Effects of contrasting photoperiods and temperatures on performance traits of confinement-reared ewe lambs.

The effects of contrasting photoperiods (16L:8D vs 8L:16D) and ambient temperatures (5 C vs 18 C vs 31 C) on performance traits of ewe lambs have been evaluated. Seventy-two lambs were paired and allotted to one of six treatment groups in a 2 x 3 factorial experiment. The lambs were fed a pelleted diet ad libitum. throughout the 14-wk study (i.e., as lambs progressed from 12 to 26 wk of age). Analysis of performance and carcass data showed that both photoperiod and temperature affected growth rate (P less than .01), feed intake (P less than .01), final weight (P less than .01) and carcass weight (P less than .01). Although feed efficiency tended to be greater for lambs exposed to the 16L:8D photoperiod, this characteristic was not affected significantly. An interaction between photoperiod and temperature was not observed for growth rate, final weight or carcass weight. Final weight and carcass weight for lambs in the six treatment groups were: 52.5 and 27.7 kg for 16L:8D, 5 C; 49.2 and 25.8 kg for 8L:16D, 5 C; 48.1 and 25.3 kg for 16L:8D, 18 C; 45.2 and 23.5 kg for 8L:16D, 18 C; 42.0 and 21.1 kg for 16L:8D, 31 C and 36.0 and 17.4 kg for 8L:16D, 31 C. Carcass merit, including quality and yield, was not affected (P greater than .05) by treatment. Whereas serum prolactin concentrations were elevated in lambs exposed to the 16L:8D photoperiod, an interaction (P less than .01) between photoperiod and temperature was found. Wool growth was similar for lambs exposed to 16L:8D and 8L:16D photoperiods, but was reduced (P less than .05) by exposure to increasing environmental temperatures. These results suggest that environmental temperature and photoperiod independently contribute to the growth and performance of confinement-reared ewe lambs and that each of these variables can be adjusted to optimize the efficiency of lamb production.