Developmental programming: prenatal and postnatal consequences of hyperthermia in dairy cows and calves

Effects of maternal blood beta-hydroxybutyrate on brown adipose tissue functions and thermogenic and metabolic health in neonatal calves

Maternal metabolic health, particularly during late pregnancy, plays a crucial role in fetal development and postnatal metabolic function. Elevated levels of BHB in dry cows, commonly observed in late gestation, may affect offspring development, but the effects on brown adipose tissue (BAT) and metabolic health remain unclear. In this study, 60 pregnant Holstein dairy cows were categorized into 2 groups based on serum BHB concentrations measured at 1, 3, 5, and 7 wk after dry-off: maternal low BHB (n = 30; mean ± SEM, 0.21 ± 0.005 mM) and maternal high BHB (n = 30; mean ± SEM, 0.64 ± 0.02 mM). Blood metabolites, including BHB, nonesterified fatty acids, and glucose, were monitored throughout the dry period. Calves born from these cows were evaluated for body growth, body temperature, glucose sensitivity, fecal, and cough score during the first month of life, with perirenal BAT and skin samples collected for analysis of thermogenic gene expression. Expression of stress genes, including CIRBP, HSP70, and HSBP1, was analyzed in skin tissue. Expression of thermogenic genes, including UCP-1, CREBP4, and CPT1B, and protein contents of UCP-1, PGC-1a were analyzed in BAT. In vitro, stromal vascular fractions were also isolated in calf's BAT, and further induced for brown adipocyte formation with dosed BHB supplementation. Results showed no differences in birth weight, body size, and body temperatures of calves born to maternal high BHB cows compared with calves born to maternal low BHB cows. However, the calves from the maternal high BHB group had higher expressions of stress genes in the skin, and decreased BAT mass and expression of thermogenic genes. Compared with the maternal low BHB group, 1-mo-old calves in the maternal high BHB group also showed significantly lower BAT mass, decreased expression of thermogenic genes, such as UCP-1, CREBP4, and CPT1B, and decreased mitochondrial density, indicating impaired BAT development. In addition, the calves from the maternal high BHB group showed reduced glucose sensitivity, as evidenced by their inability to maintain stable blood glucose levels during a glucose tolerance test. Protein concentrations of UCP-1 and PGC-1a were significantly lower in the BAT of calves born to maternal high BHB cows. In vitro, BHB supplementation inhibited brown adipocyte differentiation and thermogenesis, supporting the elevated maternal BHB impairs brown adipogenesis and mitochondrial biogenesis. Overall, this study demonstrates that calves born from elevated maternal BHB levels (∼0.64 mM) within the normal physiological range in the dry period significantly had impaired perinatal BAT development, thermogenesis, and glucose metabolism, highlighting the roles of maternal metabolic health in programming metabolic and thermoregulatory capacity in offspring.

Exploring Epigenetic and Genetic Modulation in Animal Responses to Thermal Stress

There is increasing evidence indicating that global temperatures are rising significantly, a phenomenon commonly referred to as 'global warming', which in turn is believed to be causing drastic changes to the global climate. Global warming (GW) directly impacts animal health, reproduction, production, and welfare, presenting several challenges to livestock enterprises. Thermal stress (TS) is one of the key consequences of GW, and all animal species, including livestock, have diverse physiological, epigenetic and genetic mechanisms to respond to TS. As a result, TS can significantly affect an animals' health, immune responsiveness, metabolic pathways etc. which can also influence the productivity, performance, and welfare of animals. Moreover, prolonged exposure to TS can lead to transgenerational and intergenerational changes that are mediated by epigenetic changes. For example, in several animal species, the effects of TS are encoded epigenetically during the animals' growth or productive stage, and these epigenetic changes can be transmitted intergenerationally. Such epigenetic changes can affect animal productivity by changing the phenotype so that it aligns with its ancestors' environment, irrespective of its immediate environment. Furthermore, epigenetic and genetic changes can also help protect cells from the adverse effects of TS by modulating the transcriptional status of heat-responsive genes in animals. This review focuses on the genetic and epigenetic modulation and regulation that occurs in TS conditions via HSPs, histone alterations and DNA methylation.

Long-lasting effects of in utero heat stress on subsequent performances of heifers and primiparous cows

The performance of an adult dairy cow may be influenced by heat stress that occurs during her gestation. The present study investigated potential effects of temperature-humidity index (THI) experienced by a cow during pregnancy, on the gestated daughter's performance on her first lactation, for the French Holstein and Montbeliarde dairy cattle populations. Fourteen traits were analyzed, all measured on genotyped cows: 305-d milk, fat, and protein yields, 305-d somatic cell score, clinical mastitis (both occurrence and number of events), body conformation traits, and heifer and cow conception rate. To study the effect of heat stress, we considered the THI experienced by the gestating cow, averaged for each month of her pregnancy and then categorized in 7 classes (≤40; 40-45; 45-50; 50-55; 55-60; 60-65; and >65). These average THI classes were then fitted as categorical covariates in the regression models used for this study, which included other fixed effects, and the genomic estimated breeding value as a covariate, both specific to each trait, the latter previously obtained from the official French evaluations. The THI effect was therefore estimated as the deviation between the observed and the predicted performances. In general, the estimated heat stress effects were small, presenting limited practical impact on the studied traits, and particularly for fertility and udder health, the estimated heat stress effects were not statistically significant. For the production traits, i.e., milk, fat, and protein yields, the estimated effect associated to high THI experienced at the beginning of the gestation was negative, and lightly positive when associated to high THI experienced by the dam at the end of her pregnancy. Finally, our results suggest that under the current French climate conditions, heat stress experienced by cows during any stage of their pregnancy has limited impact on future performances of their gestated daughters, however we cannot exclude that significant in utero heat stress effect may be present in climate conditions warmer than the French.

INVITED REVIEW: Impact of Maternal Health and Nutrition on the Microbiome and Immune Development of Neonatal Calves

This comprehensive review highlights the intricate interplay between maternal factors and the co-development of the microbiome and immune system in neonatal calves. Based on human and mouse studies, multiple prenatal and postnatal factors influence this process by altering the host-associated microbiomes (gut, respiratory tract, skin), microbial colonization trajectories, and priming of the immune systems (mucosal and systemic). This review emphasizes the importance of early life exposure, highlighting postnatal factors that work in synergy with maternal factors in further finetuning the co-development of the neonatal microbiome and immunity. In cattle, there is a general lack of research to identify the maternal effect on the early colonization process of neonatal calves (gut, respiratory tract) and its impact on the priming of the immune system. Past studies have primarily investigated the maternal effects on the passive transfer of immunity at birth. The co-development process of the microbiome and immune system is vital for lifelong health and production in cattle. Therefore, comprehensive research beyond the traditional focus on passive immunity is an essential step in this endeavor. Calf microbiome research reports the colonization of diverse bacterial communities in newborns, which is affected by the colostrum feeding method immediately after birth. In contrast to human studies reporting a strong link between maternal and infant bacterial communities, there is a lack of evidence to clearly define cow-to-calf transmission in cattle. Maternal exposure has been shown to promote the colonization of beneficial bacteria in neonatal calves. Nonetheless, calf microbiome research lacks links to early development of the immune system. An in-depth understanding of the impact of maternal factors on microbiomes and immunity will improve the management of pregnant cows to raise immune-fit neonatal calves. It is essential to investigate the diverse effects of maternal health conditions and nutrition during pregnancy on the gut microbiome and immunity of neonatal calves through collaboration among researchers from diverse fields such as microbiology, immunology, nutrition, veterinary science, and epidemiology.

The mammalian preimplantation embryo: Its role in the environmental programming of postnatal health and performance

During formation of the preimplantation embryo several cellular and molecular milestones take place, making the few cells forming the early embryo vulnerable to environmental stressors than can impair epigenetic reprogramming and controls of gene expression. Although these molecular alterations can result in embryonic death, a significant developmental plasticity is present in the preimplantation embryo that promotes full-term pregnancy. Prenatal epigenetic modifications are inherited during mitosis and can perpetuate specific phenotypes during early postnatal development and adulthood. As such, the preimplantation phase is a developmental window where developmental programming can take place in response to the embryonic microenvironment present in vivo or in vitro. In this review, the relevance of the preimplantation embryo as a developmental stage where offspring health and performance can be programmed is discussed, with emphasis on malnutrition and assisted reproductive technologies; two major environmental insults with important implications for livestock production and human reproductive medicine.

Disorder of Biological Quality and Autophagy Process in Bovine Oocytes Exposed to Heat Stress and the Effectiveness of In Vitro Fertilization

The main problem in dairy herds is reproductive disorders, which are influenced by many factors, including temperature. Heat stress reduces the quality of oocytes and their maturation through the influence of, e.g., mitochondrial function. Mitochondria are crucial during oocyte maturation as well as the process of fertilization and embryonic development. Disturbances related to high temperature will be increasingly observed due to global warming. In present studies, we have proven that exposure to high temperatures during the cleaving of embryos statistically significantly (at the level of p < 0.01) reduces the percentage of oocytes that cleaved and developed into blastocysts eight days after insemination. The study showed the highest percentage of embryos that underwent division in the control group (38.3 °C). The value was 88.10 ± 6.20%, while the lowest was obtained in the study group at 41.0 °C (52.32 ± 8.40%). It was also shown that high temperature has a statistically significant (p < 0.01) effect on the percentage of embryos that developed from the one-cell stage to blastocysts. The study showed that exposure to a temperature of 41.0 °C significantly reduced the percentage of embryos that split relative to the control group (38.3 °C; 88.10 ± 6.20%). Moreover, it was noted that the highest tested temperature limits the development of oocytes to the blastocyst stage by 5.00 ± 9.12% compared to controls (33.33 ± 7.10%) and cleaved embryos to blastocysts by 3.52 ± 6.80%; the control was 39.47 ± 5.40%. There was also a highly significant (p < 0.0001) effect of temperature on cytoplasmic ROS levels after 6 and 12 h IVM. The highest level of mitochondrial ROS was found in the group of oocytes after 6 h IVM at 41.0 °C and the lowest was found in the control group. In turn, at 41.0 °C after 12 h of IVM, the mitochondrial ROS level had a 2.00 fluorescent ratio, and the lowest in the group was 38.3 °C (1.08). Moreover, with increasing temperature, a decrease in the expression level of both LC3 and SIRT1 protein markers was observed. It was proved that the autophagy process was impaired as a result of high temperature. Understanding of the cellular and molecular responses of oocytes to elevated temperatures will be helpful in the development of heat resistance strategies in dairy cattle.

The Role of Brown Adipose Tissue and Energy Metabolism in Mammalian Thermoregulation during the Perinatal Period

Hypothermia is one of the most common causes of mortality in neonates, and it could be developed after birth because the uterus temperature is more elevated than the extrauterine temperature. Neonates use diverse mechanisms to thermoregulate, such as shivering and non-shivering thermogenesis. These strategies can be more efficient in some species, but not in others, i.e., altricials, which have the greatest difficulty with achieving thermoneutrality. In addition, there are anatomical and neurological differences in mammals, which may present different distributions and amounts of brown fat. This article aims to discuss the neuromodulation mechanisms of thermoregulation and the importance of brown fat in the thermogenesis of newborn mammals, emphasizing the analysis of the biochemical, physiological, and genetic factors that determine the distribution, amount, and efficiency of this energy resource in newborns of different species. It has been concluded that is vital to understand and minimize hypothermia causes in newborns, which is one of the main causes of mortality in neonates. This would be beneficial for both animals and producers.

Intergenerational impact of dietary protein restriction in dairy ewes on epigenetic marks in the perirenal fat of their suckling lambs

In sheep, nutrition during the prepubertal stage is essential for growth performance and mammary gland development. However, the potential effects of nutrient restriction in a prepuberal stage over the progeny still need to be better understood. Here, the intergenerational effect of maternal protein restriction at prepubertal age (2 months of age) on methylation patterns was evaluated in the perirenal fat of Assaf suckling lambs. In total, 17 lambs from ewes subjected to dietary protein restriction (NPR group, 44% less protein) and 17 lambs from control ewes (C group) were analyzed. These lambs were ranked based on their carcass proportion of perirenal and cavitary fat and classified into HighPCF and LowPCF groups. The perirenal tissue from 4 NPR-LowPCF, 4 NPR-HighPCF, 4 C-LowPCF, and 4 C-HighPCF lambs was subjected to whole-genome bisulfite sequencing and differentially methylated regions (DMRs) were identified. Among other relevant processes, these DMRs were mapped in genes responsible for regulating the transition of brown to white adipose tissue and nonshivering thermoregulation, which might be associated with better adaptation/survival of lambs in the perinatal stage. The current study provides important biological insights about the intergenerational effect on the methylation pattern of an NPR in replacement ewes.

A transgenerational study on the effect of great-granddam birth month on granddaughter EBV for production traits in Italian Simmental cattle

Heat tolerance is a key feature of resilient animals. Offspring of animals that suffer environmental stress during pregnancy could show physiological, morphological, and metabolic modifications. This is due to a dynamic reprogramming of the epigenetics of the mammalian genome that occurs in the early life cycle. Thus, the aim of this study was to investigate the extent of the transgenerational effect of heat stress during the pregnancy of Italian Simmental cows. The effects of dam and granddam birth months (as indicator of pregnancy period) on their daughter and granddaughter estimated breeding values (EBV) for some dairy traits as well as of the temperature-humidity index (THI) during the pregnancy were tested. A total of 128,437 EBV (milk, fat, and protein yields, and somatic cell score) were provided by the Italian Association of Simmental Breeders. The best birth months (of both dam and granddam) for milk yield and protein yield were May and June, whereas the worst were January and March. Great-granddam pregnancies developed during the winter and spring seasons positively affected the EBV for milk and protein yields of their great-granddaughters; in contrast, pregnancies during summer and autumn had negative effects. These findings were confirmed by the effects of maximum and minimum THI in different parts of the great-granddam pregnancy on the performances of their great-granddaughters. Thus, a negative effect of high temperatures during the pregnancy of female ancestors was observed. Results of the present study suggest a transgenerational epigenetic inheritance in Italian Simmental cattle due to environmental stressors.

Developmental Programming of Fertility in Cattle-Is It a Cause for Concern?

Cattle fertility remains sub-optimal despite recent improvements in genetic selection. The extent to which an individual heifer fulfils her genetic potential can be influenced by fetal programming during pregnancy. This paper reviews the evidence that a dam's age, milk yield, health, nutrition and environment during pregnancy may programme permanent structural and physiological modifications in the fetus. These can alter the morphology and body composition of the calf, postnatal growth rates, organ structure, metabolic function, endocrine function and immunity. Potentially important organs which can be affected include the ovaries, liver, pancreas, lungs, spleen and thymus. Insulin/glucose homeostasis, the somatotropic axis and the hypothalamo-pituitary-adrenal axis can all be permanently reprogrammed by the pre-natal environment. These changes may act directly at the level of the ovary to influence fertility, but most actions are indirect. For example, calf health, the timing of puberty, the age and body structure at first calving, and the ability to balance milk production with metabolic health and fertility after calving can all have an impact on reproductive potential. Definitive experiments to quantify the extent to which any of these effects do alter fertility are particularly challenging in cattle, as individual animals and their management are both very variable and lifetime fertility takes many years to assess. Nevertheless, the evidence is compelling that the fertility of some animals is compromised by events happening before they are born. Calf phenotype at birth and their conception data as a nulliparous heifer should therefore both be assessed to avoid such animals being used as herd replacements.