The effect of dietary vitamin and mineral supplements withdrawal on broiler carcass yield and meat composition

Este estudo teve por objetivo determinar o efeito da retirada dos suplementos vitamínico e mineral da dieta de frangos de corte no período final de crescimento sobre o rendimento de carcaça, a gordura abdominal e a composição da carne destas aves. Cento e doze aves de uma linhagem comercial com 21 dias de idade foram alimentadas com dietas experimentais até os 42 dias de idade. Os tratamentos foram: T1 : dieta contendo suplementos vitamínico e mineral; T2: dieta sem suplementos; T3: dieta com suplementos dos dias 21 ao 27; T4: dieta com suplementos dos dias 21 ao 34. Ao final do período experimental oito aves de cada tratamento (metade de cada sexo) foram abatidas e o rendimento de carcaça e gordura abdominal determinados como percentual do peso vivo. As carnes claras e escuras de cada carcaça foram coletadas para determinação da composição proximal. A restrição de vitaminas e minerais na dieta não afetou significativamente o rendimento de carcaça. As aves que receberam a dieta sem suplementos (T2) apresentaram percentagem de gordura abdominal significativamente (P<=0,05) superior a dos outros tratamentos. Os níveis médios de umidade e cinzas na carne dos frangos foram de aproximadamente 73,53% e 1,07%, respectivamente. A concentração de lipídios no T4 foi significativamente (P < 0,05) inferior a dos demais tratamentos e as carnes escuras (6,88%) apresentaram valores significativamente superiores aos das carnes claras (1,42%). O nível médio de proteína foi de 19% com valores variando de 17% na carne escura a 21% na carne clara.The objective of this study was to assess the effect of the withdrawal of vitamin and mineral supplements from the diets of broilers in their final period of growing on carcass and abdominal fat yields and on meat composition. One hundred and twelve birds of a commercial line were fed experimental diets from the 21st to the 42nd days of age, consisting of four treatments: T1: diet containing regular mineral and vitamin supplements; T2: diet without supplements;T3: diet with regular supplements from day 21 to day 27 and without supplements from day 28 to day 42; T4: diet with regular supplements from day 21 to day 34 and without supplements from day 35 to day 42. Eight birds from each treatment (half from each sex) were slaughtered at the end of the experimental period. Carcass yield and abdominal fat were measured. Dark and light meat from each carcass were then collected and analyzed for proximal composition. Vitamin and mineral restriction did not significantly (P>0,05) affect carcass yield. Birds from T2 showed levels of abdominal fat significantly (P<0,05) higher than those from the other treatments. Moisture and ash levels in chicken meat was about 19% with values ranging from 17% in dark meat to 21% in light meat. Results suggest that diets with vitamin and mineral restriction between the 21st and the 42nd day of age could increase the level of abdominal fat in the chicken about 73,53% and 1,07%, respectively and were not affected by treatment, sex or type of meat. Lipid content in birds from T4 was significantly (P<0,05) lower than those in birds from the other treatments. Lipid level in dark meat (6,88%) was higher(P