Genetic and non-genetic factors affecting live, carcass and non-carcass traits of New Zealand White rabbits in Egypt
Keywords:Carcass traits, Genetic and phenotypic correlations, Heritability, Live traits, Rabbits
Genetic and non-genetic factors that influence live, carcass and non-carcass traits of New Zealand White breed were evaluated by a basic model included sire and dam (as random effects), sex, delivery season and interaction between them (as fixed effects). The sire and dam effects on many carcass traits, were significant, but the sire effects were greater than dam. Sex insignificantly affected most traits, except thigh circumference and liver, giblets, edible and non-edible offals weights. Season appears to be the major non-genetic factor that affect live, carcass form and technological cuts traits. The highest live body weight, carcass traits and measurements were estimated during winter. The two-way interactions between sex and season were significant for weight greater than measurement variables. The losses in live and carcass performance traits were higher in males than in females, during summer. Regression coefficients (b) of all carcass traits, meat/bone. ratio and dressing% (as dependents) on each of live body weight before and after fasting, heart girth and humerus length (as covariates) were positive and highly significant (P<0.001). Heritabilities (hÂ²) for heart girth, pelvic girth and thigh length of live body and carcass traits were high and ranged from 0.33 and 62. The hÂ² estimates of carcass thigh length, thigh circumference, loin length, head, liver, giblets and edible offals weights were very high and ranged between 0.62 and 0.92. Genetic correlations (rG) between each of hot, reference hot, commercial and reference cold carcass and technological cuts and each of weaning, live body weight before and after fasting, heart girth and humerus length were high and positive. The rG between dressing% and each of live body weight before and after fasting, body and thigh length and lumbar circumference were high and positive. It was concluded that the hÂ² and rG were sufficiently high to pennit selection of commercial carcass traits on individual levels for some or the live traits in rabbits.
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