SEMEN TRAITS AND METABOLIC AND GONADOTROPIC HORMONE PROFILES IN RAM LAMBS TREATED WITH GLUCOSE

Two experiments were conducted to examine reproductive and endocrine r esponses of ram lambs to exogenous glucose. In Experiment 1, three ram lambs (6 mo of age) received 100 ml ip of saline (0.9%) daily and thr ee animals received 50 g glucose (100 ml 50% dextrose) daily for 18 d. In Experiment 2, ten lambs (5 per group) were treated similarly for 1 0 d. Serum samples were collected intensively before and after GnRH tr eatment on the last day of both experiments. After 15 d of glucose tre atment in Experiment 1, treated rams weighed 58 kg compared with 68 kg for the controls (P=0.08). A similar numerical trend was observed in Experiment 2, suggesting that intraperitoneal glucose decreases feed i ntake. In both experiments, 50 g of glucose induced a rapid elevation in serum glucose to greater than 120 mg/dl compared with 70 to 80 mg/d l for the controls (P<0.05). Serum insulin rose to over 6 ng/ml in bot h trials in lambs receiving glucose compared with values of about 2 ng /ml for the controls (P<0.01). Serum growth hormone was not altered (P >0.10) by glucose in either experiment and IGF-1 was similar (P>0.20) between groups in Experiment 2. Although serum concentrations of prola ctin tended (P=0.14) to be reduced by glucose treatment (64 +/- 21 ng/ ml) compared with that of the controls (120 +/- 21 ng/ml) in Experimen t 1, the opposite trend (P=0.20) was observed in Experiment 2. Serum t hyroxine was elevated (P=0.08) in glucose-treated rams compared with t hat in controls in Experiment 2 but triiodothyronine concentrations we re similar (P>0.80) between groups. in Experiment 1, area under the cu rve (AUC) for LH after a GnRH challenge tended (P=0.14) to be greater in glucose-treated (1,351 units) than in control (999 +/- 139 units) a nimals. The AUC for FSH (Experiment 1) did not differ (P=0.30) between groups. The LH AUC in Experiment 2 was about 2,500 units for both gro ups (P=0.80). The AUC for testosterone in Experiment 1, was 5,452 and 2,597 (+/- 1051) units for rams treated with 0 and 50 g glucose/d (P=0 .13), but testosterone AUC in Experiment 2 was similar between groups (P>0.70). No effect of exogenous glucose was evident in either experim ent for semen traits. Results suggest that 50 g ip glucose daily for 1 0 or 18 d induced large increases in serum insulin but other metabolic and reproductive hormones were not greatly influenced. (C) 1997 by El sevier Science Inc.