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

J. W. Zhou, H. Liu, C. L. Zhong, A. A. Degen, G. Yang, Y. Zhang, J. L. Qian, W. W. Wang, L. Z. Hao, Q. Qiu, Z. H. Shang, X. S. Guo, L. M. Ding, R. J. Long

Research output: Contribution to journalArticlepeer-review

48 Scopus citations

Abstract

Yaks (Bos grunniens) and Qaidam yellow cattle (Bos taurus) are indigenous to the Qinghai-Tibetan Plateau and graze natural pasture all year. Yaks are raised at higher elevations than cattle and are not offered supplementary feed whereas cattle receive supplementary feed and are sheltered at night during winters. We hypothesized that the species differ in metabolism of energy and nitrogen (N) and predicted that the differences would favour yaks to the harsh conditions of the plateau. To test our prediction, we examined nutrient digestibility, rumen fermentation, digestive enzymes and urinary purine derivatives (PD) in yaks and cattle offered forage-concentrate diets differing in N concentration. Four castrated yaks and 4 castrated cattle of similar ages (2.5 years) and body weights (200 kg) were used in two concurrent 4×4 Latin square designs. There was no difference (P > 0.05) between yaks and cattle in apparent digestibilities of dietary nutrients, concentrations of ruminal N components and activities of digestive enzymes (P > 0.05). Crude protein and acid detergent fiber digestibilities increased linearly (P < 0.001) while neutral detergent fiber digestibility decreased linearly (P < 0.05) with increased dietary N intake for both species. Ruminal concentration of total VFA was greater in yaks than in cattle across diets (P < 0.05), but pH was similar between species (P > 0.05), and both variables were not affected by dietary N content (P > 0.05). As dietary N increased, ruminal concentrations of ammonia, urea and amino acids increased linearly (all P < 0.001), peptides tended to increase (P < 0.10), but soluble protein remained constant (P > 0.10) for both species. The activity of carboxymethylcellulase decreased linearly (P < 0.01) while activities of deaminase and urease increased linearly (P < 0.001) with increased dietary N. Urinary PD and components did not differ between species (P > 0.10); however, the PD nitrogen index (PNI) was greater in yaks than in cattle for the lowest N diets (linear dietary N × species, P < 0.01). With an increase in dietary N, urinary total PD, allantoin and uric acid increased linearly (P < 0.001), as did microbial N synthesis (P < 0.001), whereas PNI decreased linearly (P < 0.001). In addition, microbial N production was greater in yaks than in cattle (P < 0.05). We concluded that energy and nitrogen metabolism were more efficient in yaks than in Qaidam cattle, which enable yaks to better cope with the harsh foraging conditions of the Qinghai-Tibetan Plateau.

Original languageEnglish
Pages (from-to)14-21
Number of pages8
JournalLivestock Science
Volume208
DOIs
StatePublished - 1 Feb 2018

Keywords

  • Apparent digestibility
  • Qaidam yellow cattle
  • Rumen fermentation
  • The Qinghai-Tibetan Plateau
  • Urinary purine derivatives
  • Yak

ASJC Scopus subject areas

  • Animal Science and Zoology
  • General Veterinary

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