title: Effect of active immunization against recombinant-derived chicken prolactin fusion protein on the onset of broodiness and photoinduced egg laying in bantam hens.
abstract: The hypothesis that the onset of incubation behaviour (broodiness) in the domestic hen is induced by an increase in prolactin secretion was investigated by actively immunizing bantam hens against recombinant-derived chicken prolactin. A second objective was to establish whether active immunization against prolactin affects photoinduced onset of egg laying and the rate of egg production. The immunogen was a fusion protein (beta gals-prolactin, 23 kDa) produced in Escherichia coli, comprising chicken prolactin (without the nine amino-terminal amino acids) fused to 18 amino acids of E. coli beta-galactosidase. A control immunogen was produced in the same strain of E. coli harbouring the same plasmid vector used to produce beta gals-prolactin minus the prolactin gene sequence. Hens were immunized i.m. with 1 mg of protein containing 0.8-0.9 mg of fusion protein in Freund's incomplete adjuvant at 4-8 week intervals beginning before or after egg laying, which was induced by increasing the daily photoperiod. The beta gals-prolactin immunogen, but not the control immunogen, stimulated the production of antibodies to chicken prolactin. In Expts 1, 2 and 3, hens were placed in floor pens with nest boxes after photostimulation to induce broodiness. In these experiments, immunization with beta gals-prolactin reduced the incidence or delayed the development of broodiness. This effect was more pronounced if immunization was initiated before, rather than after, the onset of egg laying. In Expts 1 and 2 hens were immunized with beta gals-prolactin before photostimulation. The presence of antibodies to prolactin in their blood did not affect photoinduced onset of egg laying.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Division of Development and Reproduction, Roslin Institute (Edinburgh), Midlothian, UK.
authors.forename: J B
authors.initials: JB
authors.lastname: March
authors.forename: P J
authors.initials: PJ
authors.lastname: Sharp
authors.forename: P W
authors.initials: PW
authors.lastname: Wilson
authors.forename: H M
authors.initials: HM
authors.lastname: Sang
mesh_terms: D000818:Animals; D002645:Chickens / Q000502:physiology*; D005260:Female; D007114:Immunization; D008027:Light; D008425:Maternal Behavior / Q000502:physiology*; D010058:Oviposition / Q000502:physiology*; D011388:Prolactin / Q000276:immunology / Q000378:metabolism*; D011994:Recombinant Proteins / Q000276:immunology
chemical_list: D011994:Recombinant Proteins; D011388:Prolactin