Nickel for Ruminants I. Influence of Dietary Nickel on Ruminal Urease Activity

Abstract

Various metal ions were added to incubating rumen fluid collected from an animal fed a purified diet low in nickel (.06 ppm). After 30 min incubation the rumen fluid was assayed for urease. Ruminal urease activity was low initially and none of the metal ions tested restored urease activity to a normal level, although Ba, Ni and Mn appeared to be slightly stimulatory. Cu, Zn and Cd were found to inhibit urease. In a second study lasting 28 days 5 ppm of supplemental nickel greatly increased ruminal urease activity in lambs fed a corn-based diet containing .32 ppm of nickel and 9.5% crude protein. Ruminal ammonia concentrations were higher in the nickel supplemented lambs 2 hr post-feeding while serum urea-nitrogen concentrations tended to be slightly lower in this group. The nickel supplemented group also tended to consume more feed and gain faster than the non-supplemented lambs. Alanine transaminase activity and glucose concentrations in serum were not affected by treatment. These studies substantiate earlier work indicating that ruminal urease requires nickel and suggest that the increased urease activity noted after nickel supplementation is not due to activation of the enzyme by nickel.