Influência da densidade populacional sobre o peso médio, percentual de calo de patas e histomorfometria da bolsa cloacal em aves (Gallus gallus)

Abstract

O estresse exerce influência sobre o sistema imunológico das aves causando imunodepressão. O objetivo desse estudo foi o de quantificar o percentual da área cortical da bolsa cloacal, peso corporal e percentual de calos de patas de frangos de corte submetidos a três diferentes densidades populacionais. Os tratamentos foram compostos de três grupos de aves alojadas em boxes de 6 m2 em galpões climatizados, sendo que a densidade foi de 10, 15 e 20 aves/m2 em cada grupo. Ao final da primeira e da última semana, uma ave de cada tratamento foi sacrificada, colhendo-se as bolsas cloacais que, após processamento através de histopatologia, foram avaliadas sob microscopia de luz. Aos 42 dias de idade também foram determinados o peso médio das aves e o percentual de calos de patas dos animais dos diferentes tratamentos. Foi possível observar uma influência diretamente proporcional da densidade sobre o percentual de calos de patas e inversamente proporcional sobre o peso corporal e o percentual de córtex do folículo linfóide. A densidade populacional recomendada está entre 10 e 15 aves/m2. Palavras chaves: Frangos de corte, densidade populacional, bolsa cloacal, calos de pé, bem-estar animal.

Brazilian livestock industry has been effective in poultry meat with low cost of production. One of the factors to get the low cost is a high stocking density used in broiler houses. During the last years there has been considerable interest in the effects of stocking density on welfare and immunity because stress causes immunodeficiency in broilers, decreasing cellular and humoral response. The immunodeficiency can increase risks to infections and can increase condemnation compromising quality of food. The aim of this study was to evaluate morphologically the bursa of Fabricius of broilers submitted to three different stock densities. Body weight and foot-pad dermatitis were also studied at 42 d. Birds were raised from hatch to 42 d of age in pens of 6 m2 with 10, 15 and 20 birds/m2 corresponded to 60, 90 and 120 birds por pen, respectively. Water and feed were provided ad libitum and light was provided 20 h/d. Three birds of each group were killed at days 7 and 42. Bursa of Fabricius were collected, fixed and processed to histomorphometric evaluation using an image analyser Kontrom KS 400. Data were analysed by Biostat 3.0 (Tukey Test). The average percentage of cortical area in bursal follicles in birds with 6 weeks of age was 45,12a (10 birds/ m2), 30,43b (15 birds/ m2) and 23,77b (20 birds/ m2). The average weight in birds with 6 weeks of age was 2,583a Kg (10 birds/ m2), 2,557a Kg (15 birds/ m2) and 2,470b Kg (20 birds/ m2). The percentage of foot-pad dermatitis in birds with 6 weeks of age was 3,33a (10 birds/ m2), 17,76b (15 birds/ m2) and 49,17c (20 birds/ m2). Conclusions:Higher stocking densities decrease the percentage of parenchyma of bursa of Fabricius. It was also possible to realize that body weight and foot-pad dermatitis is negatively affected at higher stocking densities. The recommended stocking density is between 10 and 15 birds/ m2.