Study On Regulae Lactation Of East Friesian Sheep And East Friesen-hu Hybrid Sheep

As people’s attention to healthy eating continues to increase,sheep milk is gradually becoming a healthier and more nutritious choice,which has also led to an expanding market demand for sheep milk and its dairy products,and expansion of the dairy sheep industry.The East Friesian-Hu hybrid milk sheep produced by East Friesian and Hu sheep have excellent lactation performance and good adaptability,but there are few reports on the lactation law of East Friesian-Hu hybrid milk sheep.In order to provide a selection basis for breeding work,it is necessary to explore the lactation law in order to improve the yield and quality of goat milk and provide a reliable selection basis for production.This study collected lactation information from 3102 sheep at the same breeding farm,including 228 East Friesian（EF）sheep,1145 first-generation East Friesian-Hu crossbreeds（F1）,and 1729 second-generation East Friesian crossbreeds（F2）.The data was classified by different breeds,parities,lambing seasons,and numbers of lambs.Using the average values of the group data and fitting the lactation data with a mathematical model of lactation curves,the lactation patterns of East Friesian and East Friesian crossbred dairy sheep were explored.The main research results are as follows:1.Selecting the most suitable lactation curve model by comparing different models.The Wood model and the six times polynomial model were compared,with the results showed that the Wood model was the most suitable model with a fitting degree higher than0.9 for all groups.According to the model parameters,the estimated total milk production for the different groups were 219.77 kg,230.74 kg,and 207.77 kg.Furthermore,a significant comparison of the estimated milk production and actual milk production showed no significant differences（P>0.05）.The secondary parameters of the Wood model revealed that the lactation peak periods for the East Friesian breed and cross-breeds were on 27 d,22d,and 26 d,with peak milk yields of 1.27 kg,1.39 kg,and 1.14 kg,respectively.The lactation persistence is 6.20,6.02,and 6.52,respectively.The estimated values for the lactation peak occurrence time(D_max)and lactation peak value(Y_max)were slightly lower than the actual values.Both East Friesian and East Friesian-Hu hybrid sheep reached their highest milk yield in the third parity（EF 252.44 kg,F1 245.02 kg,F2 220.41 kg）.2.The correlation between Wood model parameters and secondary parameters.The Wood model parameters and the secondary parameters have an impact on milk production in different parities.Both East Friesian and East Friesian-Hu crossbred dairy sheep reached their lactation peak at the third parity.The parameter"a"was positively correlated with the peak milk yield(Y_max)and total milk yield（0.98 and 0.99）,and negatively correlated with lactation persistence（P）and time to peak lactation(D_max)（-0.89,-1.00）.Different parities have a significant impact on the lactation curve,with lactation persistence and time to peak lactation decreasing as parity increased（P₁>P₂>P₃,Dmax1>Dmax2>Dmax3）.3.Calculate the correction coefficients for the influence of different factors on milk yieldBased on the significant results of the effects of different factors on milk yield,parity and lambing season have a significant impact on the milk yield of East Friesian and East Friesen-Hu crossbred dairy sheep（P<0.01）,and parity,lambing season,and lambing number all have a significant impact on the milk yield of first-generation East Friesen-Hu crossbred sheep（P<0.01）.East Friesian and East Friesen-Hu hybrid sheep produce the highest milk yields in summer and during their third parity.By comparing the advantages and disadvantages of different methods（linear regression method and polynomial regression method）to calculate the correction coefficient,the results showed that using the linear regression analysis method to perform single-step correction to develop the correction coefficient is more accurate.In summary,this experiment used the Wood model to reveal the lactation patterns of East Friesian and East Lake crossbred dairy sheep.Based on the influence of various factors on milk production,corresponding correction coefficients were developed,providing a basis for the breeding work of dairy sheep.