Climate is the most important ecological factor determining the growth, development, and productivity of domestic animals (Adams et al., 1998). Climate changes impact the economic viability of livestock production systems worldwide (Klinedinst et al., 1993) through a variety of routes. These include changes in food availability and quality, changes in pest and pathogen populations, alteration in immunity and both direct and indirect impacts on animal performance, such as growth, reproduction, and lactation. Lack of prior conditioning (acclimatization) to sudden change in weather often results in catastrophic losses in the domestic livestock industry (Thornton et al., 2009)

Stress is an external event or condition that places a strain on a biological system. The animal response to a stress involves the expenditure of energy to remove or reduce the impact of the stress. This increases maintenance requirements of the animal and results in loss of production. The biological response to stress is divided into acute and chronic phases, with the acute phase lasting hours to a few days and the chronic phase lasting several days to weeks. The acute response is driven by homeostatic regulators of the nervous and endocrine systems and the chronic phase by homeorhetic regulators of the endocrine system. Both responses involve alterations in energy balance and metabolism. Thermal environment affects all animals and therefore represents the largest single stressor in animal production. Other types of stressors include housing conditions, overcrowding, social rank, disease, and toxic compounds. "Acclimation" to a stress is a phenotypic response developed by the animal to an individual stressor within the environment. However, under natural conditions, it is rare for only one environmental variable to change over time. "Acclimatization" is the process by which an animal adapts to several stressors within its natural environment. Acclimation is a homeorhetic process that takes several weeks to occur and occurs via homeorhetic, not homeostatic, mechanisms. It is a phenotypic change that disappears when the stress is removed. When the stress is severe and not relieved by acclimatization or management changes, the animal is considered chronically stressed and is susceptible to increased incidence of disease and poor health. Milk yield and reproduction are extremely sensitive to stress because of the high energy and protein demands of lactation and the complexity of the reproductive process and multiple organs that are involved. Improvements in protection of animals against stress require improved education of producers to recognize stress and methods for estimating degree of stress on animals.

The preimplantation period of embryonic development can be a key window for programming of postnatal development because extensive epigenetic remodeling occurs during this time. It was hypothesized that modification of one‐carbon metabolism of the bovine embryo by addition of the methyl‐donor choline to culture medium would change postnatal phenotype through epigenetic modification. Embryos produced in vitro were cultured with 1.8 mM choline chloride or control medium. Blastocysts were transferred into females and pregnancy outcomes and postnatal phenotype of the resultant calves determined. Exposure of embryos to choline increased gestation length and calf birth weight. Calves derived from choline‐treated embryos were also heavier at weaning and had increased ratio of body weight to hip height than control calves. Choline altered muscle DNA methylation of calves 4 months after birth. A total of 670 of the 8149 CpG examined were differentially methylated, with the predominant effect of choline being hypomethylation. Among the genes associated with differentially methylated CpG were ribosomal RNAs and genes in AMPK, mTOR, integrin, and BEX2 canonical pathways and cellular functions involved in growth and proliferation. Results demonstrate that provision of the methyl‐donor choline to the preimplantation embryo can alter its developmental program to increase gestation length, birth weight, and weaning weight and cause postnatal changes in muscle DNA methylation including those associated with genes related to anabolic processes and cellular growth. The importance of the nutritional status of the embryo with respect to one‐carbon metabolism for ensuring health and well‐being after birth is emphasized by these observations.

Holstein cows (n = 30) were balanced by days in milk, milk production, and parity (91 ± 5.9 d in milk, 36.2 ± 2.5 kg/d, and 3.1 ± 1.4, respectively) and fed OmniGen-AF (OG; Phibro Animal Health, Teaneck, NJ), an immune stimulant, at 0 g/cow per d for control (CON) or 56 g/cow per d for OG for 52 d on a commercial dairy. At 52 d of the study cows were randomly selected (n = 12) from both groups (6 OG and 6 CON) and housed in environmentally controlled rooms at the Agricultural Research Complex for 21 d at the University of Arizona. Cows were subjected to 7 d of thermoneutral (TN) conditions, 10 d of heat stress (HS), and 4 d of recovery (REC) under TN conditions. Feed intake, milk production, and milk composition were measured daily. Rectal temperatures (RT) and respiration rates (RR) were recorded 3 times per day (600, 1400, and 1800 h). Blood samples were taken on d 7 (TN), 8 (HS), 10 (HS), 17 (HS), and 18 (TN) during the Agricultural Research Complex segment. Cows in HS had higher RR and RT and water intake and lower dry matter intake and milk yield than these measures in TN. There was a treatment × environment interaction with cows fed OG having lower RR and RT and higher dry matter intake during peak thermal loads than CON. However, milk yield did not differ between groups. Cows fed OG had lower milk fat percent than CON (3.7 vs 4.3%) during HS. The SCC content of milk did not differ between treatment groups but rose in both groups during the REC phase following HS. Plasma insulin and plasma glucose levels were not different between groups. However, plasma insulin in both groups was lower during acute HS, then rose across the HS period, and was highest during the REC phase. Plasma cortisol levels were highest in all cows on the first day of HS (d 8) but were lower in cows fed OG compared with CON. However, plasma ACTH concentrations were elevated in OG-fed animals at all times samples were collected. Plasma ACTH was also elevated in cows fed both OG and CON during HS. Feeding OG reduced plasma cortisol during acute but not chronic HS and increased basal plasma ACTH, suggesting that OG treatment may alter the hypothalamic pituitary adrenal axis.

Once it enters the uterus at d 4 to 5 after ovulation, the preimplantation bovine embryo is controlled in its development by regulatory signaling molecules from the mother called embryokines. Here, several cell-signaling molecules whose genes are expressed in the endometrium during d 5 to 7 after estrus were tested for the ability to affect the competence of the embryo for further development and the characteristics of the resultant blastocysts. Molecules tested were C-natriuretic peptide (CNP), IL-8, bovine morphogenetic protein 4 (BMP-4), IL-6, and leukemia inhibitory factor (LIF). None of the cell-signaling molecules tested improved the competence of the embryo to become a blastocyst; in fact, BMP-4 decreased development. All molecules modified attributes of the blastocyst formed in culture. In particular, CNP increased the number of cells in the ICM, whereas IL-8 decreased inner cell mass cell numbers and tended to increase the proportion of blastocysts that were hatching or hatched. In addition, BMP-4 decreased the proportion of blastocysts that were hatching. Interleukin-6 and, to a lesser extent, LIF activated the Janus kinase (JAK)/signal transducer and activator of transcription 3 (STAT3) signaling pathway in the inner cell mass, and LIF increased the percent of cells in the blastocyst that were positive for both NANOG and phosphorylated (activated) STAT3. In conclusion, our results indicate that CNP, IL-8, IL-6, LIF, and BMP-4 can modify embryonic development of the cow in a manner that affects characteristics of the resultant blastocyst. Further research is required to understand how these changes in characteristics of the blastocyst would affect competence of the embryo to establish and maintain pregnancy.

Cold climate shapes the genome of animals and drives them to carry sufficient genetic variations to adapt to changes in temperature. However, limited information is available about the genome-wide pattern of adaptations to cold environments in cattle. In the present study, we used 777K SNP genotyping (15 Chinese cattle breeds, 198 individuals) and whole genome resequencing data (54 cattle breeds of the world, 432 individuals) to disentangle divergent selection signatures, especially between the cold-adapted (annual average temperature of habitat, 6.24 °C to 10.3 °C) and heat-adapted (20.2 °C to 24.73 °C) Chinese native cattle breeds. Genomic analyses revealed a set of candidate genes (e.g., UQCR11, DNAJC18, EGR1, and STING1) were functionally associated with thermogenesis and energy metabolism. We also characterized the adaptive loci of cattle exposed to cold temperatures. Our study finds new candidate genes and provides new insights into adaptations to cold climates in cattle.