Theurer M L, Block E, Sanchez W K, McGuire M A
Department of Animal and Veterinary Science, University of Idaho, Moscow 83844, USA.
J Dairy Sci. 2009 May;92(5):2051-6. doi: 10.3168/jds.2008-1276.
Recent research has focused on the importance of supplying essential fatty acids to the lactating dairy cow. The addition of essential fatty acids, specifically linoleic and linolenic acid, to dairy cow diets has been investigated as a method to increase reproductive efficiency. Rumen bacteria, however, biohydrogenate polyunsaturated fatty acids (PUFA) to saturated fatty acids. This is an important issue because it can also lead to milk fat depression when unsaturated fatty acids are fed. The formation of Ca salts has previously been shown to partially protect unsaturated fatty acids from rumen biohydrogenation. The objective of this experiment was to evaluate feed intake, milk production, and milk composition of cows fed Ca salts of palm fatty acids (CS) compared with those fed Ca salts of palm fatty acids with an increased content of PUFA (CS+PUFA). Nineteen lactating Holstein cows were used in a switchback experiment to determine any differences between CS and CS+PUFA on milk production and composition. This experiment consisted of 3 consecutive periods of 14 d. Treatments were formulated to provide 450 g/d (dry matter basis) of the Ca salt supplement and were mixed with the same basal ration. Milk weights and feed intakes were recorded daily for each cow. Milk samples were collected the last 2 d of each period and analyzed for milk composition and fatty acids. Dry matter intake [28.0 vs. 27.0 kg/d; standard error of the mean (SEM) = 0.4] and milk production (44.4 vs. 44.0 kg/d; SEM = 0.7) were not different between treatments for CS and CS+PUFA, respectively. Milk fat percentage (3.34 vs. 3.22%; SEM = 0.07) and milk protein percentage (2.78 vs. 2.80%; SEM = 0.01) were not different for CS- and CS+PUFA-fed cows. Feeding CS+PUFA reduced the concentration of palmitic acid in milk fat (28.3 vs. 26.8 wt%; SEM = 0.3). Supplementation of CS+PUFA increased the linoleic acid concentration (3.96 vs. 4.61 wt%; SEM = 0.1) of milk fat, indicating that linoleic acid was partially protected from rumen biohydrogenation. Concentrations of conjugated linoleic acid were also increased (0.44 vs. 0.52 wt%; SEM = 0.02) when cows consumed CS+PUFA, indicating that some biohydrogenation did occur. Supplementing CS+PUFA did not alter milk production, milk fat percentage, or dry matter intake when compared with CS. The CS+PUFA supplement supplied more linoleic acid to the small intestine for milk fat synthesis.
最近的研究聚焦于向泌乳奶牛供应必需脂肪酸的重要性。已对在奶牛日粮中添加必需脂肪酸，特别是亚油酸和亚麻酸，作为提高繁殖效率的一种方法进行了研究。然而，瘤胃细菌会将多不饱和脂肪酸（PUFA）生物氢化成为饱和脂肪酸。这是一个重要问题，因为饲喂不饱和脂肪酸时也会导致乳脂率下降。先前已表明钙盐的形成可部分保护不饱和脂肪酸免受瘤胃生物氢化作用。本试验的目的是评估饲喂棕榈脂肪酸钙盐（CS）的奶牛与饲喂多不饱和脂肪酸含量增加的棕榈脂肪酸钙盐（CS+PUFA）的奶牛的采食量、产奶量和乳成分。19头泌乳荷斯坦奶牛用于一项折返试验，以确定CS和CS+PUFA在产奶量和乳成分上的差异。本试验由3个连续的14天周期组成。处理组按每天提供450克（干物质基础）的钙盐补充剂进行配制，并与相同的基础日粮混合。每天记录每头奶牛的产奶量和采食量。在每个周期的最后2天采集乳样，分析乳成分和脂肪酸。CS和CS+PUFA处理组之间的干物质采食量[分别为28.0对27.0千克/天；平均标准误（SEM）=0.4]和产奶量（44.4对44.0千克/天；SEM =0.7）没有差异。饲喂CS和CS+PUFA的奶牛的乳脂率（3.34对3.22%；SEM =0.07）和乳蛋白率（2.78对2.80%；SEM =0.01）没有差异。饲喂CS+PUFA降低了乳脂中棕榈酸的浓度（28.3对26.8重量%；SEM =0.3）。补充CS+PUFA增加了乳脂中亚油酸的浓度（3.96对4.61重量%；SEM =0.1），表明亚油酸部分免受瘤胃生物氢化作用。当奶牛采食CS+PUFA时，共轭亚油酸的浓度也有所增加（0.44对0.52重量%；SEM =0.02），表明确实发生了一些生物氢化作用。与CS相比，补充CS+PUFA并未改变产奶量、乳脂率或干物质采食量。CS+PUFA补充剂为小肠提供了更多的亚油酸用于乳脂合成。
