Abstract:
Proc. Aust. Soc. Anim. Prod. Vol. 18 THE EVALUATION OF A BETA-AGONIST (CLENBUTEROL) FOR INTENSIVELY MANAGED DAIRY COWS J.B. MORAN*, T. STELMASIAK** and S. VAN MOURIK*** The partitioning of nutrients from body reserves to milk production during early lactation is an important contributor to high milk yields in dairy cows. In lotfed cows at Kyabram, marginal milk responses to grain feeding during early lactation diminished whereas body condition increased in diets where grain comprised 0, 0.16, 0.33 and 0.50 of the dry matter (DM) (Moran and Trigg 1989). Beta-agonists such as clenbuterol, act as repartitioning agents by The aim of this trial was to reducing fat deposition in growing animals. determine if lactating cows respond in a similar manner, Ten Friesian cows (18 days post-partum) were fed ad libitum for 14 weeks on a complete diet (26 g N/kg DM, 0.76 in vitro DM digestibility) consisting of crushed wheat (O-40), maize silage (O-23), lucerne hay (O-20), cottonseed meal During week 4, five.of the cows (0.15) plus minerals and sodium bicarbonate. were subcutaneously implanted with an osmotic pump that released 22.5 mg These cows were each implanted with a second clenbuterol/day for 28 days. osmotic pump during week 8. An osmotic pump continuously releases its contents through increases in pressure on a bladder inside the drug reservoir. The treated and control herds were fed separately from weeks 4 to 14 and individually during weeks 9-10 and 13-14. Daily intakes of DM and yields of milk and weekly changes in milk composition and live weight were monitored. Yields of fat corrected milk (FCM), milk fat and milk protein were covariate corrected prior to split-plot analyses of variance with sub-period (weeks 4-7 and 8-11) as the main plot and clenbuterol implant as the sub-plot. Data on liveweight changes, final live weights and individual DM intakes were also analyzed for treatment effects. Table 1 Effect of clenbuterol on intake and productivity (kg/cow/day) Clenbuterol had little influence on DM intake and partitioned feed energy towards body reserves rather than milk yields. Although, this may have indirect beneficial effects on herd fertility, its potential to improve the efficiency of milk production in lotfed cows is limited. MORAN, J.B. and TRIGG, T-E. (1989). Livest. Prod. Sci. 23: 275. WILLIAMS, P-E-V. (1987). Nut. Abst. Rev. (Series B) 57, 453. * ** **+ Kyabram Research Institute, Biocene International (Vic) Park Drive, Parkville, Australian Wool Corporation, Kyabram, Vic. 3620. Pty Ltd, Veterinary Precinct, VRI Building, Vic. 3052. Royal Parade, Parkville, Vic. 3052. 532
