Influence of breed, age and body weight on organ weight in the chicken

Body, liver, heart and spleen weights were measured in 3 different breeds and 2 breed crosses over an age range of 0–8 weeks. Correlation coefficients, linear regression equations, standard deviations of observations around regression lines, and the standard errors of the slopes were calculated to study the effects of age, breed, and body weight on organ weight. The principal findings were:

1. Regardless of breed, organ weight does not change at the same rate as body weight during the first 8 weeks of life.

2. The ratio of liver or heart weight to body weight reaches a peak at about one to two weeks of age and then decreases gradually with age until 8 weeks. Spleen‐body weight ratio, however, increases to about the 3rd week of age after which it remains relatively constant.

3. Significant negative correlations were obtained between body weight and both liver‐ and heart‐body weight ratios; while significant positive correlations were obtained between body weight and spleen‐body weight ratios. The correlation between liver weight and heart weight was found to be higher than that between liver weight and spleen weight or between heart weight and spleen weight.

4. The ratio of organ weight to body weight differed with different breeds. The faster growing breeds had lower ratios of organ weight to body weight and higher correlation coefficients between body weight and organ weight ratios.

5. Regression equations are presented that enable the estimation of organ weights from body weights or from other organ weights in the three different breeds and two breed crosses studied.