Effects of diet on milk composition and yield of dairy cows with specical emphasis on milk protein content
1989
Spoerndly, E. (Sveriges Lantbruksuniv., Uppsala (Sweden). Inst. foer Husdjurens Utfodring och Vaard)
Fifty-three feeding experiments with dairy cows covering 179 treatments were analysed to study the effect of feeding on milk protein content. The difference of each treatment from the mean of the experiment was calculated for all feed variables and for milk yield and milk composition. These differences formed a new set of data (deviations). Correlations and regressions were calculated by combining deviations from all experiments. The amount and concentration of metabolizable energy in the diet had the strongest positive correlation with protein content in milk, r=0.42 and 0.31 respectively. The effect of the amount of roughage in the diet on milk protein content seemed to be mainly an indirect energy effect as the partial correlation, where the effect of dietary energy concentration had been removed, was not statistically significant. The amount of ether extract per kg dry matter in the diet had a negative effect on protein content in milk (r=-0.24). Single and multiple regressions were calculated and a dietary increase of 1 MJ metabolizable energy was estimated to increase milk protein content by 0.003 to 0.005 percentage points.
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