Cereal straw in diets for beef cattle: effects of pattern of growth and diet formulation on growth rate and food conversion efficiency

Abstract

AbstractFive groups of Hereford × Friesian steers (initial weight 340 kg) were given either a diet of rolled barley and ammonia-treated barley straw (AS) in the ratio 60: 40 ad libitum (ASB) to support continuous growth, or were offered over a 143-day period diets of either (i) AS alone (diet AS) (ii) untreated straw (US) plus cassava (diet USC) (iii) US plus grass silage (diet USS) or US plus fish meal (0·27 kg fish meal per day) (diet USF). Both the AS and US were offered ad libitum and allowances of cassava and silage adjusted to allow the USC and USS steers to match the growth of AS steers. Steers i n the restricted groups (AS, USC, USS and USF) were then given freshly cut grass ad libitum until they reached slaughter weight; some steers required additional hay and barley to reach slaughter weight. Steers in group ASB consumed 7·4 kg dry matter (DM), gained 1·16 kg live weight per day taking 112 days to achieve the 455 kg slaughter weight. AS, USC and USS animals maintained body weight over the restricted period, whereas the USF group tended to lose weight and daily DM intakes were 4·63 kg AS (AS steers); 3·81 kg US plus 0·95 kg cassava (USC steers); 0·86 kg US plus 3·31 kg silage (USS steers); 3·5 kg US plus 0·27 kg fish meal (USF steers). When grass or grass followed by barley plus hay was given the live-weight gains of the previously restricted cattle did not differ (mean 1·0 (s.e. 0·10) kg/day). AS provided proportionately 0·30 of the metabolizable energy used to produce growth rates in excess of 10 kg/day or if given as the sole food maintained cattle without supplementation.