Changes in Forage-Concentrate Ratio of Complete Feeds for Dairy Cows

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Abstract
Two high-forage complete feeds, 95% forage:5% concentrate and 80% forage:20% concentrate, each were fed ad lib to 32 cows from 28 days prepartum to 4 days postpartum. At this time treatments were changed factorially to 2 higher-concentrate complete feeds, 60% forage:40% concentrate or 40% forage:60% concentrate, for an additional 28 days. Dry-matter intakes and average milk yields following the diet change (days 4-32 postpartum) were 14.4 and 23.8 kg/day, 15.2 and 25.1 kg/day, 14.3 and 23.1 kg/day, and 15.4 and 26.0 kg/day for combinations 95% forage to 60%, 95% to 40%, 80% to 60%, and 80% to 40% forage. Volatile fatty acids (VFA), pH and lactic acid were measured in rumen fluid in 8 fistulated cows prepartum and on 1st and 8th day after ration change. Molar percentage of acetic acid was lower and molar percentage of propionic acid was higher 8 days after ration change than either prepartum or 1 day after change. Total concentration of VFA was higher and pH was lower on 60% concentrate than on 40%. Lactic acid was low (< 2.7 mmol/l rumen fluid) relative to acidosis levels in all periods and treatments. Cows can be changed from diets of nearly all forage to high concentrate complete feeds of up to 60% concentrate 4 days postpartum without adverse changes in feed intake, milk production and rumen fermentation.