THE EFFECT OF FEEDING A 

 VITAMIN A SUPPLEMENT TO DAIRY CATTLE 



J. G. Archibald, Research Professor, and 

 C. H. Parsons, Assistant Professor of Animal Husbandry 



Introduction 



Developments within the past few 3 ears in knowledge of the numerous vita- 

 mins and their relationship to health and disease have brought about a gradual 

 change in viewpoint regarding the adequacy in this respect of rations fed to 

 cattle. Formerly it was quite generally held that although certain of the vitamins 

 are doubtless essential in the ration, cattle would obtain sufficient of them from 

 their ordinary feeds, more especially from roughage. 



It is now realized that such a fortunate state of affairs does not always exist, 

 particularly with respect to vitamin A. It has been shown that the carotene 

 (vitamin A) content of our ordinary roughages is subject to great variation 

 depending upon how the roughage is cured and stored, and that it may be greatly 

 reduced or even completely destroyed by careless handling of hays and other 

 coarse feeds. 



Because of the difficulty in ordinary farm practice of obtaining at all times 

 roughages which contain a liberal amount of carotene, there has been proposed 

 an alternative method of insuring a sufficiency' of vitamin A by adding it in con- 

 centrated form to grain mixtures. Especial interest in this practice became 

 current about four or five years ago. Some commercial concerns began to include 

 a vitamin A supplement in their dairy rations at some increase in cost to the 

 consumer; others were hesitant to adopt the practice without definite evidence 

 as to its value. P 



The lack of evidence based on extensive feeding trials of considerable length, 

 led to the organization of a project at this station designed to ascertain what 

 effect the addition of a vitamin A supplement to the grain ration would have on 

 growth, reproduction, and milk production in the Massachusetts State College 

 dairy herd. The results of that project, commenced in February 1935 and carried 

 through to April 1937, form the basis of this report. 



The work was done in cooperation with two commercial firms, cne of which 

 furnished the vitamin supplement (a fortified cod liver oil), while the other mixed 

 the supplement with a special grain ration formulated at the experiment station. 

 The grain was delivered in carload lots as needed.' 



Method of Investigation 



The entire heid of milking covis, and heifers past the calfhood stage, was used 

 for the feeding trial, which was commenced February 1, 1935, and continued 

 with one interruption (the pasture season of 1935, May to September inclusive) 



' Acknowledgement is made to the Chailes M. Cox Company, Boston, which supplied the 

 grain mixtures with the vitamin A supplement properly blended; and to the National Oil Products 

 Company, which furnished the standard vitamin concentrate for blending. 



