The effect on food intake and milk production of adding concentrates to the ration of pasture-fed cows

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Abstract
Nine lactating Jersey cows were each fed pasture to appetite indoors, and the effects of addition of 2.7 kg and 4.0 kg of a concentrate mixture/cow/day on voluntary intake and on milk yield and composition were determined in a 3 × 3 Latin square design. A further 4 Jersey cows with rumen flstulae were used to provide information on the effects of supplementing pasture with 2.7 kg of the concentrate mixture on rumen pH and volatile fatty acid proportions. Supplementation with the concentrates decreased the voluntary intake of pasture dry matter by 0.63 and 0.66 kg/kg concentrate dry matter fed at the lower and higher levels respectively. The total digestible organic matter intake of cows receiving concentrates was significantly higher (P < 0.01) than that of cows receiving pasture alone. Only minor changes occurred in rumen pH and volatile fatty acid proportions with the addition of 2.7 kg concentrate/cow/day to the pasture. The supplementary feeding had little effect on milk yield, and the small changes that occurred in milk composition with concentrate feeding were not statistically significant. Live-weight gain averaged 0.5 kg/day/cow throughout the experiment, but no significant differences in live-weight gain were detected between treatments.