Maternal betaine suppresses adrenal expression of cholesterol trafficking genes and decreases plasma corticosterone concentration in offspring pullets

Unravelling the impact of epigenetic mechanisms on offspring growth, production, reproduction and disease susceptibility

Epigenetic mechanisms, such as DNA methylation, histone modifications and non-coding RNA molecules, play a critical role in gene expression and regulation in livestock species, influencing development, reproduction and disease resistance. DNA methylation patterns silence gene expression by blocking transcription factor binding, while histone modifications alter chromatin structure and affect DNA accessibility. Livestock-specific histone modifications contribute to gene expression and genome stability. Non-coding RNAs, including miRNAs, piRNAs, siRNAs, snoRNAs, lncRNAs and circRNAs, regulate gene expression post-transcriptionally. Transgenerational epigenetic inheritance occurs in livestock, with environmental factors impacting epigenetic modifications and phenotypic traits across generations. Epigenetic regulation revealed significant effect on gene expression profiling that can be exploited for various targeted traits like muscle hypertrophy, puberty onset, growth, metabolism, disease resistance and milk production in livestock and poultry breeds. Epigenetic regulation of imprinted genes affects cattle growth and metabolism while epigenetic modifications play a role in disease resistance and mastitis in dairy cattle, as well as milk protein gene regulation during lactation. Nutri-epigenomics research also reveals the influence of maternal nutrition on offspring's epigenetic regulation of metabolic homeostasis in cattle, sheep, goat and poultry. Integrating cyto-genomics approaches enhances understanding of epigenetic mechanisms in livestock breeding, providing insights into chromosomal structure, rearrangements and their impact on gene regulation and phenotypic traits. This review presents potential research areas to enhance production potential and deepen our understanding of epigenetic changes in livestock, offering opportunities for genetic improvement, reproductive management, disease control and milk production in diverse livestock species.

Parental betaine supplementation promotes gosling growth with epigenetic modulation of IGF gene family in the liver

Betaine is widely used as a feed additive in the chicken industry to promote laying performance and growth performance, yet it is unknown whether betaine can be used in geese to improve the laying performance of goose breeders and the growth traits of offspring goslings. In this study, laying goose breeders at 39 wk of age were fed basal (Control, CON) or betaine-supplemented diets at low (2.5 g/kg, LBT) or high (5 g/kg, HBT) levels for 7 wk, and the breeder eggs laid in the last week were collected for incubation. Offspring goslings were examined at 35 and 63 d of age. The laying rate tended to be increased (P = 0.065), and the feed efficiency of the breeders was improved by betaine supplementation, while the average daily gain of the offspring goslings was significantly increased (P < 0.05). Concentrations of insulin-like growth factor 2 (IGF-2) in serum and liver were significantly increased in the HBT group (P < 0.05), with age-dependent alterations of serum T3 levels. Concurrently, hepatic mRNA expression of the IGF gene family was significantly increased in goslings derived from betaine-treated breeders (P < 0.05). A higher ratio of proliferating cell nuclear antigen (PCNA)-immunopositive nuclei was found in the liver sections of the HBT group, which was confirmed by significantly upregulated hepatic expression of PCNA mRNA and protein (P < 0.05). Moreover, hepatic expression of thyroxine deiodinase type 1 (Dio1) and thyroid hormone receptor β (TRβ) was also significantly upregulated in goslings of the HBT group (P < 0.05). These changes were associated with significantly higher levels of global DNA 5-mC methylation, together with increased expression of methyl transfer genes (P < 0.05), including betaine-homocysteine methyltransferase (BHMT), glycine N-methyltransferase (GNMT), and DNA (cytosine-5-)-methyltransferase 1 (DNMT1). The promoter regions of IGF-2 genes, as well as the predicted TRβ binding site on the IGF-2 gene, were significantly hypomethylated (P < 0.05). These results indicate that gosling growth can be improved by dietary betaine supplementation in goose breeders via epigenetic modulation of the IGF gene family, especially IGF-2, in the liver.

In ovo injection of betaine promotes adrenal steroidogenesis in pre-hatched chicken fetuses

Corticosterone is critical for the maturation and survival of chicken fetus around hatching. Betaine is used as a feed additive in poultry industry to promote growth and mitigate stress. However, it remains unknown whether betaine could affect adrenal corticosterone synthesis in pre-hatching chicken fetuses. In this study, betaine (2.5 mg/egg) was injected into developing chicken fetuses at d 11 of incubation (E11) and its impact on adrenal steroidogenesis was investigated at day 19 (E19). Plasma corticosterone concentration was significantly (P < 0.05) elevated in betaine-treated fetuses, together with increased adrenal expression of melanocortin 2 receptor and steroidogenic acute regulatory protein. Accordingly, the corticosterone biosynthetic enzymes, such as cytochrome P450 family 11 subfamily A member 1, 3β-hydroxysteroid dehydrogenase and cytochrome P450 family 21 subfamily A member 2, as well as cholesterol biosynthesis or regulation-related genes, such as sterol regulatory element-binding protein 1, 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase and low-density lipoprotein receptor, were all significantly (P < 0.05) upregulated in betaine group. Meanwhile, steroidogenic factor-1 and glucocorticoid receptor were significantly (P < 0.05) enhanced, whereas expression of dosage-sensitive sex reversal-adrenal hypoplasia congenita critical region on the X chromosome gene, a nuclear receptor known as a repressor of adrenal steroidogenesis, was significantly (P < 0.05) downregulated. Betaine significantly (P < 0.05) increased adrenal expression of genes involved in one-carbon metabolism and DNA methylation, such as S-adenosyl homocysteine hydrolase, betaine-homocysteine-methyltransferase, methionine adenosyl transferase and DNA methyltransferases, yet the promoter regions of most steroidogenic genes were significantly (P < 0.05) hypomethylated. These results indicate that in ovo injection of betaine promotes adrenal glucocorticoid synthesis in chicken fetuses before hatching, which involves alterations in DNA methylation.

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.