Efeito do sistema de criação sobre o desempenho e rendimento de carcaça de frangos de corte tipo colonial / Effect of production system on performance and carcass yield of free range broiler chickens

Foram utilizados 1600 pintos de corte de um dia de idade, distribuídos em delineamento, em blocos ao acaso, com esquema fatorial 4Î2 (quatro linhagens, sendo uma delas comercial (Ross-308) e as demais específicas para a produção colonial (Caipirinha, Pescoço Pelado e Paraíso Pedrês) e dois sistemas de criação (confinado e com acesso a piquete), com quatro repetições de 50 aves cada. A ração não continha promotores químicos de crescimento e produtos de origem animal. Avaliaram-se o ganho de peso, o consumo de ração, a conversão alimentar, a mortalidade e os rendimentos de carcaça e das partes (peito, pernas, asas e dorso) aos 56, 63, 70, 77 e 84 dias de idade. O comprimento e a porcentagem (em relação ao peso vivo) dos intestinos e o peso e a porcentagem (em relação ao peso vivo) do fígado, moela e pâncreas foram avaliados aos 84 dias de idade. Houve efeito (P<0,05) da linhagem para as características de desempenho e da linhagem e do sexo para rendimentos da carcaça e das partes, assim como para as características do sistema digestório (P<0,05). O sistema de criação não influenciou as características avaliadas.

One thousand and six hundred day-old-chicks were randomly assigned to a 4Î2 factorial design (4 strains and 2 production systems) with 4 replicates of 50 birds each. A commercial strain Ross and three strains (Caipirinha, Pescoço Pelado and Paraíso Pedrês) for free range chicken production systems were used. The production systems were confined and semi-confined supplemented with grass paddock (3m²/bird). The diets did not contain chemical growth promoters and animal by products. Weight gain, feed consumption, feed conversion, mortality and carcass yield and parts were evaluated at 56, 63, 70, 77 and 84 days. Length and percentage of gut, liver, gizzard and spleen were evaluated at 84 days. Differences (P<0.05) among strains for performance, carcass yield and parts and gut characteristics and no differences (P>0.05) among production systems were observed.

Performance and physiological parameters of broiler chickens subjected to fasting on the neonatal period.

Broiler chicks aged 12 h after hatching were allotted according to a block design in a 7 x 2 factorial schedule of 14 treatments and four replications of 50 chicks each one. The main experimental factors were fasting for 0, 6, 12, 18, 24, 30, and 36 h after chick placement and sex. Independent of sex, fasting had a negative linear effect on weight and productivity of broilers at market age (42 d) without affecting feed conversion or mortality index. Groups subjected to 18 and 36 h of fasting after placement, corresponding to 30 and 48 h posthatching fasting, had lower biometrical values for small intestine (length, weight, and size; villus height; and crypt depth) than chicks fed immediately after placement. According to the Pearson test, BW of birds at 21 and 42 d were significantly correlated to BW at 7 d (r=0.77) and 21 d (r=0.45), respectively. Males performed better than females but had higher mortality rates. Fasting did not influence serum concentrations of corticosterone or sexual steroid hormones. Nevertheless, early signs of sexual dimorphism arose from the high estradiol (E2) concentration on female serum. Heterophil:lymphocyte ratio was not different among treatments, indicating that early fasting did not seem to be a stress factor 21 or 42 d after fasting. The results suggested a maximum fasting of 24 h after hatching in order to preserve broiler productivity at market age.