Effects of conjugated linoleic acids, fish oil and soybean oil on the growth performance, carcass traits, lipid characteristic and PPARs mRNA expression in broiler chickens

The conjugated linoleic acids (CLA) are known to decrease hepatic lipid deposition and overall lipid metabolism in selected animal models. These properties can be employed to reduce body fat accumulation in food animals, as in broiler chicken. In fact, every 1 % decrease in the chicken’s body fat would result in the average Malaysian eating 300 g less fat for a year from chicken meat, based on per capita chicken meat consumption figures for 2010. However, the anti-lipogenic effects of CLA are variable and complicated because of the differences in animal species, diet composition and possibly their interactions with other dietary fatty acids. We hypothesized that CLA effects on fat metabolism in broiler chickens could be altered by the presence of dietary n-3 and n-6 fatty acids. Hence, fish oil (rich source of n-3 fatty acids) and soybean oil (rich source of n-6 fatty acids) were used in this trial. This study aimed to investigate the effects of dietary conjugated linoleic acids, fish oil, soybean oil and their mixtures, as well as palm oil on broiler chickens. A total of 560 day-old Ross 308 male broiler chickens allotted randomly into 7 equal treatment groups and used in 42 days experimental period. All chicks were fed a starter corn-soybean meal-based diet for 10 days. The treatment diets used were adjusted to be isocaloric and isonitrogenous comprising the corn-soybean meal plus specific dietary fat supplements consisting of conjugated linoleic acid (CLA), fish oil, soybean oil, palm oil or their combinations. The dietary fats were included in the experimental diets at 7% for single fats and 3.5% + 3.5% for dual mixes, and because of the lower metabolisable energy of palm oil as compared to PUFAs, its inclusion rate was about 12%. The conjugated linoleic acids supplement used in this study was LUTA-CLA 60, containing 60% conjugated linoleic acid. Therefore the dietary inclusions of 7 and 3.5% LUTA-CLA 60 were effectively supplying 4.2 and 2.1% CLA, respectively. The treatment groups were 7% soybean oil (SO), 7% LUTA-CLA 60 (CL), 7% fish oil (FO), 3.5% LUTA-CLA 60+ 3.5% soybean oil (CLSO), 3.5% fish oil + 3.5% soybean oil (FOSO), 3.5% LUTA-CLA 60 + 3.5% fish oil (CLFO) and 12% palm oil (PO). The experimental diets were used at grower (11-28 d) and finisher (29-42 d) phases and performance data were collected for each period. Tissue and serum sampling was carried out at the end of experiment (42 d). The high level of palm oil inclusion in the diet did not adversely affect chicken’s feed intake or growth rate. The lowest weight gains were recorded for birds from FO and CL groups during the grower (24.2 g/b/d) and finisher (50.9 g/b/d) phases, respectively. The FO diet also reduced the feed intake of chickens (34.5 g/b/d) while dietary conjugated linoleic acids had no effect on feed intake regardless of its dosage and combinations with other fats. It was also found that palm oil supplemented at about 12 % (w/w) increased the weight of abdominal fat pads significantly (%2.4 of live weight), while higher conjugated linoleic acids content of the CL group increased post slaughter liver weights (%3.3 of live weight) (P<0.05). Lipid contents of the breast tissues were higher in the PO (%2.46), SO (%2.02) and FO (%2.02) groups (P<0.05) versus others (%1.11-1.55). Birds from the FO group had the highest amount of fats in their thigh muscles (%3.94) (P