Abstract:
This study tested whether the effects of nutrition on gonadotrophin secretionand testicular growth in mature rams are due to increases in the supply ofglucose, fatty acids (FA) or amino acids. Responses to protein (casein) andglucose, alone or in combination, were compared with responses to lupin grainand responses to a combination of protein, glucose and FA (acetate, propionateand vegetable oil). Glucose and casein were infused intra-abomasally whereaslupins and FA were added to the diet. Lupin feeding decreased blood growthhormone (GH) concentrations, but increased pulsatile luteinizing hormone (LH)secretion and increased the concentrations of follicle-stimulating hormone(FSH), prolactin, glucose and insulin. These effects were associated withtesticular growth. Glucose or casein increased insulin concentrations anddecreased GH concentrations, but did not affect gonadotrophins or testiculargrowth. There was no synergism between casein and glucose. Responses elicitedby adding FA to the glucose+casein treatment were similar to thoseobserved with lupins. In conclusion, the reproductive axis does not seem to beclosely linked with dietary intakes of amino acids or with circulatingconcentrations of glucose, insulin or GH. However, the energetic components ofthe diet, particularly the fatty acids, appear to play a key role in thereproductive responses to changes in nutrition.