Alternative fibre sources for steers and calves fed high-grain feedlot diets
V. Beretta A C , A. Simeone A , J. C. Elizalde A , J. Franco A , O. Bentancur A , A. Ferrés B , S. Ayçaguer A , J. Iriñiz A and V. Martínez AA Animal Science, University of Uruguay, Ruta 363, CP 60000, Paysandú, Uruguay.
B AUPCIN, Cattle Feeders Association, Brenda 6056, CP 11500, Montevideo, Uruguay.
C Corresponding author. Email: beretta@fagro.edu.uy
Animal Production Science 50(6) 410-413 https://doi.org/10.1071/AN09173
Submitted: 2 December 2009 Accepted: 29 April 2010 Published: 11 June 2010
Abstract
An experiment was conducted to evaluate the effect of fibre source (FS) in high-grain feedlot diets on liveweight gain (LWG) of steers and calves and carcass traits of steers at slaughter. Eighteen steers (330 ± 27.3 kg) and 18 calves (153 ± 11.9 kg) were randomly allotted within animal category to one of three high-grain diets varying in the FS, including either grass hay (H, 66% neutral detergent fibre (NDF)), rice hulls (RH, 85% NDF) or wood chips (W, 90% NDF), and a total mixed ration formulated for equal levels of digestible DM, crude protein and NDF, within category. Animals were individually fed (3 kg DM/100 kg LW, distributed in four meals) during 56 days. The LW increased linearly with time in all treatments (P < 0.01). FS did not affect calves’ LWG (P > 0.05), but it resulted in differences in steers LWG (H: 1.77b; RH: 1.51c; W: 2.02a kg/day, P < 0.05). However, no differences were observed in hot carcass weight (P > 0.05), which resulted in higher carcass yield (P < 0.05) for steers fed RH (55.0%) compared with H (53.5%) and W (53.3%). There was a significant interaction (P < 0.05) for feed : gain ratio, with an improvement of this value observed only for steers fed the W diet. Although varying the FS affected rumination of calves and steers (P < 0.01) and the time spent eating of steers (P < 0.05), it did not represent any constraint for animal production. This study suggests by-products high in fibre content, such as RH and W, could be used in substitution to H in high-grain feedlot diets when fed at equal NDF concentration in the ration, both for calves and steers. Because calves are sometimes grown on a high-concentrate diet during winter before spring grazing, further research is needed to quantify potential residual effects on LWG after they return to pasture.
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