FUNCTION OF CAROTINOIDS IN PLANTS, ANIMALS 275 



For three-quarters of a century the breeders of Guernsey cattle, one 

 of the Channel Island dairy breeds, have laid great emphasis upon the 

 fact that under comparable conditions the milk and butter from these 

 cows has a higher yellow color than is produced by any of the other 

 known breeds of dairy cattle. It is also generally recognized by the 

 breeders of these cattle that a high yellow secretion by the skin is re- 

 lated to the production of highly colored milk and butter. These yel- 

 low secretions are usually localized at certain parts of the body, espe- 

 cially in the ear, on the end of the tail bone, and about the udder. In 

 fact, at the present time the official scale of points for judging Guernsey 

 cattle includes 15 points for skin color on the parts of the body men- 

 tioned. In judging bulls a similar allowance is made for high color in 

 the ears and on the tail and body generally as indicating the ability of 

 the animal to transmit the production of highly colored milk to the 

 offspring. Jersey cattle show the same characteristics but not to so 

 great an extent. It should be stated, however, that the ability of cows 

 of the Guernsey breed to transfer the carotin from their feed to the 

 milk is not so firmly fixed in the breed generally as the enthusiastic 

 advocates of the breed would lead one to believe. Hill (1917) states 

 that on the Island of Guernsey itself there is a marked difference be- 

 tween the color of the butter brought to market from different herds. 



There is also a general feeling among the Jersey and Guernsey cattle 

 breeders that abundant yellow secretions localized on the body indicate 

 large producers of butter fat. Hooper (1921), who tried to correlate 

 these ideas from observations which he made on about 160 animals, 

 could find no relation between either the amount or color of the 

 secretions and the production of either milk or butter fat, using yearly 

 production records as the basis for his conclusions. The general idea 

 is seen to be quite the reverse of the relations found to exist between 

 the color of the skin of fowls and egg production. As a matter of 

 fact if the phenomena of milk production, especially of milk fat pro- 

 duction, and egg production are related physiologically the correlation 

 between the production of milk fat and the color of the skin secretions 

 should be between high production and low skin color and not between 

 high production and highly pigmented skin as the breeders of Jersey 

 and Guernsey cattle seem to think. Furthermore, by analogy with 

 the hen, the fresh cow or the dry cow is not suited for judging the fat- 

 producing ability by the amount or color of the skin secretions, but 

 rather only the cow at the close of her lactation period. So far as 

 the writer has been able to ascertain no observations have ever been 



