Crossbred, spring-calving cows (yr 1, n = 136; yr 2, n = 113; yr 3, n = 113) were used in a 3-yr experiment to evaluate the influence of supplemental protein prepartum and grazing subirrigated meadow postpartum on pregnancy rates and calf feedlot performance. A 2 × 2 factorial arrangement of treatments was used in a switchback design. From December 1 to February 28, cows grazed dormant upland range in 8 pastures (32 ± 2 ha each). The equivalent of 0.45 kg of supplement/cow per d (42% CP) was provided to half of the cows on a pasture basis 3 d/wk. For 30 d before the beginning of breeding (May 1 to May 31), half of the cows grazed a common subirrigated meadow (58 ha), and the remainder was fed grass hay in a drylot. Cow BW and BCS were monitored throughout the year, and steer calf performance was determined until slaughter. Feeding supplement prepartum improved (P = 0.01 to P < 0.001) BCS precalving (5.1 vs. 4.7) and prebreeding (5.1 vs. 4.9) and increased (P = 0.02) the percentage of live calves at weaning (98.5 vs. 93.6%) but did not affect (P = 0.46) pregnancy rate (93 vs. 90%).

A 2-yr study utilizing 120 mature, crossbred (Angus × Herford) cows/year, evaluated the influence of cow BCS and dried distillers grains with solubles (DDGS) supplementation during late gestation on cow performance and productivity of subsequent offspring. Treatments were arranged as a 2 × 2 factorial in a randomized complete block design with 2 BCS and with or without DDGS supplementation. Cows were nutritionally managed to enter the last trimester of gestation with a BCS of approximately 4 (LBCS) or 6 (HBCS) and were thereafter managed in a single herd (initial BCS were 4.4 and 5.7 for LBCS and HBCS treatments, respectively). During the last trimester, 12.7 kg/cow of low quality meadow hay (6.4% CP; DM basis) was provided each day. Supplemented cows were gathered and sorted into pens (12 pens; 5 cows/pen; 6 pens/BCS) every Monday, Wednesday, and Friday, and received the equivalent of 0.9 kg/cow daily of DDGS (31% CP; DM basis; supplement was consumed within 30 min on each supplementation day). Calf birth weight was greater for HBCS compared to LBCS (P = 0.001) and for supplemented compared to nonsupplemented cows (P = 0.04). Cow weight at weaning was greater for HBCS compared with LBCS (P < 0.001); however, no differences were noted because of supplementation (P = 0.16). Weaning weight was greater for the offspring of supplemented compared to nonsupplemented cows (P = 0.02). There were no differences in postweaning calf performance (growing lot and feedlot) or carcass characteristics (P > 0.05) due to treatments. Nevertheless, HBCS cows had approximately 10% more live calves at birth and at weaning (P ≤ 0.01) compared to LBCS cows. Consequently, the total weaned calf weight per cow was 26 kg greater for HBCS compared with LBCS (P = 0.004). Pregnancy rate was greater (P = 0.05) for HBCS than LBCS cows (92% vs. 79%, respectively) but not affected by supplementation (P = 0.94). This research demonstrates the potential consequences of not maintaining cows in adequate BCS at calving. Also, though it appears that supplementation of beef cows with DDGS during late gestation has a positive effect on weaning weight, there was no apparent developmental programming effect on feedlot performance and carcass characteristics of calves.

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Two experiments evaluated effects of weaning date on cow body condition score (BCS) and calf growth. In Experiment 1, 134 March-calving cows were used in a four-year experiment. Calves were weaned 18 August or 7 November and cows were fed 0 or 0.45 kg protein supplement (42% crude protein) three days per week from 1 December to 28 February while grazing upland range in a 2 by 2 factorial arrangement of treatments. In Experiment 2, spring calving cows (year 1, n 5 97; year 2, n 5 104) were assigned randomly to one of eight weaning dates at 2-week intervals from 19 August to 25 November. In Experiment 1, weaning in August increased cow BCS precalving (P , 0.001) and prebreeding (P , 0.001), but not pregnancy rates (P 5 0.56). Cows fed supplemental protein had greater BCS precalving (P , 0.001) and prebreeding (P 5 0.001) than nonsupplemented cows, but pregnancy rates were similar (P 5 0.27). Calves born to cows fed supplemental protein prepartum had greater weaning weight than calves born to nonsupplemented cows regardless of whether weaning occurred in August (P 5 0.001) or November (P , 0.001). Effects of weaning date on feedlot performance interacted with supplementation treatment. Calves born to cows fed supplement that were weaned in November generated the greatest net returns. In Experiment 2, BCS decreased linearly (P , 0.001) as date of weaning was delayed from August to November. Nursing calf gain increased cubically (P , 0.0004) and weaned calf gain from August to November increased quadratically (P , 0.002). Protein supplementation did not affect cow pregnancy rate, but calves born to cows fed protein supplement had greater pre-and postweaning gains. Cow BCS decreased as weaning date was moved later in the year but cow pregnancy rate was not affected by weaning date. Resumen Dos experimentos evaluaron los efectos de la época de destete sobre la condición corporal de la vaca (BCS) y el crecimiento del becerro. En el experimento 1, 134 vacas que parieron en marzo se usaron en un experimento de cuatro añ os. Los becerros se destetaron el 18 de agosto o el 7 de noviembre y las vacas fueron alimentadas con 0 o 0.45 kg de suplemento proteico (42% PC) tres días a la semana del 1 de diciembre al 28 de febrero mientras apacentaban en un pastizal de tierras altas. Los tratamientos tuvieron un arreglo factorial 2 3 2. En el experimento 2, vacas que parieron en primavera (añ o 1, n 5 97; añ o, 2 n 5 104) fueron asignadas aleatoriamente a una de ocho fechas de destete, con dos semanas de separación entre ellas, del 19 de agosto al 25 de noviembre. En el experimento 1, el destete en agosto incrementó la BCS de las vacas antes del parto (P , 0.001) y antes del empadre (P , 0.001), pero no aumentó las tasas de preñ ez (P 5 0.56). Las vacas suplementadas con proteína tuvieron una mayor BCS antes del parto (P , 0.001) y del empadre (P , 0.001) que las no suplementadas, pero las tasas de preñ ez de ambos grupos fueron similares (P 5 0.27). Los becerros nacidos de las vacas suplementadas con proteína antes del parto tuviero...

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