EFFECTS OF REPEATED CYCLES OF FEED-INTAKE SHIFTS ON GROWTH, FEED-EFFICIENCY AND ENDOCRINE PROFILES OF WETHER LAMBS

Fifteen wether lambs (average BW 28.8 +/- 1.8 kg) were used in a 128-d trial to examine effects of cyclical feeding changes on growth, feed efficiency and endocrine profiles. Control lambs were fed a 40% concentrate diet (40C) at 1.5 X NE(m) requirement during period 1 (64 d). Another group (1X/2X) was fed 40C at 1 and 2 X NE(m) in 4-d intervals during period 1; a third group (70/10) was fed 70% and 10% concentrate diets in 4-d intervals during period 1. To achieve dry matter intake comparable to controls, 70/10 lambs were fed at 1. 79 (70C) and 1.21 (10C) x NE(m). All lambs were placed on the control diet during period 2 (32 d) and increased to 2X maintenance during period 3 (32 d). During period 2, ADG and gain/feed of control lambs tended to be greater (P<0.10) than for lambs fed alternating treatments. Liver weight as a percentage of hot carcass weight was greater (P<0.05) for controls than for lambs fed alternating treatments. Hot carcass weight (P=0.07) and dressing percentage (P=0.09) tended to be greater for the 70/10 treatment than for controls. The 1X/2X treatment lowered (P<0.05) serum cholesterol compared with other groups on d 65, but not on d 0 or 129. Smaller liver weight per unit of hot carcass weight for lambs in the 1X/2X and 70/10 treatments suggests a possible reduction of maintenance requirements.