Objectives

2

The phenotypic correlation between the body weight and the body size of Guigan semi-fine wool sheep was studied and indexes for efficiently estimating the body weight were identified to construct an accurate prediction model to provide a scientific basis for the genetic improvement and rapid on-site estimation of weight.

Methods

2

216 healthy and disease-free adult Guiqian semi-fine wool sheep including 94 rams and 122 ewes aged 1.5 to 4 years under the uniform experimental conditions were used to measure 7 indexes of growth including the body weight

body height

body length

chest girth

chest depth

chest width

and cannon circumference. Pearson correlation analysis

path analysis

and stepwise multiple regression analysis were conducted to systematically analyze the effects of various traits of body size on the body weight to identify the optimal combination of traits for constructing a regression estimation model.

Results

2

The average body weight of Guiqian semi-fine wool sheep was 46.82 kg

with a coefficient of variation of 18.72%

indicating that there are rich phenotypic variations

with great potential for selective breeding. There was a highly significant positive correlation (

P

＜0.01) between various traits of body size and body weight

with the correlation coefficients in the decreasing order of chest girth (0.826)＞body length (0.783)＞chest depth (0.715)＞cannon circumference (0.682) body height (0.634)＞ chest width (0.597). The direct path coefficient of chest girth on body weight was the highest (0.428)

indicating that chest girth is the primary key factor affecting body weight. Through stepwise regression

the constructed opti

mal model for predicting body weight was

Y

=-87.63+20.15

X

₂+0.428

X

₃+0.376

X

₄+0.291

X

6

with a multiple correlation coefficient (

R

) of 0.891 and a coefficient of determination (

R

²) of 0.793. The fitness of model was good and highly significant (

P

＜0.01).

Conclusions

2

Chest girth and body length are the core indexes for estimating the body weight of Guigan semi-fine wool sheep. The regression model constructed can be used for the rapid on-site estimation of body weight and accurate selection of breed at early stage in production.