The effect of immunization with jackbean urease on antibody response and nitrogen recycling in mature sheep

Abstract

Immunization against Jackbean urease (JBU) has been postulated to reduce urease activity in the gastrointestinal tract (GIT) and is associated with decreased production and re-absorption of ammonia from the gut. To investigate this hypothesis, 24 mature ewes (68–75 kg) were fed a single high protein diet (164 g/kg DM) and allocated in a completely randomized design to three treatments. Sheep were injected with Freund’s incomplete adjuvant (C), 5000 IU JBU and saline (S) or 5000 IU of JBU and Freund’s incomplete adjuvant (F) on days 1 and 22 of the experiment. Treatment F sheep had IgM and IgG titers significantly greater than S and C ( P<0.05). Serum antibodies against JBU were able to reduce JBU activity in vitro over serum from C animals ( P<0.05) but were unable to reduce rumen wall bacterial urease activity ( P=0.30). Urea kinetics, determined with the 15N 15N-urea technique, among treatments was not different ( P>0.10). Mean daily urea production, urea excretion, urea recycled and returned to the ornithine cycle were 25.3, 12.8, 12.5 and 5.8 g N/days, respectively. We concluded that JBU immunization was ineffective in altering urea kinetics in mature sheep fed a high protein diet.