Performance and heat tolerance of Awassi lambs as affected by early shearing

Abstract

Summary: Forty-two Awassi lambs, 21 males and 21 females, were used to investigate the effect of early shearing, before the hottest months, on their performance and heat tolerance as indicated by rectal temperature and respiration rate.Within each sex, half the number of lambs were sheared and the rest were left unshorn. All lambs were fed for 132 days, covering the hottest period of the year, on a concentrate mixture at the daily rate of 2% of their average live weight plus green roughage offered ad libitum. Rectal temperatures and respiration rates were recorded 1 day of each week on three occasions each day.Shorn lambs of both sexes had significantly (P < 0·01) higher values for body gain and final body weight than the unshorn ones. Average total digestible nutrients intake was slightly higher for shorn lambs. However, average dry-matter intake as a percentage of body weight was almost the same for shorn and unshorn lambs. Shorn lambs of both sexes were more efficient than the unshorn ones in converting food to body gain.Shorn lambs were more heat-tolerant than the unshorn ones as indicated by their significantly (P < 0·01) lower rectal temperature and respiration rate.