EFFECTS OF CIMATEROL ON FINNISH-LANDRACE WETHER LAMBS .1. FEED CONVERSION EFFICIENCY, BODY-COMPOSITION AND SELECTED PLASMA-HORMONE AND METABOLITE CONCENTRATIONS

The effects of cimaterol on feed conversion efficiency, body compositi on, nitrogen retention and plasma concentrations of selected plasma ho rmones and metabolites in pure-bred Finnish-Landrace castrated male la mbs were examined. Lambs (initial bodyweight (BW) = 26.3 kg; n = 12/tr eatment) were individually offered a pelleted concentrate diet ad libi tum which contained either 0 or 10 ppm cimaterol. An additional group (n = 6) was slaughtered at the beginning of the study. Half of each tr eatment group was slaughtered after 36 days of treatment and the remai nder after 64 days. Full carcass dissection was carried out only on la mbs slaughtered after 64 days of cimaterol treatment. Nitrogen retenti on and ration digestibility were measured between days 20 and 36, whil e blood samples were collected once/day periodically, and intensively on day 56. Dietary inclusion of cimaterol increased (P < 0.05) BW gain and feed conversion efficiency (whether measured for 36 or 64 days), decreased (P < 0.05) internal body fat and dissectible carcass fat dep osition and increased (P < 0.05) carcass weight and lean meat depositi on in the carcass. Both absolute nitrogen retention and nitrogen reten tion as a proportion of absorbed nitrogen were higher (P < 0.05) in la mbs treated with cimaterol. Plasma concentrations of urea and insulin tended to be lower and creatinine and non-esterified fatty acids highe r in samples collected on a periodic basis during the study, but there were day of experiment by cimaterol interactions for these variables. Mean growth hormone and insulin concentrations and the frequency of g rowth hormone pulses, measured on day 56 were lower in cimaterol-treat ed lambs. It is concluded that the measured repartitioning effects of cimaterol were within the range of effects observed for other breeds o f sheep, but that its effects on growth and growth hormone parameters appear to be peculiar to this breed of sheep.