EFFECTS OF LOCOWEED (OXYTROPIS-SERICEA) ON GROWTH, REPRODUCTION, AND SERUM HORMONE PROFILES IN YOUNG RAMS

Sixteen ram lambs (5 mo old, average BW = 49 +/- 1.4 kg) received a co ntrol diet (50% concentrate, 13.1% CP) or a diet containing 7, 14, or 21% locoweed (LW, DM basis). Rams were housed in individual pens (2.5 x 3.5 m) in an enclosed facility (14 h light, 10 h dark) with free acc ess to feed and water. After 35 d of LW feeding, rams fed the 21% LW d iet ate 1.3 to 1.6 kg/d, whereas rams fed the other three diets ate 1. 6 to 2.0 kg/d. On d 35, BW (mean +/- SE) were 58.3, 57.2, 57.2, and 55 .4 (+/- 1.5 kg/d) for ram lambs receiving 0, 7, 14, and 21% LW, respec tively (P > .20). An inverse relationship for BW (P < .10) and gain (P = .04) was observed 1 mo after LW feeding ended relative to amount of LW in the diet. Serum alkaline phosphatase increased with increasing LW (P < .05), and thyroxine concentration was decreased(P < .05) by LW ingestion. On d 35, serum LH averaged 6.8, 9.9, 11.6, and 9.9 (+/- 1. 8) ng/mL (P = .56), whereas testosterone averaged 3.5, 2.6, 3.0, and 1 .6 (+/- .5) ng/mL (linear effect of LW, P = .05) over a 5-h period aft er GnRH injection (i.m., 50 mu g) in lambs fed 0, 7, 14, and 21% locow eed, respectively. Semen volume, sperm motility, sperm cell concentrat ion, and percentage of abnormal cells did not differ (P > .50) on d 35 . One month after the end of LW feeding, a linear (P = .06) decrease i n sperm motility and scrotal circumference was observed relative to pe rcentage of prior dietary LW. These data suggest that LW exerts advers e effects on the testes of young rams that may not be evident until se veral weeks after LW consumption ends.