ESTIMATION OF GENETIC PARAMETERS FOR SOME PRODUCTIVE AND REPRODUCTIVE TRAITS WITH SIX DIFFERENT MODELS FOR FRIESIAN CATTLE RAISED IN EGYPT

Abstract

the main objectives of this study were to detect the most appropriate model that fit the data, that include Lactation period (LP), Total milk yield (TMY), 305day/MY and days open (DO) traits, of Friesian cattle raised in Egypt. Data of 3977 records were collected from 1971 till 1999 (29 years) of cows at Sakha farm. Estimates of genetic parameters (heritability and correlation estimated) by DFREML program resulting from six different statistical models pure examined to determine genetic parameters for productive, reproductive traits and total gain were compared. Six models were used, each have the additive effect of the cow beside the permanent environmental (non- additive genetic) and maternal effect the parameters were estimated by using Variance Component estimation (VCE 6.0) software. Nongenetic factors (fixed effects) had highly significant (p < 0.001) for all studied traits. The overall means of LP, TMY, 305-day/MY and DO were 337 day, 4040Kg, 3523Kg and 135day, respectively. Akaike Information Criterion (AIC) was used to determine the most appropriate model for the studied traits. Model 3 which had additive and maternal effect with their covariance are equal zero, which was the best model. Estimates of direct heritability thatwas relatively low to moderate ranged from (0.001 to 0.14), The same trend was observed in the case of maternal heritability were relatively low for studied traits ranged from (0.01 to 0.04). However, The correlation coefficients between all studied traits were highly significant (p < 0.001) ranged from (0.3 to 0.99). Which means that when the genetic improvement of one of the trait improve the rest of the traits.