Active immunization of broiler breeder hens with a recombinant chicken inhibin fusion protein enhances egg lay

Department of Poultry Science, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Louisiana State University, Baton Rouge 70803, USA. dsatterlee@agctr.lsu.edu

We have demonstrated that inoculation of female Coturnix with an inhibin-based immunogen (MBP-cINA521) accelerated puberty and enhanced hen-day egg production (HDEP). Herein, MBP-cINA521, a fusion protein, which consists of the bacterial maltose binding protein (MBP) and a fragment of the infinity-subunit of chicken inhibin (cINA521), was tested for its ability to enhance production performance in broiler breeders. Pullets (Arbor Acres Classic Females; n = 60 birds/treatment group) were given (subcutaneously) 0, 1, 3, or 5 mg of MBP-cINA521 in Freund's complete adjuvant at 20 wk and 4 d of age. Booster immunizations (one-half of the primary dosages) were given at 23 wk of age. The vehicle for controls (CON; no booster) and MBP-cINA521-boosted birds was Freund's incomplete adjuvant. Blood samples were obtained at the end of the trial to assess immunological response to the antigen with a titer ELISA. The onset of puberty was assessed by calculation of the average ages at first lay (FIRST) and at 50% egg production (FIFTY). Cumulative percentage HDEP was determined weekly throughout the laying period (40 wk). Egg weight (EWT) and specific gravity (SG) assessments were made periodically during the trial. Body weight gain (BWG) and mortality (MORT) data were also collected. Significant injection treatment differences (P < 0.01) in inhibin antibody titers were detected according to the following order: low dose = intermediate dose > high dose > CON. A dose of MBP-cINA521 capable of accelerating puberty and increasing overall egg lay was identified. FIRST and FIFTY responses were decreased (P < 0.05) in birds given the intermediate dose (3.0 mg) of MBP-cINA521 when compared to the CON. FIFTY responses were also lower (P < 0.05) than CON responses in those birds given the highest dose (5.0 mg) of the inhibin antigen. Cumulative HDEP was also higher (P < 0.05), beginning at 3 wk of lay and weekly thereafter (P < 0.05, for the remaining 40 wk), in birds given the intermediate immunogen dosage when compared to the CON. By Week 40, an average increase of 9.5% HDEP was realized in birds given 3.0 mg of MBP-cINA521. MORT rates were similar in the CON and in the two lowest MBP-cINA521 treatment groups but were higher (P < 0.05) in those birds given 5.0 mg of the antigen. EWT, SG, and BWG measurements were unaffected by treatment with the inhibin vaccine. In agreement with our findings in quail, immunoneutralization of inhibin enhanced production performance in breeder hens.