Protein and fat composition and some manufacturing properties of milk from dairy cows fed on hay and concentrate in various ratios

Abstract

Seven Friesian cows in each of four treatment groups consumed hay and a rolled barley concentrate in the ratios of 100:0, 80:20, 60:40 and 37:63 respectively. Cows fed on only hay consumed less dry matter than cows fed on barley and hay and produced less milk, fat, solids not fat, protein and casein. Solids not fat, protein, casein, β-lactoglobulin and α-lactalbumin percentages were generally higher when the ration contained a higher proportion of concentrate, although milk fat percentages were similar for all treatments. Casein, β-lactoglobulin and α-lactalbumin concentrations relative to the concentration of total protein were similar for all treatments. Milk fat from cows fed on hay only was generally lower in C₁₀, C₁₂, C_18:2 fatty acids and higher in C_18:1 and C_18:3 fatty acids than milk fat from cows fed on hay and concentrate.

The rennet curd firmness of the milk increased as the proportion of concentrate in the diet increased. The mean maximum heat stability of the skimmed milk from individual cows generally decreased as the proportion of concentrate in the diet increased.