Plasma very low density lipoproteins, abdominal fat lipase, and fatness during rearing in two strains of broiler chickens

Abstract

Experimental control Strains 30, representative of commercial broiler dam stocks in the late 1970's, and K, representative of commercial broiler stocks of 20 years earlier, were compared. Development of carcass fatness and related traits and physiological traits from 3 to 17 weeks of age were studied. About 12 chickens of mixed sex of each strain were bled and killed at 2-week intervals beginning at 3 weeks of age for measurement of traits. From 3 to 17 weeks of age, percentage abdominal fat of carcass, carcass fat (ether extract) and plasma very low density lipoproteins (VLDL) increased with age. Percentage carcass nitrogen, ash, and water, lipase activity of abdominal fat expressed per mg protein or per g of fat (LIP/g F), and protein concentration of the abdominal fat enzyme preparation (P/ml EPrep) decreased with age. Strain 30 had a higher percentage of abdominal fat and carcass fat, but less carcass nitrogen, ash, and water than Strain K, although there were interactions with sex and age. For physiological traits, Strain 30 had more LIP/g F and less P/ml EPrep than Strain K. Males had lower percentages of abdominal fat, carcass fat, and plasma VLDL, and higher percentages of carcass nitrogen, ash, and water than females. There were no significant differences between sexes for the other physiological traits. There were significant (P less than .01) partial correlations between plasma VLDL and percentage abdominal fat (.22), and between P/ml EPrep and percentages of abdominal fat (-.25), carcass fat (-.29), carcass nitrogen (.30), and carcass water (.30). These observations in conjunction with multiple regression analyses indicated that, in addition to plasma VLDL, protein concentration of adipose tissue expressed as P/ml EPrep might be a useful predictor of fatness in chickens.