Causes and incidence of superficial pectoral myopathy in broiler chickens at a processing plant in Iwate Prefecture
2015
Sasaki, Y. (Iwate Veterinary Medical Association, Morioka, Iwate (Japan). Chicken Inspection Center) | Sato, R. | Oike, Y.
To clarify causes and incidence of superficial pectoral myopathy in broiler chickens, we inspected 4,020,289 carcasses at a chicken processing plant in Iwate Prefecture from April in 2013 to March in 2014. Histopathological examination of samples from two carcasses confirmed these lesions as superficial pectoral myopathy. The chickens were composed of two groups (Ross [R] strain and a domestic strain [T]). The annual incidence of superficial pectoral myopathy in R strain was low with 0.081 % (2,084/2,578,480 chickens), but this symptom occurred in many farms (80/99, 80.8 %). This symptom was not recognized in T strain. Male was overrepresented (1,816/2,084 chickens, 87.1 %) and there was a sexual predisposition. More chickens were confirmed to be affected with this symptom from July to October and from December to January. In these seasons, some lots exhibited high incidence (>0.2%). Logistic regression analysis of the disease suggested quantitatively that higher incidence of the disease was associated with rapid growth of chickens and that the season at slaughter significantly influenced the incidence. From these findings, the causes are thought to be growth rate and environmental temperature, and it is speculated that, in chicken strains bred for rapid growth such as R strain, individuals with rapid growth will develop the symptoms by exposure to high environmental temperatures.
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