Effect of fasting on luteal function, leptin and steroids concentration during oestrous cycle of the goat in natural photo-status

The effect of fasting during oestrous cycle on the occurrence of oestrous and concentration of leptin and steroid hormones was investigated in goats. Sixteen Ardi goats of 10–12 month of age were split into two groups (control and fasting). Oestrous was synchronized with intravaginal progesterone sponges and detected 24 h after sponge removal. Blood samples were collected at the days 5, 10, 15 of each cycle. Fasting of mature goats twice for 4 days starting on day 10 of two successive oestrous cycles inhibited oestrous behaviour and resulted in reduced concentration of leptin, progesterone and testosterone with different timing. Day 5 of the second cycle showed significant decrease in the plasma level of leptin (1.6 ± 0.15 ng/ml) and progesterone (1.6 ± 0.1 ng/ml) as compared to control group (3.2 ± 0.15 ng/ml and 4.1 ± 0.2 ng/ml, respectively). Testosterone started to decrease from day 10 of the second cycle (35.0 ± 12.0 pg/ml) as compared to control group (65.0 ± 15.0 pg/ml); the decrease in this hormone was significant in day 15 of the second cycle (65.0 ± 16.0 pg/ml) as compared to the control (320.0 ± 50.0 pg/ml). These data suggest that fasting-induced inadequate corpus luteum function, hence, lowering progesterone plasma level may partly be more leptin-dependent than the following decrease in plasma level of testosterone.