Yield and composition of milk from Friesian cows grazing either perennial ryegrass or white clover in early lactation

The yield and composition of milk from Friesian cows grazing either perennial ryegrass ( Lolium perenne ) (G, ten cows) or white clover ( Trifolium repens ) (C, nine cows) were evaluated between d 21 and 129 post partum. The two forages, of similar digestible energy content, were the sole source of nutrients and were offered ad lib . (exp. 1). Digestion and flow at the duodenum were measured on 13 occasions in early lactation with comparable cows fitted with rumen and duodenal cannulae and grazing similar forages (exp. 2). The gross milk yield (22·2, G; 25·0, C, kg/d P P P ad lib . and 502 kg dry matter of concentrates. The total (305 d) difference in lactation response to grazing C compared with G was 931 1 (5657 1, C; 4726 1, G); this was a direct response during the experiment of 301 1 and a residual response of 630 1. In exp. 2, more organic matter (6·47, G; 8·01, C, kg/ d, P P