The effects of a moderate level of undernutrition on the release of luteinizing hormone (LH) at oestrus and after luteinizing hormone releasing hormone (LHRH) treatment was investigated. Plasma levels of glucose, non-esterified fatty acids (NEFA), cortisol and prolactin were also investigated.
During the early breeding season 10 mature ewes were placed on either a maintenance (M) or a restricted (R) diet. After 50 days of dietary treatment their oestrous cycles were synchronized and blood samples were taken over the oestrous period. Eight days later LHRH was administered and blood samples were taken for the following 6 h.
After 50 days of treatment mean body- weights were 66 (s.e. 4) and 53 (s.e. 3) kg, and mean body condition scores were 3·5 and 2·0 for the M and R groups respectively. The pre-ovulatory and LHRHinduced LH peaks were similar in both groups as were the prolactin profiles. However, plasma NEFA levels were elevated and glucose and cortisol levels were reduced in the restricted group.
It is concluded that the reduction in energy intake achieved in this experiment, although sufficient to cause significant metabolic changes had no effect on the release of LH either at oestrus or after LHRH treatment.