Effect of oil-enriched diets on the milk yield and composition, and on the composition and physical properties of the milk fat, of dairy cows receiving a basal ration of grass silage

Summary The effects of supplementing a basal diet of grass silage with various oil-enriched mixtures on milk yield and composition, fatty acid composition and the melting characteristics of the milk fats are reported. In the first experiment, various dietary fats (soya oil, tallow and a palm oil/palmitic acid mixture) were fed at a fixed level (10% by weight of the concentrate ration). Soya oil had no effect on the proportion or yield of milk fat, and increased the proportion of low melting material in the milk fat; tallow increased the proportion of milk fat, and had little effect on the melting characteristics of the milk fat; the palm oil/palmitic acid mixture increased both the content and the yield of milk fat, and increased the proportion of high-melting material in the milk fat. In the second experiment, soya oil was fed at 3 levels (10, 15 and 20% by weight of the concentrate ration). No statistically significant effect on the yield of milk or of its constituents was observed; the proportion of low-melting material in the milk fat increased progressively with increasing intake of soya oil.