INFLUENCE OF GRADED LEVELS OF DIETARY PROPIONIC ACID ON PERFORMANCE AND CARCASS TRAITS OF SWINE FED DIETS SUPPLEMENTED WITH SOYBEAN MEAL OR CANOLA MEAL

Sixty-four crossbred pigs (averaging 24 kg) were used to study the effects of dietary propionic acid (PA) on backfat measurements and fatty acid (FA) composition and on rate of gain and feed:gain ratio. Isonitrogenous and isoenergetic diets, based on either barley-soybean meal or barley-conola meal, contained either 0, 3, 6 or 9% PA. Inclusion of PA depressed feed intake in a linear manner, with daily gain being reduced when pigs received 6 or 9% PA. Feed:gain ratio did not differ significantly for PA treatments. Backfat thickness was significantly reduced by PA inclusion in the diet, while carcass grade was slightly improved. Inclusion of PA significantly increased levels of 15:0, 17:0 and 17:1 FA in the outer subcutaneous backfat layers with an accompanying decrease in 16:0 and 18:0 FA. Higher levels of odd-chain FA observed in the backfat of PA-supplemented pigs suggest that not all the propionic acid was metabolized; some is being incorporated directly into FA. Pigs fed diets containing 15.9–18.9% canola meal had reduced feed intake, lower daily gains, poorer feed:gain ratio, and reduced total backfat compared with those fed soybean meal diets. Pigs fed canola meal had higher backfat levels of 17:0 FA compared with those fed soybean meal. These results do not invalidate the current recommendation that 10% canola meal may be fed in diets of growing pigs.