Effect of calfhood nutrition on metabolic hormones, gonadotropins, and estradiol concentrations and on reproductive organ development in beef heifer calves

Abstract

This study examined the effect of plane of nutrition on the endocrinological regulation of the hypothalamic pituitary- ovarian (HPO) axis in beef heifer calves during a critical sexual developmental window early in calf hood. Forty Holstein-Friesian × Angus heifers (mean age 19 days, SEM = 0.63) were assigned to a high (HI; ADG 1.2 kg) or moderate (MOD; ADG 0.50 kg) nutritional level from 3 to 21 wk of life. Intake was recorded using an electronic calf feeding system, BW was recorded weekly, and blood samples were collected on wk of age 5, 10, 15 and 20 for metabolite, reproductive and metabolic hormone determination. At 19 wk of age, on sequential days an 8 h window bleed was carried out for luteinising hormone (LH), follicle stimulating hormone (FSH) and estradiol analysis. To characterize anterior pituitary gland function an intravenous GnRH challenge was conducted (19 wk of age). Blood was collected via jugular cathether every 15 min for 135 min for analysis of LH, FSH and estradiol. Calves were subsequently euthanized at 21 wk of age the anterior pituitary, metabolic organs and reproductive tract were weighed, and ovarian surface follicular numbers and oocytes recovered were recorded. Mean ADG was 1.18 kg and 0.50 kg for HI and MOD, respectively, resulting in a 76.6 kg difference in BW (P < 0.001). Blood insulin, glucose and IGF-1 concentrations were greater (P < 0.001) for HI compared with MOD. There was a diet × time interaction for leptin (P < 0.01); concentrations were greater in HI compared with MOD at 20 wk of age with no difference between treatments before this. Dietary treatment did not alter concentrations of adiponectin or anti-mullerian hormone (AMH). There was a diet × time interaction for FSH, whereby MOD had greater concentrations than HI at 10, 15 and 20, but not at 5 wk of age. Over the duration of an 8 h window bleed (19 wk of age) serum concentrations of LH, LH pulse frequency and amplitude were unaffected by treatment, whereas FSH (0.23 v 0.43 ng/ml) and estradiol (0.53 v 0.38 ng/ml) concentrations were less than and greater, respectively, for HI than MOD (P < 0.05). Likewise, following a GnRH challenge, area under the curve (AUC) analysis revealed greater (P < 0.01) estradiol and lesser (P < 0.01) FSH concentrations in calves on the HI relative to MOD diet, whereas concentrations of LH were unaffected (P = 0.26) between treatments. Ovarian surface follicle numbers were greater (P < 0.05) in HI compared with MOD. Total reproductive tract, uterus and ovarian tissue expressed relative to BW were greater (P < 0.05) for HI compared with MOD. In conclusion, enhanced nutrition in early calfhood advances the ontogeny development of the HPO axis.

Effect of plane of nutrition in early life on the transcriptome of visceral adipose tissue in Angus heifer calves

“…Both AGPAT2 and LEP were previously identified as up-regulated in bull calves fed a high-energy diet for the first 18 weeks of life 28 . Indeed, systemic concentrations of leptin were significantly higher in the HI calves compared to the MOD calves used for the current study at 20 weeks of age 26 . Together these results indicate that HI calves were further along the adipogenic trajectory compared to MOD calves following differential feeding up to 21 weeks of age.…”

“…Indeed, the energy reserve function of adipose tissue may be largely influenced by anabolic hormones of the endocrine system such as insulin and IGF-1, which have the capacity to contribute to adipogenesis, through inducing adipogenesis in pre-adipocytes 39 . Systemic concentrations of both IGF-1 and insulin of the heifers used in the current study were consistently higher in the HI calves throughout the trial 26 , thus there is potential that these two anabolic hormones may be contributing to the development of visceral adipose tissue and also to the differential expression of adipogenic genes. A number of genes that were differentially expressed in the current study are involved in the pre-adipocyte stage of differentiation, these included AKT1 , FGF1 , FGFR3 , PPIP5K1 .…”

“…The effect of plane of nutrition on feed intake and growth related traits as well as on a comprehensive blood analyte characterisation is outlined in detail by Kelly et al 26 and is only briefly described here. When euthanasia was performed at 21 weeks of age, calves in the HI group were on average 76.6 kg heavier than their MOD contemporaries ( p < 0.001) consistent with the planned design of the study.…”

“…Additionally, leptin can also have a direct effect on the anterior pituitary gland, directly stimulating the release of luteinizing hormone 55 . Thus, an increase in LEP gene expression as well as systemic concentrations of leptin 26 may represent an early signal for the initiation of puberty and development of reproductive function 55 . This potential early development of reproductive development in the calves on the high plane of nutrition is further evidenced by the differential expression of genes directly involved in reproductive development and function.…”

“…Tissue samples used in this study were derived from a larger study aimed at uncovering the impact of plane of nutrition during early calfhood on the physiological and molecular control of sexual development in the heifer calf 26 , the background experimental design is only briefly described here. Thirty Angus × Holstein–Friesian heifer calves with a mean (± SD) age and bodyweight of 19 (± 4) days and of 51.2 (± 7.8) kg, respectively, were blocked on age, bodyweight and sire and allocated within block to one of two dietary plane of nutrition groups: High (HI, n = 15) or Moderate (MOD, n = 15).…”