Magnesium metabolism in the dairy cow. I. Metabolism on stall rations

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Abstract
1. The results are reported of a series of 8-day magnesium metabolism trials carried out with milking cows fed a variety of typical winter stall rations. 2. Twelve cows fed a standard ration of 15 lb. hay plus 12 lb. of a concentrate mixture containing 3 parts dredge corn, 1 part bran, 1 part decorticated groundnut meal and 1 lb./cwt. Churn 105 minerals, showed variations in the proportion of the feed magnesium excreted in the faeces of from 66·53 to 76·98%, probably reflecting individual differences in the capacity of animals to absorb magnesium. 3. Wide differences in the utilization of the magnesium in typical winter rations were observed. Mean values, with a standard error, obtained for the proportion of the feed magnesium excreted in the faeces with various types of ration were as follows: hay plus concentrates, 71·48 ± 0·94; hay plus proprietary dairy cubes, 62·15 ± 2·73%; hay, proprietary dairy cubes plus decorticated groundnut meal, 91·98 ± 1·93%; hay, silage (1) plus concentrates, 79·53 ± 0·99%; hay, silage (2) plus concentrates, 74·07 ± 4·24%; hay, mangolds plus concentrates, 74·28 ± 5·91%.
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