EFFECT OF FORAGE TYPE ON MILK-YIELD, CHEMICAL-COMPOSITION AND CLOTTING PROPERTIES OF MILK

Fifty-four lactating multiparous cows were used in a 3 x 3 latin squar e trial. During each 3-week period cows were offered a diet composed e ither of perennial ryegrass silage (11 kg dry matter/d), or second-cut ting cocksfoot hay (13 kg dry matter/d) or maize silage (11 kg dry mat ter/d). Each diet was supplemented with a mixture of barley, soya-bean meal and urea in proportions calculated to keep the overall rations i socaloric and isonitrogenous. The cows fed grass silage yielded, respe ctively, 0.4 (P > 0.05) and 1.9 kg/d (P < 0.01) more milk than those f ed maize silage or hay, but their milk was significantly poorer in pro teins and caseins. This result is linked to a distribution of ingested energy in favour of milk yield rather than the deposition of body res erves with the grass silage-based diets. The casein/protein ratio, cal cium concentration, pH and rheological characteristics of the milk wer e not significantly different between the types of forages.