Performance Testing of Pigs for Lean Tissue Growth Rate in a Selection Experiment with Low and High Protein Diets: II. Correlated Responses of Lean Percentage and Growth Rate

Abstract

In a selection experiment, halothane gene-free Swedish Yorkshire pigs were performance tested for improved lean tissue growth rate (LTGR) on a high protein [HP, 18.5% crude protein (CP)] or a low protein (LP, 13.1% CP) diet. LTGR was determined based on ultrasonic measurements and repeated weighings. In total, 2885 pigs were tested in generation zero and four selected generations. Genetic parameters were estimated with REML using a multiple trait animal model. Heritabilities for growth rate and lean percentage were 0.37 and 0.49 in the LP-line and 0.31 and 0.46 in the HP-line. The genetic correlation between growth rate and lean percentage was favourable (0.25) in the HP-line but unfavourable (-0.67) in the LP-line. As a result, lean percentage in the LP-line decreased during the course of selection. Growth rate increased in both lines, since it was highly correlated (0.96) with LTGR.

Key Words:

• swine
• heritability
• pig breeding
• genetic parameters
• genetic correlations