Lipids and Proteins in Eggs and Blood Serum from two Strains of Hens

Abstract

IntroductionIn evaluating genetic improvement of the egglaying capacity of hens !ittle attention has been given t o date t o the internal composition of the eggs. For marketing purposes eggs are usually classified only by size, shell strength, and whatever can be seen by passing light through them. Therefore breeders have little incentive t o obtain any changes in the internal composition.Recently Rodda et al. (1977) has reported some genetic relation between egg weight and conipositional traits and several papers have appeared on the effect of breed or inheritance on cholesterol and fat content of eggs (Edwards et al., 1960; Clark et al., 1964;Cunningham et al., 1974; Washburn et al., 1974).The main objective of the project reported here was to look for a possible quantitative difference in the protein and lipid components of the eggs as a result of specialized selection for high rate of lay and high egg weight. Furthermore, we looked for relations bettveen blood parameters, production parameters and egg composition traits. MaterialsTwo strains originating from the same basic population of highly productive hens \yere selected during two generations for high rate of lay (strain EN) and high egg weight (strain EW) respectively.The criterion used for selection for strain EN was the number of eggs laid from the first egg to the age of 40 weeks. For strain E W the criterion was egg weight at the age of 40 iveeks.In each strain 400 hens ivere tested in order to select 100 for breeding purposes. This selection was made on the basis of a n index which took into account information about the individual hen, her full-sibs and her half-sibs, iveighted in the optimal way. 100 males \\ere reared from each strain and 20 males \\ere selected from each of those groups for breeding purposes on the basis of the merits of their full sisters and half sisters. The effect of two generations of selection is reported in Table 1.Among the selected hens in the third generation 14 hens from each of the two strains were randomly chosen as a basis for the investigation of eggs and blood. For each of the hens a number of production parameters \vere determined including fertility and hatchability of 16 eggs pcr hen.The hens were fed on a market diet containing 11.29 MJ and l 3 y b crude protein. At the age of 52 \vceks 2 eggs were collected from each hen for investigation. The blood samples were taken at slaughter which occurred 5 days after egg collection and which was preceded by 18 hours' starvation before the blood sample was taken.The eggs \\ere stored for not more than 3 days before they were cooked and then the yolk and albumen \\ere separated and stored below -I 8 T . MethodsThe determination of protein in albumen and yolk were carried o u t by the Kjcldahl method using a Kjel-Foss Automatic apparatus, whcrcas protein in blood serum was determined by the biuret method as described by Kokot (1969). The protein fractions in blood serum were separated by means of acctat-cellulosc clectrophoresis on Millipore membrane with neckman Micro...

Cholesterol content in market hen eggs

“…It becomes evident that advances in hen breeding for egg-production capacity result in decreasing cholesterol content in egg yolk. As BARTOV et al [3], BAIR et al [4] and ROTENBERG et al [5] noted, an increased egg-production rate had pronounced effects on decline in yolk cholesterol content. With highly productive laying hybrids, SEMJANOVA et al [6] showed that this relationship was expressed by a correlation coefficient r = -0.619.…”