Monensin, Forage Intake and Lactation of Range Beef Cows2

Abstract

Effects of monensin on forage intake and lactation of cows grazing low quality dry winter range grass were examined in two trials. In trial 1, cows were fed a 30% protein soybean meal supplement with 0, 50 or 200 mg of monensin per cow per day; and in trial 2, cows were fed the same supplement with 0 or 200 mg of monensin. Cow weight change during the winter was unchanged by adding 200 mg of monesin to the supplement in both trials. Relative forage intake (trial 1) was reduced 13.6% (K.05) and 19.6% (P<.05) when SO and 200 mg of monensin werefed, respectively. Grazing time in trial 2 was reduced 14.6% when monensin was fed at 200 mg. Ruminal acetate and butyrate were consistently decreased and propionate was increased when 200 mg of monensin was fed. Milk yield and milk composition were not appreciably affected by monensin, but calves reared by monesin fed cows gained weight more rapidly (P<.05), suggesting that calves reared by cows fed monensin utilized milk and/ or forage more efficiently. This may be due to calf consumption of the supplement containing monensin. Copyright © 1978. American Society of Animal Science . Copyright 1978 by American Society of Animal Science.