D.Vl K V K.V 1 1 M I NO DAIRYING AGROTECllN Y. 



669 



necessarily vary coiisidci-.-ihly willi (lirt'crcnt <u\vs. ncconlius to their ability to 

 utilize their feed, the kind ;iiid (|uality of the \\h-i\ eaten, and the auiuuut and 

 character of milk iirediiccd. esiieciiilly its uitro.^eii coiiteiit. 



Aiiiirn.rinnilc iiiiii i in ii iii of iiilroi/cii for (hiirii coics. 



It will be seen that the niinininm protein content of rations for niileh cows, 

 accordinj,' to these results, will ranice between 2.75 and 2.28 lbs. for cows i)ro- 

 ducin.ic .">."> to 22 lbs. of milk containini; :i to 4 per cent of fat. In the rations as 

 fed, these amounts corresponded to about 2.0() to 1,70 lbs, of digestible protein 

 per head daily. 



The conditions under which changes occur in the protein requirements of 

 dairy cows and the physiological ett'ects of variations in the suppl.v of protein 

 in the rations are discussed at considerable length in the I'eport, as well as the 

 bearing of the results of the investigation on mooted questions of methods of 

 study of feeding problems with dairy cows. — f. w. woli,. 



The fat content of cows' milk, its normal variations and transmission, 

 K. A. IirxisTKciM (A'. LiiiKlthi: Akad. llaiidl. och TUJslr.. J,.5 {1906), No. .]-',. 

 PI). 137-176). — This in\estigation was conducted with a large herd of pure-bred 

 or high-grade Ayrshire cows during a period of eight years, the object in view 

 being to study the causes of normal variati<ms in the fat content of cows' milk, 

 aside from immediate changes brought about through the influence of difler- 

 ences in weather or temperature conditions, manner of feeding, etc., and to 

 determine, if possible, the laws of transmission of the quality of the milk. The 

 material at hand included nearly 18,500 fat determinations in the milk from ,'>9'? 

 cows. These calved throughout the year, although more freshened during tU(» 

 fall months than in the spring. 



The author discusses variations in the fat content of milk under three head- 

 ings — accidental variations, depending on exterior influences affecting the nerv- 

 ous systeui of the cows; normal variations, based u[)on the nature of the cows; 

 and individual variaticms, depending on hereditary influences. Only inllueuces 

 coming under the last two lieadings are discussed in this paper. 



Und(M- norniMl variations are considered the following: 



(1 ) Tlic ptrjodjcal variation for the lactation of the cow: The fat content of 

 the milk, which at the lieginning of the period is above average, falls rapidly 

 and reaches its minimum during the third month from calving, after whicii 

 there, is a gradual increase until a ma.ximum is reached at the close of the lacta- 

 tion. The average data for all cows obtaiued by the author for the first to th(! 

 thirteenth months froui calving were as lojlows: ;i.75, ;>.57, ',',.50, 3.54, 3.01, 3,07, 

 3,78, 3.80, .3.00, 4.00, 4.11. 4.13. .■ind l.l.". per cent. 



(2) The periodical variation for the life of the cow : The fat content is higliest 

 at three years of age. is high ;it foui' years, .nnd remains close to tlie average 

 for the family during the full activity of the cow. .after which it again rises 

 slightly. The average of all data was as follows: Third year, 3.83 per cent; 

 fourth, 3.74 per cent ; fifth, 3.05 per cent ; sixth, 3.05 per cent ; seventh, 3.00 per 



