Effects of cereal grain, lupins-cereal grain or hay supplements on the intake and performance of grazing dairy cows

Abstract

Summary. Three experiments of 5 weeks duration, using 32 Friesian cows per experiment, were conducted in northern Victoria during 1994–95. Experiment 1 was conducted during spring (October–November), experiment 2 was carried out in summer (January–February), and experiment 3 was in autumn (April–May). In each experiment, there was a pasture only treatment and 3 treatments in which 5 kg dry matter (DM)/cow of different supplements were offered in 2 equal feeds each day. The supplements were either pelleted cereal grain (75% barley and 25% wheat), pelleted mixed grains (50% lupins, 25% barley, 25% wheat) or hay. The hay used in experiment 1 was made from lucerne (Medicago sativa), while that used in experiments 2 and 3 originated from irrigated annual and perennial pastures, respectively. Cows strip-grazed irrigated pasture at a herbage allowance of about 30 kg DM/cow.day in each experiment. There were 4 cows per treatment and treatments were replicated twice.

All supplements significantly (P<0.05) increased milk production. The lupins–cereal grain supplement resulted in the greatest response and the hay the smallest response, both in terms of absolute level of production and the marginal return to additional total DM consumed (1.4, 1.7 and 0.9 kg of extra milk for each additional kg DM of total intake associated with the cereal grain, lupins–cereal grain and hay supplement treatments, respectively). However, the marginal response to each kg of a supplement varied (P<0.05) with the time of the year. There were no differences between supplements in spring whilst in summer and autumn, the cereal grain and lupins–cereal grain supplements were better (P<0.05) than hay. Milk solids yield responded in a manner similar to milk yield. This was principally due to the fact that none of the supplements affected (P>0.05) milk protein content and, although milk fat content was reduced (P<0.05) by both concentrate supplements, the effects were not biologically large (a difference of about 0.05 percentage units). The cereal grain and lupins–cereal grain supplements also improved (P<0.05) the body condition of cows relative to those that were unsupplemented or were supplemented with hay. Levels of substitution were similar across types of supplement, averaging 0.28 kg DM reduction in pasture intake for each kg DM of supplement eaten. It was concluded that, at low pasture allowances (high stocking rates) with moderate supplementation, large differences in substitution between readily fermentable concentrate supplements, such as cereal grain or lupins–cereal grain, and hay are unlikely. Hence, responses in milk will largely be based on the energy content of the supplement. At higher pasture allowances and/or higher levels of supplementary feeding, variations in substitution will probably play an important role in determining the responses observed.