Effect of sward surface height on herbage intake and performance of finishing beef cattle

This study examined the effects of contrasting sward surface height (SSH) on the herbage intake, ingestive behaviour, and performance of steers grazing perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) pastures in New Zealand during summer, and the influence of this initial treatment contrast on subsequent cattle performance under common grazing conditions during early autumn. Twenty-four Angus-cross steers, 26 months old and with an initial liveweight of 522 ± 7.6 kg, were continuously stocked on swards maintained at SSH of 5 and 10 cm (L versus H) from 18 November 1996. Six steers from each treatment were slaughtered on 4 March and the remaining animals were grazed for another 5 weeks on common pastures until the final slaughter on 8 April 1997. Herbage intake (estimated by the n-alkane technique) and liveweight gain over the SSH contrast period, and carcass weight at first slaughter, were higher for steers grazed at 10 cm than for those grazed at 5 cm (7.5 ± 0.21 versus 5.0 ± 0.18 and 7.8 ± 0.38 versus 5.0 ± 0.33 kg DM d -1 from two intake estimates, P < 0.05 for each comparison; 1.10 ± 0.23 versus 0.32 ± 0.21 kg d -1, P < 0.01; and 332 ± 10.6 versus 287 ± 7.5 kg, P < 0.05, respectively). SSH did not affect carcass or meat quality characteristics. Liveweight and carcass weight gain per hectare were 71% and 43% greater (318 versus 186 kg and 166 versus 116 kg over 105 days) for steers grazing at 10 cm despite the lower stocking rate (2.86 versus 5.80 steers ha -1) maintained by the tall swards. Significant differences in carcass weight were still evident at the end of the compensatory period between the steer groups originally on treatments H and L (335 ± 9.4 versus 297 ± 9.4 kg, P < 0.05). These results suggest that maintaining a sward height of 10 cm offers advantages in terms of individual animal output and output per hectare compared with grazing at 5 cm, and that compensatory growth does not seem to be an important phenomenon in heavy (over 500 kg liveweight) finishing steers.