Department of Animal and Range Sciences, New Mexico State University, Las Cruces, NM 88003, USA.
J Anim Sci. 2012 Aug;90(8):2811-7. doi: 10.2527/jas.2011-4189. Epub 2012 Jun 4.
Body condition score is used as a management tool to predict competency of reproduction in beef cows. Therefore, a retrospective study was performed to evaluate association of BCS at calving with subsequent pregnancy rate, days to first postpartum ovulation, nutrient status (assessed by blood metabolites), and calf BW change in 2- and 3-yr-old cows (n = 351) managed and selected to fit their environment of grazing native range over 6 yr at the Corona Range and Livestock Research Center, Corona, NM. Cows were managed similarly before calving, without manipulation of management, to achieve predetermined BCS at parturition. Palpable BCS (scale of 1 to 9) were determined by 2 experienced technicians before calving. Cows were classified to 1 of 3 BCS groups prior calving: BCS 4 (mean BCS = 4.3 ± 0.02), 5 (mean BCS = 5.0 ± 0.03), or 6 (mean BCS = 5.8 ± 0.06). Cows were weighed weekly after calving and serum was collected once weekly (1 yr) or twice weekly (5 yr) for progesterone analysis to estimate first postpartum ovulation beginning 35 d postpartum. Year effects also were evaluated, with years identified as either above or below average precipitation. Days to first postpartum ovulation did not differ among calving BCS groups (P = 0.93). Pregnancy rates were not influenced by calving BCS (P = 0.83; 92%, 91%, 90% for BCS 4, 5, and 6, respectively). Days to BW nadir was not influenced by BCS at calving (P = 0.95). Cow BW was different at all measuring points (P < 0.01) with BCS 6 cows having the heaviest BW and cows with BCS 4 the lightest. Cows with calving BCS 4 and 5 lost more (P = 0.06) BW from the initiation of the study to the end of breeding than cows with BCS 6. However, cow BW change at all other measurement periods was not different (P ≥ 0.49) among calving BCS groups. Serum glucose and NEFA concentrations were not influenced by calving BCS (P ≥ 0.51). Calf BW at birth (P = 0.60), branding (55-d BW; P = 0.76), and weaning (205-d BW; P = 0.60) were not impacted by cow calving BCS. Body condition score did not influence overall pregnancy rates, indicating that young cows can have a reduced BCS and still be reproductively punctual. Therefore, these results indicate that reproductive performance of young cows with reduced BCS may not be affected when managed in extensive range conditions.
体况评分被用作预测肉牛繁殖能力的管理工具。因此，进行了一项回顾性研究，以评估产犊时的 BCS 与随后的妊娠率、产后首次排卵的天数、营养状况（通过血液代谢物评估）以及 2-3 岁牛的小牛 BW 变化之间的关系（n = 351），这些牛在新墨西哥州科罗纳牧场和畜牧研究中心的天然牧场环境中经过 6 年的管理和选择，以适应其环境。在产犊前，牛被类似地管理，而不操纵管理，以达到分娩时预定的 BCS。在产犊前，由 2 名经验丰富的技术员通过触诊确定可触知的 BCS（1 至 9 级）。在产犊前，牛被分为 3 个 BCS 组之一：BCS 4（平均 BCS = 4.3 ± 0.02）、BCS 5（平均 BCS = 5.0 ± 0.03）或 BCS 6（平均 BCS = 5.8 ± 0.06）。牛在产犊后每周称重一次，在产犊后 35 天开始，每周收集一次（1 年）或两次（5 年）血清进行孕激素分析，以估计产后首次排卵。还评估了年份影响，将年份确定为高于或低于平均降水量。产犊时的 BCS 组之间首次产后排卵的天数没有差异（P = 0.93）。妊娠率不受产犊 BCS 的影响（P = 0.83；BCS 4、5 和 6 的妊娠率分别为 92%、91%和 90%）。产犊时的 BCS 对 BW 最低点没有影响（P = 0.95）。牛的 BW 在所有测量点都不同（P < 0.01），BCS 6 牛的 BW 最重，BCS 4 牛的 BW 最轻。与 BCS 6 牛相比，产犊时 BCS 为 4 和 5 的牛从研究开始到繁殖结束时 BW 损失更多（P = 0.06）。然而，在所有其他测量期，产犊时 BCS 组之间的 BW 变化没有差异（P ≥ 0.49）。产犊时 BCS 对血清葡萄糖和 NEFA 浓度没有影响（P ≥ 0.51）。牛犊出生时的 BW（P = 0.60）、烙印（55 日 BW；P = 0.76）和断奶时的 BW（205 日 BW；P = 0.60）不受母牛产犊 BCS 的影响。体况评分不影响总妊娠率，表明年轻牛可以降低 BCS 并仍然具有生殖准时性。因此，这些结果表明，在广泛的条件下管理时，降低 BCS 的年轻牛的繁殖性能可能不会受到影响。
