Endocrine Regulation of Bull Reproductive Development

The maturation of the bull reproductive system is orchestrated by a finely tuned endocrine network centred on the hypothalamic–pituitary–gonadal axis. Pulsatile release of gonadotrophin-releasing hormone (GnRH) from the hypothalamus stimulates luteinising hormone (LH) and follicle-stimulating hormone (FSH) secretion from the anterior pituitary. LH drives Leydig cell differentiation and testosterone synthesis, while FSH promotes Sertoli cell function and supports the progression of spermatogenesis. Insulin-like peptide 3 (INSL3), a constitutive Leydig cell hormone, provides an index of Leydig cell functional capacity and complements androgen signalling. Insulin-like growth factor 1 (IGF-1) and metabolic cues further modulate testicular cell proliferation and steroidogenic enzyme expression, linking nutritional status to reproductive timing. Increasingly, epigenetic mechanisms—such as DNA methylation, small RNAs and RNA modifications—have emerged as mediators of both developmental programming and paternal environmental effects, with implications for bull fertility, genetic selection and herd productivity worldwide.

Research from Nature Portfolio

Recent studies have elucidated how early-life nutrition reprogrammes testicular development through multi-omics approaches. In one investigation, contrasting feeding regimes in pre-pubertal bull calves revealed differential expression of miRNAs and mRNAs in testicular tissue, with cadherin 13 (CDH13) identified as a hub in networks enriched for insulin, IGF-1, androgen signalling and cholesterol biosynthesis. This work highlighted the capacity of enhanced nutrition to accelerate testis growth and Sertoli cell junction maturation. A complementary study demonstrated that a high-protein, high-energy diet from two weeks of age upregulated genes governing cholesterol and fatty acid biosynthesis, activated sterol regulatory element binding protein pathways and promoted Sertoli cell maturation markers. Together, these findings underscore the critical window during which diet modulates steroidogenesis and cell differentiation to advance puberty and sperm-production potential.

Endocrine Regulation of Bull Reproductive Development publication trend

The graph below shows the total number of articles in endocrine regulation of bull reproductive development across all publications each year (not limited to Nature Index journals).

Technical terms

Hypothalamic–pituitary–gonadal (HPG) axis: Endocrine system whose sequential hormonal signals regulate testicular function and sexual maturation.

Leydig cell functional capacity: The ability of Leydig cells to synthesise steroid hormones, indexed by constitutive INSL3 output.

Sertoli cell: Somatic cell in the seminiferous tubule that nurtures germ cells and mediates the effects of FSH and testosterone on spermatogenesis.

INSL3: Insulin-like peptide 3, a Leydig cell–derived hormone reflecting cell differentiation and complementing testosterone in reproductive regulation.

m^5C-mediated splicing: RNA modification where 5-methylcytosine influences the selection of splice sites, affecting transcript diversity.

SREBP pathway: Sterol regulatory element binding protein cascade that controls transcription of genes involved in cholesterol and fatty acid biosynthesis.

References

1. MAEL gene contributes to bovine testicular development through the m5C-mediated splicing. iScience (2023).
2. Early life nutrition affects the molecular ontogeny of testicular development in the young bull calf. Scientific Reports (2023).
3. International Symposium on Ruminant Physiology: Paternal Nutrient Supply: Impacts on Physiological and Whole Animal Outcomes in Offspring. Journal of Dairy Science (2024).
4. Insulin-Like Factor 3 and the HPG Axis in the Male. Frontiers in Endocrinology (2014).
5. Enhanced early-life nutrition upregulates cholesterol biosynthetic gene expression and Sertoli cell maturation in testes of pre-pubertal Holstein bulls. Scientific Reports (2019).
6. Accelerating Onset of Puberty Through Modification of Early Life Nutrition Induces Modest but Persistent Changes in Bull Sperm DNA Methylation Profiles Post-puberty. Frontiers in Genetics (2020).