Zanton G I, Toledo M Z
USDA-Agricultural Research Service, US Dairy Forage Research Center, Madison, WI 53706.
Department of Animal and Dairy Sciences, University of Wisconsin-Madison, Madison, WI 53706.
JDS Commun. 2024 Mar 2;5(4):293-298. doi: 10.3168/jdsc.2023-0512. eCollection 2024 Jul.
Balancing dairy cow diets for AA is an effective strategy to reduce dietary CP concentration, maintain levels of productivity, and increase nitrogen use efficiency. Most studies evaluating supplemental rumen-protected Met (sRPMet) focus on cows in established lactation; however, there is an increasing body of evidence suggesting that initiating sRPMet feeding to transition dairy cows is beneficial to production, reproduction, and health. Therefore, the objective of this study was to evaluate the effects of feeding sRPMet before and after calving through meta-analysis on pre- and postpartum performance and selected metabolic parameter responses. A literature search was conducted for published papers reporting on the effects of feeding sRPMet starting before parturition and continuing through early lactation, resulting in 21 publications with 40 treatment comparisons. Studies provided sRPMet both before (average of 8.20 [±2.94 SD] g of metabolizable sRPMet/d, which began at 19.3 [±4.23 SD] d before calving) and after calving (10.53 [±3.30 SD] g of metabolizable sRPMet/d for an average of 85.9 [±38.36 SD] DIM). Prepartum DMI and pre- and postpartum BW and BCS were unaffected by sRPMet. In contrast, postpartum DMI, milk yield, milk fat and true protein yield, and milk fat and true protein concentration were increased by sRPMet. Most production responses to sRPMet declined as lactation progressed where the predicted response in milk fat and true protein yield was 118 and 92 g/d at 21 DIM, respectively. Postpartum circulating metabolites were unaffected by sRPMet; however, the sample sizes for these analyses were much lower than for production responses. This meta-analysis indicates that feeding sRPMet before and after calving results in increased productivity beyond that which would be expected by providing sRPMet in established lactation alone.
平衡奶牛日粮的氨基酸组成是降低日粮粗蛋白浓度、维持生产水平并提高氮利用效率的有效策略。大多数评估补充瘤胃保护性蛋氨酸（sRPMet）的研究都集中在处于泌乳盛期的奶牛；然而，越来越多的证据表明，对围产奶牛开始饲喂sRPMet对生产、繁殖和健康有益。因此，本研究的目的是通过荟萃分析评估产犊前后饲喂sRPMet对产前和产后性能以及选定代谢参数反应的影响。对已发表的关于产前开始饲喂sRPMet并持续至泌乳早期的效果的论文进行了文献检索，得到21篇出版物，包含40个处理比较。研究在产犊前（平均8.20 [±2.94标准差] g可代谢sRPMet/d，于产犊前19.3 [±4.23标准差] d开始）和产犊后（10.53 [±3.30标准差] g可代谢sRPMet/d，平均85.9 [±38.36标准差] 泌乳天数）都提供了sRPMet。产前干物质采食量以及产前和产后体重和体况评分不受sRPMet影响。相比之下，产后干物质采食量、产奶量、乳脂和真蛋白产量以及乳脂和真蛋白浓度因sRPMet而增加。随着泌乳进展，大多数对sRPMet的生产反应下降，其中在泌乳21天时，乳脂和真蛋白产量的预测反应分别为118和92 g/d。产后循环代谢物不受sRPMet影响；然而，这些分析的样本量远低于生产反应的样本量。这项荟萃分析表明，产犊前后饲喂sRPMet可提高生产力，其提高幅度超过仅在泌乳盛期提供sRPMet时的预期。
