Relationship of Variation to Rate of Growth

UNIFORMITY of performance is highly desirable in commercial animal production. Unfavorable nutritional and environmental conditions appear to increase the variability in a given population. Factors which correct such conditions increase rate of growth. Thus, there should be a relationship between variability and rate of growth. Observations supporting this assumption have been made by several workers. Went (1953) concluded from work with tomatoes and peas that “the more optimal growing conditions are, the smaller is phenotypic variability.” Searle (1954) studied the influence of maternal diet on variation of skeletal measurements in mice. Poor diets increased variation and the frequency of anomalies. McLaren and Michie (1956) measured responses to a narcotic drug in mice of various genetic and environmental origins. They conclude that the variability of such traits, which are affected during growth and development by environmental influences or which are physiologically correlated with fitness, will be increased by adverse conditions of . . .