The banding procedure produced fewer acute effects, but a greater suppression of growth than surgical castration and induced prolonged wound formation in the older age group, suggesting that this procedure may not be as suitable for yearling cattle.

An elevated concentration of water soluble carbohydrate (WSC) in grasses may increase the availability of readily degradable energy, increase milk production and improve the efficiency of nitrogen utilisation. Two ryegrasses with elevated WSC, a tetraploid Italian (IRG) and a diploid perennial selected for higher WSC (HSG), were compared against a standard diploid perennial (STG) during spring 2004 and 2005, and autumn 2006 and 2007. Groups of cows (n=20) grazed each grass type for periods of 6 weeks in spring and 2 weeks in autumn. During spring, the 'high' WSC grasses were 20-40 g/kg DM higher in concentration of WSC than the standard (P

A trial was conducted to see whether reducing the interval from castration to slaughter could produce steer-like carcasses but retain the weight advantage of bulls. Ninety Angus, Friesian × Hereford, and Friesian x Simmental bulls were allocated to nine groups. Four groups were castrated at 8 months of age (steers), and three groups were castrated on January 17 (Day 0) at 17 months of age (castrates). One group of bulls and one group of steers were slaughtered on Day 5, groups of steers and castrates were slaughtered on Days 62, 111, and 166, and the remaining group of bulls was also slaughtered on Day 166. On Day 0, bulls and steers were 455 ± 6 and 426 ± 5 kg liveweight, respectively. Liveweight gain of castrates was lower than that of steers for 106 days following castration and the carcass weight (CW) advantage of bulls over steers at 17 months of age was lost in castrates slaughtered at Day 62. The rate of change in carcass, meat, and fat characteristics varied with the attribute under consideration. For castrates the proportion of carcasses classified as steer at slaughter on Days 62, 111, and 166 was 20%, 60%, and 73%, respectively. We conclude that the loss of the weight advantage is faster than most other carcass attributes change and there is little opportunity to exploit postpubertal castration for economic advantage.

Lean beef from grass-fed cattle was analysed for fatty acid (FA) content to determine the between-animal variation and the effects of various traits on FA composition, and indices and FA ratios that have human health implications. In Experiment 1, samples were from three muscles from five bulls, five cows, and five heifers. In Experiment 2, samples were from the m. longissimus lumborum of 50 3 / 4 Jersey 1/ 4 Limousin and 50 3 / 4 Limousin 1/ 4 Jersey cattle, born over 2 years and sired by two bulls. The heifers and steers grazed on similar pastures until slaughter. In both experiments, after adjusting for differences in total FA content of the meat, there were large coefficients of variation (CV) for trans-vaccenic, cis-9 trans-11

The effect of dietary vitamin A supplements on plasma carotenoid (PC), liver B-carotene, and fat carotenoid concentrations, and on fat colour in cattle were determined in three experiments. In Experiment 1, thirteen 2-year-old Angus × Friesian steers were grazed on pasture, and 6 of the steers were supplemented daily with 1 × 10 6 IU vitamin A for 83 days. In Experiment 2, twenty 2-year-old Angus crossbred heifers were grazed on pasture with 5 being supplemented daily with 1 × 10 6 IU and 5 with 2.5 × 10 6 IU vitamin A for 31 days. Cattle in Experiments 1 and 2 were slaughtered at the end of the experiments, and liver and fat samples were analysed for retinol and carotenoid concentrations respectively in Experiment 1, and liver samples were analysed for both retinol and carotenoid concentrations in Experiment 2. Experiment 3 involved ninety 3-year-old Angus steers, 10 of which were slaughtered at the beginning of the experiment, 20 were grazed on pasture, and the remaining 60 steers were fed a diet of 70% barley and 30% pasture-silage on a feedlot either without vitamin A supplement, or with a supplement of 1 × 10 6 or 0.5 × 10 6 IU vitamin A daily. Ten steers from each group were slaughtered after 62 days and the other 10 after 104 days of treatment. Daily supplements of 1 × 10 6 IU vitamin A caused a linear decrease in PC concentration of 0.13-0.20 µg/ml per day for about 30 days. In Experiments 1 and 2, this represented a reduction of about 40-50% in PC concentration, equivalent to a decrease of 4.2-6.4 µg/ml, but in Experiment 3 where steers were fed a low carotenoid diet the decrease was only 0.8-1.0 µg/ml. PC concentrations in Experiments 2 and 3 were not affected by either the dose of vitamin A or the decline in pasture carotenoid concentration over the duration of the experiments. Vitamin A supplementation reduced the liver P-carotene concentration by 40-48%, and increased the retinol concentration. Subcutaneous fat colour and carotenoid concentration were not affected by vitamin A supplements in any experiment, possibly because PC concentration was still too high in Experiment 1 (5-7 µg/ml), and because the PC concentration was already low in Experiment 3 (under 2 µg/ml). These experiments suggest that for vitamin A to be effective in reducing fat colour, the initial PC concentration may need to be less than 6-7 µg/ml.