determination of the effects of organic antioxidants and fat sources on performance, carcass and bone characteristics of broilers under heat stress

introduction heat stress is one of the major environmental stressors that negatively influence feed intake, body weight gain, feed conversion ratio, nutrient digestion, absorption, and retention in the poultry production. in the two last decades, several researches were done to find approaches for decreasing the undesirable effects of high ambient temperatures. supplementation of powder, extract and essence of some medicinal plants were proposed that could be used in poultry production to improve the performance, immune system and antioxidant status in heat stress condition. turmeric powder is known as a natural antioxidant, because it has several antioxidant component specially curcumin that prevent the oxidative reaction and the free radicals production in the live body. on the other hand, some of by-products in food industry may also be used in heat stressed birds. tomato pomace is a reachable source of vit e, c and a and several carotenoids specially lycopene that has antimutagenic, anticancer and antioxidant properties. therefore the objective of this research was to investigate the effects of organic antioxidants including turmeric powder and tomato pomace and fat sources including soybean oil, canola oil and tallow on performance, carcass and bone characteristics of broilers under heat stress. materials and methods an experiment with factorial arrangement 3× 2× 2 (3 oils involved: canola, soybean, tallow, 2 turmeric powder (trp) levels involved 0.4, 0.8% and 2 tomato pomace (tp) levels 3, 5 of tp%) in a completely randomized design in heat stressed birds was done. five hundred four one-d-old male ross broilers were randomly allocated to 36 experimental units with 12 dietary treatments (3 replicates with 12 birds in each). the feed and water were supplied ad libitum. all diets were balanced to meet the nutrient requirement proposed by the ross committee. a daily heat stressed (hs) schedule (33oc for 5 h) was applied from 29 to 42d of experiment. the photoperiod schedule, vaccination, ventilation and humidity were applied according to the recommendation of ross management catalog. at 28 d. (before heat stress phs) and 42 d. (after heat stress ahs) of age, two chicks per replicate were bled and slaughtered. the relative weight of carcass, intestine, thigh, liver, spleen, intestine, pancreases, gall bladder and abdominal fat were determined. the bone characteristics including dry matter, ash, calcium, phosphorous, bone length, diaphysis diameter were studied. the data were analyzed by glm procedure of sas software and the differences among mean were investigated by tukey test. results and discussions the results indicated that body weight gain enhanced when chicks fed diets containing canola oil or 5% tp. canola oil including diet decreased the fcr at 28d (p<0.05). the animal production index, energy efficiency and protein efficiency ratio were higher in birds fed canola oil at phs (p<0.05). the relative weight of burs at phs and burs and spleen at ahs increased when birds fed canola oil as compared to tallow. the percentage of abdominal fat decreased by dietary treatments (p<0.05). the abdominal fat is an undesirable factors that negatively affect poultry meat palatability. thus reduction of abdominal fat and cholesterol could improve the meat quality of broiler. canola oil is a source of omega-3 fatty acid that affects the fat absorption and retention in broilers body. previous studies also revealed that inclusion of canola oil to broiler diets decreased the abdominal fat, cholesterol. the other relative weights of organs were not influenced by dietary treatments at phs and ahs. the diet containing canola oil improved the percentage of ash, ca, and length of bone, diaphysis diameter and thickness. the percentage of ca and ash were higher at 0.8 % of trp (p<0.05). the diets containing tomato pomace did not significantly influence bone parameters such as percentage of ash, ca, and length of bone, diaphysis diameter and thickness. there is an interaction between oil and tp about energy efficiency and protein efficiency ratio. conclusion therefore, inclusion of canola oil with lower levels of trp and tp to diets may improve the performance, bone characteristics, and abdominal fat of broiler under heat stress.