Changes of serum macromineral concentrations relative to the body weight gain of growing yaks throughout a year-round

Concentrations of blood serum macromineral calcium, phosphorus, sodium, chlorine and potassium of 6 to 40 months old growing yaks were determined bi-monthly with Beckman Synchron CX System, and body weights were also recorded in a production year-round. The body weight of growing yaks showed a pattern of rapidly gaining more weight in warm seasons and gradually losing about one fifth of it in cold seasons except of the uncompleted weaned younger animals. In the harsh cold seasons, the serum P dropped to an abnormally low level, while the serum Ca was maintained in a relatively constant level, which implied that much more restored Ca may be released to blood stream from the animal's skeleton to maintain the Ca in homeostasis during the prolonged deficiency of forage intake. Both of the serum levels of Ca and P peaked in September, correspondently, the greatest body weight gain occurred in the same month. Except serum level of K, all the serum levels of macrominerals studied have positive correlations with the living body weight of growing yaks(P < 0.05). Providing supplements with macrominerals, especially P and Ca in cold seasons, are necessary for the growth of yaks and will be benefit local farmers in the improvement of the yak production performance.