Abstract:
Proc. Aust. Soc. Anim. Prod. Vol. 17 FEED EFFICIENCY OF PEN FED HEREFORD, ANGUS X HEREFORD AND FRIESIAN X HEREFORD COWS JOHN F. GRAHAM* and ALAN Jo CLARK* 405 Crossbred cows produce more beef than British bred straightbreds (Morgan 1986), but more information is needed on all aspects of their relative feed efficiency. The effect of genotype and feeding level on feed efficiency for maintenance was examined during pregnancy and lactation in Hereford (HxH), Angus x Hereford (AxH) and Friesian x Hereford (FxH) cows (n = 41) calving in autumn of 1985 and 1986. Cows were fed at three levels {Maintenance (M), M x 1.25 (H) and M x 0.75 (L)} during the final 8 weeks of pregnancy and two levels ((M) plus feed for 4 kg (L) or 8 kg milk/cow/day (H)} during the first 8 weeks of lactation. Daily feed amounts were calculated from MAFF (1976), using the 24 hour fasted liveweights (FLW) of each cow at the start of each feeding period and adjustments for stage of pregnancy and milk production. Metabolizable energy of feed was calculated from in vitro digestibility. Maintenance energy (MEm)(MJ) was calculated using the formula MEm = Intake energy - energy used for pregnancy or milk production + energy of liveweight change (LWC) (assuming constant efficiencies .between genotypes, of feed use for foetal growth, LWC and milk production). Table 1 Fasted cow live weight (FLW)(kg), feed intake (I) (MJME/kg LWoo7'/ cow/day), liveweight change (LWC) (kg/cow/day), calculated maintenance requirement (MEm), (MJME/kgLW0'75/cow/day) and milk production (MILK) (kg/cow/day), in the different treatments Contrary to the results of Ferrell and Jenkins (1984) using non-pregnant, non-lactating cows, there was no significant effect of genotype on MEm during pregnancy or lactation but maintenance efficiency tended to decrease as feeding level increased. The MEm values in this experiment are similar to those reported by Ferrell et al. (1976) and Neville (1974) for pregnancy and lactation respectively. FERRELL, C.L., GARRETT, W.N., HENMAN N. and GRITCHING G. (1976). J. Anim. Sci. 42: 937. FERmL, C.L., and JENKINS, T.G. (1984). J. Anim. Sci. 58: 234. MAFF (1976). Technical Bulletin 33 (H.M.S.O.:London). MORGAN, J.H.L. (1986). Proc. Wld. Gong. Genet. Appl. Livest. Prod. 9: 319. = NEVILJZ JR. W.E. (1974). J. Anim. Sci. 38: 681. C *Pastoral Research Institute, P.O. Box 180, Hamilton, Vic., 3300.
