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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]

Traditional heifer feeding strategies typically involve modest rates of body weight (BW) gain and include a relatively low proportion of concentrate feeds. In situations of limited forage or high feed costs, additional concentrates may be included in the diets and fed at a limited rate. High-concentrate diets can enhance the efficiency of nutrient utilization, alter characteristics of the gastrointestinal tract (GIT), and influence the composition of gain. The objective of this study was to evaluate the strategy of limit-feeding highconcentrate diets on feeding behavior, carcass characteristics, and GIT morphometrics in replacement beef heifers. Crossbred beef heifers (n = 20) began receiving either a high forage (75% forage:25% concentrate; HF, n =10) or high concentrate (25% forage:75% concentrate; HC, n =10) diet 74 ± 4 d before breeding. Heifers were inseminated with sexed male semen from a single bull. Individual intake and feeding behavior data were recorded using the Insentec Roughage Intake Control system, and heifers were weighed, and diet deliveries were adjusted every 2 wk to target a BW gain of 0.45 kg/d for both groups. Heifers were harvested at 180 d of gestation, where the viscera were removed, and weights of the full gastrointestinal tract, including the stomach complex, and small and large intestines were recorded. After removing digesta, weights of the empty gastrointestinal tract, rumen-reticulum, omasum, abomasum, small and large intestine, and mesenteric fat were recorded. Carcass characteristics were assessed 24 h after slaughter. Data were analyzed using the MIXED procedure of SAS, with heifer as the experimental unit. No differences were observed in final BW, average daily gain, or body condition score (P ≥ 0.18) between treatments (Table 1). Reflecting that HC heifers were limit-fed to a greater extent than HF heifers, therefore, dry matter intake, number of meals, visits to the feed bunk, time spent eating, and time per meal were less in HC heifers than in the HF group (P ≤ 0.001). In contrast, HC heifers had greater (P ≤ 0.001) eating rates of DM per minute, per visit and per meal compared with HF heifers. Though no differences were observed in back (P = 0.31) or rib fat (P = 0.37), HC heifers had greater (P = 0.04) marbling score and tended to have greater carcass weight (P = 0.06) and ribeye area (P = 0.07) as compared with HF heifers (Table 2). Greater (P < 0.001) full weights of GIT and stomach complex, empty weight of rumen-reticulum, weight of total digesta, and digesta as a proportion of BW (i.e., fill) were observed in HF heifers. In contrast, HC heifers had greater (P < 0.001) weights of full small intestine and mesenteric fat than HF heifers. These findings demonstrate that, despite similar rates of gain, limit-feeding high-concentrate diets can alter the composition of weight gain, favoring fat, muscle, and GIT development, potentially altering dam efficiency throughout her productive life. [ABSTRACT FROM AUTHOR]