THE EFFECT OF DIVERGENT SELECTION FOR TOTAL PLASMA PHOSPHORUS IN JAPANESE-QUAIL ON FEARFULNESS AND SELECTED BLOOD AND HEART PARAMETERS

A selection experiment utilizing Japanese quail was initiated to study the genetic relationship of growth and reproduction traits. In this s tudy, lines were selected for increased (HP line) and decreased (LP li ne) total plasma phosphorus at the beginning of lay. The HP and LP lin es were derived from a randombred control population (R1 line) that wa s maintained with the selected lines to remove environmental variation over generations. During the course of selection, it was observed tha t blood from HP line females was more viscous than that of the LP and R1 females. In later generations of selection, mortality of females du ring a 120-d egg production period was higher in the HP line than in t he LP and R1 lines. The purpose of this experiment was to identify pos sible factors contributing to the increased mortality in the HP line. Fearfulness, as measured by tonic immobility, was greater in the HP an d LP lines than in the R1 line. Indirect blood pressure measurements w ere made near the beginning and near the end of the 120-d egg producti on period. No significant line differences were observed in either mea surement. Weight of the heart at the end of the laying period was high er in the HP and LP lines than in the R1 line. Histological study of t he hearts of the HP and R1 lines indicated significant increases in th e HP line in collagen content of the coronary arteries and in myocardi al fibrosis. The data suggest that the increased mortality of females of the HP line relative to the RI Line during the laying period may be related to increased fearfulness and changes in the coronary structur e leading to heart abnormalities.