EFFECTS OF SEX AND LIVEWEIGHT ON FEEDING-BEHAVIOR OF CROSSBRED WEANERLAMBS RECEIVING OATEN GRAIN SUPPLEMENT ON LUCERNE PASTURE

The response of 96 weaner, crossbred lambs to oat grain on lucerne pas ture was examined where they were fed in single sex ewe or cryptorchid groups or in mixed sex groups. All groups had a similar profile of we ights (range 16-34 kg). Intakes of lucerne and air dry oats fed daily in troughs at 300 g/head and later at 200 g/head were estimated at int ervals over 4 weeks commencing 4 weeks after weaning. Overall mean (+/ - s.e.) growth rate (cryptorchid 144 +/- 6 v. female 115 +/- 7 g/day) of cryptorchid or female lambs was not significantly different when fe d as a single sex group or combined. Intake of supplement when offered up to 300 g, was not affected by sex of lamb but was significantly (P <0.001) affected by liveweight at the start of the experiment. Mean in itial liveweight of lambs that consistently ate least supplement was 2 0.0 kg compared with 26.1 kg for the remainder and they were 12 days y ounger than the remainder. The behaviour of some of these lighter lamb s at feeding suggested that a form of dominance was operating. Cryptor chid lambs ate more lucerne pasture than female lambs at the same live weight (746 v. 586 g dry matter at the middle, and 904 v. 759 g dry ma tter at the end of the experiment). We conclude that our weaner crossb red lambs did not need to be segregated on sex for supplementary feedi ng on pasture. However, many of the lightest lambs were shy feeders an d could benefit from segregation. Shy feeders represented 11% of this flock.