Palmquist D L, Jenkins T C
J Dairy Sci. 1980 Jan;63(1):1-14. doi: 10.3168/jds.S0022-0302(80)82881-5.
Recent research has demonstrated the effectiveness of added fat in diets to maintain milk production and fat percent. Much of the earlier work which indicated that fat affects digestion negatively may not be applicable because of great differences in the nature of diets and fats fed and especially in total feed intake. Nevertheless, much remains to be learned about interactions of fat, fiber, calcium, and rumen microorganisms if feeding of fat is to be maximized. The uniquely high acidity in the duodenum combined with detergent action of bile acids, lysolecithin, and fatty acids causes saturated fatty acids to be more digestible in ruminants than in nonruminants. Large quantities of added dietary fat increase concentrations in plasma of very low density lipoprotein triglyceride which increases their uptake by the mammary gland with inhibition of short chain fatty acid synthesis and consequent changes in milk fatty acid composition. In some cases, secretion of milk fat is increased. Current research and practice demonstrate that 3 to 5% fat may be added to diets for lactation to increase energy intake of high-producing cows and/or to reduce starch feeding, thereby increasing the ratio of forage to concentrate to prevent depression of milk fat.
最近的研究表明，在日粮中添加脂肪对于维持产奶量和乳脂率是有效的。许多早期研究表明脂肪会对消化产生负面影响，但由于所饲喂日粮和脂肪的性质存在很大差异，尤其是总采食量不同，这些早期研究结果可能并不适用。然而，如果要最大程度地发挥脂肪的饲喂效果，关于脂肪、纤维、钙和瘤胃微生物之间的相互作用仍有许多需要了解的地方。十二指肠中独特的高酸度，再加上胆汁酸、溶血卵磷脂和脂肪酸的去污剂作用，使得反刍动物对饱和脂肪酸的消化率高于非反刍动物。大量添加日粮脂肪会增加血浆中极低密度脂蛋白甘油三酯的浓度，这会增加乳腺对其的摄取，同时抑制短链脂肪酸的合成，从而导致乳脂肪酸组成发生变化。在某些情况下，乳脂肪分泌会增加。目前的研究和实践表明，泌乳日粮中可添加3%至5%的脂肪，以增加高产奶牛的能量摄入量和/或减少淀粉饲喂量，从而提高粗饲料与精饲料的比例，防止乳脂肪含量下降。
