Fontes lipídicas e níveis de suplementação de vitamina a em rações para frangos de corte

Abstract

In this work, two experiments have been carried out. In the first one, the influence of vitamin A on performance, carcass and organ yields, blood parameters, protein and fat deposition, meat quality and bone parameters of broilers were evaluated. 2,300 chicks were distributed in a 2x2x5 factorial scheme, with two lipid sources (soy and palm), two supplementation periods, five levels of vitamin A (0; 3,000; 6,000; 12,000; 24,000 IU kg-1) and 10 repetitions with 23 birds each one. At 22 days old, treatments were redistributed; five repetitions continued to receive the initial diet and five repetitions received a diet supplemented with 6,700 IU kg-1. At 21 days old, the lipid source influenced the feed consumption, feed conversion and abdominal fat. The vitamin A influenced feed intake and weight gain (quadratic response). Vitamin A also influenced the weight of the liver, proventricle and abdominal fat at 21 days old. At 42 days old, the lipid source and vitamin A level influenced feed intake. Weight gain and feed conversion were influenced by period of supplementation and vitamin A level. Carcass yield and meat pH were influenced by vitamin A supplementation. From 1 to 21 days old, vitamin A supplementation was estimated at 15,585 IU kg-1 and at 42 days, 15,527 IU kg-1 and 15,148 IU kg-1 were estimated for periods 1 to 21 and 1 to 42 days, respectively. The second experiment evaluated the influence of vitamin A on performance, carcass and organ yields, bone and skin characteristics, meat quality and myopathies in broilers. 1,920 birds were distributed in a randomized design, with 6 vitamin A supplementations (0; 6,000; 16,000; 26,000; 36,000 and 46,000 IU kg-1), into 16 repetitions with 20 birds. In the period from 22 to 42 days old, treatments were divided, 8 repetitions continued in the initial treatment and 8 repetitions with diets without vitamin A (0 IU kg-1). The level of vitamin A influenced feed intake, weight gain and weight of the proventricle at 21 days old (quadratic response). At 42 days, vitamin A influenced the weight gain and feed intake of birds not supplemented after 21 days. In birds supplemented up to 42 days, weight gain, feed intake and feed conversion obtained quadratic responses. There was an influence of vitamin A on the weight of the wings, chest, legs, small intestine, pancreas, gizzard, abdominal fat, Seedor index, bone rupture strength and yellow intensity (b *). The incidence of WB with higher scores was found in birds supplemented from 5 to 42 days. WS showed a quadratic response to vitamin A supplementation. At 21 days old, supplementation of 28,209 IU kg-1 was estimated, while birds supplemented up to 42 days supplementation of 29,375 IU kg-1 and 27,775 IU kg-1 of vitamin A showed better results for weight gain and feed conversion, respectively.