The effect of a blend of dietary unesterified and saturated long-chain fatty acids on the performance of dairy cows in mid-lactation
1990
King, K.R. | Stockdale, C.R. | Trigg, T.E. (Victorian Dept. of Agriculture and Rural Affairs, Kyabram (Australia). Irrigated Pastures Research Inst.)
Twenty-three cows in their fourth month of lactation were individually fed ad libitum, a mixed balanced ration based based on maize silage, lucerne hay and rolled grain. Varying quantities, up to 1020 g per cow per day of the fatty acid supplement were mixed into the ration. Yields of milk and milk products were linearly related to total long-chain fatty acid intake. Milk fat content increased linearly while milk protein content averaged 3. 59 percent. The marginal returns from feeding 1 kg of the supplement were 3.3 kg milk, 0.33 kg fat and 0.07 kg protein. The proportions of C10:0, C12:0 and C14:0 fatty acids in milk were decreased, while those of C18:0 and C18:1 were increased as the result of feeding long-chain fatty acids. The concentration of lipid in plasma was increased, but acetate and D-(3) -hydroxybutyrate levels in blood remained unchanged with increased levels of dietary long-chain fatty acid. Efficiency of milk production was increased by 11 percent from feeding 1 kg of the supplement. In vivo digestibilities of dry matter, neutral and acid detergent fibres, and dietary long-chain fatty acids were unaffected by supplement.
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