14 MASS. EXPERIMENT STATION BULLETIN 357 



5. The vitamin A content of composite milk samples from cows receiving 

 the supplement was somewhat higher than that of similar samples from cows 

 that did not receive it. The efficiency of transfer of the vitamin from feed to 

 milk was very low in all cases. 



Conclusions 



If New England dairymen could always feed good qualit}- alfalfa haj through 

 the winter and if they could be sure of having well-preserved corn silage stored 

 before frost, it is probable that their cows would not need additional vitamin A. 

 But since for most of them such a state of afifairs is not attainable, some other 

 source of the vitamin must be relied upon; and it seems justifiable to recommend 

 for average New England conditions the inclusion of some form of supplemental 

 vitamin A in the rations of dair\' cattle during that period of the }'ear when they 

 are not on pasture. The practice will be of most value on those farms where 

 silage is not fed and the hay is of poor qualit>'. 



Grass silage is a partial answer to the problem, but only partial because much 

 of the grass silage stored on New England farms fits into the farm program best 

 as a late summer supplement to short pastures. Carrots are a wonderful source 

 of the vitamin, but they are costly to grow and, because of the price they bring 

 for human food, it is only rarely that they can be fed to cattle to advantage. 



About the only alternative left, then, is a concentrated source of the vitamin 

 incorporated in the grain mixture. Since it has been shown that cod liver oil fed as 

 such tends to lower the butterfat percentage in milk, the plain oil cannot be 

 recommended for cows in milk. Fortunately it is possible by adding a concen- 

 trate of the vitamin to cod Jiver oil to make it much more potent than the plain 

 oil; and such a product, because of the much smaller amount used, does not affect 

 the butterfat test unfavorably when it is fed to cows. Such a fortified oil was 

 used in the work here reported. 



It must be admitted that the results here obtained, although favorable to the 

 supplement in their general trend, were not marked. On the other hand, it should 

 be borne in mind that these cows were on better than average rations, some of 

 them being fed for Advanced Registry- records. It seems reasonable to assume 

 that response to the supplement might be more marked under average farm con- 

 ditions than it was in this case. 



All things considered, it is our opinion that the slight additional cost of grain 

 mi.xtures fortified with a vitamin A concentrate is cheap insurance against troubles 

 due to deficiency of this \'itamin, particularh when the roughage is of poor 

 (juality. 



Publication of this Doctment Approved by Commission on Administration and Finance 

 4500-4-'3Q. No. 6916 



