The influence of nutrition on reproduction in the ewe 2. Effects of undernutrition on pituitary responsiveness to luteinizing hormone-releasing hormone stimulation

ABSTRACTTwo groups of ewes in good body condition at the start of the breeding season were given either sufficient feed to maintain their body weight or 500 g/kg of a maintenance ration such that they showed a continuous fall in body weight. On three separate occasions after introducing the nutritional regimens, all ewes were challenged on day 12 of the oestrous cycle with 150 μg luteinizing hormone-releasing hormone. Prolonged chronic undernutrition resulted in a significant increase in luteinizing hormone release in response to luteinizing hormone-releasing hormone injection (P < 0·05), whereas the mean pre-injection luteinizing hormone concentrations were significantly reduced by undernutrition (P < 0·01).