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0000-0003-1999-815X
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Publisher: American Dairy Science Association
Date: 04-2018
Abstract: The aim of this study was (1) to examine the effect of plane of nutrition during the first and second 6 mo of life on systemic concentrations of reproductive hormones and metabolites in Holstein-Friesian dairy bulls, and (2) to establish relationships with age at puberty and postpubertal semen production potential. Holstein-Friesian bull calves (n = 83) with a mean (standard deviation) age and body weight of 17 (4.4) d and 52 (6.2) kg, respectively, were assigned to a high or low plane of nutrition for the first 6 mo of life. At 24 wk of age, bulls were reassigned, within treatment, either to remain on the same diet or to switch to the opposite diet until puberty, resulting in 4 treatment groups: high-high, high-low, low-low, and low-high. Monthly blood s les were analyzed for metabolites (albumin, urea, total protein, β-hydroxybutyrate, glucose, nonesterified fatty acid, triglycerides and creatinine), insulin, insulin-like growth factor-1, leptin, adiponectin, FSH, and testosterone. A GnRH challenge was carried out at 16 and 32 wk of age (n = 9 bulls per treatment). Blood was collected at 15-min intervals for 165 min, with GnRH administered (0.05 mg/kg of body weight, i.v.) immediately after the third blood s le. Blood s les were subsequently analyzed for LH, FSH, and testosterone. Stepwise regression was used to detect growth and blood measurements to identify putative predictors of age at puberty and subsequent semen quality traits. Metabolic hormones and metabolites, in general, reflected metabolic status of bulls. Although FSH was unaffected by diet, it decreased with age both in monthly s les and following GnRH administration. Testosterone was greater in bulls on the high diet before and after 6 mo of age. Testosterone concentrations increased dramatically after 6 mo of age. Luteinizing hormone was unaffected by diet following GnRH administration but basal serum LH was greater in bulls on a high diet before 6 mo of age. In conclusion, the plane of nutrition offered before 6 mo of age influenced metabolic profiles, which are important for promoting GnRH pulsatility, in young bulls.
Publisher: Elsevier BV
Date: 07-2017
DOI: 10.1016/J.THERIOGENOLOGY.2017.04.002
Abstract: The onset of puberty in the bull is regulated by the timing of early GnRH pulsatility release from the hypothalamus, which has been demonstrated to be affected by plane of nutrition during calf-hood. The aim of this study was to determine the effect of plane of nutrition on growth rate, scrotal development, metabolite concentrations and exogenous gonadotrophin (GnRH) induced release of luteinizing hormone (LH), follicle stimulating hormone (FSH) and testosterone (TT) in pre-pubertal bulls of two contrasting dairy breeds. Holstein-Friesian and Jersey bull calves were assigned to either a high or low plane of nutrition from 3 to 49 weeks of age. Intensive blood s ling was conducted at 16, 24 and 32 weeks of age, every 15 min from 30 min prior to intravenous administration of exogenous GnRH to 135 min after. Monthly blood s les were also collected and analyzed for insulin like growth factor 1 (IGF-1), insulin, leptin, adiponectin and metabolite concentration. Insulin and IGF-1 were higher in bulls on a high plane of nutrition (P 0.05). Leptin was not affected by plane of nutrition or breed (P > 0.05). Adiponectin tended to be higher in bulls on a high plane of nutrition (P = 0.05), but was not affected by breed (P > 0.05). Bulls on a high plane of nutrition had a greater concentration of LH in response to GnRH (P 0.05). FSH concentration was not influenced by breed or plane of nutrition but FSH concentrations did decrease with age (P 0.05). Jersey bulls, particularly those on a high plane of nutrition, had higher TT production in the pre-pubertal period (P < 0.001). Using 28 cm as a proxy for age at puberty, bulls on a high plane of nutrition were predicted to reach puberty earlier than bulls on a low plane. In conclusion, the data clearly demonstrate that a high plane of nutrition positively affects several key nutritional and reproductive hormones which are critical to the endocrinological functionality of the hypothalamic-pituitary-testicular axis in dairy-bred bull calves.
Publisher: Bioscientifica
Date: 08-2018
DOI: 10.1530/REP-17-0671
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, 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 and reproductive hormones (at four week intervals) were assessed. Testicular histology, targeted gene and protein expression of the arcuate nucleus, anterior pituitary and testes were also assessed using qPCR and immunohistochemistry, respectively. Testicular tissue from post pubertal 19 month old Holstein Friesian bulls (n=10) that were reared under similar conditions was also available for comparative gene expression analysis. The metabolites and metabolic hormones generally reflected the improved metabolic status of the calves on HIGH bull calves (P .001). Only ghrelin receptor was upregulated in the anterior pituitary (P .05) and arcuate nucleus (P .10) in LOW compared to HIGH bull calves. Calves offered a high plane of nutrition were heavier at slaughter (P .001), had larger testes P .001), larger seminiferous tubule diameter P .001), more mature spermatogenic cells P .001) and more Sertoli cells (P .05) in accordance with both morphological and transcriptional data. This study indicates that a high plane of nutrition during early calf-hood alters gene expression which advances testicular development and hastens spermatogenesis
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