DAIRYING 51 



efforts to develop the milk giving tendency in cows. Some investi- 

 gators have suggested that since the fluctuations in the flow of milk- 

 has a great effect on the per cent of fat in the milk the secretion 

 of fat is a controlling factor in milk formation. Collier* found 

 that when the time between milkings was exactly 12 hours the 

 average for 9 cows of five breeds was .696 pounds of milk per hour 

 during the night and .7 pounds of milk per hour during the day; 

 the average per cent of fat in the morning milk was 4.26 and of 

 the night's milk 4.22 showing a great uniformity in the milk 

 secretion, and in the fat per cent when there are no fluctuations in 

 milking. The great activity of the milk gland has also been illus- 

 trated by Collier in a calculation based on the figure obtained above 

 .7 pounds or 19.6 cc milk per hour, and on an -average of 150 obser- 

 vations on the milk of 15 cows of six breeds which later showed 

 152 fat globules in one-one-thousandth of a millimeter of milk; 

 his calculation showed that under these conditions the milk gland 

 is secreting 136,000,000 fat globules per second. This gives some 

 idea of the great activity of the milk gland. The subject of the 

 source of the fat in milk has been studied by a number of investi- 

 gators; but this question can not be discussed at this point. One 

 experiment made by Collier showed that for every one pound of 

 fat in the milk, the cows received 1.21 pounds of fat in their feed; 

 and although it may be possible that a cow converts some of the 

 other constituents of her feed into milk fat, there is usually more 

 fat in the feed than in the milk. 



AA. The Breed of the Cow. 



208. The general characteristics of certain breeds of dairy 

 cows are well known. The Jersey and the Guernsey cows as a rule 

 give less and richer milk than the Ayrshire and the Holstein cows, 

 while the Brown Swiss, Shorthorn, Red Polled and Devon breeds 

 come about half-way between the two extremes in the amount and 

 quality of the milk they produce. 



The richness of the milk, or the per cent of fat it contains, is 

 a breed characteristic, as is also the size of the animal, earliness 

 of maturity, disposition, persistency of milking, length of milking 



*N. Y. Geneva Report 1891, page 28. 



