Field investigations into hypomagnesaemia in dairy cattle, with particular reference to changes in the concentration of blood constituents during the early grazing period

摘要: 1. In five experiments, groups of milking cows were changed abruptly from winter-stall feeding to graze a number different swards, and changes in the concentration blood-serum magnesium other blood constituents have been studied. 2. Wide variations severity hypomagnesaemia individual cattle found all experimental groups, due possibly such factors as intake herbage, requirement body reserves capacity absorb gut. 3. The degree observed was independent level milk production, but generally less severe Friesian than Shorthorn Guernsey cattle. onset delayed for few days with high serum-magnesium at commencement grazing. 4. two out three experiments which effect fertilizer treatment studied, incidence increased by application sward heavy dressings nitrogenous fertilizer. third experiment, occurred on plot had received no nitrogen fertilizer, due, it is thought, restricted herbage magnesium, since extremely sparse. supplements flaked maize, crushed barley, dredge corn, molassed sugar-beet pulp or concentrate mixture balanced grazing did not reduce hypomagnesaemia. 5. cutting grass stall prevent development 6. Blood pH concentrations bloodserum calcium, sodium, potassium glucose unaffected change winter feed spring grazing, marked non-protein urea ammonia nitrogen, any serum, observed. serum highest swards dressing content. 7. there close group association between low magnesium. High levels during are thought reflect production gut, may be responsible disturbance metabolism produces