Table 2.

Factor affecting urease and ureolytic bacteria in the gastrointestinal tract of livestock animals.

Factor	Response	Reference
Ni, urea	Urea (10 g/kg) increased urease activity in the rumen of sheep; Ni further increased urease activity when the diet contained 5 mg/kg of nickel	Spears et al. [65]
Mn, Mg, Ca, Sr, Ba, Co	Purified ruminal urease activity was decreased by the bivalent metals (5 and 10 mM)	Mahadevan et al. [66]
Ba, Ni, Mn	Stimulated urease activity at 2 and 20 mM metal ion concentrations in vitro with the fluid from the rumen of sheep	Spears et al. [67]
Cu, Zn, Cd	Inhibited urease activity at 2 and 20 mM in vitro with the fluid from the rumen of sheep	Spears et al. [67]
Sr, Ca, Co	Inhibited at 20 mM concentration, but not at 2 mM concentration in vitro with the fluid from the rumen of sheep	Spears et al. [67]
Mn, Mg, Ca, Sr, Ba	Stimulated urease activity in whole cell preparation of rumen bacteria	Jones et al. [68]
Na, K, Co	Inhibited urease activity in whole cell preparation of rumen bacteria	Jones et al. [68]
Ni	Sheep fed diets containing Ni at 5.32 mg/kg (5 mg/kg of Ni added) and urea at 10 g/kg had greater urease activity (2.5 vs. 12.7 µM ammonia nitrogen/min/mL) and ammonia concentration (66 vs. 88 mg/L) in the rumen	Spears et al. [67]
Monensin	Monensin at 33 mg/kg diet inhibited urease activity (5.80 vs. 1.97 7 µM ammonia/min/mL) in the rumen of steers	Starnes et al. [69]
Lasalocid	Lasalocid at 33 mg/kg diet inhibited urease activity (5.80 vs. 4.18 7 µM ammonia/min/mL) in the rumen of steers	Starnes et al. [69]
pH	Urease activity was optimum at pH 6.8–7.6. On both sides of this range, activity decreased linearly with pH	Muck [70]
Urea	Urea infusion in Rusitec increased urease activity	Czerkawski and Breckenridge [30]
Urea	Increased ureolytic bacterial population in rusitec fermenter	Jin et al. [55]
Urea	With isonitrogenous diets fed to cattle, ureolytic bacterial population was not affected or below 0.1% level	Zhou et al. [71]
Urea	Urea (160 g/day) addition to the basal diet (CP content of 167 g/kg) of cows did not alter the diversity and composition of the ureolytic bacteria and urease activity	Jin et al. [51]
Ammonia	High concentration reduces urease activity	Smith et al. [53]
Protein	With 23 g protein intake, high urease activity in ruminal wall associated bacteria, followed by ruminal fluid bacteria and lowest in solid feed associated bacteria. With 123 g protein intake, lower urease activity in sheep compared with a low protein diet; the lowest urease activity in bacteria associated with ruminal feed particles	Javorský et al. [34]
Protein	Urease activity in the rumen wall of lambs was lowered with a high-protein diet (253 g/kg DM) compared with a low-protein diet (98 g/kg DM)	Marini et al. [35]
Protein	Urease activity in ruminal fluid of both cattle and yak increased with increasing concentrations (64–235 g/kg diet) of dietary protein	Zhou et al. [64]
Nitrogen sources	In a pure culture study with Ruminococcus albus 8 and different sources of nitrogen (i.e., urea, ammonia and peptides), increased urease activity in urea-grown cultures	Kim et al. [54]