Comparison of two varieties of Italian ryegrass (Lolium multiflorum) for milk production, when fed as silage and when grazed

Abstract

SUMMARYTwo varieties of Italian ryegrass (Lolium multiflorum Lam.), Tribune and RvP, were cut in each of 2 years, ensiled and individually fed, ad libitum, to dairy cows. In one year, two rates of supplementary concentrate feeding were compared and, in the other year, two types of concentrate and a silage-only diet. Tribune silage was more digestible, in vitro, and was lower in neutral detergent fibre and fibrosity index than RvP silage. There was no difference between the varieties, however, in the cows’ intake of silage. On the silage-only diet, the cows fed Tribune produced a higher yield of milk solids than did those fed RvP; on the other diets, there was no significant difference between varieties in the yield or composition of milk.The same two varieties were compared when grazed by herds of dairy cows in spring, summer and autumn of the first harvest year on six farms and in the second harvest year on four of the farms. Tribune persisted much better than RvP, in numbers of plants and tillers/m2 and in ground cover, and the herbage was more digestible than that of RvP. Milk yield/cow was c. 0·6 kg per day higher when grazing Tribune than when grazing RvP.