Fecal Microbiota Dynamics Reveal the Feasibility of Early Weaning of Yak Calves under Conventional Grazing System

SIMPLE SUMMARY: Yak (Bos grunniens) is the most economically and culturally important domestic bovine species adapted to the extreme ecological environment of the Qinghai–Tibetan Plateau (QTP), which provides milk, meat, transportation, fuel (yak dung), and wool for local nomads as well as major sources of income. Calves are an important part of the sustainable development of the yak industry on the QTP, and the quality of calf rearing directly determines the production performance of adult animals. Under the traditional grazing management, late weaning (>180 days) of yak calves seriously affects the improvement of their production performance. A comparative study of fecal microbiota dynamics of yak and cattle (Bos taurus) calves in different months after weaning will help to understand the changes in intestinal microbiota structure, and will aid in in improving growth rate and survivability of early weaned calves. Our research will contribute to the development of appropriate strategies to regulate the gut microbiome and thus improve the growth and health of the grazing ruminants on the QTP. ABSTRACT: Background: The gut microbiota plays an important role in the health and production of animals. However, little information is available on the dynamic variations and comparison of intestinal microbiota in post-weaning yak calves living on the QTP. Methods: We explored the fecal bacterial microbiota succession of yak calves at different months after early weaning (60 d) compared with cattle calves by 16S rRNA gene amplicon sequencing and functional composition prediction. Results: We found no significant difference in blood biochemical parameters related to glucose and lipid metabolism between yaks and calves in different months after weaning. The core fecal bacterial microbiota from both species of calves was dominated by Ruminococcaceae, Rikenellaceae, and Bacteroidaceae. The fecal microbial community has a great alteration within the time after weaning in both cattle and yak calves, but cattle showed a larger change. After five months, the microbiota achieves a stable and concentrated state. This is also similar to the functional profile. Conclusions: Based on the exploration of dynamic changes in the fecal microbiota at an early stage of life, our results illustrated that there were no negative effects of intestinal microbiota succession on yak calves when early weaning was employed.