The effect of feed quality and particle length on the short-term intake rate of Friesian heifers

Abstract

Short-term intake rate measurements were performed on four 20 month old Friesian heifers with mean live weight of 344 kg. Treatments were forages of two qualities; ryegrass straw (low), and oaten hay (high), and four particle lengths (5, 10,20 and 40 cm). The intake rates of each forage type offered singly (S-straw and S-oat) and in all possible paired combinations of particle lengths (40-20,40-10,40-5,20-10,20-5,10-5) for both forage types (P-straw, P-oat) were measured over 3-5 minute periods. Feed quality had a highly significant effect (P<0.01) on intake rate. Mean intake rates were 36 and 69 g/min for S-straw and S-oat respectively. There was no significant difference in intake rate between the particle sizes in either the S-straw or S-oat experiments. When the between-animal variation was removed the particle length of oaten hay had a significant effect on intake rate. The change in intake rate between 5 and 20, and 20 and 40 cm was significant for both S-straw and S-oat. The particle lengths giving the faster intake rates in the single offerings experiments were generally consumed in higher proportions in the paired feeding trials. Intake rates in the P-straw and P-oat experiments reflected the intake rates associated with the two feeds induded in the combination, as indicated by the S-straw and S-oat experiments.