Dairy and Food Science Department, South Dakota State University, Brookings 57007.
Dairy and Food Science Department, South Dakota State University, Brookings 57007; US Dairy Forage Research Center, USDA-Agricultural Research Service, Madison, WI 53706.
J Dairy Sci. 2019 Sep;102(9):7970-7979. doi: 10.3168/jds.2018-15760. Epub 2019 Jul 10.
This study was designed to evaluate the effects of substituting corn grain with nonforage fiber sources in diets containing soybean meal (SBM) or canola meal (CM) as the primary protein source. Sixteen Holstein cows were assigned to a replicated 4 × 4 Latin square design with 4 periods of 28 d each. Treatments were arranged as a 2 × 2 factorial with 2 protein sources (SBM and CM) and 2 dietary starch concentrations (21 and 27% dry matter, DM). Diets were formulated to contain 16.5% CP, and the 21% starch diets were obtained by replacing corn grain with soybean hulls and beet pulp. Protein source × starch interactions were observed for DM intake (DMI), milk fat and protein concentrations, milk protein yield, milk urea nitrogen, and feed efficiency. Cows fed CM diets had a higher DMI when dietary starch concentration was 27% compared with 21%, but those cows had DMI similar to that of cows on SBM diets regardless of the starch concentration. Milk fat percentage was decreased in cows fed CM with 27% starch compared with cows fed CM with 21% starch and cows fed SBM with 27% starch. Milk protein percentage and yield and milk lactose percentage were least in cows fed CM with 21% starch compared with the other 3 diets, but feed efficiency was greater for cows fed CM with 21% starch. Milk urea nitrogen was least in cows fed CM with 27% starch compared with the other 3 diets. Cows fed diets with 27% starch produced 2.5 kg/d more milk and 1.9 kg/d more energy-corrected milk compared with cows fed 21% starch. Digestibility of DM and organic matter was higher in cows fed SBM diets than in cows on CM diets, and cows fed 27% starch showed greater DM and organic matter digestibility than cows on 21% starch. Digestibility of neutral detergent fiber and acid detergent fiber was greater in diets with SBM than in those with CM. Molar proportion of acetate was the lowest for cows fed CM with 21% starch compared with cows fed SBM with 21% starch, with the remaining cows fed being intermediate and similar. However, propionate was highest for cows fed CM with 21% starch than for cows fed SBM with 21% starch, but the remaining treatments were intermediate and similar. Isobutyrate was greater for cows fed CM with 21% starch, which resulted in the lowest acetate:propionate ratio compared with cows fed the remaining treatments. Overall, we confirmed that the interaction of protein with starch in CM diets can sustain similar cow performance as with the SBM diets. Those making decisions about starch concentration and protein source should consider feed price when SBM or CM and different starch levels are being formulated in diets for lactating dairy cows.
本研究旨在评估用非饲料纤维来源替代日粮中玉米谷物，同时以豆粕（SBM）或菜粕（CM）作为主要蛋白质来源对奶牛的影响。将 16 头荷斯坦奶牛分为 4 个重复 4 拉丁方设计，每个周期 28 天，共 4 个周期。处理方法采用 2×2 因子设计，包括 2 种蛋白质来源（SBM 和 CM）和 2 种日粮淀粉浓度（21%和 27%干物质，DM）。日粮的 CP 含量为 16.5%，21%淀粉日粮是通过用大豆皮和甜菜浆替代玉米谷物来获得的。观察到蛋白质来源×淀粉互作对干物质采食量（DMI）、乳脂和蛋白质浓度、乳蛋白产量、乳尿素氮和饲料效率的影响。与 21%淀粉日粮相比，当饲料淀粉浓度为 27%时，饲喂 CM 日粮的奶牛 DMI 较高，但无论淀粉浓度如何，这些奶牛的 DMI 与饲喂 SBM 日粮的奶牛相似。与饲喂 CM 21%淀粉日粮和饲喂 SBM 27%淀粉日粮的奶牛相比，饲喂 CM 27%淀粉日粮的奶牛乳脂率降低。与其他 3 种日粮相比，饲喂 CM 21%淀粉日粮的奶牛乳蛋白率和产量以及乳乳糖率最低，但饲喂 CM 21%淀粉日粮的奶牛饲料效率更高。与其他 3 种日粮相比，饲喂 CM 27%淀粉日粮的奶牛乳尿素氮最低。与饲喂 21%淀粉日粮的奶牛相比，饲喂 27%淀粉日粮的奶牛产奶量每天增加 2.5 公斤，校正乳能量每天增加 1.9 公斤。与饲喂 CM 日粮的奶牛相比，饲喂 SBM 日粮的奶牛 DM 和有机物消化率更高，饲喂 27%淀粉日粮的奶牛 DM 和有机物消化率高于饲喂 21%淀粉日粮的奶牛。与 CM 日粮相比，SBM 日粮的中性洗涤纤维和酸性洗涤纤维消化率更高。与饲喂 SBM 21%淀粉日粮的奶牛相比，饲喂 CM 21%淀粉日粮的奶牛乙酸摩尔比例最低，其余奶牛的乙酸摩尔比例居中且相似。然而，与饲喂 SBM 21%淀粉日粮的奶牛相比，饲喂 CM 21%淀粉日粮的奶牛丙酸摩尔比例最高，其余处理居中且相似。与饲喂其他日粮的奶牛相比，饲喂 CM 21%淀粉日粮的奶牛异丁酸摩尔比例较高，导致乙酸：丙酸比例最低。总的来说，我们证实了 CM 日粮中蛋白质与淀粉的相互作用可以维持与 SBM 日粮相似的奶牛生产性能。在为泌乳奶牛配制日粮时，在考虑淀粉浓度和蛋白质来源时，应考虑饲料价格，无论是 SBM 还是 CM 以及不同的淀粉水平。
