Effects of cimaterol on Finnish-Landrace wether lambs. 1. Feed conversion efficiency, body composition and selected plasma hormone and metabolite concentrations

Abstract

The effects of cimaterol on feed conversion efficiency, body composition, nitrogen retention and plasma concentrations of selected plasma hormones and metabolites in pure-bred Finnish-Landrace castrated male lambs were examined. Lambs (initial bodyweight (BW) = 26.3 kg; n = 12/treatment) were individually offered a pelleted concentrate diet ad libitum which contained either 0 or 10 ppm cimaterol. An additional group (n = 6) was slaughtered at the beginning of the study. Half of each treatment group was slaughtered after 36 days of treatment and the remainder after 64 days. Full carcass dissection was carried out only on lambs slaughtered after 64 days of cimaterol treatment. Nitrogen retention and ration digestibility were measured between days 20 and 36, while 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 deposition and increased (P < 0.05) carcass weight and lean meat deposition in the carcass. Both absolute nitrogen retention and nitrogen retention as a proportion of absorbed nitrogen were higher (P < 0.05) in lambs treated with cimaterol. Plasma concentrations of urea and insulin tended to be lower and creatinine and non-esterified fatty acids higher 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 growth hormone pulses, measured on day 56 were lower in cimaterol-treated lambs. It is concluded that the measured repartitioning effects of cimaterol were within the range of effects observed for other breeds of sheep, but that its effects on growth and growth hormone parameters appear to be peculiar to this breed of sheep.