THE EFFECT OF SPACE ALLOWANCE AND SEX ON BLOOD CATECHOLAMINES AND CORTISOL, FEED CONSUMPTION AND AVERAGE DAILY GAIN IN GROWING LAMBS

The effect of space allowance (0.37, 0.62 and 0.99 m2 per lamb) and sex (ewe and ram) on plasma norepinephrine, epinephrine and cortisol concentrations, feed consumption and average daily gain in 11-week-old Dorset lambs weighing 21.7 kg (ewe) and 25.7 kg (ram) was examined. Lambs raised in a common pen were trucked 2 km to the experimental site where they were housed in elevated metal pens in a barn and fed a 16% crude protein (CP) pelleted diet ad libitum for 56 days. Jugular blood samples were collected 2 days prior to shipping and 4, 8, 16, 24, 36 and 48 h after arrival at the site, and once per week thereafter. There was no space allowance by sex interactions on feed intake, average daily gain or feed efficiency. The ram lambs consumed more feed and gained more weight than the ewe lambs (P < 0.05); sex had no effect on the feed-to-gain ratio. Reducing the space allowance from 0.99 to 0.62 m2 per lamb reduced feed intake and average daily gain (P < 0.05). Feed efficiency decreased when the floor space was reduced from 0.99 to 0. 37 m2 per lamb. There was no effect of pen size on plasma epinephrine, norepinephrine or cortisol concentrations at a particular time point, nor were there any differences within treatment over time.