Variation of egg cholesterol level in the domestic fowl

• Main Author: Hall, L. Malcolm
• Published: University of Edinburgh 1990
• Subjects: 572.57
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.651973

Variation for yolk cholesterol concentration, egg cholesterol content and egg cholesterol concentration in the domestic fowl (<i>Gallus domesticus</i>) is assessed. Changes in yolk cholesterol concentration and egg cholesterol content throughout the first year of egg production have been evaluated. The pattern of change for yolk concentration is non-linear, with a decrease between 20 and 30 weeks of age, followed by relative stability until the end of the experiment. Egg cholesterol content increases throughout the first year of egg production. There is an interaction between age and birds for both yolk cholesterol concentration and egg cholesterol content. For yolk cholesterol concentration the interaction is caused primarily by values during 20 weeks of age, and bid means between 30 and 70 weeks of age are relatively consistent. The interaction for egg cholesterol content is caused primarily by values during 20 and 30 weeks of age, and bird means between 40 and 70 weeks of age are relatively consistent. Variation between eggs for yolk cholesterol concentration is statistically significant during 20 weeks of age, but is negligible during subsequent assessment periods. Differences in yolk cholesterol concentration, egg cholesterol content and egg cholesterol concentration amongst five lines, and a cross between two of the lines, were assessed. The five lines had been developed for the production of commercial egg laying hybrids, and include representatives of the White Leghorn, Rhode Island Red, and New Hampshire breeds. Differences in yolk cholesterol concentration between the lines were negligible, although the yolk cholesterol concentration of the cross was lower than either parent. It is proposed that there is genetic variation for yolk cholesterol concentration even though the phenotype of the lines is similar. Differences between the lines for egg cholesterol content and egg cholesterol concentration are bigger than for yolk cholesterol concentration. The egg cholesterol content for the cross is intermediate to the parent lines, although tending towards the lower parent line, and egg cholesterol concentration was lower than both parent lines. The relationship between bird means for egg cholesterol content and egg weight within lines is positive, and the relationship between egg cholesterol concentration and egg weight negative. It is proposed that yolk cholesterol concentration, egg cholesterol content, and egg cholesterol concentration be regarded as three distinct, but related, traits. Phenotypic variation for yolk cholesterol and total lipid concentration are essentially independent. There is a consistent negative phenotypic relationship between yolk cholesterol concentration and egg production throughout the first year of egg production. There is a negative phenotypic relationship between yolk cholesterol concentration and yolk weight during 30 weeks of age which is not apparent during subsequent assessment periods. There is evidence of a small positive phenotypic relationship plasma cholesterol concentration at 52 weeks of age and yolk cholesterol concentration.