Study On Ovarian Follicle Development Of Murrah And Nili-ravi Buffalo In Different Breeding Seasons

Buffalo has the excellent characteristics of adapting to harsh environment and resisting roughage,but it also has some disadvantages,such as poor reproductive performance,short sunshine seasonal reproduction and so on.At present,most studies mainly focus on the performance of buffalo summer estrus and the countermeasures to overcome summer estrus.There is still a lack of relevant theoretical basis for the development of ovarian follicles and the changes of blood hormones and biochemical indexes in buffalo in different breeding seasons.Murrah and Nili-Ravi buffalo are river buffalo with excellent milk production performance introduced from abroad.They have carried out cross improvement with local buffalo in China for many years.Therefore,this study takes Murrah and Nili-Ravi buffalo as the research objects,and uses experimental techniques such as B-ultrasound imaging and enzyme-linked immunosorbent assay to observe and study the development dynamics of ovarian follicles,ovulation law and blood biochemical indexes of buffalo in different breeding seasons.It is found that:1.During the off-season of buffalo estrus,6 Murrah buffaloes and 4Nili-Ravi buffaloes were estrus and ovulated at the same time.Only 4 Murrah buffaloes and 1 Nili-Ravi buffalo estrus and ovulate duiring the monitoring period;6 Murrah buffaloes and 5 Nili-Ravi buffaloes were estrous and ovulated during the same estrous period and monitoring period of the peak estrous season.The estrus and ovulation of buffalo in the peak estrus season was better than that in the off-season,and the estrus and ovulation of Murrah buffalo was better than that of Nili-Ravi buffalo.2.During the monitoring period of estrous off-season and peak season,there were 12 buffaloes with 2-wave cycle and 4 buffaloes with 3-wave cycle,that indicated the buffalo follicular development wave was dominated by2-wave cycle.The first and second waves of 2-wave cycle appeared at Day0.20-0.33 and Day 9.00-11.20 respectively;These waves lasted 17.67-21.00days and 10.60-13.00 days;9.00-12.00 and 6.75-8.80 follicles were collected;1.60-1.75 and 1.00-1.40 follicles were selected;Dominant follicles appeared at Day 2.20-3.00 and Day 11.33-14.00,and the maximum diameters of dominant follicles were 11.40-12.96 mm and 13.64-14.45 mm.3.The concentrations of serum FSH,P₄ and IGF-1 of Murrah and Nili-Ravi buffalo in the peak estrous season were significantly higher than those in the off estrous season（P<0.05）,and the concentrations of E₂ were significantly lower than those in the off estrous season（P<0.05）;The concentrations of serum LH and INH in off-season and peak season showed an overall upward trend,and there was no significant difference between Murrah and Nili-Ravi buffalo.4.The activities of serum SOD and the contents of CHOL,MDA,HSP70,K⁺,Na⁺,Cl^-in the heat stress period of Murrah buffalo were significantly higher than those in the non stress period（P<0.05）,while the activities of ALT,AST,GPx and the contents of T-AOC,CORT,LEP and Ca²⁺were significantly lower than those in the non stress period（P<0.05）;The levels of ALB,CHOL and GGT activity of Nili-Ravi buffalo in heat stress period were significantly higher than those in non stress period（P<0.05）,and the content of GLOB was significantly lower than that in non stress period（P<0.05）.The results showed that heat stress reduced the level of endocrine hormones and antioxidant capacity of Murrah and Nili-Ravi buffalo,imbalance the electrolyte balance,and decreased the immune function of Nili-Ravi buffalo.5.During the heat stress period,the ALT activity and the contents of TP,GLOB,CHOL,BUN and TG of Murrah buffalo were significantly higher than those of Nili-Ravi buffalo（P<0.05）,and the contents of ALB,T₄ and K⁺were significantly lower than those of Nili-Ravi buffalo（P<0.05）.The results showed that under heat stress,Murrah buffalo showed stronger ability to scavenge free radicals,and Nili-Ravi buffalo showed better metabolism,thermoregulation and electrolyte compensation.In conclusion,the follicle development wave in the estrous cycle of Murrah and Nili-Ravi buffalo was mainly two wave cycle.The estrous ovulation in the peak season was better than that in the off-season.The concentrations of serum FSH,P₄ and IGF-1 increased and the concentration of E₂ decreased;In the off-season of estrus,Murrah and Nili-Ravi buffalo were in a state of heat stress,the level of endocrine hormones and antioxidant capacity were decreased,and the electrolyte balance of the body was unbalanced.Murrah buffalo had a stronger ability to scavenge free radicals than Nili-Ravi buffalo,while Nili-Ravi buffalo had a stronger ability of metabolism,thermoregulation and electrolyte compensation.