THE EFFECTS OF METHOD OF PROCESSING OF STARTERS, TALLOW INCLUSION AND ROUGHAGE SUPPLEMENTATION ON THE PERFORMANCE OF EARLY-WEANED CALVES

Two experiments involving 63 Friesian calves were carried out to investigate the effect of fat inclusion and method of processing of starters on the performance and roughage requirements of the early-weaned calf. Milk replacer was fed at the rate of 0.41 kg DM per calf daily for 23 days. Three starters, WPT, GPN, GTPN, based on 63.5% barley and 25% soya-bean meal, were fed ad libitum throughout each experiment. WPT and GPN were identical in composition, but differed in that whole barley was used in the production of an 8-mm pellet in WPT, whereas the barley was ground prior to the production of a 5-mm pencil in GPN. Starter GTPN differed from starter GPN in that it contained 3.5% tallow in place of 3.5% cassava. In Experiment 1, 18 calves were kept on expanded metal floors without access to long roughage for 62 days, followed by 10 days when they were bedded on straw and had free access to hay; in Experiment 2, 45 calves were bedded on straw and had free access to hay for a 58-day period. Apparent digestibility coefficients, based on a total 10-day collection (Days 49-58) in Experiment 1 were significantly different in the case of fat, where GTPN was higher (P < 0.001) than GPN and in N-free extract where WPT was lower (P < 0.05) than the others; otherwise differences failed to reach significance. Whole barley voided in the faeces for WPT, expressed as a percentage (.+-.SE) of dietary barley, amounted to 4.27 .+-. 1.03% in Experiment 1 and 4.56 .+-. 1.13% in Experiment 2. Rumen fluid pH values were significantly higher at four sampling dates in the post-weaning period with WPT than with the other starters when no supplementary roughage was provided in Experiment 1. Provision of long roughage during the final 10 days of Experiment 1 and in Experiment 2 resulted in a significant increase in rumen fluid pH values on all starters. Bloat was not observed on WPT in either Experiment 1 or 2, or on any starter in Experiment 2. Persistent bloat occurred with GPN when no long roughage was provided in Experiment 1; bloating almost completely disappeared when long roughage was introduced towards the end of Experiment 1. In Experiment 2, liveweight gains were not significantly affected by starter type, except during the post-weaning period when GTPN gave lower gains than GPN (P < 0.05). In contrast, in Experiment 1, when no long roughage was provided, WPT fed calves gained 14.1 and 9.1 kg more than calves fed the pencils with (GTPN) or without tallow (GPN) over a 62-day period. In both experiments, intake of WPT was highest and intake of GTPN was lowest.