Effects Of Supplementation With L-Arginine On Fertility And Blood Parameters Of Mares

Two experiments were carried out in this study to investigate the effects of supplementary feeding of L-arginine on fertility and blood parameters of producing mares.Experiment 1.Effect of supplementation with L-arginine on fertility and blood parameters of perinatal Yili mares.Thirty Yili mares with similar age,body weight,height at withers,and due date were selected for test and divided into 2 groups,control group（n=15）and L-arginine group（n=15）.The mares in control group were fed a basal diet,and those in the L-arginine group were fed an experimental diet which supplemented with 0.5%L-arginine on the basis of the basal diet formula,and the supplementary feeding amount of L-arginine was 60 g/（horse·d）.Newborn foal body weight and body size parameters were measured within 12 h on mares after childbirth,and pregnancy rate and re-service rate during mating were counted.Mares venous blood samples were collected on days 0（before the supplementary feeding trial）,21,and 45 of trial.The results showed that compared with the control group,there were no significant differences in the body weight,body size parameters,and mating pregnancy rate of mares after delivery in the L-arginine group（P>0.05）,and the mating re-service rate of mares after delivery in the L-arginine group was significantly decreased（P<0.05）.Compared with the control group,there were no significant differences in the plasma total nitric oxide synthase（TNOS）and endothelial nitric oxide synthase（eNOS）activities and nitric oxide（NO）content on the day 21 of trial in the L-arginine group（P>0.05）;the plasma TNOS activity was significantly reduced（P<0.05）,the NO content was extremely significantly reduced（P<0.01）,and the eNOS activity was not significantly changed on the day 45 of trial in the L-arginine group（P>0.05）.Compared with the control group,there were no significant differences in ammonia（NH₃）and urea nitrogen（UN）contents on the day 21 of trial in the L-arginine group（P>0.05）;the plasma NH₃ content was extremely significantly reduced（P<0.01）,and there was no significant difference in the UN content on the day 45 of trial（P>0.05）.Compared with the control group,there were no significant differences in the plasma growth hormone（GH）,insulin-like growth factor-Ⅰ（IGF-Ⅰ）,and insulin（INS）contents on the days 21 and 45 of trial in the L-arginine group（P>0.05）;Compared with the control group,the antioxidant capacity of the L-arginine group was significantly improved.The results suggest that supplementary feeding L-arginine during peripartum of Yili mares can change the plasma TNOS activity,NO and NH₃ contents in the mares’body circulation,increased antioxidant capacity and reduce mating re-service rate after delivery of mares,but no significantly affect the body weight,body size parameters of newborn foals and the mating pregnancy rate after delivery of mares.L-arginine can be used as a nutritional regulator for nutritional supplement of mares during last trimester or the nursing after childbirth to improve fertility of mares.Experiment 2.Effect of supplementation with L-arginine on the pregnancy rate and blood parameters of re-service thoroughbred horses.14 re-service thoroughbred horses were randomly divided into 2 groups,7 in each group（n=7）,as the control group and L-arginine group.When the re-service thoroughbred horses is in heat again,L-arginine is replenished on the day of the end of the first artificial infusion.At the end of breeding,the pregnancy was examined by rectum B-ultrasound again,and the pregnancy rate was calculated.Blood was collected from the jugular vein of mares at day 0,day 15 and day 30 respectively.The results showed that compared with the control group,the pregnancy rate of the L-arginine group had a tendency to increase（P<0.05）.Compared with the control group,there was no significant difference in plasma TNOS,eNOS,NO,ODC,IGF-Ⅰ、IGF-Ⅱ and VEGF levels at 0,15 and 30 days（P>0.05）.Compared with the control group,the contents of NH₃ and UN in plasma were significantly reduced by 13.49%and 26.91%at 30 days（P<0.05）.Compared with the control group,the plasma GH content at 30 days was significantly increased by 50.26%（P<0.01）.Compared with the control group,there was no significant difference in the contents of IgA,IgM and IgG in mares at 0,15 and 30 days（P>0.05）.The results suggest that supplementary feeding L-arginine had significant effect on the pregnancy rate of re-service thoroughbred horses,could change the contents of circulating plasma,NH₃,UN,GH of re-service thoroughbred horses.L-arginine can be used as a nutrient regulator to improve the pregnancy success rate of thoroughbred mares.Under the condition of this experiment,the supplementation with L-arginine improved the fertility of Yili mares and thoroughbred horses,and the supplementation with L-arginine after childbirth reduced the rate of breeding return to affection of Yili mares after childbirth,and the pregnancy rate on supplementation with L-arginine pair of returning to affection thoroughbred mares had a trend of increasing.Supplementation with L-arginine can change the contents of circulating plasma TNOS,eNOS,NO,NH₃,GH of Yili mares and re-service thoroughbred horses,and improve the antioxidant capacity.L-arginine can be used as a nutrient regulator to improve the fertility of mares.