Yield and composition of milk from cows fed pasture herbage supplemented with maize and pasture silages

Abstract

Abstract Groups of six cows were fed rations consisting of freshly cut pasture herbage and maize silage in the ratios 1:0, 3:1, 1:3, and 0:1 on a dry matter (DM) basis in two experiments. One, in spring 1970, wa> with cows in early lactation; the other, in summer 1972, with cows in mid lactation. An additional ration of pasture silage and pasture herbage (1: 3) was included in 1972. Treatment effects during a 3-week period were assessed using covariance procedures. When maize silage was fed as a sole ration, feed intake and milk yield declined as the experiments progressed. The effect was so marked in 1972 that the treatment was abandoned. In 1970, the inclusion of 25% maize silage resulted in a 6% higher intake of digestible energy (DE) (p < 0.10) and 5% more milk yield (p > 0.10) than did pasture alone. Apparent DM digestibility of the maize was 60% and of pasture 75%. In 1972, when the DM digestibility of the maize silage was 73% and of pasture 67%, DE intake of the 25% maize silage ration was less than that of pasture alone (p < 0.05), but yield of fat-corrected milk was similar. Feed intake and milk yield decreased with increasing proportions of maize silage in both experiments. When comprising 25% of intake, maize silage resulted in significantly higher milk, fat, lactose, and protein yields than did pasture silage, even though digestibility of silage DM and DE intake were similar. The observed effects are discussed in relation to feed intake and efficiency of utilisation of DE. Up to 40% of the grain in the maize silage was not digested in 1970 and 17% in 1972. It was suggested that this was due to differences in fineness of chopping of the maize at harvest.