Influence of sire plane of nutrition and targeted body weight gain on ewe lamb growth, glucose metabolism, and ovarian reserve.

Rambouillet rams were managed on either a positive (POS ; gain 12% body weight [ BW ]; n  = 8), maintenance (MAINT ; maintain BW; n  = 8), or negative (NEG ; lose 12% BW; n  = 8) plane of nutrition before breeding. Rams were bred to ewes (n  = 10 per ram) that were managed similarly throughout gestation, and lambs were fed a common diet postnatally. Two ewe lambs (7.6 ± 0.02 mo of age, BW = 47.1 ± 1.17 kg) from each sire were selected and within-pair, randomly assigned to be managed for a moderate (MOD , 0.11 kg/d; n  = 23) or accelerated (ACC , 0.20 kg/d; n = 22) rate of gain for 56 d. Ewe lamb BW was recorded on a weekly basis and blood was collected on days 0, 28, and 56 for analysis of insulin-like growth factor 1 (IGF-1), triiodothyronine (T ₃ ), thyroxine (T ₄ ), glucose, blood urea nitrogen (BUN), and non-esterified fatty acids (NEFA). Intravenous glucose tolerance tests (IVGTT) were conducted from days −7 to −4 and days 57 to 64. A unilateral ovariectomy was performed and ovarian follicles were staged and counted macro and microscopically. Sire treatment × day and ewe treatment × day interactions were present for BW (P  ≤ 0.05), where POS had slower growth than MAINT and NEG, and tended (P  = 0.10) to have reduced average daily gain (ADG) when managed at an accelerated rate of gain. By design, ACC had greater BW and ADG than MOD (P  < 0.05). Concentrations of IGF-1 and T₄ were greater in ACC than MOD (P  ≤ 0.05), and NEG tended to have greater concentrations of IGF-1 than POS and MAINT (P  = 0.08). At the first IVGTT, the concentration of insulin was influenced by a sire treatment × time interaction (P  ≤ 0.05), suggesting impaired secretion in NEG-sires ewes, but no differences in area under the curve (AUC) for glucose, insulin, or their ratio (P  ≥ 0.11). No interactive effects of sire and ewe treatment (P  ≥ 0.52) were observed at the second IVGTT, but insulin and insulin:glucose ratio were influenced by sire treatment × time (P  ≤ 0.02), as NEG had greater insulin concentration at 60 min than MAINT (P  = 0.03) and greater AUC than POS and MAINT (P  ≤ 0.04). No differences in ovary size, weight, or total counts of macro and microscopic follicles were observed (P  ≥ 0.23). Ewes-fed ACC had a greater number of small surface follicles (P  = 0.02), whereas MOD tended to have a greater number of large surface follicles and tertiary follicles (P  < 0.06). These findings suggest that the paternal plane of nutrition influences female offspring physiology, particularly at varying growth rates. [ABSTRACT FROM AUTHOR]