ACTIVE IMMUNIZATION OF JAPANESE-QUAIL HENS WITH A RECOMBINANT CHICKENINHIBIN FUSION PROTEIN ENHANCES PRODUCTION PERFORMANCE

The effects of active immunization against inhibin on production perfo rmance in female Japanese quail (Coturnix coturnix japonica) were asse ssed in two separate trials using an MBP-cINA521 fusion protein as an immunogen. The fusion protein, MBP-cINA521, consisted of the bacterial maltose binding protein (MBP) and a truncated form of the mature alph a-subunit of chicken inhibin (cINA521). MBP-cINAI521 was constructed b y: 1) excising a 521-bp PstI fragment from a chicken inhibin alpha-sub unit cDNA (cINA6; gift of P. A. Johnson), 2) cloning this fragment, wh ich encodes all but the first 11 amino acid residues of the mature alp ha-subunit, into the pMal-c2 vector of the MBP fusion expression syste m, and 3) expressing the fusion protein (MBP-cINA521) from the Escheri chia coli and purifying it using affinity chromatography. In each tria l, quail were randomly and equally assigned to one of two injection tr eatments as follows: 1) MBP-cINA521 in Freund's adjuvant, or 2) Freund 's adjuvant (vehicular controls; CON). All immunizations were given su bcutaneously and Freund's complete and incomplete adjuvant were used f or primary and booster injections, respectively. In Trial 1, birds wer e given a primary challenge of 0.2 mg MBP-cINA521 per bird at 25 d of age, followed by booster immunizations (0.1 mg MBP-cINA521 per bird) a t 33, 40, 47, 54 and 61 d of age and every 35 d thereafter. The CON bi rds received vehicular immunizations at the same time intervals. In Tr ial 2, birds treated with MBP-cINA521 received a primary challenge of 0.2 mg MBP-cINA521 per bird at 26 d of age, followed by booster immuni zations (0.1 mg MBP-cINA521 per bird) using the same schedule as that used in Trial 1, with the exception that no boosters were given after 61 d of age. The CON birds received vehicular immunizations at the sam e time intervals. Collection of production performance data was initia ted coincident with the laying of the first egg in each trial (i.e., b eginning at 41 and 44 d of age for Trials 1 and 2, respectively) and c ontinued for 30 l-wk periods of lay. Combined data from Trials 1 and 2 indicated that the mean + SE age at first egg lay was markedly decrea sed (P < 0.005) in MBP-cINA521-treated quail (53.4 +/- 0.9 d of age) w hen compared to the CON (57.6 +/- 1.3 d of age). Likewise, the mean +/ - SE age at 50% egg production was reduced (P < 0.03) in quail immuniz ed against inhibin (65.4 +/- 2.1 d of age) when compared to the CON (7 7.6 +/- 9.7 d of age). Total hen-day egg production was also higher (P < 0.05, Trial 1; P < 0.01, Trial 2) in MBP-cINA521-treated quail (88. 7 +/- 1.4%, Trial 1; 90.1 +/- 1.2%, Trial 2) than in the CON birds (81 .9 +/- 2.9%, Trial 1; 73.6 +/- 6.5%, Trial 2). Collectively, these fin dings provide evidence that inhibin immunoneutralization accelerated p uberty and enhanced hen-day egg production during a 30-wk period of eg g lay in Japanese quail.