A comparison of liveweight gain of two groups of weaners of different entry liveweight in an ad libitum fodder beet feeding system for finishing beef cattle

Abstract

The use of fodder beet as the primary diet for finishing beef cattle is a recent New Zealand innovation. A system using ad libitum grazed fodder beet through autumn and winter to finish spring-born steers between 12 and 18 months old was developed. Fodder beet is a high energy yet comparatively low protein content feed, and the fodder beet system requires high liveweight gains on the crop and an early slaughter age for cost effective production. Lower liveweight weaners have a greater protein requirement for optimal weight gain, and the threshold entry liveweight for satisfactory performance in this feeding system was not yet established. The objective of this study was to quantify the effect of the entry liveweight of weaners on liveweight gain in the fodder beet feeding system. A group of 392 rising 1-year-old beef cattle fed using this system were divided at entry into three groups on unfasted liveweight (kg): A, 290-370; B, 240-260; and the remaining animals. The heaviest (group A: steer n=67, 316 ±2.7 kg; heifer n=45, 312 ±2.5 kg) and lightest (group B: steer n=77, 249 ±0.7 kg; heifer n=19, 251 ±1.0 kg) groups were then treated identically on ad libitum fodder beet to compare liveweight gain across 130 days on crop. The mean liveweight daily gain (kg/ day) for group A was significantly greater than group B, and greater for the steers compared to heifers in group A (0.98 and 0.85), but not in group B (0.82 and 0.81). Mean liveweight gain as a proportion of entry liveweight was greater in group B, and greater in steers. Both mean daily liveweight gain and mean liveweight gain as a proportion of entry liveweight were positively correlated with entry liveweight, but the R2 of both was low (0.14 and 0.05, respectively). Mean daily liveweight gain values of this magnitude are greater than those previously reported for alternative winter crops, and satisfactory for finishing beef cattle in this system. This study suggests the use of beef cattle above 240 kg liveweight as weaners in this fodder beet feeding system, both steers and heifers, is satisfactory for achieving acceptable slaughter liveweight before 18 months old. Keywords: beef production, fodder beet, finishing cattle, ad libitum fodder beet intakes.