Effect of corticosterone and prolactin on fattening in broiler chicks.

The influence of temporal interaction of corticosterone and prolactin on fattening in broilers was studied in male chicks subjected to continuous illumination. Injections were started at 26 days of age and each experiment continued for 10 days. Corticosterone, injected daily during nine days at a concentration of 300 or 600 microgram/bird/day significantly (P less than .01) decreased weight gain and increased abdominal fat pad size, skin dry matter, relative liver size, and liver fat content. Corticosterone injected at eight 1600 or 1000 hr elicited essentially the same response. Prolactin, injected daily either at 1600 or 1000 hr during nine days at a concentration of 232 microgram/bird/day, did not significantly affect any of the above parameters. The combination of corticosterone (600 microgram/bird/day for nine days) injected at 1600 hr and prolactin (232 microgram/bird/day) injected simultaneously or 18 hr or 42 hr later, caused a further significant (P less than .05) decrease in weight gain in two out of the three experiments. This combination, however, as well as that of 300 microgram corticosterone/bird/day, had no consistent effect on the parameters of fattening. It is concluded that fattening of chicks induced by injections of corticosterone and prolactin is mainly due to the effect of corticosterone.