Department of Agriculture, Nutrition, and Food Systems, University of New Hampshire, Durham 03824.
Instituto de Ciências Agrárias e Ambientais, Universidade Federal de Mato Grosso - Campus Sinop, MT, Brazil 78557-267.
J Dairy Sci. 2020 Apr;103(4):3161-3176. doi: 10.3168/jds.2019-17186. Epub 2020 Feb 20.
We showed previously that dairy cows fed [diet dry matter (DM) basis] 25% finely ground field pea (GFP) plus rumen-protected (RP)-Met and RP-Lys had greater milk true protein yield and plasma Met concentration, but lower plasma His, compared with those fed GFP without rumen-protected AA supplementation. The goal of the present study was to investigate the effects of diets containing soybean meal (SBM) or canola meal (CM) with or without a source of RP-Met on production, nutrient digestibility, and N metabolism in cows fed 25% GFP. Sixteen mid-lactation Holstein cows were used in a replicated 4 × 4 Latin square with a 2 × 2 factorial arrangement of treatments (21-d periods). Cows were fed (DM basis) 35% corn silage, 14% grass-legume haylage, 25% GFP, and 11% SBM or 13.5% CM with or without 0.095% RP-Met supplementation as Smartamine M (Adisseo USA Inc., Alpharetta, GA). Protein source effects were observed for most production variables; cows fed diets containing CM plus GFP had greater DM intake, yields of milk and milk fat and true protein, and milk N efficiency than those offered SBM plus GFP. Feeding CM plus GFP also reduced the concentrations of milk urea N and plasma urea N, and the urinary excretion of NH N and urea N, suggesting improved N use efficiency. Moreover, replacing SBM with CM increased the concentrations of all essential AA (except Arg) in plasma collected from the coccygeal blood vessels. A protein source × RP-Met interaction was observed for the concentration of His in coccygeal plasma, with circulating His decreasing only when RP-Met was supplemented to the diet containing SBM plus GFP. Based on the arteriovenous difference method, Lys was the first limiting AA overall, with Met being the first limiting AA in diets that did not receive RP-Met. Apparent total-tract digestibilities of DM, organic matter, N, and acid detergent fiber increased with feeding SBM plus GFP versus CM plus GFP. Most variables were not affected by RP-Met supplementation, except plasma Met concentration, which increased by 63%. Collectively, our results indicate that CM appears to be a better companion rumen-degradable protein source to GFP than SBM, due to improved yields of milk and milk protein and N use efficiency.
我们之前表明，与饲喂未添加瘤胃保护性氨基酸（AA）的精细研磨豌豆（GFP）的奶牛相比，饲喂 25%精细研磨豌豆（GFP）加瘤胃保护性蛋氨酸（RP-Met）和赖氨酸（RP-Lys）的奶牛的产奶量、真蛋白产量和血浆 Met 浓度更高，但血浆 His 浓度更低。本研究的目的是研究含有豆粕（SBM）或菜粕（CM）且添加或不添加 RP-Met 源的日粮对饲喂 25% GFP 的奶牛生产性能、养分消化率和氮代谢的影响。采用 21 天重复 4×4 拉丁方设计，以 2×2 因子设计安排处理（21 天期），对 16 头泌乳中期荷斯坦奶牛进行了试验。奶牛日粮（干物质基础）由 35%玉米青贮、14%牧草-豆科干草青贮、25% GFP 和 11% SBM 或 13.5% CM 组成，并添加或不添加 0.095%的 RP-Met 作为 Smartamine M（Adisseo USA Inc.，Alpharetta，GA）。大多数生产性能变量都表现出蛋白质源的影响；与饲喂含 SBM 的 GFP 日粮的奶牛相比，饲喂含 CM 的 GFP 日粮的奶牛的干物质采食量、牛奶和牛奶脂肪及真蛋白产量以及牛奶氮效率更高。饲喂 CM 加 GFP 还降低了牛奶尿素氮和血浆尿素氮的浓度，以及尿液中 NH 3-N 和尿素氮的排泄量，表明氮利用效率提高。此外，用 CM 替代 SBM 增加了从尾血管采集的血浆中所有必需氨基酸（Arg 除外）的浓度。在尾血浆 His 浓度方面观察到蛋白质源×RP-Met 互作，只有当向含有 SBM 和 GFP 的日粮添加 RP-Met 时，循环 His 才会降低。根据动静脉差法，Lys 是整体上的第一限制 AA，而在未添加 RP-Met 的日粮中，Met 是第一限制 AA。与饲喂 SBM 加 GFP 相比，DM、有机物、N 和酸性洗涤剂纤维的全肠道消化率均增加。除血浆 Met 浓度增加 63%外，大多数变量不受 RP-Met 补充的影响。总的来说，我们的结果表明，由于产奶量、牛奶蛋白和氮利用效率提高，CM 似乎是比 SBM 更好的 GFP 瘤胃可降解蛋白源。
