Effects of space allowance on the grazing behaviour and spacing of sheep

In each of two experiments, four groups of 10 female Scottish Blackface sheep grazed for 2 weeks at each of four space allowances, according to a Greco-Latin Square design. Space allowances were 80, 100, 133 or 200 m(2) per head in Experiment 1 and 50, 67, 100 or 200 m2 per head in Experiment 2. Confounding of space allowance and grazing pressure was avoided by the use of a rotational grazing system. Mean distances between sheep were measured from video recordings and distances expected by chance were calculated from simulations in which sheep were located within plot areas using randomly selected co-ordinates. Total time spent grazing was higher at 200 m(2) per head and less at 50 m(2) per head than at other space allowances, but there was no evidence for an effect of space allowance on herbage intake or digestibility, biting rate or the proportion of grazing time spent in ingestive behaviour. At space allowances from 50 to 133 m(2) per head, there were no significant differences between mean observed inter-animal distances and those expected by chance, but observed values were lower than expected values at 200 m(2) per head. At all space allowances, mean observed distances between sheep and their nearest neighbours were lower than distances expected by chance. The results show that, on relatively high quality, homogeneous vegetation, female Scottish Blackface sheep will graze at space allowances between 50 and 200 m(2) per animal with no evidence of repulsion between individuals and with no clear evidence of grouping until space allowance reaches 200 m(2). It is concluded that the relationship between grazing time and space allowance may reflect the extra activity required to maintain group cohesion as space allowance increases. (C) 2000 Elsevier Science B.V. All rights reserved.