GROWTH AND CARCASS COMPOSITION OF RAM LAMBS TREATED WITH CLONIDINE
Average daily gain (ADG), feed efficiency and carcass composition were studied in ram lambs treated with a continuously administered low or high dose of clonidine. Groups of 10 Suffolk lambs and 10 Strain 2 lambs (a synthetic Finnish Landrace, Suffolk, Shropshire line) were implanted at 28-d intervals with Alzet® osmotic pumps containing either sterile H2O (control), a low dose of clonidine (5–8 μg kg−1 d−1; D) or a fivefold higher dose of clonidine (24–41 μg kg−1 d−1; 5D). The effect of clonidine on average daily gain was dose-, breed- and time-dependent. Growth response was only observed during the latter part of the trial. At this time the effects of both the low and high doses of clonidine were positive in Suffolk lambs whereas in Strain 2 lambs the effects were negative. Clonidine caused a reduction in dressing percent and kidney fat as a percentage of slaughter weight in a dose-related manner with the effect more pronounced in the fatter Strain 2 lambs. Percentage fat in the longissimus dorsi muscle of the 10th–12th rib section of lambs treated with the low dose of clonidine (3.42 ± 0.24) was greater than that of control lambs (2.55 ± 0.24) and lambs treated with the high dose of clonidine (2.52 ± 0.24). Key words: Clonidine, growth, carcass composition, lambs