Abstract:
Proc. Aust. Sot. Arzim. Prod. 1994 Vol. 20 COMPARISON OF THE EFFECT OF LUPIN SUPPLEMENTATION DURING THE NONBREEDING SEASON ON REPRODUCTIVE FUNCTION IN SUFFOLK AND MERINO RAMS MARIA J. HOTZLLA , GRAEME B. MARTINAB and JAMES S. FISHER . A AFaculty of Agriculture, The University of Western Australia, Nedlands, W.A. 6009 BCSIRO Division of Animal Production, Private Bag, PO Wembley, W.A. 6014 Merino rams respond to changes in nutrition with changes in testicular size, pituitary and testicular hormones, and these changes are associated with changes in sperm production (Oldham et al. 1978; Martin et al. 1994). The effect of nutrition on the reproductive function of the ram has been thoroughly investigated only in Merino rams, so this experiment was designed to test whether Suffolk rams show similar responses. In the non-breeding season (August), 12 mature Merino and 12 mature Suffolk rams were fed to maintain liveweight or were supplemented with 1.5 kg lupins/day for 6 weeks. Liveweight and scrotal circumference were measured weekly. On Day 0 (the day before supplementation began), 12 and 35, blood was sampled every 20 minutes for 24 hours and assayed for luteinising hormone (LH), folliclestimulating hormone (FSH) and testosterone. Lupin supplementation increased liveweight (P c 0.001) and this effect was independent of breed (Figure 1). In Merino rams fed lupins, there was an increase in scrotal circumference (P c O.OOl), LH pulse frequency (P c 0.05) and the concentrations of testosterone and FSH (P < 0.05). In the Suffolk rams, there was no significant effect of diet on any of the hormonal variables or on scrotal circumference (Figure 1). Figure 1. Change in liveweight (a) and scrotal circumference (b) in Suffolk (closed symbols) and Merino (open symbols) rams fed a maintenance diet (M) or the maintenance diet supplemented with lupin grain (L) We conclude that lupin supplementation does not affect testicular g Growth in Suffolk rams during the non-breeding season. This differs from Merino rams, which show reproductive responses at all times of the year (Murray et al. 1991). Compared with Merino rams, Suffolk rams show greater variation in plasma concentrations of gonadotrophins and testosterone in response to changing photoperiod, and are maximally suppressed as daylength increases (D' Occhio et al. 1984). They may therefore respond to enhanced nutrition during the breeding season, when they are not photoperiodically inhibited. Maria Hotzel was supported by a scholarship from CNPq, Brazil. D' OCCHIO, M.J., SCHANBACHER, B.D. and KINDER, J.E. (1984). BioZ. Reprod. 30: 1039-54. MARTIN, G.B., TJONDRONEGORO, S. and BLACKBERRY, M. (1994). J. Reprod. Fertil. (in press). MURRAY, P.J., ROWE, J.B. and PETHICK, D.W. (1991)Aust. J. Exp. Agric. 31: 753-6. OLDHAM, C.M., ADAMS, N.R., GHERARDI, P.B., LINDSAY, D.R. and MACKINTOSH, J.B. (1978). Amt. J. Agric. Res. 29: 173-9. 425
