The effect of plane of winter nutrition and sward height on the performance of steers grazing grass/white clover swards

An experiment was carried out over 2 years to examine the interactions between two planes of winter nutrition and summer grazing at 5.5 and 7.5 cm compressed sward height on the performance of Limousin X Friesian steers grazing grass/white clover swards. Diets were offered in winter to give liveweight gains of either 0.5 (low) or 0.8 (high) kg d(-1). The experiment was repeated over 2 years. Liveweights gains (low 0.50 vs. high 0.84 kg d(-1), s.e.d. +/- 0.044) were achieved in winter 1 and (low 0.55 vs. high 0.91 kg d(-1), s.e.d. +/- 0.041) in winter 2. These differences resulted in animals from the high treatment being 44 and 60 kg head(-1) heavier at rum-out than the low-treatment animals in years 1 and 2, respectively. There was evidence of compensatory growth with animals from the low treatment subsequently tending to grow faster than those from the high treatment, with liveweight gains during the period from turn-out to 84 d of 1.27 vs. 1.18 s.e.d. +/- 0.65 kg d(-1); P = 0.213 and 1.11 vs. 0.95 s.e.d. +/- 0.062 kg d(-1); P = 0.015 in summers 1 and 2 respectively. In general, animals grazing the short award tended to grow more slowly than those on the tall swards (1.18 vs. 1.27 s.e.d. +/- 0.065 kg d(-1); P = 0.166 and 0.93 vs. 1.13 s.e.d. +/- 0.062 kg d(-1) P = 0.002) for years 1 and 2 respectively. Growth rates in year 1 were significantly higher than those in year 2. However, increased summer growth rates did not compensate for the differences in live weight established during the winter, and more animals reached slaughter weight in a shorter time from the high than the low treatment. Mean stocking rate on treatments 5.5 and 7.5 over the 2 years were 5.2 and 4.3 animals ha(-1); differences were significant in year 2 (P<0.01). The 5.5 cm award treatment also gave a greater liveweight gain ha(-1) than the 7.5-cm sward treatment in both years with a mean for the two years of 670 vs. 572 kg ha(-1) but differences were not significant.