Piantoni P, Lock A L, Allen M S
Department of Animal Science, Michigan State University, East Lansing 48824.
Department of Animal Science, Michigan State University, East Lansing 48824.
J Dairy Sci. 2015 Mar;98(3):1938-49. doi: 10.3168/jds.2014-8634. Epub 2014 Dec 18.
Effects of stearic acid supplementation on feed intake and metabolic and production responses of dairy cows with a wide range of milk production (32.2 to 64.4 kg/d) were evaluated in a crossover design experiment with a covariate period. Thirty-two multiparous Holstein cows (142±55 d in milk) were assigned randomly within level of milk yield to treatment sequence. Treatments were diets supplemented (2% of diet dry matter) with stearic acid (SA; 98% C18:0) or control (soyhulls). The diets were based on corn silage and alfalfa and contained 24.5% forage neutral detergent fiber, 25.1% starch, and 17.3% crude protein. Treatment periods were 21 d with the final 4 d used for data and sample collection. Compared with the control, SA increased dry matter intake (DMI; 26.1 vs. 25.2 kg/d) and milk yield (40.2 vs. 38.5 kg/d). Stearic acid had no effect on the concentration of milk components but increased yields of fat (1.42 vs. 1.35 kg/d), protein (1.19 vs. 1.14 kg/d), and lactose (1.96 vs. 1.87 kg/d). The SA treatment increased 3.5% fat-corrected milk (3.5% FCM; 40.5 vs. 38.6 kg/d) but did not affect feed efficiency (3.5% FCM/DMI, 1.55 vs. 1.53), body weight, or body condition score compared with the control. Linear interactions between treatment and level of milk yield during the covariate period were detected for DMI and yields of milk, fat, protein, lactose, and 3.5% FCM; responses to SA were positively related to milk yield of cows. The SA treatment increased crude protein digestibility (67.4 vs. 65.5%), tended to increase neutral detergent fiber digestibility (43.6 vs. 42.3%), decreased fatty acid (FA) digestibility (56.6 vs. 76.1%), and did not affect organic matter digestibility. Fatty acid yield response, calculated as the additional FA yield secreted in milk per unit of additional FA intake, was only 13.3% for total FA and 8.2% for C18:0 plus cis-9 C18:1. Low estimated digestibility of the SA supplement was at least partly responsible for the low FA yield response. Treatment did not affect plasma insulin, glucagon, glucose, and nonesterified FA concentrations. Results show that stearic acid has the potential to increase DMI and yields of milk and milk components, without affecting conversion of feed to milk, body condition score, or body weight. Moreover, effects on DMI and yields of milk and milk components were more pronounced for higher-yielding cows than for lower-yielding cows.
在一项带有协变量期的交叉设计实验中，评估了补充硬脂酸对不同产奶量（32.2至64.4千克/天）奶牛采食量、代谢及生产反应的影响。32头经产荷斯坦奶牛（产奶142±55天）按产奶量水平随机分配到处理顺序中。处理方式为在日粮中补充（占日粮干物质的2%）硬脂酸（SA；98% C18:0）或对照（大豆皮）。日粮以玉米青贮和苜蓿为基础，含有24.5%的饲草中性洗涤纤维、25.1%的淀粉和17.3%的粗蛋白。处理期为21天，最后4天用于数据和样本采集。与对照相比，SA增加了干物质采食量（DMI；26.1对25.2千克/天）和产奶量（40.2对38.5千克/天）。硬脂酸对乳成分浓度无影响，但增加了脂肪产量（1.42对1.35千克/天）、蛋白质产量（1.19对1.14千克/天）和乳糖产量（1.96对1.87千克/天）。SA处理增加了3.5%乳脂校正乳（3.5% FCM；40.5对38.6千克/天），但与对照相比，对饲料效率（3.5% FCM/DMI，1.55对1.53）、体重或体况评分无影响。在协变量期，处理与产奶量水平之间的线性相互作用在DMI以及乳、脂肪、蛋白质、乳糖和3.5% FCM产量方面被检测到；对SA的反应与奶牛产奶量呈正相关。SA处理提高了粗蛋白消化率（67.4%对65.5%），倾向于提高中性洗涤纤维消化率（43.6%对42.3%），降低了脂肪酸（FA）消化率（56.6%对76.1%），且对有机物消化率无影响。脂肪酸产量反应（以每单位额外FA摄入量在乳中分泌的额外FA产量计算），总FA仅为13.3%，C18:0加顺式-9 C18:1为8.2%。SA补充剂估计消化率低至少部分是FA产量反应低的原因。处理对血浆胰岛素、胰高血糖素、葡萄糖和非酯化FA浓度无影响。结果表明，硬脂酸有增加DMI以及乳和乳成分产量的潜力，而不影响饲料转化为乳、体况评分或体重。此外，对高产奶牛而言，硬脂酸对DMI以及乳和乳成分产量的影响比对低产奶牛更显著。
