreeding were observed across the Tunisian, Sudanese, and Nigerian populations, although the global fixation index indicated that only 2.2% of the genetic variance is related to ecotype differences. Instead, phylogenetic analysis revealed a closer link between the Tunisian and Sudanese populations through a clade subdivision with 3 main branches among the ecotypes. This study represents the first attempt to understand casein gene variability in Tunisian camels; with further study, milk traits and genetic differentiation among populations can be associated with the history of camel domestication.

LCA to Estimate the Environmental Impact of Dairy Farms: A Case Study

Intensive farming is responsible for extreme environmental impacts under different aspects, among which global warming represents a major reason of concern. This is a quantitative problem linked to the farm size and a qualitative one, depending on farming methods and land management. The dairy sector is particularly relevant in terms of environmental impact, and new approaches to meeting sustainability goals at a global scale while meeting society’s needs are necessary. The present study was carried out to assess the environmental impact of dairy cattle farms based on a life cycle assessment (LCA) model applied to a case study. These preliminary results show the possibility of identifying the most relevant impacts in terms of supplied products, such as animal feed and plastic packaging, accounting for 19% and 15% of impacts, respectively, and processes, in terms of energy and fuel consumption, accounting for 53% of impacts overall. In particular, the local consumption of fossil fuels for operations within the farm represents the most relevant item of impact, with a small margin for improvement. On the other hand, remarkable opportunities to reduce the impact can be outlined from the perspective of stronger partnerships with suppliers to promote the circularity of packaging and the sourcing of animal feed. Future studies may include the impact of drug administration and the analysis of social aspects of LCA.

Livelihood Capitals, Income Inequality, and the Perception of Climate Change: A Case Study of Small-Scale Cattle Farmers in the Ecuadorian Andes

The Sustainable Development Goals (SDG) of 2015 identify poverty, growth, and inequality as three key areas of intervention towards the UN 2030 Agenda for human well-being and sustainability. Herein, the predominant objectives are: (a) To determine the poverty groups by quintiles through the cattle income in households of small milk producers; (b) To characterize rural livelihoods by using capital theory; and (c) To assess the perception of climate change (CC) and the willingness to accept adaptation as well as mitigation measures. The current study was performed in communities that are located in the Ecuadorian Andes, where some 178 surveys were conducted with indigenous Kichwa and mestizo heads of households. From the total net income determined, five groups were organized. The Lorenz curve was applied as a general indicator of the relative inequality, as well as the Gini coefficient (G). On the basis of the theory of capital, the human, social, natural, physical, and financial characteristics were determined, and seven variables were considered to evaluate the perception and willingness to accept mitigation and adaptation actions of the given quintiles. The result of the Gini coefficient was 0.52, which indicates that the poorest 20% of the population only receives 3.40% of the income, while the richest 20% of the quintile obtain about 54% of the total income. It is evident that most producers know little about CC, but that they are willing to receive strengthening programs. Therefore, it is essential to establish strategic guidelines from public policy in order to reduce inequality and to improve the social welfare of producers, with a transversal axis in the strengthening of the capacities on the impact, mitigation, and adaptation to CC, as well as the provision of several tools, such as access to climate information.

UHPLC-ESI-QqTOF Analysis and In Vitro Rumen Fermentation for Exploiting Fagus sylvatica Leaf in Ruminant Diet

In recent years, animal husbandry has aimed at improving the conditions of livestock animals useful for humans to solve environmental and health problems. The formulation of animal feeds or supplements based on antioxidant plant compounds is considered a valuable approach and an alternative for livestock productivity. Forest biomass materials are an underestimated source of polyphenolic compounds whose sustainable recovery could provide direct benefits to animals and, indirectly, human nutrition. In this context, an alcohol extract from leaves of Fagus sylvatica L. was first investigated through an untargeted ultra-high-performance liquid chromatography-high-resolution tandem mass spectrometry (UHPLC-HRMS/MS) approach. Then, it was fractionated into a fatty acid-rich and a polyphenolic fraction, as evidenced by total lipid, phenol, and flavonoid content assays, with antiradical and reducing activity positively correlated to the latter. When tested in vitro with rumen liquor to evaluate changes in the fermentative parameters, a significant detrimental effect was exerted by the lipid-rich fraction, whereas the flavonoid-rich one positively modulated the production of volatile fatty acids (i.e., acetate, butyrate, propionate, etc.).

Genome-wide association study of a thermo-tolerance indicator in pregnant ewes exposed to an artificial heat-stressed environment

Environmental heat stress negatively influences sheep production in warm semi-arid regions. An animal's ability to tolerate warm weather is difficult to measure naturally due to environmental variability and genetic variation between animals. In this study we developed a thermo-tolerance indicator (TTI) to define heat stress tolerance in pregnant sheep in a controlled environment. Next, we performed a genome-wide association study (GWAS) to identify genomic regions and target genes associated with thermo-tolerance in sheep. Pregnant Columbia-Rambouillet crossbred ewes (n = 127) were heat-stressed inside a climate-controlled chamber for 57 days by increasing the temperature-humidity index to ≥30. Rectal temperature (RT) and feed intake (FI) data were collected daily and used for the predictive TTI analysis. After the tenth day of heat stress, the regression analyses revealed that FI was stable; however, when the ewe's RT exceeded 39.8 °C their FI was less than thermo-tolerant ewes. This average predicted temperature was used to classify each ewe as heat stress tolerant (≤39.8 °C) and non-heat stress tolerant (>39.8 °C). A GWAS analysis was performed and genomic regions were compared between heat stress tolerant and non-tolerant ewes. The single-marker genomic analysis detected 16 single nucleotide polymorphisms (SNP) associated with heat stress tolerance (P < 0.0001), whereas the multi-marker Bayesian analysis identified 8 overlapped 1-Mb chromosomal regions accounting for 11.39% of the genetic variation associated with tolerance to heat stress. Four intragenic SNP showed a remarkable contribution to thermo-tolerance, and these markers were within the genes FBXO11 (rs407804467), PHC3 (rs414179061), TSHR (rs418575898) and STAT1 (rs417581105). In conclusion, genomic regions harboring four intragenic SNP were associated with heat stress tolerance, and these candidate genes are proposed to influence heat tolerance in pregnant ewes subjected to an artificially induced warm climate. Moreover, these genetic markers could be suitable for use in further genetic selection programs in sheep managed in semi-arid regions.

Examining the Environmental Impacts of the Dairy and Baby Food Industries: Are First-Food Systems a Crucial Missing Part of the Healthy and Sustainable Food Systems Agenda Now Underway?

Food systems are increasingly being understood as driving various health and ecological crises and their transformation is recognised as a key opportunity for planetary health. First-food systems represent an underexplored aspect of this transformation. Despite breastfeeding representing the optimal source of infant nutrition, use of commercial milk formula (CMF) is high and growing rapidly. In this review, we examine the impact of CMF use on planetary health, considering in particular its effects on climate change, water use and pollution and the consequences of these effects for human health. Milk is the main ingredient in the production of CMF, making the role of the dairy sector a key area of attention. We find that CMF use has twice the carbon footprint of breastfeeding, while 1 kg of CMF has a blue water footprint of 699 L; CMF has a significant and harmful environmental impact. Facilitation and protection of breastfeeding represents a key part of developing sustainable first-food systems and has huge potential benefits for maternal and child health.

Effects of dietary supplementation with alpha-lipoic acid on apparent digestibility and serum metabolome alterations of sheep in summer

To investigate the effects of alpha-lipoic acid (LA) on the nutrition metabolism of sheep (36.72 ± 1.44 kg) in the summer, twenty-one sheep were randomly assigned to three treatments addressing LA supplementation: 0.00 (CTL), 600 (LA-L), and 900 (LA-H) mg/kg of dry matter (DM) per day for each sheep. Whole feces and urine collection methods were used to analyze apparent digestibility; ELISA kits to determine the hormones, antioxidant, and immune parameters in the blood; and serum metabolomics to detect and analyze small molecular substances. The results showed the DM intakes in the LA-L and LA-H groups were significantly increased by 8.22% and 8.02%, respectively, compared to that in the CTL group, and there was no significant effect on average daily gain, feed conversion ratio, nitrogen digestibility, calcium digestibility, and phosphorus digestibility. Regarding hormones, antioxidant, and immune indicators, the concentrations of triiodothyronine, superoxide dismutase, glutathione reductase, HSP70, and IgA significantly increased after LA supplementation, while adrenaline and malondialdehyde levels significantly decreased. With the pairwise comparison of the three groups, metabolomics analysis identified 22 differential metabolites in the positive/negative modes, respectively, which suggested LA supplementation can significantly affect sheep's lipid, amino acid, and nucleic acid metabolism. Additionally, 3-indolepropionic acid, cinnamoylglycine, butyric acid, dodecanedioic acid, indoxyl sulfate, and pantothenic acid were the common differential metabolites with higher concentrations after LA supplementation. In summary, dietary supplementation of LA can increase the sheep's DMI, energy digestibility, antioxidant capacity, and immunity. These changes provide evidence to support the use of LA supplementation for livestock.

Environmental stress and livestock productivity in hot-humid tropics: Alleviation and future perspectives

Tropical environments are characterized by persistently high temperature and relative humidity and the harsh environmental conditions pose a serious limitation on the optimal performance of the animals raised in this region. Heat stress causes deleterious effects on welfare, immunology and physiology of farm animals with a resultant impact on their productivity as the use of body resources is re-organized and the metabolic priorities of animals shift away from production, growth, health and reproduction. It is imperative to understand the mechanisms involved in the thermoregulation of animals under tropical conditions in order to develop appropriate strategies for their improvement. This review focuses on the available data on the increasing global temperature and the adverse impact of tropical conditions on animals' adaptive mechanism affected during thermal stress on production performance, intestinal and ileal microbiome, physiological responses, antioxidant system, metabolic responses, cellular and molecular response, adaptive mechanism strategies to heat stress and also strategies to palliate environmental stress on livestock under humid tropical conditions including environmental manipulation, genetic opportunity, epigenetic and feeding modification. Overall, the present review has identified the disturbance in the physiological indices of tropical livestock and the need for concerted efforts in ameliorating the adverse impacts of high ambient temperature aggravated by high humidity on livestock in tropical environments. Further research is needed on genotype-by-environment interaction on the thermotolerance of different livestock species in the tropics.

Redox Biomarker Baseline Levels in Cattle Tissues and Their Relationships with Meat Quality

Cattle breeds or crossbreds with high productivity traits have been developed to meet a growing demand for food. When intensive farming practices are followed, animals face several challenges which can result in poor performance, compromised welfare and the reduced quality of their products. Our study aims to highlight the resting values of the physiological oxidative stress that three cattle breeds exhibit, and their potential relationship with meat quality. For this purpose, we determined the levels of five common redox biomarkers (glutathione (GSH), catalase (CAT), total antioxidant capacity (TAC), thiobarbituric reactive substances (TBARS) and protein carbonyls (CARBS)) in the tissues of three commonly used beef cattle breeds (Charolais (CHA), Limousin (LIM) and Simmental (SIM)) and their association with specific meat quality traits that depend on color, pH and texture. The results revealed that LIM cattle breed animals have elevated intrinsic antioxidant defense systems in comparison to CHA and SIM cattle breed animals. In addition, the meat quality parameters were associated with the redox biomarkers. We propose that the determination of specific antioxidant parameters in the blood might be used as potential biomarkers to predict meat quality. This would allow farmers to nutritionally intervene to improve the quality of their products.

An updated review on cattle thermoregulation: physiological responses, biophysical mechanisms, and heat stress alleviation pathways

Heat stress is one of the main obstacles to achieving efficient cattle production systems, and it may have numerous adverse effects on cattle. As the planet undergoes climatic changes, which is predicted to raise the earth's average temperature by 1.5 °C between 2030 and 2052, its impact may trigger several stressful factors for livestock. Among these, an increase in core body temperature would trigger physiological imbalance, consequently affecting reproduction, animal health, and dry matter intake adversely. Core body temperature increase is commonly observed and poses challenges to livestock farmers. In cattle farming, thermal stress severely affects milk production and weight gain, and can compromise food security in the coming years. This review presents an updated approach to the physiological and thermoregulatory responses of cattle under various environmental conditions. Strategies for mitigating the harmful effects of heat stress on livestock are suggested as viable alternatives for the betterment of production systems.

Impacts of climate change on the livestock food supply chain; a review of the evidence

The potential impacts of climate change on current livestock systems worldwide are a major concern, and yet the topic is covered to a limited extent in global reports such as the ones produced by the Intergovernmental Panel on Climate Change. In this article, we review the risk of climate-related impacts along the land-based livestock food supply chain. Although a quantification of the net impacts of climate change on the livestock sector is beyond the reach of our current understanding, there is strong evidence that there will be impacts throughout the supply chain, from farm production to processing operations, storage, transport, retailing and human consumption. The risks of climate-related impacts are highly context-specific but expected to be higher in environments that are already hot and have limited socio-economic and institutional resources for adaptation. Large uncertainties remain as to climate futures and the exposure and responses of the interlinked human and natural systems to climatic changes over time. Consequently, adaptation choices will need to account for a wide range of possible futures, including those with low probability but large consequences.

•

Risk results from the interaction of climate-related hazards with the exposure and vulnerability of human and natural systems.

•

Climate change will impact the livestock sector throughout the food supply chain⁠—from farm production to human consumption.

•

Key hazards relate to climate change trends but also, and importantly, to climate variability and climate extremes.

•

Large uncertainties remain as to climate futures and the exposure and responses of the interlinked human and natural systems.

•

Adaptation choices will need to account for a wide range of possible futures.

Genetic Diversity and Signatures of Selection for Thermal Stress in Cattle and Other Two Bos Species Adapted to Divergent Climatic Conditions

Understanding the biological mechanisms of climatic adaptation is of paramount importance for the optimization of breeding programs and conservation of genetic resources. The aim of this study was to investigate genetic diversity and unravel genomic regions potentially under selection for heat and/or cold tolerance in thirty-two worldwide cattle breeds, with a focus on Chinese local cattle breeds adapted to divergent climatic conditions, Datong yak (Bos grunniens; YAK), and Bali (Bos javanicus) based on dense SNP data. In general, moderate genetic diversity levels were observed in most cattle populations. The proportion of polymorphic SNP ranged from 0.197 (YAK) to 0.992 (Mongolian cattle). Observed and expected heterozygosity ranged from 0.023 (YAK) to 0.366 (Sanhe cattle; SH), and from 0.021 (YAK) to 0.358 (SH), respectively. The overall average inbreeding (±SD) was: 0.118 ± 0.028, 0.228 ± 0.059, 0.194 ± 0.041, and 0.021 ± 0.004 based on the observed versus expected number of homozygous genotypes, excess of homozygosity, correlation between uniting gametes, and runs of homozygosity (ROH), respectively. Signatures of selection based on multiple scenarios and methods (F ST, HapFLK, and ROH) revealed important genomic regions and candidate genes. The candidate genes identified are related to various biological processes and pathways such as heat-shock proteins, oxygen transport, anatomical traits, mitochondrial DNA maintenance, metabolic activity, feed intake, carcass conformation, fertility, and reproduction. This highlights the large number of biological processes involved in thermal tolerance and thus, the polygenic nature of climatic resilience. A comprehensive description of genetic diversity measures in Chinese cattle and YAK was carried out and compared to 24 worldwide cattle breeds to avoid potential biases. Numerous genomic regions under positive selection were detected using three signature of selection methods and candidate genes potentially under positive selection were identified. Enriched function analyses pinpointed important biological pathways, molecular function and cellular components, which contribute to a better understanding of the biological mechanisms underlying thermal tolerance in cattle. Based on the large number of genomic regions identified, thermal tolerance has a complex polygenic inheritance nature, which was expected considering the various mechanisms involved in thermal stress response.

Understanding the seasonality of performance resilience to climate volatility in Mediterranean dairy sheep

As future climate challenges become increasingly evident, enhancing performance resilience of farm animals may contribute to mitigation against adverse weather and seasonal variation, and underpin livestock farming sustainability. In the present study, we develop novel seasonal resilience phenotypes reflecting milk production changes to fluctuating weather. We evaluate the impact of calendar season (autumn, winter and spring) on animal performance resilience by analysing 420,534 milk records of 36,908 milking ewes of the Chios breed together with relevant meteorological data from eastern Mediterranean. We reveal substantial seasonal effects on resilience and significant heritable trait variation (h² = 0.03–0.17). Resilience to cold weather (10 °C) of animals that start producing milk in spring was under different genetic control compared to autumn and winter as exemplified by negative genetic correlations (− 0.09 to − 0.27). Animal resilience to hot weather (25 °C) was partially under the same genetic control with genetic correlations between seasons ranging from 0.43 to 0.86. We report both favourable and antagonistic associations between animal resilience and lifetime milk production, depending on calendar season and the desirable direction of genetic selection. Concluding, we emphasise on seasonal adaptation of animals to climate and the need to incorporate the novel seasonal traits in future selective breeding programmes.

'Rotatinuous' stocking as a climate-smart grazing management strategy for sheep production

We aimed to evaluate the effect of different grazing management strategies on carcass characteristics traits, meat quality and CH₄ intensity and yield of lambs grazing Italian ryegrass pastures in Southern Brazil. A grazing trial was performed (2014 and 2015) in a randomized complete block design with two grazing management targets and four replicates. Treatments were traditional rotational stocking (RT), with pre- and post-grazing sward heights of 25 and 5 cm, respectively, and 'Rotatinuous' stocking (RN), with pre- and post-grazing sward heights of 18 and 11 cm, respectively. Castrated crossbred Texel and Polwarth lambs were used. Results indicated that diet cost per kg of dry matter (p = 0.001) and per hectare (p < 0.001) were lower for RN than for RT treatment. Final live weight (p = 0.022) and hot and cold carcass weight (p = 0.006) were greater for the RN treatment. All commercial cuts were greater for RN than for RT treatment. The RN treatment presented greater (p < 0.001) production of carcass, edible food and crude protein. Feed efficiency and feed cost conversion were better for RN than for RT treatment. CH₄ intensity per kg of carcass, edible food and crude protein gain were 2.6, 2.7 and 2.1 times lower (p < 0.001) for RN. Moreover, CH₄ yield was lower (p = 0.014) for RN than for RT treatment, with an average of 7.6 and 8.3% of the gross energy intake, respectively. We conclude that the 'Rotatinuous' stocking results in a greater carcass production, carcass quality and lower diet cost, and CH₄ intensity and yield of grazing lambs. Adopting this grazing management strategy could enhance both lamb production and mitigation of CH₄ intensity and yield in grazing ecosystems, which could be considered a good example of climate-smart livestock production.

Estimation of heat exchanges in Boer crossbred goats maintained in a climate chamber

Exposure of goats to high air temperatures can induce physiological and behavioral adjustments, increasing the dissipation of excess body heat in the latent form, and intensification of the use of these thermoregulatory tools can result in physiological and productive damage to animals. With this, the objective of the research was to quantify the levels of thermal stress and the sensible and latent heat losses of Boer crossbred goats submitted to different air temperatures, in a climatic chamber. Six male crossbred goats of the Boer breed, with an average weight of 25.06 ± 4.43 kg and mean age of six months, were grouped using a completely randomized design, with three treatments (air temperatures of the 26, 30 and 34 °C, respectively) and six replicates (animals) with 68% relative humidity. The temperature and relative humidity of the air were collected to calculate the temperature and humidity index (THI) and heat exchanges. Were collected the physiological responses rectal temperature (RT) and surface (ST) and respiratory rate (RF), with these data were estimated the heat exchanges by radiation (L), convection (C_r), total sensitive (G_s), latent of the respiratory tract (E_r), cutaneous (E_c), total latent (E_t) and total heat exchange (W_t). It was found that the THI values were classified as thermal comfort, moderate stress and very stressful, respectively, in the three conditions evaluated. With the increase in AT, the animals significantly increased (P < 0.05) the RT, ST and RF, and consequently reduced sensitive heat exchanges, from 38 to 8%, and increased latent heat exchanges, from 62 to 92%, when compared air temperatures of 26 and 34 °C, respectively. Physiological responses showed a significant negative (P < 0.05) correlation with sensitive heat exchanges and a positive correlation with latent heat exchanges. In very stressful thermal conditions, the animals lost almost all of the excess metabolic heat by latent means (skin and respiratory tract).

Controlled elevated temperatures during early-mid gestation cause placental insufficiency and implications for fetal growth in pregnant pigs

It is known that pig offspring born from pregnant pigs exposed to elevated ambient temperatures during gestation have altered phenotypes, possibly due to placental insufficiency and impaired fetal growth. Therefore, the objective of this study was to quantify the effect of maternal heat exposure during early-mid gestation, when pig placentae grow heavily, on placental and fetal development. Fifteen pregnant pigs were allocated to thermoneutral (TN; 20 °C; n = 7) or cyclic elevated temperature conditions (ET; 28 to 33 °C; n = 8) from d40 to d60 of gestation. Following euthanasia of the pigs on d60, placental and fetal morphometry and biochemistry were measured. Compared to TN fetuses, ET fetuses had increased (P = 0.041) placental weights and a lower (P = 0.013) placental efficiency (fetal/placental weight), although fetal weights were not significantly different. Fetuses from ET pigs had reduced (P = 0.032) M. longissimus fibre number density and a thicker (P = 0.017) placental epithelial layer compared to their TN counterparts. Elevated temperatures decreased (P = 0.026) placental mRNA expression of a glucose transporter (GLUT-3) and increased (P = 0.037) placental IGF-2 mRNA expression. In conclusion, controlled elevated temperatures between d40 to d60 of gestation reduced pig placental efficiency, resulting in compensatory growth of the placentae to maintain fetal development. Placental insufficiency during early-mid gestation may have implications for fetal development, possibly causing a long-term phenotypic change of the progeny.

Genome-Wide Analysis of Nubian Ibex Reveals Candidate Positively Selected Genes That Contribute to Its Adaptation to the Desert Environment

Simple Summary

The Nubian ibex is a wild relative of the domestic goat found in hot deserts of Northern Africa and Arabia. The domestic goat is an important livestock species that is mainly found in arid and semi-arid regions of Africa and Asia. The Nubian ibex is well adapted to challenging environments in hot deserts characterized by high diurnal temperatures, intense solar radiation, and scarce water resources. It is therefore important to understand the genetic basis of its adaptation for scientific and economic importance. To identify genes with adaptive traits, the Nubian ibex genome was sequenced and compared with that of related mammals. We identified twenty-five genes under selection in the Nubian ibex that play diverse biological roles such as immune response, visual development, signal transduction, and reproduction. Three other genes under adaptive evolution involved in protective functions of the skin against damaging solar radiation in the desert were identified in Nubian ibex genome. Our finding provides valuable genomic insights into the adaptation of Nubian ibex to desert environments. The genomic information generated in this study can be used in developing appropriate breeding programs aimed at enhancing adaptation of local goats to less favorable habitats in response to changing climates.

Abstract

The domestic goat (Capra hircus) is an important livestock species with a geographic range spanning all continents, including arid and semi-arid regions of Africa and Asia. The Nubian ibex (Capra nubiana), a wild relative of the domestic goat inhabiting the hot deserts of Northern Africa and the Arabian Peninsula, is well-adapted to challenging environments in hot deserts characterized by intense solar radiation, thermal extremes, and scarce water resources. The economic importance of C. hircus breeds, as well as the current trends of global warming, highlights the need to understand the genetic basis of adaptation of C. nubiana to the desert environments. In this study, the genome of a C. nubiana individual was sequenced at an average of 37x coverage. Positively selected genes were identified by comparing protein-coding DNA sequences of C. nubiana and related species using dN/dS statistics. A total of twenty-two positively selected genes involved in diverse biological functions such as immune response, protein ubiquitination, olfactory transduction, and visual development were identified. In total, three of the twenty-two positively selected genes are involved in skin barrier development and function (ATP binding cassette subfamily A member 12, Achaete-scute family bHLH transcription factor 4, and UV stimulated scaffold protein A), suggesting that C. nubiana has evolved skin protection strategies against the damaging solar radiations that prevail in deserts. The positive selection signatures identified here provide new insights into the potential adaptive mechanisms to hot deserts in C. nubiana.

Non-Invasive Sheep Biometrics Obtained by Computer Vision Algorithms and Machine Learning Modeling Using Integrated Visible/Infrared Thermal Cameras

Live sheep export has become a public concern. This study aimed to test a non-contact biometric system based on artificial intelligence to assess heat stress of sheep to be potentially used as automated animal welfare assessment in farms and while in transport. Skin temperature (°C) from head features were extracted from infrared thermal videos (IRTV) using automated tracking algorithms. Two parameter engineering procedures from RGB videos were performed to assess Heart Rate (HR) in beats per minute (BPM) and respiration rate (RR) in breaths per minute (BrPM): (i) using changes in luminosity of the green (G) channel and (ii) changes in the green to red (a) from the CIELAB color scale. A supervised machine learning (ML) classification model was developed using raw RR parameters as inputs to classify cutoff frequencies for low, medium, and high respiration rate (Model 1). A supervised ML regression model was developed using raw HR and RR parameters from Model 1 (Model 2). Results showed that Models 1 and 2 were highly accurate in the estimation of RR frequency level with 96% overall accuracy (Model 1), and HR and RR with R = 0.94 and slope = 0.76 (Model 2) without statistical signs of overfitting.

Resilience of Small Ruminants to Climate Change and Increased Environmental Temperature: A Review

Simple Summary

Small ruminants are critical for food security and livelihood, especially under extreme stressful and diverse climatic environments. Generally, sheep and goats are farmed on grazing land in relatively large groups relying on low inputs in terms of feed, water and labor, and possess high thermotolerance compared to large ruminants such as cattle. Climate change has been recognized as a harmful factor influencing sheep and goat production. Small ruminants are vulnerable to direct and indirect effects of climate change, including heat stress, limited and low-quality pasture availability and emerging infectious diseases. In this context, selection of animals for thermotolerance is one viable strategy that exploits natural variation within and between breeds for desirable traits. The various biological markers used to improve thermotolerance in small ruminants include behavioral (feed intake, water intake), physiological (respiration rate, rectal temperature, sweating rate), hormonal (T3, T4 and growth hormone) responses and the response of molecular regulators.

Abstract

Climate change is a major global threat to the sustainability of livestock systems. Climatic factors such as ambient temperature, relative humidity, direct and indirect solar radiation and wind speed influence feed and water availability, fodder quality and disease occurrence, with production being most efficient in optimal environmental conditions. Among these climatic variables, ambient temperature fluctuations have the most impact on livestock production and animal welfare. Continuous exposure of the animals to heat stress compromises growth, milk and meat production and reproduction. The capacity of an animal to mitigate effects of increased environmental temperature, without progressing into stress response, differs within and between species. Comparatively, small ruminants are better adapted to hot environments than large ruminants and have better ability to survive, produce and reproduce in harsh climatic regions. Nevertheless, the physiological and behavioral changes in response to hot environments affect small ruminant production. It has been found that tropical breeds are more adaptive to hot climates than high-producing temperate breeds. The growing body of knowledge on the negative impact of heat stress on small ruminant production and welfare will assist in the development of suitable strategies to mitigate heat stress. Selection of thermotolerant breeds, through identification of genetic traits for adaption to extreme environmental conditions (high temperature, feed scarcity, water scarcity), is a viable strategy to combat climate change and minimize the impact on small ruminant production and welfare. This review highlights such adaption within and among different breeds of small ruminants challenged by heat stress.

Review: Fifty years of research on rumen methanogenesis: lessons learned and future challenges for mitigation

Meat and milk from ruminants provide an important source of protein and other nutrients for human consumption. Although ruminants have a unique advantage of being able to consume forages and graze lands not suitable for arable cropping, 2% to 12% of the gross energy consumed is converted to enteric CH4 during ruminal digestion, which contributes approximately 6% of global anthropogenic greenhouse gas emissions. Thus, ruminant producers need to find cost-effective ways to reduce emissions while meeting consumer demand for food. This paper provides a critical review of the substantial amount of ruminant CH4-related research published in past decades, highlighting hydrogen flow in the rumen, the microbiome associated with methanogenesis, current and future prospects for CH4 mitigation and insights into future challenges for science, governments, farmers and associated industries. Methane emission intensity, measured as emissions per unit of meat and milk, has continuously declined over the past decades due to improvements in production efficiency and animal performance, and this trend is expected to continue. However, continued decline in emission intensity will likely be insufficient to offset the rising emissions from increasing demand for animal protein. Thus, decreases in both emission intensity (g CH4/animal product) and absolute emissions (g CH4/day) are needed if the ruminant industries continue to grow. Providing producers with cost-effective options for decreasing CH4 emissions is therefore imperative, yet few cost-effective approaches are currently available. Future abatement may be achieved through animal genetics, vaccine development, early life programming, diet formulation, use of alternative hydrogen sinks, chemical inhibitors and fermentation modifiers. Individually, these strategies are expected to have moderate effects (<20% decrease), with the exception of the experimental inhibitor 3-nitrooxypropanol for which decreases in CH4 have consistently been greater (20% to 40% decrease). Therefore, it will be necessary to combine strategies to attain the sizable reduction in CH4 needed, but further research is required to determine whether combining anti-methanogenic strategies will have consistent additive effects. It is also not clear whether a decrease in CH4 production leads to consistent improved animal performance, information that will be necessary for adoption by producers. Major constraints for decreasing global enteric CH4 emissions from ruminants are continued expansion of the industry, the cost of mitigation, the difficulty of applying mitigation strategies to grazing ruminants, the inconsistent effects on animal performance and the paucity of information on animal health, reproduction, product quality, cost-benefit, safety and consumer acceptance.

Genetic Selection for Thermotolerance in Ruminants

Variations in climatic variables (temperature, humidity and solar radiation) negatively impact livestock growth, reproduction, and production. Heat stress, for instance, is a source of huge financial loss to livestock production globally. There have been significant advances in physical modifications of animal environment and nutritional interventions as tools of heat stress mitigation. Unfortunately, these are short-term solutions and may be unsustainable, costly, and not applicable to all production systems. Accordingly, there is a need for innovative, practical, and sustainable approaches to overcome the challenges posed by global warming and climate change-induced heat stress. This review highlights attempts to genetically select and breed ruminants for thermotolerance and thereby sustain production in the face of changing climates. One effective way is to incorporate sustainable heat abatement strategies in ruminant production. Improved knowledge of the physiology of ruminant acclimation to harsh environments, the opportunities and tools available for selecting and breeding thermotolerant ruminants, and the matching of animals to appropriate environments should help to minimise the effect of heat stress on sustainable animal genetic resource growth, production, and reproduction to ensure protein food security.

Transcriptome analysis reveals corresponding genes and key pathways involved in heat stress in Hu sheep

Heat stress (HS) seriously affects animal performance. In view of global warming, it is essential to understand the regulatory mechanisms by which animals adapt to heat stress. In this study, our aim was to explore the genes and pathways involved in heat stress in sheep. To this end, we used transcriptome analysis to understand the molecular responses to heat stress and thereby identify means to protect sheep from heat shock. To obtain an overview of the effects of heat stress on sheep, we used the hypothalamus for transcriptome sequencing and identified differentially expressed genes (DEGs; false discovery rate (FDR) < 0.01; fold change > 2) during heat stress. A total of 1423 DEGs (1122 upregulated and 301 downregulated) were identified and classified into Gene Ontology (GO) categories and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Heat stress triggered dramatic and complex alterations in gene expression in the hypothalamus. We hypothesized that heat stress induced apoptosis and dysfunction in cells and vital organs and affected growth, development, reproduction, and circadian entrainment via the calcium signaling pathway, which influences ribosome assembly and function. Real-time PCR was used to evaluate the expression of the genes regulating important biological functions or whose expression profiles were significantly changed after acute heat stress (FDR < 0.01; fold change > 4), and the results showed that the expression patterns of these genes were consistent with the results of transcriptome sequencing, indicating that the credibility of the sequencing results. Our data indicated that heat stress induced calcium dyshomeostasis, blocked biogenesis, caused ROS accumulation, impaired the antioxidant system and innate defense, and induced apoptosis through the P53 signaling pathway activated by PEG3, decreased growth and development, and enhanced organ damage. These data is very important and helpful to elucidate the molecular mechanism of heat stress and finally to find ways to deal with heat stress damage in sheep.