Pre-slaughter factors affecting mortality, live weight loss, and carcass quality in broiler chickens

A field study was conducted to evaluate the influence of some pre-slaughter factors as journey time, stocking density, and lairage time on mortality, live weight loss and carcass defects on 321 flocks of broiler chickens slaughtered at a commercial processing plant. For each flock, the following traits were evaluated: birds dead-on-arrival (DOA); live weight loss; condemned carcasses; downgraded breasts, legs and wings (percentage of breasts, legs and wings presenting red discoloured haemorrhages); incidence of full gizzards. Flocks transported for short time in respect with those transported for medium and long time exhibited lower DOA percentage (0.24 vs. 0.41 and 0.45%; P<0.01) and live weight loss (1.27 vs. 1.87 vs. 2.09%; P<0.01), as well as they had significantly higher percentage of full gizzard (4.86 vs. 1.98 and 1.53%; P<0.05). The birds transported at a low stocking density exhibited higher live weight loss than those held at the medium or high densities (1.92 vs. 1.70 and 1.61%; P<0.05). Moreover low stocking density produced lower percentage of downgraded legs (1.43 vs. 1.70 and 1.75%; P<0.05). Otherwise the lairage time did not exhibit any significant effect. Because of the large number of processed birds, even small effects on the considered parameters may be economically significant to the industry as a whole. For instance, considering an average-sized plant (100,000 birds per day; 260 working day/year), processing 2.5 kg live weight birds with a carcass yield of 69%, a 0.21% higher DOA percentage and a 0.82 % greater live weight loss (long vs. short transport time) can produce a 1.8 and 462.0 tons higher product weight lost per day and year, respectively. In conclusion, this research has shown that journey time and stocking density affect mortality rate, process yield and carcass quality with detrimental effects on the economy of production, whereas lairage time impacts neither mortality nor carcass quality.