Role of early life nutrition on the hypothalamic-pituitary-testicular axis of the bull

Abstract

The objective of this study was to examine the effect of nutrition during the first 18 weeks of life on the physiological and transcriptional functionality of the hypothalamic (arcuate nucleus region), anterior pituitary and testes in Holstein–Friesian bull calves. Holstein–Friesian bull calves with a mean (±s.d.) age and bodyweight of 19 (±8.2) days and 47.5 (±5.3) kg, respectively, were assigned to either a HIGH (n = 10) or LOW (n = 10) plane of nutrition, to achieve an overall target growth rate of 1.2 or 0.5 kg/day, respectively. At 126 ± 1.1 days of age, all calves were euthanised. Animal performance (weekly) and systemic concentrations of metabolic (monthly) and reproductive hormones (fortnightly) were assessed. Testicular histology, targeted gene and protein expression of the arcuate nucleus region, anterior pituitary and testes were also assessed using qPCR and immunohistochemistry, respectively. The expression of candidate genes in testicular tissue from post pubertal 19-month-old Holstein–Friesian bulls (n = 10) was compared to that of the 18-week-old calves. Metabolite and metabolic hormone profiles generally reflected the improved metabolic status of the calves on the HIGH (P < 0.001). Calves offered a HIGH plane of nutrition were heavier at slaughter (P < 0.001), had larger testes (P < 0.001), larger seminiferous tubule diameter (P < 0.001), more mature spermatogenic cells (P < 0.001) and more Sertoli cells (P < 0.05) in accordance with both morphological and transcriptional data. Overall, testicular gene expression profiles suggested a more mature stage of development in HIGH compared with LOW and were more closely aligned to that of mature bulls. Ghrelin receptor was the only differentially expressed gene between LOW and HIGH calves in either the anterior pituitary (P < 0.05) or arcuate nucleus region of the hypothalamus (P < 0.10) and was upregulated in LOW for both tissues. This study indicates that an enhanced plane of nutrition during early calfhood favourably alters the biochemical regulation of the hypothalamus–anterior pituitary–testicular axis, advancing testicular development and hastening spermatogenesis.

Effect of Early Calf-Hood Nutrition on the Transcriptional Regulation of the Hypothalamic-Pituitary-Testicular axis in Holstein-Friesian Bull Calves

“…Weight gain and other indicators of animal performance were outlined previously 21 . In brief, calves on a high plane of nutrition had larger testes, greater seminiferous tubule diameter, more mature spermatogenic cells and more Sertoli cells (Supplementary Table 4 ).…”

Effect of plane of nutrition during the first 12 weeks of life on growth, metabolic and reproductive hormone concentrations, and testicular relative mRNA abundance in preweaned Holstein Friesian bull calves

“…In total, 30 Holstein Friesian bull calves were used for this study. All calves were sourced from four commercial dairy herds in Ireland, and following an acclimatization period (5 to 7 d) ( English et al, 2018b ), all calves were blocked on age, sire, initial body weight, and farm of origin and were randomly assigned to one of two dietary groups: a high (HI, n = 15) or a moderate (MOD, n = 15) plane of nutrition. The 30 calves used in this study were derived from 17 separate sires with a maximum of 3 calves bred by any one sire.…”

“…Primers with PCR efficiencies between 90% and 110% were deemed acceptable. The expression of four reference genes, previously used for bovine testes relative mRNA abundance ( English et al, 2018b ), was also evaluated across all testes cDNA samples for determination of the most stably expressed reference gene. These included ribosomal protein S9 ( RPS9 ), glyceraldehyde-3-phosphate dehydrogenase ( GAPDH ), tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein, zeta ( YWHAZ ), and ubiquitin ( UBQ ).…”

Calves’ management conditions affect sperm count in adult bulls

“…Enhanced nutrition plan during the first weeks of life results in increased testes' size and seminiferous tubule diameter, together with an increased number of Sertoli cells and mature sperms cells in adult bulls. In the same study, smaller testes were detected in bulls subjected to a restrictive diet with growth limited to 0.5 kg per day [21]. In our study, we have not estimated the differences in nutrition between nursed and maternally separated bulls.…”