The effects of starter feed on intestinal fungi and non-targeted metabolomics of blood in calf yaks

Yaks are the primary ruminant on the Qinghai-Xizang Plateau, playing a central role in the livelihoods of local farmers and herders. They serve as a vital source of food, clothing, shelter, and transportation in the region. Over the course of long-term natural selection, yaks have evolved distinct regulatory mechanisms related to their physiology, nutritional metabolism and feeding behaviors. Despite these adaptive traits, traditional yak breeding faces challenges such as slow growth, delayed gastrointestinal maturation, and low weaning weights, which lead to reduced breeding efficiency. This study investigated the effects of early supplementary feeding of starter feed on the intestinal health of calves, focusing on the benefits of timely and appropriate supplementation during the early stages of development. Utilizing ITS sequencing and LC-MS non-targeted metabolomics, this study investigated the mechanism by which supplementary feeding of starter feed affects the intestinal health of calves, focusing on changes in the composition of the intestinal microbiota and metabolites present in the calves. The study found that supplementary feeding enhanced the abundance of beneficial fungi, including Plectosphaerella, Mortierella, and Aspergillus, while simultaneously reducing the prevalence of harmful fungi such as Comoclathris, Arthrographis, and Cryptococcus neoformans. Further research utilizing non-targeted metabolomics has revealed that supplementary feeding of starter food influences several metabolic pathways, including fat digestion and absorption, glycerophospholipid metabolism, vitamin digestion and absorption, autophagy (both yeast and animal), and the VEGF signaling pathway. Metabolites such as dexamethasone and benzamidine are commonly associated with inflammatory and protease-inhibition pathways, which can influence gastrointestinal integrity and stress responses in ruminants. This feeding regimen was found to increase the concentrations of metabolites such as dexamethasone, benzamidine, norethindrone acetate, and tamoxifen, while simultaneously reducing the levels of metabolites like dinoterb and monoisobutyl phthalate. In conclusion, early supplementary feeding of starter feed is conducive to the colonization of beneficial fungi in the intestinal tract of calves, reduces the colonization of harmful bacteria, and increases the concentration of metabolites related to anti-inflammation, anti-tumor activity, and signal transduction in the blood of calves. Moreover, a feed formula consisting of 1.4 kg of alfalfa and 1.4 kg of starter feed proves advantageous for maintaining intestinal homeostasis and optimizing blood metabolism in calves, which could improve the overall productivity and health of yak calves.starter feedstarter feed.