The relative intake of three Merino strains under different grazing regimes estimated using alkane technology

M.A. Friend, G.E. Robards, A.R. Lindsay, S.C. Champion

Department of Wool and Animal Science, University of New South Wales, Sydney NSW 2052, Australia

Proceedings of the New Zealand Society of Animal Production. 1995, 55: 127-129

Ninety 1991 drop Merino wethers, thirty from each of fine, medium and strong wool strains were randomly allocated on the basis of stratified live weight within strains to one of three treatment groups. The first treatment involved grazing ample good quality natural or irrigated pasture (H) throughout the experiment so that the sheep remained in good to excellent condition throughout. The second involved grazing restricted amounts of pool quality nature pasture (L) throughout the experiment so that the sheep remained in backward store condition. As a control, a third group (C) grazed natural pasture such that the sheep subject to seasonal variations in pasture quality and quantity and their condition varied from store to forward store throughout the experiment.

Intake was estimated on two occasions; in February 1994, and July 1994, by dosing with controlled-release alkane capsules. Pasture samples were taken at these times based on observation of sheep grazing patterns. However, later analysis showed that the pattern of alkanes in the collected herbage was different to the alkane pattern in faecal samples, indicating that the herbage samples were not truly representative of the herbage consumed by the sheep, particularly at the summer sampling.

Actual intake (AI) (expressed as kgOM/day ± SE), averaged over the three strains and three pasture types was estimated to be 1.54 ± 0.034 in February and 1.52 ± 0.037 in July; a non-significant difference. The average AI of group L (1.61 ± 0.037) was significantly higher than either group H (1.55 ± 0.033) or C (1.42 ± 0.032). No significant difference in AI existed between the strains. When intake was corrected for live weight (metabolic intake, MI = kgOM/day/kgLW0.75±SE), fine wool sheep had a significantly higher MI (0.088±0.0021) than either strong (0.082±0.0019) or medium wool (0.082±0.00190 sheep.

Keywords: NZSAPAB; alkanes; grazing intake; Merino sheep

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