Published online by Cambridge University Press: 02 September 2010
Thirty-six British Friesian castrated male cattle (steers) were included in an experiment to measure the response in live-weight gain and body composition to feeding barley-based diets containing increasing levels of formaldehyde-treated soya bean meal. The response was measured between 100 kg and 350 kg or 450 kg live weight. The basal diet of pelleted whole barley and 10% ground oat straw contained 16·6g to 38·5 g nitrogen per kg dry matter. There were no overall differences in live-weight gain or in feed intake. Between 100 kg and 250 kg live weight, live-weight gain increased significantly from 1 08 to 1·24 kg/day when the lowest and highest nitrogen diets respectively were fed (P<0·05). Animals given the highest nitrogen diets also consumed significantly more feed (P<0·05). Conversely, in the subsequent growth period between 250kg and 350kg live weight, live-weight gain decreased from 109 to 0·89 kg/day when the highest nitrogen diet was fed. There were no significant differences in feed intake.
Groups of four animals per treatment were slaughtered at 365 kg and 465 kg fasted live weight. When animals were fed 23·7 g nitrogen per kg dry matter and slaughtered at 365 kg fasted live weight there was significantly more omental fat (P<0·05) and the fat depth at the 12th rib was greater than in animals fed the higher levels of nitrogen. The differences in omental fat weight between the 23·7 g nitrogen and 16·6g nitrogen per kg dry matter diets were not significant. The proportion of crude protein (nitrogen × 6·25) in the boneless 9-10-1 lth rib of animals fed 23·7 g nitrogen per kg dry matter was the lowest of all diets and significantly less than the two highest nitrogen diets (P<0·05). When similar animals were slaughtered at 465kg there was a non-significant trend for omental fat weight and fat depth at the 12th rib to decrease as the nitrogen content of the diet increased.