Physiological rhythmicity in Malpura ewes to adapt to cold stress in a semi-arid tropical environment

Stress Factors and Their Effects on Productivity in Sheep

Products obtained from sheep have an economically important place in the world. Their adaptability to different climatic conditions, their ease of care and feeding, their high utilization of poor pasture areas with low yield and quality, the ease of flock management, their high twinning rate, and their short intergenerational period are some of the advantages of sheep production. Sheep production has the ability to adapt better to environmental stress factors, as can be understood from the presence of sheep in different geographical regions at a global level. However, the changes in environmental conditions and production cause some negative results in animals. All these negative results expose animals to various stress factors (heat, cold, transport, treatment, nutritional, shearing, weaning, etc.). All stress factors that directly and indirectly affect sheep production ultimately lead to compromised performance, decreased productivity, increased mortality, and adverse effects on the immune system. In order to cope with the current stress parameters in animals and to achieve optimum production, a holistic approach is needed according to the environmental conditions and available resources. It is important to consider the factors involved in these responses in order to manage these processes correctly and to develop adequate strategies and improve sheep welfare. This review aimed to reveal the importance of some stress factors in sheep and their effects on sheep productivity.

Metabolome profiling of plasma reveals different metabolic responses to acute cold challenge between Inner-Mongolia Sanhe and Holstein cattle

Low-temperature conditions influence cattle productivity and survivability. Understanding the metabolic regulations of specific cattle breeds and identifying potential biomarkers related to cold challenges are important for cattle management and optimization of genetic improvement programs. In this study, 28 Inner-Mongolia Sanhe and 22 Holstein heifers were exposed to -25°C for 1 h to evaluate the differences in metabolic mechanisms of thermoregulation. In response to this acute cold challenge, altered rectal temperature was only observed in Holstein cattle. Further metabolome analyses showed a greater baseline of glycolytic activity and mobilization of AA in Sanhe cattle during normal conditions. Both breeds responded to the acute cold challenge by altering their metabolism of volatile fatty acids and AA for gluconeogenesis, which resulted in increased glucose levels. Furthermore, Sanhe cattle mobilized the citric acid cycle activity, and creatine and creatine phosphate metabolism to supply energy, whereas Holstein cattle used greater AA metabolism for this purpose. Altogether, we found that propionate and methanol are potential biomarkers of acute cold challenge response in cattle. Our findings provide novel insights into the biological mechanisms of acute cold response and climatic resilience, and will be used as the basis when developing breeding tools for genetically selecting for improved cold adaptation in cattle.

Transcriptome Profiles of the Liver in Two Cold-Exposed Sheep Breeds Revealed Different Mechanisms and Candidate Genes for Thermogenesis

Cold-induced thermogenesis plays an important role in the survival of lambs exposed to low air temperatures. The liver produces and mediates heat production in mammals; however, to date, little is known about the role of liver genes in cold-induced thermogenesis in lambs. In this study, the difference in the liver transcriptome between Altay and Hu ewe lambs was compared. Because of different backgrounds of the two breeds, we hypothesized that the transcriptome profiles of the liver would differ between breeds when exposed to cold. Cold-exposed Altay lambs activated 8 candidate genes (ACTA1, MYH1, MYH2, MYL1, MYL2, TNNC1, TNNC2, and TNNT3) involved in muscle shivering thermogenesis; 3 candidate genes (ATP2A1, SLN, and CKM) involved in muscle nonshivering thermogenesis related to the Ca²⁺ signal and creatine cycle; and 6 candidate genes (PFKM, ALDOC, PGAM2, ENO2, ENO3, and ENO4) involved in enhancing liver metabolism. In contrast, the liver may not act as the main tissue for thermogenesis in cold-exposed Hu lambs. We concluded that Altay lambs rely on liver-mediated shivering and nonshivering thermogenesis by muscle tissue to a greater extent than Hu lambs. Results from this study could provide a theoretical foundation for the breeding and production of cold-resistant lambs.

Transcriptome Analysis Reveals Genes Involved in Thermogenesis in Two Cold-Exposed Sheep Breeds

Thermogenesis plays an important role in the survival of sheep exposed to low temperatures; however, little is known about the genetic mechanisms underlying cold adaptation in sheep. We examined 6 Altay (A) and 6 Hu (H) six-month-old ewe lambs. Altay sheep are raised in northern China and are adapted to dry, cold climates, while Hu sheep are raised in southern China and are adapted to warm, humid climates. Each breed was divided into two groups: chronic cold sheep, exposed to -5 °C for 25 days (3 A^c; 3 H^c), and thermo-neutral sheep, maintained at 20 °C (3 A^w; 3 H^w). The transcriptome profiles of hypothalamus, tail-fat and perirenal fat tissues from these four groups were determined using paired-end sequencing for RNA expression analysis. There are differences in cold tolerance between Hu and Altay sheep. Under cold exposure of the lambs: (1) UCP1-dependent thermogenesis and calcium- and cAMP-signaling pathways were activated; and (2) different fat tissues were activated in Hu and Altay lambs. Several candidate genes involved in thermogenesis including UCP1, ADRB3, ADORA2A, ATP2A1, RYR1 and IP6K1 were identified. Molecular mechanisms of thermogenesis in the sheep are discussed and new avenues for research are suggested.