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Mineral Supplements for Dairy Cows^*

Massachusetts Agricultural Experiment Station, Amherst

ABSTRACT

The object of this work has been to determine the value for dairy cows of a mineral supplement consisting of 80 per cent dicalcic phosphate and 20 per cent carbonate of lime added to a ration supposedly deficient in lime. Previous work with tricalcic phosphate in the form of steamed bone meal as a source of lime and phosphorus showed little, if any, advantage in supplying these elements in that form. As dicalcic phosphate is somewhat more soluble and had given better results elsewhere with lambs and goats that the tricalcic phosphate did, it was thought worthy of a trial with cows.

A special effort was made to have the basal ration of the cows low in lime. To this basal ration there was added for half of the herd (known as the "mineral" group) sufficient of the phosphate-carbonate mixture to theoretically make good the deficiency. The experiment was carried on for two years with the following results:

1. With one exception all the cows in the herd maintained their general condition well. The mature cows that received the mineral supplement maintained themselves slightly better in this respect than did those not receiving the supplement. They also made a considerable gain in weight while the non-mineral group showed little change.
   
2. The supplement had little, if any, effect on the growth of the young cows and heifers.
   
3. The low ash ration apparently had no immediate adverse effect on milk production and the mineral supplement apparently had no immediate favorable effect.
   
4. The composition of the milk was not significantly affected.
   
5. Reproductive troubles were not serious in either group but the cows receiving the mineral supplement were a little nearer normal and produced on the whole somewhat better calves than did those that did not receive it.
   

It must be emphasized that none of the differences between the groups were sufficiently striking to warrant as a general recommendation the use of the dicalcic phosphate-calcium carbonate mixture. Where cows are average producers (5000 to 8000 pounds) and where they are fed normally on good quality roughage the need of a mineral supplement is not indicated. For heavy producers (10,000 and upwards) it is probably good insurance to supply supplemental lime and phosphorus, but the efficacy of such a practice is by no means well established. It has been nothing short of amazing to note the persistency with which the herd of cows devoted to this study have maintained their milk production and for the most part their own well-being on low ash rations over a period of years. If these cows which average over 9000 pounds of milk yearly, several of them being eleven to twelve thousand pound cows, can make such a showing on abnormal rations, it seems reasonable to infer that the average New England cow on good quality roughage must have a considerable margin of safety as far as minerals are concerned.

This paper is presented with full realization of the beneficial effects reported by numerous other investigators who have fed mineral supplements and without prejudice to their results. Our negative results are attributed in the case of calcium to a considerably higher content of this element in the hays fed than has been found in similar hays elsewhere (0.4 to 0.5 per cent as contrasted with 0.2 to 0.3 per cent), and in the case of phosphorus to quite liberal grain feeding. This latter is normal for New England, and analyses of a large number of Massachusetts hays in addition to those we have fed shows an average calcium content of 0.41 per cent.

It is our opinion that the problem of mineral deficiency in rations is largely a regional one, and that where the roughage carries a reasonably high percentage of calcium and liberal grain feeding is practiced mineral supplements will not be necessary for the average cow.

Regarding Kellner's standard it would seem with respect to calcium that his minimum is well above the danger line, and with respect to phosphorus that where cows are grain fed the amounts of this element they receive are well above the minimum he prescribes.

^* Published with the permission of the Director of the Station.