886 EXPERIMENT STATION RECORD. 



years old or over. "According to the scheme [of equivalent records] 

 adopted by the Holsteiu-Friesian Association for tbe admission of cattle 

 into the Advanced Registry, each two-year-old must have produced 7.2 

 lbs. of fat, three-year-old 8.8; four-year-old 10.4, and each cow 5 years 

 old or older 12 lbs. of butter fat in 7 days.'' 



Tbe data are discussed from various standpoints and the following 

 general summary is given : 



"The largest total yield of fat among two, three, four year old, or full-aged cows 

 is, mider every age, accompanied l>y the highest percentage <>f fat found among cows 

 of that age. 



"The smallest yield of fat for each age of animal is accompanied in only one case 

 by the lowest percentage of fat, and that among the two-year-olds. 



"The largest yields of milk do not contain the lowest percentages of fat, nor do 

 the smallest yields of milk contain the highest percentages of fat. 



''The stall-fed cows average higher in total yield of milk and fat and in percent- 

 age of fat than the cows at pasture. 



" Equal quantities of the same kinds of food or similar quantities of different kinds 

 of food produce widely varying amounts of milk and butter in different animals. 



"To produce the same or similar amounts of milk and butter different animals 

 require -widely varying amounts of food. 



"Cows, although of the same breed and raised in the same herd, vary greatly in 

 their power to make an economic use of food. 



"The cost of production is greatest among two-year-olds, and decreases gradually 

 as the age increases up to 4 years, after which there is little if any variation. 



" Within a period of 90 days from calving there is but little average variation 

 in the percentage of fat among the different ages, except that the average of all the 

 tests made at 31 to 60 days from calving is lower than for any other period. 



"There is a slight variation in the average percentage of fat between two, thrse, 

 and four year olds, and full-aged cows. 



"The highest percentages of fat usually follow the shortest period between milk- 

 ings. The lowest percentages of fat usually follow the longest period between 

 milkings. W here the cows are milked at equal intervals the highest percentages occur 

 most often at or near the noon hour, and the lowest percentages about equally often 

 at morning and night, with a much larger number at midnight than at noon. 



"The average range of variation during 7 days between the highest and lowest 

 percentages of fat for individual animals is greater among four-year-olds and full- 

 aged cows than among the younger animals. 



"Neither the cows which show very great variation during 7 days in the percent- 

 ages of fat nor those which show slight variation are abnormal animals, since their 

 total product of milk and fat is near the average for their class. 



"Cows which have been once tested and forced to their greatest capacity for a 

 week rarely reach the same height of production again during the same period of 

 lactation, even though the circumstances beotherwise most favorable, but frequently 

 have made increased records in succeeding periods of lactation. 



"There is an increase of only 7.5 per cent of milk and 7.7 per cent in fat of full- 

 aged cows over four-year-olds, which shows that, on an average, cows have very 

 nearly reached their largest production between the ages of 4 and 5. 



"The 'equivalent record' plan is supported by the records of individual cows 

 which have been tested at various times from 2 to 5 years of age, but not by the aver- 

 age records of all the cows of the different ages." 



Butter investigations, H. Kreis (Yerhandl. Naturf. Forsch. Gesell. 

 Basel, 12 (1898), Ao. 1, pp. 108-125). — The author reviews, at consider- 

 able length, the principal literature on the volatile fatty acids of butter 

 and tbe methods for their determination, and reports an investigation 



