Abstract:

【Objective】 The aims of this study were to estimate the correction coefficients CF and A of days to 100 kg (D100) and to compare their correction powers to each other in Licha black pig and its intercross with Berkshire boars, so as to provide a reference of correction coefficients for estimating D100 in Licha black pig and other Chinese indigenous pig breeds. 【Method】 In this study, 554 Licha black pigs with pigs from its intercross with Berkshire boars, including 941 F₁ pigs and 755 F₂ pigs, were randomly selected, and their body weights and ages in days had been automatically collected everyday by Winland performance testing system during their fatting periods. The data quality control was carried out according to the criteria, such as age ≥60 days and body weight ≥25 kg at start testing. Only the data have been passed quality control, which were used to estimate CF and A. CF was the ratio of two slopes, namely, the numerator was the slope of the regression line of weight to age, and the denominator was the slope of the straight line through the end point of performance testing (age and body weight at the testing end) and the original point (both age and weight were 0). A was the intercept of the regression equation of body weight to age, which could be obtained directly by fitting a regression equation of body weight to age. After the correction coefficients were estimated, an analysis of variance was carried out to test whether gender and population had effects on them, and the estimated CF and A were substituted into their respective correction formulae to calculate D100 (D100_CF and D100_A). A t-test was used to test whether there was a significant difference between D100_CF and D100_A, and their correlation coefficient was also calculated. Then, the regression equation of body weight to age for each individual was established, and regressive D100 (D100_reg) for each individual was estimated by its regression equation. The corrected accuracies of CF and A were compared to each other by the correlation coefficients of D100_CF and D100_A with D100_reg, and the means and standard deviations of the differences of D100_CF and D100_A to D100_reg. Finally, the correction coefficients estimated from other two populations were used to estimate D100 in a certain population, and the correlation coefficients of D100_CF and D100_A with D100_reg were calculated to evaluate whether the correction coefficient estimated from one population could be used in other populations. 【Result】 Gender and population had significant effects on the correction coefficients, so it was necessary to estimate the correction coefficient for each gender in each population. CF of stags (gilts) in Licha black pig and the F₁ and F₂ of its intercross with Berkshire boars were 1.426 (1.346), 1.340 (1.389) and 1.372 (1.380), respectively, and A were 60.65 (54.15), 49.92 (57.00) and 54.25 (57.53), respectively. There was no significant difference between D100_CF and D100_A (P = 0.3071), and their correlation coefficient was 0.9998 (P <0.0001). The correlation coefficients of D100_CF and D100_A with D100_reg were equal or greater than 0.9917 (P<0.0001), there was no significant (P>0.05) between the differences of D100_CF and D100_A to D100_reg. The means of the differences were -0.1385 and -0.2741 days, and the standard deviations were 2.5532 and 2.5446 days, respectively. The correlation coefficients of D100_reg with D100_CF and D100_A, which were adjusted using the correction coefficients estimated from other two populations, were equal or greater than 0.9793 (P < 0.0001). 【Conclusion】 The correction coefficients CF and A of D100 estimated in this study were quite different from their counterparts using in National Swine Industry Technology System. There was no significant difference between the correction powers of CF and A, and both CF and A had a very high correction power under an appropriate range of body weight at the end of performance testing. In the three populations, the correction coefficients from other two populations had a very high correction power to a certain population, which indicated that the correction coefficient of D100 from Licha black pig could be used as a reference to other Chinese indigenous pig breeds.

Key words: Licha Black pig, days to 100 kg, correction coefficient CF, correction coefficient A