Physiologie der Zellen, Gewebe und Organe. 249 



result. The greatest absolute mean fat produetion per day was in May, although 

 there is no significant difference in this respect between May, July and October. 

 The Influence of pasture conditions in stimulating the flow seeras clear here. In 

 the Variation constants the percentage fat content of the mixed milk of a 

 large herd exhibits a considerable Variation from day to day. The milk of the 

 herd under consideration was most variable in percentage fat content in March 

 and October and least variable in May and July. In general, it appears from 

 these data that the degree or amount of daily Variation in the percentage fat 

 content of mixed milk is not significantly affected by such changes in feed and 

 other conditions as are here involved. The absolute amount of fat produced 

 per day is roughly about twice as variable relatively as the percentage fat con- 

 tent of the milk. This result is of particular interest in relation to the rather 

 widespread view that the variations in fat percentage of milk are to be ac- 

 counted for in the main by fluetuations in the water content. It should be re- 

 membered that the result here set forth is for the mixed milk of a whole herd. 

 The relative Variation in absolute fat produced, as measured by the coefficient, 

 decreases steadily from March on through October. The amount of this decrease 

 is, however, rather small. There is no indication that the milk of any particular 

 milking of the day is, either absolutely or relatively significantly more variable 

 in percentage fat content than the milk of any other milking of the day. In 

 absolute amount of fat, the evening milk is relatively much more variable than 

 the morning's milk. The midday milk oecupies an intermediate position in this 

 respect. This result would appear to indicate that during the night, when the 

 cows are at rest, fat produetion in the udder is a more uniform process from 

 cow to cow and from day to day, than during the day time when the cows are 

 in some degree active. Pearl. 



754) Eckles, C. H. ? Nutrients Required for Milk Produetion. In: Res- 

 earch Bull., Nr. 7, Agr. Expt. Sta., Univ. of Missouri, S. 91—140, 1913. 



The objeet of the investigation was to secure data regarding the require- 

 ments for milk produetion by cows yielding milk of varying richness. Data are 

 presented giving the feed consumed, with chemical analyses, and of milk produ- 

 ced, with analyses, for eight cows during an entire year. The milk of these cows 

 ranged from 3.4% to 6.09% fat. Data for two other cows are included for 

 shorter periods. These cows were all fed a ration of practically the same com- 

 position. The quantity fed was regulated so as to maintain a uniform weight. 

 The data confirm the results of others that more energy value is required in the 

 ration for rieh milk than for milk lower in fat. According to average digestion 

 coefficients the five cows should have digested 70.8% of the ration reeeived 

 during the digestion trial when in milk. The results showed only slight Variation 

 with individuals and an average of 65.57% digested. On maintenance the same 

 cows should have digested 66.69 % of the ration reeeived according to average 

 figures but the results were higher in every case and showed an average 71.2%. 

 The cow producing milk with 3.4% fat actually used only 0.235 therms per 

 pound milk while for 6.09% fat the requirements was 0.442 therms. The total 

 energy required in the feed was slightly less per pound fat produced in the 

 rieh er milk. However, after subtracting maintenance the energy per pound fat 

 is consistently higher for the richer milk. The energy value of the milk solids 

 is greater in proportion to the energy value of the feed required with the milk 

 lower in fat. This indicates that the produetion of rieh milk requires an increase 

 in feed in excess of the increase in energy value of the milk. Pearl. 



