Changes in the frequency and size of smooth muscle tumors in Japanese quail lines differing in body weight.

The purpose of this investigation was to study the incidence and size of smooth muscle tumors in several Japanese quail lines and to report recent correlated changes in mature BW and egg production. Laying females from lines selected solely (HW) or partly (HW-HP; HW-LP) for increased 4-wk BW or for decreased 4-wk BW (LW) and from the corresponding randombred control (R1) were used. Lines HW-HP and HW-LP were sublines of Line HW in which males were selected for increased 4-wk BW and females were selected for high or low level of total plasma phosphorus, respectively. Laying hens were examined for the presence of smooth muscle tumors after about 170 d of egg production (240 d of age). During Generations 19 through 26, mature BW was increasing in the HW line and decreasing in the LW line. Selection for either increased or decreased 4-wk BW resulted in decreased egg production, but the only significant change with generations was a decrease of 2.7 eggs per hen for a 120-d laying period in the LW line. Frequency and weight of the smooth muscle tumors were greater for females from the large-bodied lines than females from Line R1. No tumors were detected in LW females. Based on the linear regression of response on generations, tumor frequency was increasing in Line HW-LP but tumor weight was decreasing in this line. Tumor weight was increasing in the HW line. No other changes in tumor frequency or size were noted across generations. Weight of the tumors was not correlated with egg production. The presence of tumors did not seem to affect mortality during the laying period. The Japanese quail lines may serve as a useful animal model for the study of smooth muscle tumors in humans, chickens, and turkeys.