An Assessment of the Mineral Supply to Dairy Cows Fed Mixed Diets

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Aggrey, A.
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In on-farm trials in Kenya, a total of 18 lactating dairy cows were fed for three months, various types of fodder, pasture and concentrate in separate zero grazing, semi zero-grazing and grazing systems of small holder milk production. Intake of the major minerals Ca, P, Mg and Na from these sources were determined and averaged 46.7±14.9, 32.2±12.9, 31.2±1D.9 and 16.9±7.3 g respectively per animal per day. Linear regression of intake on requirement sufficiently reflected conditions of over or undersupply from plant and concentrate sources. Adequate intake of minerals was discussed in relation to forage content of the mineral, its source, milk yield and animal body weight. For Ca heavy and high producing animals were under-supplied while intake of the mineral by low producers seemed satisfactory to meet demand. Intake of P for most animals was below requirement because forage, which was the major source of all elements, was low in P. High contents of Mg in fodder and pasture ensured intake of this mineral above requirement. Cases of slight Na deficiency were noted as a result of low intake by heavier and higher yielding cows. It was suggested that the use of increased amounts of fodder in the feeding system could alleviate the problem of mineral deficiency.
East African Agricultural And Forestry Journal, 59 (No. 3), p. 235-240