Comparison of Nitrogen Metabolism in Yak (Bos grunniens) and Indigenous Cattle (Bos taurus) on the Qinghai-Tibetan Plateau

A comparison of nitrogen utilization and urea metabolism between Tibetan and fine-wool sheep1

“…In agreement with other studies (Marini et al, 2004;Wang et al, 2011), we observed adaptive changes in N metabolism when sheep were fed a low-N diet. Urinary N, urinary urea N, and the proportion of urea N in total excreted urinary N increased as dietary N increased (Ergene and Pickering, 1978;Leng et al, 1985;Tebot et al, 1998;Marini et al, 2004;Guo et al, 2012), indicating that the increase in urinary N was largely associated with increases in the urinary urea N, especially when dietary N was sufficient .…”

“…The concentration of PUN of Tibetan sheep was greater than that for fine-wool sheep when they were fed the diet with 11.0 g N/kg DM, as was GER. The PUN in our sheep was similar to concentrations reported in yaks fed restricted diets (10.4 mM, Wang et al, 2011;16.4 mM, Long et al, 1999) but greater than concentrations reported in other ruminants fed diets with restricted N content (4.4 mM, Ferrell et al, 1999;2.6 mM, Sunny et al, 2007;1.6 mM, Muscher et al, 2010). Normally, a high concentration of PUN leads to more urea N excreted in the urine, but little UUE was detected in our sheep fed the low-protein diet, supporting the high rates of renal urea reabsorption previously discussed.…”

“…The efficiency of N utilization and the ability of the animal to adapt to low N diets is affected by various factors, such as the dietary energy content, N digestion, urea kinetics, rumen microbial activity, urea reabsorption by the kidney, the physiological state of the animal, and animal species (Wang et al, 2011;Marini et al, 2004).…”

Yak Response to High-Altitude Hypoxic Stress by Altering mRNA Expression and DNA Methylation of Hypoxia-Inducible Factors

“…Yak can fully use alpine grasslands, which other livestock find difficult to utilize, and provide necessary resources (such as meat and milk) and means of subsistence for Tibetans and other nomadic pastoralists in high-altitude environments (13,14). Yaks have numerous differences to the closely related low altitude cattle that equip them for life at high altitudes by eliminating the hypoxic vasoconstrictive drive (15). Minimal bioinformatics of yak, as a model animal for understanding the molecular basis of adaptation, exists until the completion of the sequencing of its whole genome (13).…”

Rumen prokaryotic communities of ruminants under different feeding paradigms on the Qinghai-Tibetan Plateau

“…Once every five weeks during the experimental period three quadrates of 50 cm × 50 cm were randomly cut to ground level for later analysis of forage grass nutritional content. The daily feed intake data for yak and Tibetan sheep in the grazing groups were estimated according to the results of previous studies [79,82]. The live-weight changes of the ruminants in both groups during the experimental period are shown in Table S1.…”