Thermal stress related with mortality rates on broilers' preslaughter operations: a lairage time effect study

Concerning the reduction of preslaughter death losses, high temperature and relative humidity in the tropics are the major concerns regarding broiler survival prior slaughtering. However, the relationship between different lairage times under controlled environment and the thermal condition outside the holding area is still unclear. Thus, the aim of this study was to compare different intervals of lairage time with different environmental temperature and relationship with poultry mortality rates. A study was conducted in a commercial poultry abattoir in the State of Sao Paulo, Brazil, in the year of 2006. The historical data set from 13,937 trucks, about broiler mortality during preslaughter operations, was given by the abattoir. Factors that influence the welfare of birds were studied, such as lairage time in abattoir and hourly dry-bulb temperature. The statistical analysis was performed using the Double Generalized Linear Models. The lower incidence of death losses before arrival at the processing plant (approximately 13 dead birds per truck) was observed when the lairage time was between 1 to 3 hours, under high temperatures (above 22°C). This effect was more pronounced under critical (25-28°C) and lethal intervals (above 29°C) (12 and 13 dead birds per truck, respectively). In relation to lairage time, the reduction in mortality rates was more pronounced in the intervals up to 1 hour of lairage under climatized conditions, with a reduction of 3 dead birds per truck. It was concluded that thermal stress have negative influence for broilers welfare kept under preslaughter conditions and variations on mortality rate are strongly related with different lairage times. No que diz respeito à redução das perdas por mortalidade pré-abate, as temperaturas e umidades relativas elevadas nos trópicos são as maiores preocupações quanto à sobrevivência de frangos de corte antes do abate. Entretanto, a relação entre diferentes tempos de espera em ambiente controlado e a condição térmica fora do galpão de espera ainda não está clara. Dessa forma, objetivou-se por meio deste trabalho comparar diferentes tempos de espera com diferentes temperaturas externas e a influência nas taxas de mortalidade de frangos de corte. O estudo foi conduzido em um abatedouro comercial de frangos de corte, situado no Estado de São Paulo, Brasil, durante o ano de 2006. Dados históricos de mortalidade de aves durante as operações pré-abate foram obtidos no abatedouro, provenientes de 13.937