Department of Animal Science, Michigan State University, East Lansing 48824.
Department of Animal Science, Michigan State University, East Lansing 48824.
J Dairy Sci. 2020 Jun;103(6):5131-5142. doi: 10.3168/jds.2019-17242. Epub 2020 Apr 3.
We evaluated the effects of commercially available fatty acid (FA) supplements containing palmitic (C16:0) and stearic acid (C18:0) on nutrient digestibility and production responses of dairy cows. Thirty-six mid-lactation (146 ± 55 d in milk) multiparous Holstein cows were randomly assigned to twelve 3 × 3 balanced truncated Latin squares, with 3 treatments and 2 consecutive 35-d periods, with the final 5 d used for sample and data collection. Treatments were (1) a control diet containing no supplemental FA (CON), (2) a control diet supplemented with a commercially available C16:0 supplement (PA), and (3) a control diet supplemented with a commercially available C16:0 and C18:0 supplement (MIX). Supplements were fed at 1.5% dry matter and replaced soyhulls in CON. The statistical model included the random effect of cow nested within square and the fixed effects of treatment, period, square, and their interactions. Preplanned contrasts were (1) overall effect of FA treatments [CON vs. the average of the FA treatments (FAT); 1/2 (PA + MIX)], and (2) effect of FA supplement (PA vs. MIX). Treatment had no effects on dry matter intake, body weight, or body weight change. Compared with CON, FAT decreased digestibilities of total FA and 18-carbon FA but did not affect dry matter and neutral detergent fiber digestibility. Compared with MIX, PA increased dry matter and neutral detergent fiber digestibilities by 3.6 and 4.8 percentage units, respectively. The PA also increased total FA and 18-carbon FA digestibilities but did not alter 16-carbon FA digestibility compared with MIX. Using a Lucas test, we estimated apparent digestibility coefficients of 0.768 and 0.553 for the PA and MIX supplements, respectively. Compared with CON, FAT increased milk yield and tended to increase energy-corrected milk, but did not affect yield of milk fat or milk protein. The PA increased energy-corrected milk and milk fat yield but had no effect on milk protein yield compared with MIX. Our results indicate that dairy cows producing around 45 kg of milk respond better to a FA supplement enriched in C16:0 compared with a supplement containing both C16:0 and C18:0, which is likely due in part to PA increasing FA and neutral detergent fiber digestibility compared with MIX.
我们评估了含有棕榈酸（C16:0）和硬脂酸（C18:0）的市售脂肪酸（FA）补充剂对奶牛养分消化率和生产性能的影响。36 头泌乳中期（泌乳 146±55 天）经产荷斯坦奶牛随机分配到 12 个 3×3 平衡截断拉丁方中，每个处理有 3 个重复，每个重复期为 35 天，最后 5 天用于采样和数据收集。处理包括（1）不含补充 FA 的对照日粮（CON），（2）用市售 C16:0 补充剂补充的对照日粮（PA），和（3）用市售 C16:0 和 C18:0 补充剂补充的对照日粮（MIX）。补充剂以干物质的 1.5%添加，并替代 CON 中的大豆皮。统计模型包括随机效应（嵌套在方内的奶牛）和固定效应（处理、时期、方和它们的相互作用）。预设计的对比包括（1）FA 处理的整体效果[CON 与 FA 处理的平均值（FAT）；1/2（PA+MIX）]，和（2）FA 补充剂的效果（PA 与 MIX）。处理对干物质采食量、体重或体重变化没有影响。与 CON 相比，FAT 降低了总 FA 和 18 碳 FA 的消化率，但不影响干物质和中性洗涤纤维的消化率。与 MIX 相比，PA 分别提高了 3.6 和 4.8 个百分点的干物质和中性洗涤纤维消化率。PA 还增加了总 FA 和 18 碳 FA 的消化率，但不改变 MIX 中 16 碳 FA 的消化率。使用 Lucas 检验，我们估计 PA 和 MIX 补充剂的表观消化率系数分别为 0.768 和 0.553。与 CON 相比，FAT 增加了产奶量，并倾向于增加能量校正奶，但不影响乳脂或乳蛋白产量。与 MIX 相比，PA 增加了能量校正奶和乳脂产量，但对乳蛋白产量没有影响。我们的结果表明，产奶量约为 45kg 的奶牛对富含 C16:0 的 FA 补充剂的反应优于含有 C16:0 和 C18:0 的补充剂，这可能部分是由于 PA 与 MIX 相比增加了 FA 和中性洗涤纤维的消化率。
