376 EXPEEIMENT STATION EECORD. 



of the hypophysis on lactic secretion is not alone on the quantity but also on 

 the quality of milk, as denoted by an increased amount of fat. 



[Relation between an increase of the average fat content of milk and the 

 economy of production], N. Hansson (E. Landfbr. Akad. Handl. och Tidskr.^ 

 52 (1913), No. 5, pp. 289-369, figs. 12; Meddel. Centralanst. Forsoksv. Jordhruk- 

 somrddet, 1913, No. 78, pp. 85, figs. 12). — The author studied the possibilities 

 of increasing the value of milk production by improving the fat content of the 

 milk, and on the basis of results obtained in Swedish cow-testing associations 

 ascertained the variations in the feed consumption per kilogram of milk fat in 

 the case of milks of high and low fat contents and per kilogram of milk of 

 different fat contents. The results thus reached are held to furnish an answer 

 to the question as to whether it is economically advantageous to increase the 

 average fat content of the milk by systematic breeding operations. 



It is shown that the percentage of milk sugar and ash are practically con- 

 stant in relation to the milk yield, while the albuminoids stand in a definite re- 

 lation to the total solids, making up about 25 per cent of these. The milk fat 

 of milk of low fat content is, therefore, accompanied by considerably more non- 

 fatty solids than that of milk of high fat content; hence where the milk is 

 used for butter production, or where it is paid for by the test, it is advantageous 

 to increase the fat content of the milk so far as possible. 



The amount of fat eaten per kilogram of milk fat (as measured by the " feed 

 unit system") is decreased with an increasing fat content of the milk. An 

 increase in the fat of the milk from 3 to 4 per cent, under otherwise similar 

 conditions, means a saving of from 4 to 4^ feed units in the amount of feed 

 required per kilogram of milk fat. This saving is more marked in the case of 

 milk low in fat than with rich milk, and is greatly reduced when the fat con- 

 tent reaches 4J to 5 per cent or more. The amount of feed eaten per kilogram 

 of milk fat also depends on the milk yield obtained, since the returns for the 

 feed eaten are lowest in case of poor yields. Eich milk requires a greater feed 

 consumption than milk low in fat, and this greater consumption nearly corre- 

 sponds to the increased solids content of the richer milk. Where all milk re- 

 presents the same price, it pays best, therefore, to produce milk low in fat, 

 while when payment is made according to fat content or nutritive value it is 

 of advantage to produce milk high in fat or to increase the fat content of the 

 milk so far as possible, since only about 30 per cent of the value of the fat 

 secured by the increased fat content is required to pay for the resulting increase 

 in the feed consumption. 



The studies of the quality of the milk transmitted by breeding animals to 

 their progeny show that it is possible to increase gradually the fat content of 

 the milk by careful selection of individuals with an inbred faculty for produc- 

 ing milk of a fat content above that of the average for the family. The in- 

 fluence of male and female animals appears to be equal with regard to the fat 

 content of the milk of the offspring, provided both represent a similar degree of 

 constancy in their fat contents. Within the herd, however, the bull exercises 

 the greatest influence through the larger number of his descendants. Variations 

 always appear in the transmission of the fat content, for tlie reason that not 

 only the special fat content of the sire and the dam and the faculty to transmit 

 this fat content varies but there are also various plus and minus variants. The 

 individual can thus have a fat content appreciably different from that of either 

 parent, while the average for all progeny lies quite near to the average figure 

 for the genotypic fat content of either parent. The aim of the herd improve- 

 ment, when payment according to quality is decided upon, should be to reach 

 not the highest possible percentage of fat in the milk, but the highest possible 

 production of fat. The direct method of improvement in the average fat con- 



