Effect of Gibberellic Acid on Production Characteristics of Aged and Force Molted Chickens in Cages

Abstract

Production characteristics of individually caged 72-week-old brown egg type hens or 86-week-old hens of a similar strain that had previously been subjected to different watering systems (continuous flow cups vs. intermittent flow troughs) and the stress and recovery of a forced molting program were evaluated in two trials over a 4 to 5-week interval following 6 alternate day subcutaneous injections (2.4 mg/bird) of gibberellic acid (GA3).Egg production and feed consumption of the 72-week-old hens maintained at constant temperature (20.0 ± 1.0 C), humidity (55%), and light intensity (10.76 lx) were significantly greater (GA3 × time, P<.05) in the GA3 treated birds and were accompanied by significantly larger eggs (GA3 × time, P<.05) with generally thinner shells. In the second trial, the 86-week-old hens responded with similar trends but the differences were less and related in part to prior watering system. No statistically significant differences were found for egg production, feed consumption, and egg weight as previously observed, but there was significantly greater shell thickness of eggs from the GA3-treated birds previously adapted to cups as compared to trough waterers (GA3 × time × waterer, P<.025). No statistically significant effects of GA3 on body weight were observed in either trial.The data suggest that the differences in response between the two trials may be related to the initial differences in egg production and, thus, the levels of circulating gonadal hormones, since GA3 has been shown to have androgenic activity in chicks, and estrogenic as well as other hormonal activity in other species.