Research On The Heart Rate Variability And Serum Hormone Changes In Yili Horse In Different Gestation States

This paper aims to investigate the heart rate variability（HRV）and serum hormone changes during pregnancy in aborted and delivered Yili horses in the Zhaosu region to prevent adverse pregnancy outcomes.Twenty-one Yili horses at 29 weeks of pregnancy and seven Yili horses without pregnancy were selected for the 24-h HRV measurements at the 30th week of pregnancy,the 45th week of pregnancy and the day before and after delivery.Blood samples were collected from 28 mares during the 30th week of pregnancy,the 45th week of pregnancy and at 12:00 am on the day after delivery.Five pregnant mares had spontaneous abortions between 45 and 47 weeks of pregnancy.The HRV and serum hormone levels were analyzed at different gestation stages.The results were as follows:analysis of heart rate variability across gestation conditions and periods showed that the mean heart rate of mares in the abortion and normal parturition groups was significantly higher than that of the non-pregnant group（P<0.01）.Mean RR,RMSSD,NN50,PNN50,SDNN,SD1 and SD2 were significantly higher in the non-pregnant group than in the abortion and normal parturition groups（P<0.01）;VLF was much higher in mares of the abortion and non-pregnant groups than in the normal parturition group（P<0.01）.HF and LF in the non-pregnant group were significantly higher than those in the abortion and normal delivery groups（P<0.01）.SD2/SD1 was significantly higher in the normal parturition group than in the abortion and non-pregnant groups（P<0.01）.Analysis of heart rate variability across gestational conditions and periods showed that Mean RR,SDNN,RMSSD,NN50,PNN50,SD2,HF,LF,VLF,and LF/HF were significantly higher in the 30th gestational week than in the 45th gestational week and the days before and after delivery.Mean RR and PNN50 were significantly higher in the 45th gestational week than in the antepartum and postpartum periods（P<0.01）.Mean HR and SD2/SD1 before and after delivery were significantly higher than those in the 30th and 45th gestational weeks（P<0.01）.LF,SDNN,SD2,HF and LF/HF were significantly higher before noon on the day of delivery than LF/HF at noon,afternoon and night after delivery（P<0.01）.VLF and LF/HF were significantly higher at night and afternoon before delivery than LF/HF before noon（P<0.01）.There was a significant crossover effect between LF/HF and SD2/SD1 in HRV frequency domain indices across gestational conditions and periods（P<0.01,P<0.05）.The changes of serum hormones in Yili horse under different gestation conditions revealed that serum cortisol in the non-pregnant group was significantly higher than that in the abortion and normal delivery groups at the 30th week of gestation（P<0.01）;estradiol was significantly lower than that in the abortion and normal delivery groups（P<0.01）.At 45 weeks of gestation,insulin was significantly higher in the non-pregnant group than in the miscarriage and normal delivery groups（P<0.01）;thyroxine was significantly higher than in the normal group（P<0.05）and extremely significantly higher than in the miscarriage group（P<0.01）;estradiol was significantly lower than in the miscarriage and normal groups（P<0.01）.Thyroxine in the normal group was significantly higher than that in the abortion group at 1 day after delivery（P<0.01）.Serum hormones of Yili horses differed throughout gestation.In particular,postpartum insulin and cortisol levels were abnormally elevated in aborted mares and thyroid levels were decreased compared to normal parturient mares.Comparison of serum hormone and heart rate variability in mares in the non-pregnant,aborted and normal parturition groups showed that COR,Mean RR,SDNN,RMSSD,NN50,PNN50 and SD1 were significantly positively correlated with serum INS in normal pregnant mares（P<0.01）.Mean RR,SDNN,RMSSD,NN50,PNN50,HF,LF,SD1,and SD2 were significantly positively correlated with serum E₂（P<0.01）.Mean HR,SD2/SD1 were significantly negatively correlated with serum E₂（P<0.01）.Correlation analysis of serum hormones and heart rate variability index in aborted mares showed that Mean RR was significantly positively correlated with serum E₂（P<0.01）and Mean HR was negatively correlated with serum E₂（P<0.01）.Mean HR of pregnant mares was positively correlated with serum P（P<0.01）;Mean RR was negatively correlated with serum P（P<0.01）;Mean HR and Mean RR were significantly negatively correlated（P<0.01）.T₄,LF/HF,SD2/SD1 indicators predicted whether the mare would abort or have an adverse pregnancy.INS,P,E₂,Mean RR,SDNN,Mean HR,RMSSD,NN50,PNN50,VLF,LF,HF,SD1,SD2,SD2/SD1 predicted whether the mare would have a pregnancy.The results of the study suggest that when the mare is in gestation,the parasympathetic nerves are dominant and the autonomic nervous system is inhibited.When abortion occurs,parasympathetic nerves are dominant,thus exciting the autonomic nervous system.Serum hormone levels change during pregnancy,especially after abortion,with abnormally increased levels of insulin and cortisol and decreased levels of thyroid compared to those of normal parturient mares.The pregnancy status of the mare is closely related to heart rate variability and serum hormones.In the management and breeding of pregnant horses,heart rate variability can be used as a non-invasive test instead of testing serum hormones to show the full picture of a mare’s pregnancy status in real time and provide a reliable reference for predicting pregnancy outcome.