Effects of Developmental Programming Caused by Maternal Nutrient Intake on Postnatal Performance of Beef Heifers and Their Calves

Developmental Programming, Evolution, and Animal Welfare: A Case for Evolutionary Veterinary Science

The conditions animals experience during the early developmental stages of their lives can have critical ongoing effects on their future health, welfare, and proper development. In this paper we draw on evolutionary theory to improve our understanding of the processes of developmental programming, particularly Predictive Adaptive Responses (PAR) that serve to match offspring phenotype with predicted future environmental conditions. When these predictions fail, a mismatch occurs between offspring phenotype and the environment, which can have long-lasting health and welfare effects. Examples include metabolic diseases resulting from maternal nutrition and behavioral changes from maternal stress. An understanding of these processes and their evolutionary origins will help in identifying and providing appropriate developmental conditions to optimize offspring welfare. This serves as an example of the benefits of using evolutionary thinking within veterinary science and we suggest that in the same way that evolutionary medicine has helped our understanding of human health, the implementation of evolutionary veterinary science (EvoVetSci) could be a useful way forward for research in animal health and welfare.

Review: Gestational and postnatal nutritional effects on the neuroendocrine control of puberty and subsequent reproductive performance in heifers

Pubertal attainment is an intricate biological process that involves maturation of the reproductive neuroendocrine axis and increased pulsatile release of gonadotropin-releasing hormone (GnRH) and luteinizing hormone. Nutrition is a critical environmental factor controlling the timing of puberty attainment. Nutrient restriction during early postnatal development delays puberty, whereas increased feed intake and adiposity during this period hasten pubertal maturation by imprinting the hypothalamus. Moreover, the dam's nutrition during gestation can program the neuroendocrine system in the developing fetus and has the potential to advance or delay puberty in the offspring. Leptin, a hormone produced primarily by adipose cells, plays an important role in communicating energy status to the brain and regulating sexual maturation. Leptin's regulation of GnRH release is mediated by an upstream neuronal network since GnRH neurons do not contain the leptin receptor. Two groups of neurons located in the arcuate nucleus of the hypothalamus that express neuropeptide Y (NPY), an orexigenic peptide, and alpha melanocyte-stimulating hormone (αMSH), an anorexigenic peptide, are central elements of the neural circuitry that relay inhibitory (NPY) and excitatory (αMSH) inputs to GnRH neurons. Moreover, KNDy neurons, neurons in the arcuate nucleus that co-express kisspeptin, neurokinin B (NKB), and dynorphin, also play a role in the metabolic regulation of puberty. Our studies in beef heifers demonstrate that increased rates of BW gain during early postweaning (4-9 mo of age) result in reduced expression of NPY mRNA, increased expression of proopiomelanocortin and kisspeptin receptor mRNA, reduced NPY inhibitory inputs to GnRH neurons, and increased excitatory αMSH inputs to KNDy neurons. Finally, our most recent data demonstrate that nutrition of the cow during the last two trimesters of gestation can also induce transcriptional and structural changes in hypothalamic neurocircuitries in the heifer progeny that likely persist long-term after birth. Managerial approaches, such as supplementation of the dam during gestation (fetal programming), creep feeding, early weaning, and stair-step nutritional regimens have been developed to exploit brain plasticity and advance pubertal maturation in heifers.

Livestock exposure to future cumulated climate-related stressors in West Africa

A large range of climate change impacts is expected during the twenty-first century in vulnerable regions such as West Africa, where local populations largely rely on livestock systems as their main food production and income source. As climate change threatens livestock systems in various ways, here we assess how regional livestock could be exposed to cumulated climate-related stressors in the future. Using the world's largest multi-model climate impacts simulations database ISIMIP, we find that a large part of West Africa will experience at least 5-6 cumulated multiple climate stressors before the 2030s, including amplified severe heat stress conditions and flood risks. Consequently, about 30% of the current total regional livestock could be exposed to these cumulated stressors, with sheep and goat as the most affected species. This paper brings new quantifications that may help policy makers to prioritize decisions that could prepare local populations to face multiple climate-related impacts.

Effects of Maternal Nutrition on Female Offspring Weight Gain and Sexual Development

Maternal nutrition during pregnancy influences postnatal life of animals; nevertheless, few studies have investigated its effects on the productive performance and reproductive development of heifers. This study evaluated the performance, reproductive development, and correlation between reproduction × fat thickness and performance × ribeye area (REA) traits of heifers. We also performed an exploratory genomic association during the rearing period in heifers submitted to fetal programming. The study comprised 55 Nellore heifers born to dams exposed to one of the following nutritional planes: control, without protein-energy supplementation; PELT, protein-energy last trimester, protein-energy supplementation offered in the final third of pregnancy; and PEWG, protein-energy whole gestation, protein-energy supplementation upon pregnancy confirmation. Protein-energy supplementation occurred at the level of 0.3% live weight. After weaning, heifers were submitted to periodic evaluations of weight and body composition by ultrasonography. From 12 to 18 months, we evaluated the reproductive tract of heifers to monitor its development for sexual precocity and ovarian follicle population. The treatments had no effect (p > 0.05) on average daily gain; however, the weight of the animals showed a significant difference over time (p = 0.017). No differences were found between treatments for REA, backfat, and rump fat thickness, nor for puberty age, antral follicular count, and other traits related to reproductive tract development (p > 0.05). The correlation analysis between performance traits and REA showed high correlations (r > 0.37) between REA at weaning and year versus weight from weaning until yearling; however, no correlation was found for reproductive development traits versus fat thickness (p > 0.05). The exploratory genomic association study showed one single-nucleotide polymorphism (SNP) for each treatment on an intergenic region for control and PEWG, and the one for PELT on an intronic region of RAPGEF1 gene. Maternal nutrition affected only the weight of the animals throughout the rearing period.

Long-term effects of early maternal undernutrition on the growth, physiological profiles, carcass and meat quality of male beef offspring

The effects of maternal undernutrition in early gestation on growth, metabolic and endocrine profiles, carcass and meat quality of male offspring in cattle were assessed. Twenty-one Parda de Montaña and 14 Pirenaica cows received a CONTROL (100% nutrition requirements) or a SUBNUT (65%) diet from day 0 to 82 of gestation and thereafter were fed to requirements until calf weaning at 4 months of age. The performance and physiological profiles of male offspring during an 8-month fattening period were analyzed. Bulls were slaughtered at 12 months of age, and their carcasses and meat color, tenderness and intramuscular fatty acid profile were evaluated. Maternal undernutrition increased plasma NEFAs and impaired the growth of Pirenaica bulls, resulting in lower weights at slaughter and fatter carcasses with impaired meat tenderness. Irrespective of the breed, maternal undernutrition affected meat color and increased the meat content of some healthy fatty acids. In summary, early maternal undernutrition affected the fetal programming of beef male offspring with persistent consequences at slaughter.

Late Gestation Maternal Feed Restriction Decreases Microbial Diversity of the Placenta While Mineral Supplementation Improves Richness of the Fetal Gut Microbiome in Cattle

Feed intake restriction impacts both humans and ruminants in late gestation, although it is unknown whether this adverse maternal environment influences the microbiome of the reproductive tract, and through it, the colonization of the fetal gut. A 2 × 2 factorial design including a 70% feed intake restriction (feed restricted 'FR' or control diets 'CON') and mineral supplementation (unsupplemented 'S-' or supplemented 'S+') was used to analyze these effects in multiparous cows (n = 27). Vaginal swabs were obtained 60, 30, and 10 days prior to the estimated calving date, along with neonatal rumen fluid and meconium. Placental tissues and efficiency measurements were collected. Microbial DNA was extracted for 16S sequencing of the V4 region. Feed restriction decreased the diversity of the placental microbiome, but not the vagina, while mineral supplementation had little impact on these microbial communities. Mineral supplementation did improve the richness and diversity of the fetal gut microbiomes in relation to reproductive microbes. These differences within the placental microbiome may influence individual health and performance. Adequate maternal nutrition and supplementation yielded the greatest placental efficiency, which may aid in the establishment of a healthy placental microbiome and fetal microbial colonization.

Attainment and maintenance of pubertal cyclicity may predict reproductive longevity in beef heifers†

We hypothesized the manner that heifers achieve puberty may indicate their future reproductive longevity. Heifers with discontinued or delayed cyclicity during puberty attainment may have irregular reproductive cycles, anovulation, and infertility in their first breeding season contributing to a shorter reproductive lifespan. Therefore, plasma progesterone (P4) was measured from weaning to breeding on 611 heifers born 2012-2017 and four pubertal classifications were identified: (1) Early; P4 ≥ 1 ng/ml < March 12 with continued cyclicity, (2) Typical; P4 ≥ 1 ng/ml ≥ March 12 with continued cyclicity, (3) Start-Stop; P4 ≥ 1 ng/ml but discontinued cyclicity, and (4) Non-Cycling; no P4 ≥ 1 ng/ml. Historical herd records indicated that 25% of heifers achieved puberty prior to March 12th in the 10 years prior to the study. Start-Stop and Non-Cycling yearling heifers were lighter indicating reduced growth and reproductive maturity traits compared with Early/Typical heifers. In addition, Non-Cycling/Start-Stop heifers were less responsive to prostaglandin F2 alpha (PGF2α) to initiate estrous behavior and ovulation to be artificially inseminated. Non-Cycling heifers had fewer reproductive tract score-5 and reduced numbers of calves born in the first 21-days-of-calving during their first breeding season. Within the Start-Stop classification, 50% of heifers reinitiated cyclicity with growth traits and reproductive parameters that were similar to heifers in the Early/Typical classification while those that remained non-cyclic were more similar to heifers in the Non-Cycling group. Thus, heifers with discontinued cyclicity or no cyclicity during puberty attainment had delayed reproductive maturity resulting in subfertility and potentially a shorter reproductive lifespan.

Impacts of Epigenetic Processes on the Health and Productivity of Livestock

The dynamic changes in the epigenome resulting from the intricate interactions of genetic and environmental factors play crucial roles in individual growth and development. Numerous studies in plants, rodents, and humans have provided evidence of the regulatory roles of epigenetic processes in health and disease. There is increasing pressure to increase livestock production in light of increasing food needs of an expanding human population and environment challenges, but there is limited related epigenetic data on livestock to complement genomic information and support advances in improvement breeding and health management. This review examines the recent discoveries on epigenetic processes due to DNA methylation, histone modification, and chromatin remodeling and their impacts on health and production traits in farm animals, including bovine, swine, sheep, goat, and poultry species. Most of the reports focused on epigenome profiling at the genome-wide or specific genic regions in response to developmental processes, environmental stressors, nutrition, and disease pathogens. The bulk of available data mainly characterized the epigenetic markers in tissues/organs or in relation to traits and detection of epigenetic regulatory mechanisms underlying livestock phenotype diversity. However, available data is inadequate to support gainful exploitation of epigenetic processes for improved animal health and productivity management. Increased research effort, which is vital to elucidate how epigenetic mechanisms affect the health and productivity of livestock, is currently limited due to several factors including lack of adequate analytical tools. In this review, we (1) summarize available evidence of the impacts of epigenetic processes on livestock production and health traits, (2) discuss the application of epigenetics data in livestock production, and (3) present gaps in livestock epigenetics research. Knowledge of the epigenetic factors influencing livestock health and productivity is vital for the management and improvement of livestock productivity.