Abstract:
Proc. Aust. Soc. Anim. Prod. 1996 Vol. 21 EFFECT OF TYPE OF SUPPLEMENT ON THE REDUCTION OF PASTURE INTAKE IN GRAZING DAIRY COWS C.R. STOCKDALE Kyabram Dairy Centre, Institute of Sustainable Irrigated Agriculture, Kyabram, Vic. 3620 Kellaway and Porta (1993) suggested that type of supplement affected the level of substitution occurring in lactating dairy cows, with fibrous concentrates resulting in lower levels of substitution than starchy concentrates. Further, substitution with protein supplements was lower than that with cereal grains. However, much of the limited research has involved feeding supplements at levels in excess of those commonly used on dairy farms in Victoria. The effect of type of supplement, fed at 5 kg DM/cow.day, on the reduction in pasture intake in several grazing experiments at Kyabram is examined. In 6 experiments, each of about 5 weeks duration, 5 kg of starch, protein or fibre supplements were fed to lactating dairy cows offered about 30 kg DM/cow.day of pasture while, in a further 4 experiments, 5 kg of maize silage-based supplements were fed to cows offered 20 kg DM/cow.day of pasture (see Table 1 for a description of the supplements). One treatment in each experiment was a pasture-only control; other treatments incorporated a comparison of types of supplement. Variations in pasture intakes and milk yields between experiments were large, due to the timing of individual experiments in relation to season and stage of lactation. Measurements included group pasture intakes, which were obtained by a sward sampling technique using a rising plate meter to estimate pre- and post-grazing herbage mass. Levels of substitution were obtained by comparing pasture intakes of cows eating pasture alone with those measured for cows offered the various supplements. In the first series of experiments, there tended to be greater substitution with the fibre supplement than with either of the other supplements (Table 1). With the maize silage-based supplements, there were no differences (Table 1). reduction in pasture intake per kg supplement Table 1. Effects of type of supplement on levels of substitution (kg eaten) KELLAWAY, R. and PORTA, S. (1993). 'Feeding Concentrates. Supplements for Dairy Cows', (DRDC: Glen Iris). 383