Pituitary responsiveness to GnRH in lambs undernourished during fetal life

A study was conducted to investigate the effect of undernutrition in utero on pituitary responsiveness to GnRH stimulation in lambs after birth. Thirty-four lambs were used which were born to ewes fed 110% of the energy maintenance plus two embryos requirements during pregnancy (control, C) or 90% of the maintenance with no additional allowances for embryo growth (restricted, R) from 30 day of pregnancy to lambing. A GnRH stimulation test was performed on all lambs at 55 days of age. erage energy consumed daily by each ewe in the R group was only the 60% of that consumed by the ewes in the C group. Following injection of GnRH, peak LH values were observed within 15 min in both groups. Animals in Group C (n = 19) showed a significantly greater LH response than animals in Group R (n = 15) at 15 min and at 30 min post-injection (43.3 vs. 33.9 and 39.0 vs. 32.2 ng ml−1, respectively). The significant treatment × time interaction found revealed that the rate of increase of LH concentration above the basal value within the first 15 min after GnRH administration was higher in C than in R lambs, while the rate of decrease from 30 to 120 min was lower in R than in C lambs. concluded that the timing as well as the magnitude of maternal undernutrition may be significant factors affecting the subsequent reproductive potential of the progeny in sheep by reducing pituitary activity.