The present study was conducted to investigate the causes of anestrus in buffaloes during their breeding season in Basrah and Thi-Qar governorates, south of Iraq. The research was done on a sample of 91 buffaloes that showed anestrus and five buffaloes in the estrus phase as a control. The reproductive system of these animals was examined by trans-rectal ultrasonography for evaluation of the causes of anestrus. Anestrus buffaloes and a control group were subjected to hormonal studies on progesterone, estrogen, and cortisol.
Ultrasonographical findings showed anestrus buffaloes with ovarian inactivity, anovulatory follicles, persistent corpus luteum, and luteal cysts at the rate of 34.07, 22.18, 16.48, and 13.19%, respectively. Silent estrus was observed in 12.08% buffaloes with a normal estrous cycle. The results of hormonal analysis were consistent with the ultrasonographic findings that showed a significant increase (p<0.05) in the progesterone levels in persistent corpus luteum and luteal cyst cases compared to the control group and significant decrease (p<0.05) of estrogen level in cases of inactive ovaries, anovulatory follicles as compared to control group while there was no significant difference (p>0.05) between silent estrus cases and normal cyclic control group. The study also observed significant increase (p<0.05) in cortisol level in all cases of anestrus as compared to control group. The study concluded that the buffaloes of southern Iraq were under oxidative stress as a result of heat stress and poor diet and the efficiency of ultrasound in the diagnosis of anestrus in buffaloes.