Tissue distribution and net maintenance and growth requirements of key trace minerals in fattening yaks (

Introduction: This study aimed to characterize the tissue distribution of key trace elements in fattening yaks and to establish empty body weight (EBW)-based prediction models for the net growth requirement (NRG) of copper (Cu), manganese (Mn), zinc (Zn), iron (Fe), selenium (Se), and cobalt (Co), as well as to derive their net maintenance requirement (NMR). Methods: A comparative slaughter plus graded feeding design was used. Forty approximately 4-year-old male yaks (234.20 ± 9.86 kg) were assigned to baseline slaughter (BL), midterm slaughter (M), and terminal slaughter groups stratified by intake: ad libitum (AL), 70% of ad libitum (IR70, n = 8), and 40% of ad libitum (IR40). Tissue concentrations of target elements were determined by ICP-OES and ICP-MS. Body weight and intake data were used to develop EBW-based NRG models and derive NMR. Results: Cu and Fe were primarily distributed in viscera, Mn predominantly in bone, and Zn, Se, and Co mainly in muscle. For the 230 to 320 kg body-weight range, the EBW-based NRG prediction models were: NRG Discussion: EBW-based models provide robust NRG and NMR parameters for Cu, Mn, Zn, Fe, Se, and Co in late-fattening yaks. These yak-specific values offer practical targets for precise mineral supplementation and ration formulation in yak production systems across Asia, helping prevent deficiency or excess and improve production efficiency.