Ryegrass varieties in relation to dairy cattle performance

Abstract
The influence of three varieties of ryegrass on milk yield and composition was examined using lactating monozygous twin cattle in a series of experiments. During the spring period the mean milk yields produced by the different groups, in decreasing order, were: Manawa ryegrass > Ariki ryegrass > Ruanui ryegrass (P < 0.01). The butterfat yields and the solids-not-fat contents of the milk from the three groups did not differ significantly (P > 0.05). In the autumn experiments the cows on the Ruanui ryegrass produced higher milk and butterfat yields than those on the Ariki ryegrass (P < 0.01). Possible reasons for the differences in nutritive value of the ryegrasses are discussed in relation to results of other recent work.