Nitrogen and sulfur metabolism and plasma thyroid hormone concentrations in fleeceweight-selected and control Romney sheep at two ambient temperatures
1994
Sun, Y.X. | Blair, H.T. | McCutcheon, S.N. (Massey Univ., Palmerston North (New Zealand). Dept. of Animal Science) | Lee, J. | Harris, P.M. | Sinclair, B.R. | Shelton, I.D. (AgResearch, Palmerston North (New Zealand). Grasslands Research Centre)
Under a constant photoperiod, intake and faecal output of dry matter and N were lower at 25 deg. C than at 6 deg. C, but there was no effect of ambient temperature on digestibility of either dry matter or N. Nitrogen balance was lower at 25 deg. C than at 6 deg. C, but none of the parameters relating to nitrogen balance was influenced by selection line. There were also no effects of ambient temperature or selection line on clearance rates of urea or creatinine. There were no consistent interactions between the effects of selection line and ambient temperature on plasma concentration of urea, creatinine, thyroxine and triiodothyronine. There were no consistent effects of selection line, or interactions of selection line with ambient temperature, on S and sulfate balances, concentrations of leucine, cyst(e)ine and glutathione in whole blood or on irreversible loss rates of leucine and cyst(e)ine. It was concluded that none of the metabolic measurements explained previous inconsistencies observed in metabolic differences between sheep from lines divergently selected on the basis of fleeceweight.
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