Linear Appraisal And Correlation Analysis With Lactation Traits In Laoshan Dairy Goats

In this study,149 ewes of Laoshan dairy goats were used as research objects,and their body size and lactation traits were measured,and linear appearance was assessed after statistical analysis;at the same time,their milk composition and lactation amount were collected,and lactation curves were fitted to the lactation amount;the correlation analysis between the measured body size traits,lactation traits and lactation shape was carried out to identify the traits with strong correlation with lactation traits,and to identify the traits with good genetic performance.The correlation analysis between the measured body size traits,mammary shape traits and lactation shape was carried out to identify the traits with strong correlation with lactation traits and to identify the Laoshan dairy goats with good genetic performance,providing theoretical and guidance for the direction of body size improvement in Laoshan dairy goats.The above study indicates the direction of genetic improvement for the Laoshan dairy goat population,and provides theoretical support for future breeding work and a scientific basis for the correct evaluation of the economic value of Laoshan dairy goats.The main findings are summarised as follows.（1）Regarding the most suitable lactation curve fitting models for Laoshan dairy goats,a total of five lactation curves were used in this study,of which the AS model had the highest fit of 0.9628,followed by the Wood model with a fit of 0.9435,then the ML model with a fit of0.9122,and finally the IQP model with a fit of 0.8375.The fit of the WIL model was lower,with a fit of 0.7856.The WIL model had a lower fit of 0.7856,and the Wood model was the most suitable model for fitting the lactation curve of Laoshan dairy goats,judging from the fit,the maximum daily milk yield and the maximum milk yield date.（2）Statistical analysis of the results of linear external appearance assessment of Laoshan dairy goats revealed that there were no individual goats with excellent（EX）or good（VG）and no individual with poor（P）grades in this Laoshan dairy goat group,the number of good（G）accounted for 53%of the total group,the number of fair（F）accounted for 35%and the number of good（GP）accounted for 12%;the number of body volume（BC）,lactation body volume（BC）,lactation organ（MS）,and dairy characteristics（DC）spanned a larger range and were more discrete than the other two scores,indicating that the growth and development of this Laoshan dairy goat was more uneven,and the next step should be to strengthen feeding management and unify feeding conditions.（3）Comparative analysis of body size traits and mammary shape traits revealed that the Laoshan dairy goat group had a certain gap between the best and the best scores in the linear appearance assessment: traits with a difference of < 5 points included hind leg measurement（Z1）,udder depth（W5）and shiri angle（Y1）,which performed well;traits with a difference of5-20 points included body height（X1）,body strength（X2）,breast depth（X3）,angularity（X3）and body strength（X4）.The traits with a difference score of >20 include six traits,namely coccyx width（Y3）,posterior mammary area height（W2）,posterior mammary area shape（W3）,central suspensory ligament（W4）and posterior view of teat position（W6）,which are poor performers and should be improved upon in the next step.The next step is to focus on improving these traits.（4）Correlations between body size,mammary shape and lactation traits revealed that:lactose was significantly negatively correlated with body height（r=-0.172,P<0.05）,hindquarters（r=-0.169,P<0.05）,body length（r=-0.169,P<0.05）,loin angle width（r=-0.182,P<0.05）,and highly significantly negatively correlated with maximum frontal width（r=-0.219,P<0.01）;non-fat solids were significantly negatively correlated with maximum frontal width（r=-0.179,P<0.05）;lactation was significantly positively correlated with sciatic end height（r=0.197,P<0.05）,with posterior mammary area height（r=0.194,P<0.05）and a highly significant positive correlation with coccyx width（r=0.230,P<0.01）.The correlation between the linear external appearance assessment component scores and milk component traits was found to be: body volume was significantly negatively correlated with lactose（r=-0.173,P<0.05）,significantly positively correlated with lactation（r=0.194,P<0.05）;hind limb component was highly significantly positively correlated with milk fat（r=0.303,P<0.01）,and highly significantly positively correlated with total solids（r= 0.283,P<0.01）;and coccyx was highly significantly positively correlated with lactation（r=0.311,P<0.01）.The results suggest that a dairy goat with high lactation quality should satisfy the conditions of small body volume,low hindquarters length as a percentage but full coccyx,full hind milk area,moderate hind leg curvature and small maximum forehead width.（5）The applicability of linear appearance assessment on Laoshan dairy goats was demonstrated: the correlation between linear appearance assessment and milk component traits was found to be significantly positively correlated with general appearance（r=0.167,P<0.05）,with lactation organs（r=0.186,P<0.05）,with mastication traits（r=0.285,P< 0.01）,a highly significant positive correlation with body volume（r=0.222,P<0.01）and a highly significant positive correlation with total grade（r=0.280,P<0.01）.In summary,the lactation curve fitting models suitable for Laoshan dairy goats were the AS model and the Wood model,of which the lactation curve fitting model that best reflects the lactation cycle is the Wood model;the linear appearance assessment method used in this paper is applicable to Laoshan dairy goats,through which we can evaluate whether the appearance traits of Laoshan dairy goats are good and identify individuals with higher lactation volume;the body condition of this Laoshan dairy goat group varies greatly between groups and should be strengthened.The next direction of improvement should focus on the posterior traits of coccyx width,hind mammary area height,hind mammary area shape,central suspensory ligament and teat position,and also on body height,body strength,chest depth,angularity,coccyx length and fore udder attachment as supplementary synchronous and stable improvement.