Canonical discriminant analysis of early maturity traits of parent stock layer strains in the tropics

Abstract

tepwise discriminant analysis was conducted to classify pullet strains into Early maturing or Late maturing. Reproductive, Age and body traits examined were Age at first egg (AFE), Hen weight at first egg (HWFE), Hen weight at 20 weeks (H20wks), Egg weight at full maturity (EWT), Hen house production at full maturity (HHP), Fertility of egg set at full maturity (FES), Hatchability of egg set at full maturity (HES) and Pullet day-old chicks hatched at full maturity (PDC). Test of equality of Class means observed significant (p<0.001) differences for AFE on the Discriminant Variables (DV) table. Box’s M indicated that the assumption of equality of covariance matrices was violated (p<0.002), but the log determinants were quite similar (11.554 to 13.544). Two body traits namely AFE and HWFE were entered by the stepwise procedure into the discriminate Function (DF). The DF revealed a significant association between Maturity Classes and all discriminators, accounting for 67.3% of between group variability, although closer analysis of the structure matrix revealed three significant predictors, namely AFE (0.771), HES (-0.314) and PDC (–0.304), while others were poor predictors (0.292 to -0.102). The stepwise procedure however identified the best set of discriminating variables in the DF for maximizing classification as AFE and HWFE. The cross validated classification showed that overall 93.3% of cases were correctly classified. The function thus obtained could be used successfully by farmers to classify any batch of Bovan Nera, Isa Brown or other Parent stock strains in tropical environment for sexual maturity status. The best discriminating pair of traits for ESM in pullets was AFE and HWFE. Results obtained significant differences between the mean of early and late maturing pullets to allow for their classification.