Hormonal control of the breeding activity in Churra Galega Bragançana ewes

This study aimed to evaluate the efficiency of different hormonal treatments to control the breeding activity in Churra Galega Bragançana (CGB) ewes. Material and Methods This experiment took place at Bragança (latitude 41° 49' N, longitude 6° 40' W, altitude 720 meters) and involved 94 adult CGB ewes. At March 9, 25 ewes received a melatonin implant (18 mg) – Melatonin. Forty-five days later a vaginal sponge with 20 mg of FGA was inserted in all ewes. FGA treatment lasted for 12 days. Twenty-four hours before sponge removal 32 non-melatonin treated ewes were injected with 500 UI of eCG (D-1). At sponge removal melatonin ewes and all remaining non-melatonin ewes (n = 37; Control) were injected with 500 UI of eCG. Heat detection was performed by 5 intact rams provided with harness markers. Ovarian activity was assessed by progesterone (P4) plasmatic levels 2 weeks before melatonin and FGA treatments and for 5 days after sponge removal. Pregnancy diagnosis was performed 41 days after sponge withdraws by ultrasonography. Results In the fortnight prior to melatonin treatment 74.5% of all ewes had high plasmatic levels of P4 (> 0.5 ng/ml). In the previous 2 weeks to FGA treatment 80.0% of Melatonin and 56.5% of non-melatonin treated ewes had high levels of P4 (Chi-square = 13.2; P≤0.001). About 76.6% of all ewes showed heat. Around 83.3% were Control and 76.0% Melatonin ewes (Chi-square = 2.0; P>0.05). Time at eCG injection affected the percentage of ewes in heat: Control (83.3%) vs. D-1 (71.9%) ewes (Chi-square = 4.2; P≤0.05). Over 98.6% of all ewes had high levels of P4, 1 to 5 days post sponge withdraws. About 97.3% were Control and 100.0% Melatonin ewes (Chi-square = 3.0; P>0.05). Time at eCG injection had no influence in the percentage of ewes with high levels of P4: Control (97.3%) vs. D-1 (100.0%) ewes (Chi-square = 3.0; P>0.05). Forty-one days after sponge removal, only 41.5% of all ewes were pregnant. About 45.9% were Control and 48.0% Melatonin ewes (Chi-square = 0.1; P>0.05). Fertility rate was higher in Control (45.9%) than in D-1 (31.3%) ewes (Chi-square = 4.8; P≤0.05). Conclusions – Initially 74.5% of all ewes presented high plasmatic levels of P4 (> 0.5 ng/ml). – Melatonin enhanced the percentage of ewes with high levels of P4 prior to FGA treatment. – Melatonin had no effect in post FGA near breeding activity. – Preceding in 24 hours the eCG administration had negative impact in sexual behavior and fertility rate. – Fertility rates were fairly poor