Prevention of incubation behavior expression in turkey hens by active immunization against prolactin

The consequences of active immunization against prolactin on expression of incubation, reproductive performance and hormonal profiles were evaluated in turkey hens. Hens were injected weekly for 4 wk starting 8 wk before being submitted to a stimulatory photoperiod and 3 times thereafter at intervals of 4 to 5 wk. The hens were injected i.d. with 0.5 mL of a mixture diluted half in Freund's adjuvant. The mixture was prediluted in .9% saline and contained 100 micrograms of a fusion protein (GST-tPRL), GST, oPRL or vehicle. The results indicate that active immunizations with GST-tPRL or oPRL both induce production of specific prolactin antibodies. The onset of egg production was unaffected but higher egg production was observed for the GST-tPRL immunized hens. No GST-tPRL immunized hens expressed incubation behavior, whereas 20 to 30% of hens in the other experimental groups did so. Apparent hyperprolactinemia was detected by RIA for the GST-tPRL immunized groups starting before photostimulation and lasting until Week 10 of egg production but not in other groups. No significant differences were observed in either plasma LH or estradiol concentrations of immunized and nonimmunized turkey hens. In conclusion, both GST-tPRL or oPRL induced the production of antibodies against prolactin in turkey hens. However, only active immunization using GST-tPRL induced higher antibody titers as well as full prevention of incubation behavior expression. Such a pharmacological approach is of great practical interest, although its uses need to be carefully evaluated under commercial conditions.