AUTHOR=Zhu Yanbin , Sun Guangming , Luosang-dunzhu  , Li Xin , Luosang-zhaxi  , Suolang-zhaxi  , Suolang  , Ciyang  , Cidan-yangji  , Basang-wangdui  , Pan Feng , Peng Quanhui 

TITLE=High energy level diet improves the growth performance and rumen fermentation of yaks in cold weather

JOURNAL=Frontiers in Veterinary Science

VOLUME=Volume 10 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2023.1212422

DOI=10.3389/fvets.2023.1212422

ISSN=2297-1769

ABSTRACT=This research investigated the effect of different dietary energy feed levels on the growth performance, immunity, rumen fermentation characteristics, and rumen methanogens of growing yak in the cold season. A total of 24 healthy yaks of 2 years old with similar body weight (141.7 ± 3.34kg) were randomly divided into three treatment groups according to a randomized complete block design. Three groups of yaks were fed with diets containing metabolizable energy 7.20, 7.89, 8.58 MJ/kg DM and named with low, medium, and high energy groups, respectively. Before the 56 days growth trial, the animals were given a 15-day acclimatization period to get familiar with enclosure and diet. The results showed that the average daily feed intake of the high-energy group was higher than the low-energy group (p = 0.006). Plasma aspartate aminotransferase (p = 0.004), alanine aminotransferase (p < 0.001), and interferon-γ (p < 0.001) in the high-energy group were lower than the low-energy group. In contrast, the superoxide dismutase (p < 0.001), immunoglobulin G (p < 0.001), and interleukin 2 (p = 0.002) were higher than the low energy group. The rumen microbial protein (p = 0.025), total volatile fatty acids (p = 0.029), and neutral detergent fiber digestibility (p = 0.050) in high energy group were higher than low energy group, whereas the acetate: propionate (p = 0.001) and ammonium nitrogen (p = 0.001) were lower than the low energy group. The plasma metabolomics results displayed that yak fed with a high-energy diet augmented the metabolism of arginine, proline, purine, taste transduction, pyrimidine, and glutathione pathways. The relative abundance of Methanobrevibacter in the high-energy group was lower (p < 0.001), whereas the relative abundance of Methanosphaera (p < 0.001) was higher than in the low-energy group. The results of the current study suggested that a high-energy diet in growing yaks during the cold season can improve growth performance, rumen microbial protein synthesis, antioxidants, and immunity.