Herbage intake and liveweight gain of bulls and steers continuously stocked at fixed sward heights during autumn and spring

Abstract

Twu experiments were conducted to examine the relationship between sward surface height, herbage intake and liveweight gain in beef cattle grazed on pasture. In Experiment 1, two 'animal types" (18 Charolais x Angus steers and 18 Friesian bulls) were continuously grazed for 22 days during the late autumn on replicated swards maintained at sward surface heights of 6, 10 and 15 cm. Herbage intakes, assessed from the faecal concentration of chromium delivered from an intraruminal controlled release capsule and the in vitro digestibility of hand-plucked herbage samples, were curvilinearly related to sward height {r = 0-76. F<0-Ol). Average liveweight gains were 002, 0-61 and 1-31 kg d'^ (P<0-05) and increased linearly (r = 0'84. P < 0-001) with sward height. The maintenance organic matter intakes of the steers and bulls, with initial mean (± s.e.) live weights of 225 ± 15 kg and 172 ± 15 kg respectively, were estimated to be 3-6 and 3-5 kg d^' respectively. In Experiment 2 (spring) 36 cattle, including 35 of those used in Experiment 1, were reallocated to sward heights of 5, 10 and 15 cm using the same design as for Experiment 1. Average liveweight gains were

Herbage intake, liveweight gain, and grazing behaviour of Friesian, Piedmontese × Friesian, and Belgian Blue × Friesian bulls

“…Herbage aMI of around 10 kg/head per day measured in this experiment for 430 kg bulls is similar to the 8.7 kg OM/day reported by Morris et al (1993) for 288 kg Friesian bulls growing at 1.67 kg/day, and the 8.2 kg OM/day recorded by 439 kg Friesian steers growing at 1.51 kg/day in the trial of Zoby & Holmes (1983). It was not possible to establish whether the use of hand-plucked samples of herbage, to represent the feed apparently consumed, introduced any bias in the estimates of herbage intake for the genotypes.…”

“…The herbage intake data suggest that all genotypes consumed similar quantities of DM and DOMI under grazing conditions (8-10 cm SSH) which should have allowed ad libitum intakes (Morris et al 1993). Heavily muscled genotypes should therefore have reflected a greater efficiency of pasture conversion to meat gain.…”

“…The bulked material was ashed over-night at 550°C and the ash was assayed for Cr using the procedure described by Parker et al (1989). The release rate of chromic oxide from the CRC, of 1172 mg Cr/day, and an estimate of the recovery of Cr in the faeces (95%), was based on the previous work of Nasution et al (1991) and Morris et al (1993).…”

“…Each bull was dosed with a single chromium (Cr) controlled release capsule (CRC, Captec New Zealand Limited) on Day O. Faecal collections from each bull, by observing bulls defaecating (Morris et al 1993), were made between Day 8 and Day 15. Eight animals regurgitated their capsules and their faecal samples were discarded from the analysis.…”

Liveweight gain, herbage intake, and ingestive behaviour in Compudose®‐treated and untreated steers at pasture

“…This reflects the fact that herbage allowances were at the maximum of the LWG/ allowance asymptote relationship (Reardon 1977;Marsh 1979;Taylor & Scales 1985;Reid 1986) and were designed to allow treated animals to exhibit maximum LWG. The higher allowance in the autumn (5570 kg DM/ha) would also have allowed the animals to exhibit maximum LWG as several researchers have reported that higher pasture allowances are required in autumn than in spring for maximum growth rates of beef cattle (Reid 1986;Morris et al 1993a). Pasture quality, as measured by in vitro digestibility, was average for the type of pasture and, like herbage allowance, would have been unlikely to limit the ability of Compudose animals to express a response in voluntary intake.…”