Effects of different dietary fat and oil supplements on performance , carcass , and blood characteristics in broiler chickens

An excess body fat deposition in broilers has been a major concern for producers and consumers. Decreasing broiler abdominal fat is of particular interest, as the abdominal fat content at slaughter may represent more than 3 percent of live weight (SANZ et al., 1999). In addition, human studies have shown an association between higher dietary fat intake and cardiovascular diseases. Dietary levels of cholesterol (HAYES, 1995) and fatty acid profiles in lipid fractions (BLANCH and GRASHORN, 1996) are associated with the development of atherosclerosis and coronary artery diseases in humans. Studies either in birds or in mammals showed the inhibitory effect of polyunsaturated fatty acids (PUFA) on fat tissue synthesis (SANZ et al., 2000), describing the decreased abdominal fat content following dietary PUFA inclusion. The fats containing the enriched unsaturated fatty acids (UFA) have been reported to be more digestible and absorbable compared to those rich in short-chain saturated fatty acids (SFA; DÄNICKE, 2001). Beef tallow, as a source of fat, has a lower digestibility and metabolisable energy (ME) content in comparison to vegetable oils, attributing to higher long-chain SFA content (BLANCH et al., 1995). Other reports indicated that broiler chickens fed diets enriched in PUFA had lower abdominal (SANZ et al., 1999) or total body (SANZ et al., 2000) fat deposition than those fed diets containing SFA. It has been reported that sunflower oil produced less abdominal fat deposition in broilers than did tallow at different levels of fat inclusions, although the ME content of tallow was lower than that of sunflower oil (VILA and ESTEVE-GARCIA, 1996). SANZ et al. (1999) found a lower abdominal fat content in broilers fed sunflower oil compared to those fed tallow or lard. Furthermore, using conjugated linoleic acid has been addressed to produce low-fat broiler carcasses (JAVADI et al., 2007). Nonetheless, POTENÇA et al. (2008) found no effect of including animal or vegetable dietary lipid sources on performance, abdominal fat deposition, or tibia density and strength in broilers. The local oil and fat by-products must be properly analyzed chemically and biologically to determine their using merit and appropriate mixture for animal feeding purposes. Furthermore, despite a good body of literature on the effects of using different dietary fat and oil supplements on performance in broiler chickens, there is a paucity of data on simultaneous usage of saturated and unsaturated fatty acid sources on performance and blood profile in broilers. The previous studies mostly investigated the effects of diets different in ME content; however, the effect of feeding fat and oil supplements in isonitrogenous and isocaloric diets may reveal the differences among treatments based on net energy and show the performance and carcass or blood characteristics responses more precisely. Therefore, the present study was conducted to evaluate the effect of using different fat and oil supplements in isonitrogenous and isochaloric diets on performance and several carcass and blood characteristics in broiler chickens.