-The objective of this study was to evaluate the effect of three levels of crude cottonseed oil on performance, organ weights, and blood parameters of growing broilers. Carcass and cut yields after 33 and 42 days of age and the economic viability of the diets were also evaluated. Male broilers of the Ross line were distributed in a completely randomized design, in a 4 × 2 factorial arrangement (0, 2, 4, and 6% inclusion of cottonseed oil, with and without ferrous sulfate) with five replicates. In the period from 22 to 33 days, quadratic and increasing linear effects were observed on feed intake and weight gain, respectively. Feed conversion during the same period was better with the addition of ferrous sulfate. The addition of ferrous sulfate caused a reduction in heart weight. From 22 to 42 days, carcass and cuts yield, organ weight, and intestine length were not influenced by the levels of oil or by the addition of ferrous sulfate. Supplementation with iron salts provided a lower red blood cell count and increased mean cell volume. Balanced diets formulated with up to 6% of crude cottonseed oil for broilers from 22-33 and 22-42 days of age do not affect their performance or the weight of their organs. Supplementation with ferrous sulfate improved feed conversion up to 33 days. Diets formulated with 4% cottonseed oil supplemented with ferrous sulfate are economically viable in the period from 22 to 42 days.

Bioquímica sérica e carcaça de frangos de corte, em condições naturais de calor, suplementados com zinco orgânico e vitamina E. Serum biochemistry and carcass of broilers, in natural heat conditions, supplemented with organic zinc and vitamin E. ________________________________________________________________________________ ResumoObjetivou-se avaliar o efeito do zinco orgânico e vitamina E nas dietas de frangos de corte expostos a condições naturais de calor cíclico, no período de 1 a 21 dias de idade, sobre o rendimento de carcaça e cortes, resistência da pele e bioquímica sérica. Foram utilizados 600 pintos de corte, machos e fêmeas da linhagem Ross 308, distribuídos em delineamento inteiramente casualizado. Os tratamentos consistiram na inclusão de zinco orgânico em associação a vitamina E nas dietas das aves. O rendimento de carcaça foi maior com a inclusão de 120 mg zinco orgânico/kg quando comparado ao tratamento sem o mineral. Os triglicerídeos séricos foram mais baixos com a suplementação de 300 mg e 600 mg de vitamina E. Houve interação entre os níveis de zinco e vitamina E promovendo a queda dos níveis de albumina sanguínea. O zinco orgânico confere maior rendimento de carcaça e a vitamina E, associada ou não ao zinco, melhora a bioquímica sérica de frangos de corte, em condições naturais de calor cíclico, até os 21 dias de idade. Palavras-chave: aves, mineral, tocoferol, triglicerídeos. AbstractThe objective of this study was to evaluate the effect of organic zinc and vitamin E on diets for broilers exposed to natural cyclic heat conditions, from 1 to 21 days of age, on carcass and cut yield, skin resistance and serum biochemistry. A total of 600 male and female Ross 308 chicks were used and distributed in a completely randomized design in a factorial scheme. The treatments consisted on inclusion of organic zinc (0 and 120 mg/kg) in association with vitamin E (0, 300 and 600 mg/kg) in the birds' diets. The carcass yield was higher with 120 mg of organic zinc/kg when compared to the treatment without the mineral. Serum triglycerides decreased with 300 mg and 600 mg of vitamin E supplementation. There was interaction between the levels of zinc and vitamin E promoting the fall of blood albumin levels. Organic zinc provides higher carcass yield and vitamin E, associated or not with zinc, improves the serum biochemistry of broiler chickens under natural cyclical heat conditions up to 21 days of age.