Harper Adams University College, Newport, Shropshire, United Kingdom.
J Dairy Sci. 2012 Jan;95(1):109-16. doi: 10.3168/jds.2011-4165.
Trans-10,cis-12 conjugated linoleic acid (CLA) inhibits milk fat synthesis in dairy ewes, but the effects under varying dietary metabolizable protein (MP) levels when energy-limited diets are fed have not been examined. The objectives of the study were to evaluate the response of lactating dairy ewes to CLA supplementation when fed diets limited in metabolizable energy (ME) and with either a low or high MP content. Twelve multiparous ewes in early lactation were randomly allocated to 1 of 4 dietary treatments: a high MP (110% of daily MP requirement) or low MP (93% of daily MP requirement) diet unsupplemented or supplemented with a lipid-encapsulated CLA to provide 2.4 g/d of trans-10,cis-12 CLA, in each of 4 periods of 25 d each in a 4×4 Latin square design. All diets were restricted to supply each ewe with 4.6 Mcal of ME/d (equivalent to 75% of ME requirement). Supplementation with CLA decreased milk fat percentage and yield by 33% and 24%, respectively, and increased milk, milk protein, and lactose yields by 16, 13, and 17%, respectively. Feeding the high MP diet increased the yields of milk, fat, protein, and lactose by 18, 15, 19, and 16%, respectively. Milk fat content of trans-10,cis-12 CLA (g/100g) was 0.09 and <0.01 for the CLA-supplemented and unsupplemented ewes, respectively. Ewes supplemented with CLA had a reduced yield (mmol/d) of fatty acids of <C16, C16, and >C16, although the effect was greatest for <C16. Feeding a high MP level increased the yield of fatty acids of C16 and >C16. Plasma urea concentrations were lowest in ewes supplemented with CLA compared with those unsupplemented (6.5 vs. 7.4 mmol/L, respectively) and receiving low compared with high MP diets (5.6 vs. 8.3 mmol/L, respectively). In conclusion, dairy ewes fed energy-limited diets and supplemented with CLA repartitioned nutrients to increase yields of milk, protein, and lactose, with the response to CLA supplementation and additional MP intake being additive.
反式-10、顺式-12 共轭亚油酸（CLA）抑制奶羊乳脂合成，但在能量受限的饲粮中，当代谢能（ME）水平不同且蛋白代谢能比（MP）含量不同时，CLA 的效果尚未被检验。本研究的目的是评估 CLA 补充剂对处于泌乳早期、ME 限制饲粮且 MP 含量分别为低或高的奶羊的影响。12 只泌乳中期的经产母羊被随机分配到 4 种饲粮处理组之一：高 MP（每日 MP 需要量的 110%）或低 MP（每日 MP 需要量的 93%）饲粮，不添加或添加脂包被 CLA 以提供 2.4 g/d 的反式-10、顺式-12 CLA，在 4×4 拉丁方设计中，每个处理组各有 4 个 25 d 的周期。所有饲粮都被限制为每只羊提供 4.6 Mcal ME/d（相当于 ME 需要量的 75%）。CLA 补充降低了乳脂率和乳脂产量，分别降低了 33%和 24%，并分别增加了 16%、13%和 17%的乳产量、乳蛋白产量和乳糖产量。高 MP 饲粮增加了乳产量、脂肪产量、蛋白产量和乳糖产量，分别增加了 18%、15%、19%和 16%。CLA 补充组的反式-10、顺式-12 CLA（g/100g）为 0.09，CLA 不补充组为 <0.01。CLA 补充组 <C16、C16 和 >C16 的脂肪酸产量降低，尽管对 <C16 的影响最大。高 MP 水平增加了 C16 和 >C16 的脂肪酸产量。与不补充 CLA 的羊相比，补充 CLA 的羊的血浆尿素浓度最低（分别为 6.5 和 7.4 mmol/L），与低 MP 饲粮相比，补充 CLA 的羊的血浆尿素浓度最低（分别为 5.6 和 8.3 mmol/L）。总之，饲喂能量限制饲粮并补充 CLA 的奶羊重新分配了养分，增加了乳、蛋白和乳糖的产量，CLA 补充和额外 MP 摄入的反应是累加的。
