羊の血清マグネシウム濃度に及ぼす早春放牧の影響

Abstract

For a month before grazing, wethers (group 1) and ewes (group 3) were given appropriate feed, and other wethers (group 2) only 0.6kg/head/day of hay. An orchardgrass ward was divided into four blocks according to the amounts of N and K2O fertilizers applied. Block I: 20kg/ha N and 20 kg/ha K2O, II: 20 and 120 III: 80 and 20, and IV: 80 and 120. The pasturing period was about 2 weeks in early spring.In herbage, the average N content was over 5% DM in blocks III and IV, the Mg content about 0.16% DM in blocks I, II and IV, the average K content over 4% DM in blocks II and IV, and the maximum K/Ca + Mg mEq 6.32 in block II. Two or three days after pasturing began, the concentration of serum Mg decreased by 3 to 17% in group 1, by 39 to 48% in group 2 and 12 to 32% in group 3, as compared with the prepasture level. Of the 20 wethers of group 2, twelve had under 1 mg/dl of serum Mg, but showed no symptoms of tetany.There were no significant differences in the decrease in amount of serum Mg among the sheep of the same group grazing in the four blocks. The condition of sheep before pasturing and lactation seemed to be a more important factor than the contents of herbage for the decrease in serum Mg in sheep grazing on early spring pasture.