Supplements improve the production of dairy cows grazing either white clover or paspalum-dominant pastures in late lactation

Abstract

Summary. Thirty-six Friesian cows in late lactation, with an initial average daily milk yield of 15.4 kg/day, grazed pure white clover (Trifolium repens cv. Haifa) or paspalum (Paspalum dilatatum)-dominant swards for up to 6 weeks in autumn and were supplemented with maize (Zea mays) silage with or without barley grain, urea or cottonseed meal. Five groups of 4 cows were offered about 21 kg dry matter (DM)/cow. day of paspalum-dominant pasture. One group was unsupplemented while the other groups were offered one of the following supplementary feeding treatments: (i) 5 kg DM/cow of maize silage; (ii) 5 kg DM/cow of maize silage and 75 g of urea; (iii) 3 kg DM/cow of maize silage plus 2 kg DM of rolled barley; or (iv) 3 kg DM/cow of maize silage plus 2 kg DM of cottonseed meal each day. A further 4 groups of 4 cows were offered 21 kg dry matter/cow. day of white clover pasture, and the same supplement treatments, with the exception of maize silage–cottonseed meal. All cows were individually fed their supplement but they grazed the pastures as groups according to treatment. Cows offered white clover and no supplements ate 12.9 kg DM/cow.day of herbage and maintained milk production. All supplements increased total DM intake and improved milk production, to about 18 kg/cow. day, with a mean marginal response of 0.8 kg of milk per 1.0 kg of extra total DM eaten. There were no differences in production due to the type of supplement. Cows grazing paspalum ate less pasture, and levels of substitution of pasture by supplement were higher than when white clover was fed. Milk yields of the unsupplemented cows dropped rapidly and consistently with the cows virtually ceasing production. All supplements successfully arrested the decline in milk production, and to about the same degree; the marginal response to extra feeding was 1.4 kg of milk for each kilogram of additional total DM eaten.