Improved growth in the progeny of hens immunized with jackbean urease.

Three experiments were conducted with Single Comb White Leghorn and broiler breeder hens. Half of the experimental hens were injected with jackbean urease enzyme and the other half served as uninjected or adjuvant-injected controls. Chicks hatched from urease-injected or control hens were placed factorially (2 x 2) on diets with or without antibiotics. Urease injection of hens resulted in significant improvements in percent fertility and hatch compared with values for control hens. Depending on age, both urease injection and antibiotic feeding stimulated chick growth, independently of one another. Additive effects of these treatments resulted in significant improvements in body weight of chicks injected with urease and consuming antibiotics at all time periods compared with body weights of untreated controls.