Genetic Parameters of Plasma Very Low Density Lipoproteins, Abdominal Fat Lipase, and Protein, Fatness, and Growth Traits of Broiler Chickens

Abstract

Genetic parameters of physiological, growth, and fatness traits were investigated in one control and two selected dam strains of broiler chickens. Feed consumption and efficiency were measured between 28 and 42 days of age but were adjusted to estimate values of population average body weights at these ages. Birds were bled at 45 days of age for assay of plasma very low density lipoproteins (VLDL) and killed at 47 days of age for carcass and fat measurements. Abdominal fat was assayed for lipase activity expressed per milligram of protein (LIP/mgP) or per gram of fat (LIP/gF) and protein content of the enzyme preparation expressed as μg protein/mL (P/mLEPrep).Absolute values of partial correlations corrected for sex and strain were low between production and physiological traits and between fatness and LIP/mgP but were moderate at .3 between fatness and plasma VLDL, LIP/gF, and P/mLEPrep. Heritabilities were moderate to high (≥ .32) for growth and fatness traits, moderate (.25) for plasma VLDL, and low (≤ .16) for P/mLEPrep, LIP/mgP, and LIP/gF. Genetic correlations involving plasma VLDL were as follows: .49 with body weight at 42 days, −.74 with feed consumption, .64 with feed efficiency, .24 with carcass weight at 47 days, 1.07 with abdominal fat weight, and .97 with abdominal fat percentage. Similarly, absolute values of genetic correlations involving P/mLEPrep tended to be as high or higher but genetic correlations involving LIP/mgP and LIP/gF tended to be lower than those involving plasma VLDL. After considering genetic gain by various methods of selection, it was concluded that to reduce fatness, indirect selection for low plasma VLDL was at least as effective as direct selection against abdominal fat percentage measured in sibs. However, concurrent selection for body weight would be necessary to improve this trait as well as feed efficiency.