Abstract :
Seasonal weight loss (SWL) is a serious constraint to ruminant production in tropical and
Mediterranean climates. SWL is controlled using supplementation, costly and difficult to
implement in extensive production systems; or alternatively, using breeds with a natural
adaptation to tropical climates, namely hair and fat tailed sheep. Albeit a 15-year presence in
Australia, little is known on how Dorper and Damara sheep compared to the most widely
used sheep breed in Australia, the Australian Merino. In this trial, the responses of the
Damara, Dorper and Merino breeds to nutritional stress were compared during a 42-day
trial. Seventy-two ram lambs, 24 from each breed, were randomly allocated to a growth
(gaining 100 g/day) or a restricted diet (losing 100 g/day). Animals were weighed twice
weekly. Individual rations were calculated from bodyweight, with animals being confined
to consume their ration daily. The breeds were compared for bodyweight changes as a
percentage of their initial weight for three periods (Days 0–10, 10–21 and 21–42). The
significant differences between breeds in the percentage growth rates were that the Damara
breed lost more weight than the other breeds on the restricted diet from Days 10 to 21 and
gained less weight on the growth diet during Days 21–42. For all other periods the weights
of Damara, Dorper and Merino breeds were not significantly different. By Day 24 all breeds
had stopped losing weight on the restricted diet. We conclude that under confined feeding
and considering growth parameters, the three breeds performed similarly.
