Social dominance difference, given limited access to common food, between hens selected and unselected for increased egg production

Synopsis

White Leghorn hens, belonging to a population (P) selected on an index for high egg number combined with slightly increased egg size, were compared for social dominance with a control line (R) derived from P in 1958 and reproduced independently over ten generations of random selection. The P line matured 12 d earlier, laid 18 more eggs in the part year to 1st January, had an increased egg production from 1st January to 1st October in the second year, laid heavier (2 g) eggs and had slightly longer shanks than the R line. Body size of the two lines, however, was similar.

Observations on the social dominance of hens were made in pens containing four hungry P‐ and four hungry R‐hens when they were 70 or more weeks of age. Observations focused on the hens’ ability to take and maintain a place at a food trough allowing only limited access. Larger scores, corresponding to high ranks, were given to the hens which were able to spend the most time eating.

Clear‐cut differences of social rank in favour of the selected production line were found in all 20 pens. Phenotypic correlations between production characteristics of individual R‐hens and their social rank scores were in agreement with other studies, showing that within genetic lines hens of high social status matured earlier and had larger body size than the more timid individuals.