Apparent digestibility, rumen fermentation, digestive enzymes and urinary purine derivatives in yaks and Qaidam cattle offered forage-concentrate diets differing in nitrogen concentration

Rumen parameters of yaks (Bos grunniens) and indigenous cattle (Bos taurus) grazing on the Qinghai‐Tibetan Plateau

“…The higher VFA in summer by yaks than the other two genotypes may have been due to a greater dry matter intake by yaks, by dietary selection or due to a higher digestibility of nutrients by yaks. The latter is consistent with a previous study by Zhou et al () who reported a higher VFA concentration in yaks than in cattle fed the same diet.…”

“…Propionic acid is the main precursor of gluconeogenesis, producing glucose for metabolism whereas butyric acid is converted mainly to β-hydroxybutyrate as an energy source for ruminants (Phillips & Black, 1966). Previous studies showed that yaks produced higher molar proportions of propionate and butyrate than lowland cattle when fed a high forage-low concentrate diet (Hu et al, 1992;Zhou et al, 2018). In the present study, propionate was higher in yaks than in cattle and in C × Y in summer but butyrate did not differ among genotypes and, consequently, our results were in partial agreement with TA B L E 3 Rumen concentrations of ammonia, urea and total free amino acids (TFAA) in three genotypes of cattle after grazing in summer the previous reports.…”

Effect of dietary energy on digestibilities, rumen fermentation, urinary purine derivatives and serum metabolites in Tibetan and small‐tailed Han sheep

“…Consequently, we assumed that the microbial communities differed between Tibetan and Han sheep as well, which conferred the Tibetan sheep an advantage in digestion of nutrients. Of interest was a report that the activity of fibrolytic enzymes in yaks was greater than in lowland cattle (Zhou, Liu, et al, ). It appears that ruminants on the Qinghai–Tibetan Plateau have evolved special adaptations, when compared to lowland ruminants, to better utilize poor pasture.…”

Ureases in the gastrointestinal tracts of ruminant and monogastric animals and their implication in urea-N/ammonia metabolism: A review

“…In a recent in vivo study, urease activity in the ruminal fluid of both cattle and yak increased linearly with increasing concentrations (64–235 g/kg diet) of dietary protein. At the same time, it seemed that ruminal ammonia concentrations (5.1–105 mg/L) were not increased enough to suppress urease activity of the rumen microbiota [64] .…”

“…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] …”