Effects of Pelleting Concentrate Mixtures of Varying Starch Content on Milk Yield and Composition

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Abstract
Twenty-four Holstein cows were used to study the effects of meal, pellet, and ground pellet forms of concentrates fed with roughage at either 1.0 or 1.5 kg of hay equivalent per 100 kg body weight on the yield and composition of milk. Pellets and ground pellets depressed the milk fat test slightly, but significantly, when compared to the meal form. There were no differences in milk yield or composition due to the rations fed. Cows on low roughage, however, exhibited significantly higher solid-not-fat and protein than those fed the higher roughage level. Another experiment was conducted with 9 cows to observe the effect of ingredient composition of pelleted concentrates on the yield and composition of milk. The diets contained several levels of corn starch, developed by a selective use of common feed ingredients. A level of 36% corn starch in the concentrate (equivalent to about 34% corn in the feed) resulted in a depression in milk fat content. A level of 33.5% starch from other feeds, but only 15% corn starch, maintained the milk fat test. Both the quantity and type of starch in the diet seem to be important factors influencing the fat content of milk. The molar proportions of rumen volatile fatty acids (VFA) were not greatly altered by diets fed.