Study On Estrus Regularity Of Guanzhong Dairy Goats

Dairy goat industry is one of the characteristic animal husbandry industries in Shaanxi Province,which plays an important role in promoting the development of agricultural and rural economy and ensuring the supply of animal products.With the popularization and application of artificial insemination and other modern breeding technology in dairy goat industry,the production efficiency of breeding enterprises has been greatly improved.However,there are still some problems in the process of artificial insemination of dairy goats.For example,ewe estrus identification still relies on the method of ram estrus testing and external observation in small-scale family rearing mode.Ram estrus testing greatly increases the labor intensity of the staff and is easy to cause mismatching.External observation method is difficult to detect recessive estrus ewe,the identification result is not accurate,which leads to difficult to grasp the timing of sperm insemination,affecting the effect of artificial insemination.Therefore,in this study,60 two-parity,good body condition and similar body weight（50.50±1.75 kg）of Guanzhong dairy goats were selected as test animals,and one to two estrus cycles were observed from August to September when they began to estrus successively.During the experiment,0 h was recorded when ewe started to show signs of estrus such as tail-wagging,flushing of vulva,and active approach to ram（this 0 h was slightly later than the theoretical estrus initiation time）.The changes of cervix opening status,vaginal cell morphology and number were continuously observed and recorded during estrus cycle,the changes of serum reproductive hormones FSH,LH,P₄ and E₂ contents were monitored,and the metabolic characteristics of cervix vaginal mucus at different times during estrus were further explored.Finally,the 30 ewes were divided into three groups（natural estrus state second estrus symptoms after 0 h,12 h,24 h）for artificial insemination,another 30 ewes using PIDR+PMSG+PG method for the same period of estrus treatment,and divided into three groups（12 h,24 h,36 h after suppositing）for artificial insemination.Pregnancy was recorded 30 days after insemination,and lambing was recorded in February of the following year.By comparing the conception rate and lambing rate of ewe under different estrus modes and at different time of artificial insemination of Guanzhong dairy goats,the best time of insemination during estrus was explored,providing theoretical reference for the efficient application of artificial insemination technology of dairy goats.This study mainly obtained the following results:1.The cervical opening of Guanzhong dairy goats was obviously opened during estrus,and the opening time remained from 36 to 48 hours,and then gradually closed;In estrus,the amount of mucus secreted by the cervical opening was the largest,the consistency was low,and the color tended to be transparent.In late estrus,the mucus gradually decreased,the consistency increased,and the color of the mucus gradually became darker.Vaginal cells were mainly nucleated epithelial cells,incomplete keratinized epithelial cells,complete keratinized epithelial cells and leukocytes.The proportion of nucleated epithelial cells in preestrus was significantly higher than that of the other three cell morphology（P<0.05）,the proportion of complete keratinized epithelial cells during estrus was significantly higher than that of the other three cell morphology（P<0.05）,the proportion of white blood cells in late estrus and interestrus was significantly higher than the other three cell morphologic types（P<0.05）.Therefore,the opening of the cervix,the accumulation of a large amount of mucus in the cervix or the presence of a large number of complete keratinized epithelial cells on the smear of vaginal cells can be used as the criteria to determine the estrus of Guanzhong dairy goats.2.In the estrus cycle of Guanzhong dairy goats,the secretion of FSH gradually increased from early estrus and reached the maximum value（44.44 IU/L）10 h after the onset of estrus symptoms,and then decreased gradually.The average content of FSH in estrus was significantly higher than that in late estrus,interestrus and early estrus（P<0.05）;The maximum value of LH reached 32.5 ng/L 15 h after the onset of estrus,and the average content of LH in estrus was significantly higher than that in late,interestrus and early estrus（P<0.05）;E₂ reached its maximum value（200.45 pmol/L）15 h after the onset of estrus,and the average content of E₂ in estrus and late estrus was significantly higher than that in interestrus and early estrus（P<0.05）;P₄ maintained the lowest level in estrus,gradually increased in late estrus,reached the peak value in interestrus（1685.21 pmol/L）,and gradually decreased in early estrus of the next estrus cycle.The average content in late estrus and interestrus was significantly higher than that in early estrus and estrus（P<0.05）.The peaks of LH and E₂ appeared at the same time after the end of the peak of FSH at 10 to15 h after the onset of estrus in Guanzhong dairy goats,indicating that the ovaries of ewes approached ovulation at 15 h after the onset of estrus symptoms.Therefore,starting sperm insemination a few hours before this can improve the conception rate of ewes.3.A total of 221 metabolites were detected at 12 h,24 h and 36 h after the occurrence of estrus of Guanzhong dairy goats,mainly involving carbohydrates,lipids,amino acids,nucleotides,vitamins,peptides and other substances.There were 7 different metabolites at12 h vs 24 h vs 36 h,among which the contents of 2-Hydroxybutyric acid,D-Glucose,D-Galactose and Diethyl phthalate showed an increasing trend.The contents of2,3-Diaminopropionic acid,Galactosylglycerol and Hypotaurine generally showed a downward trend,and these differential metabolites were mainly concentrated in Galactose metabolism,Carbohydrate digestion and absorption,Insulin secretion,Insulin resistance and other pathways.The contents of 2,3-Diaminopropionic acid,Galactosylglycerol and Hypotaurine in the cervical and vaginal mucus of Guanzhong dairy goats were the highest12 h after the occurrence of estrus symptoms,and decreased rapidly in the later stage of estrus,which could be used as biomarkers of the estrus stage of Guanzhong dairy goats.4.In the natural estrus state,0 h,12 h and 24 h after the occurrence of estrus symptoms in the second estrus,the pregnancy rate was 40%,70%and 40%,and the lambing rate was150%,200%and 183.33%,respectively.At 12 h,24 h and 36 h after the same period of estrus,the birth rate of ewe was 50%,80%and 60%,and the lambing rate was 140%,187.5%and 166.67%,respectively.The results of this study showed that there were no significant differences in conception rate and lambing rate of ewe under the two estrus modes（P>0.05）.Therefore,in natural estrus,12 h after the onset of estrus is the best effect.In the condition of estrus at the same time in the breeding season,the best effect was obtained 24 h after the removal of progesterone suppositories and the injection of follicle-stimulating or luteinolytic hormones.In conclusion,in the estrus cycle of Guanzhong dairy goats,estrogen and progesterone co-regulated the periodic changes of cervical ostium and vaginal cells,and the cervical ostium remained open for 36～48 h.More than 60%of the vaginal smear cells were complete keratinized epithelial cells,which could be used as an important indicator for the identification of estrus of Guanzhong dairy goats.The ovaries of ewe approached ovulation15 h after the onset of estrus,and fertilization several hours before this could improve the conception rate of ewe.The different metabolites of 2,3-Diaminopropionic acid,Galactosylglycerol and Hypotaurine in cervical and vaginal mucus at different time of estrus of Guanzhong dairy goats showed a certain time-dependent change,which could be used as biomarkers of estrus of Guanzhong dairy goats.In the breeding season,artificial insemination was performed 12 h after the occurrence of estrus of natural Guanzhong dairy goats,while artificial insemination was performed 24 h after the withdrawal of supposition of natural estrus of Guanzhong dairy goats,which could achieve better reproductive results.