Carcass-Wide Mapping of Fat and Lean Responses to Late-Finishing Conjugated Linoleic Acid Supplementation in Castrated Male and Female Pigs

This study examined the effects of dietary conjugated linoleic acid (CLA) fed during the final fattening period on growth, slaughter traits, backfat and carcass tissue composition in castrated male and female Swedish Landrace pigs. A total of 112 pigs were assigned to a 2 × 2 factorial design with diet (control or CLA) and sex as factors. From 130 to 175 days of age, pigs were fed either a control diet or a diet in which 0.5% CLA oil (about 0.3% CLA) replaced part of the soybean oil. The left halves of 60 randomly chosen carcasses (15 per group) were dissected into muscle, subcutaneous fat, intermuscular fat, skin and bone. CLA did not affect final body weight, daily gain, carcass weight or dressing percentage. With pen as the experimental unit, it reduced mean backfat thickness (primary end-point, p = 0.008) and subcutaneous fat percentage (p = 0.021) and increased muscle percentage (p = 0.036) and the muscle-to-fat ratio (p = 0.018), independently of slaughter weight. In the individual-pig analysis, backfat was also lower at all four sites (p ≤ 0.045), as was total fat percentage (p = 0.015). Whole-carcass diet × sex interactions were not significant, and two nominally significant cut-level interactions in the belly did not remain significant after adjustment for multiple testing. Dissection showed that CLA lowered subcutaneous fat in all ten cuts (significantly after adjustment for multiple testing in seven) and shifted the carcass composition towards muscle, without affecting growth or slaughter yield. No sex-specific response was demonstrated.