UBC Theses and Dissertations
Genetic evaluation of egg mass and egg component traits in 3 lines of domestic fowl Jain, Genda Lal
A study was conducted to make a genetic evaluation of egg mass (weight of the total eggs laid in a given period) in order to determine its genetic potential as a new criterion for selection as compared to the conventional selection program based on egg number (early and full production records). In addition, biometrical evaluations of some egg component traits: yolk weight, albumen weight, shell weight, percent yolk, percent albumen, percent shell, albumen percent solid, yolk percent solid, yolk percent protein, albumen percent protein, yolk solid and albumen solid were made. The aforementioned traits were measured on 3 random bred lines of chickens in quarterly periods through the laying year. Within each line, the heritability estimates of egg number and egg mass for any given period (275, 325, 450 and 540 days of age) were found to be in close agreement. In general, for egg number and egg mass, selection from early production records showed higher gains per unit of time than full year production records, A negative genetic correlation between egg number traits and egg weight traits and a positive genetic correlation between egg mass and egg weight traits was found, therefore, selection for egg mass was recommended. Relative merit of early and full year egg records as selection criterion was discussed in the light of the results obtained for the three lines. It was concluded that the decision as to which criterion should be used would have to depend upon the genetic properties of the population in question. Line effects were found to be significant for all the egg component traits studied, except percent shell, A season-age effect was also found to be significant in all the traits studied. Season-age by sire interactions were found to be non-significant for all the traits in all the three lines. The importance of yolk size from a human nutrition standpoint was discussed. A selection program based on total yolk weight produced by a hen in a given period (yolk mass) was suggested. Because of the water in the egg being an essential nutrient for the developing chick embryo, it was suggested that selection be made on the egg solid or egg solid mass (total amount of solid laid by a hen in a given period). The heritability estimates of albumen percent solid and albumen percent protein were high and of the same magnitude. It was, therefore, suggested that an increase in percent protein in albumen should be achieved by selection of albumen percent solid.
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