272 EXPERIMENT STATION RECORD. [Vol.36 



feeds that can not be marketed, where a cheaper system of management is 

 used, and where the cows are housed in cheaper buildings and given less care, 

 they may pay the cost of production of milk. Under some conditions, summer 

 dairying would be more profitable than the all-year practice. It does not pay 

 to use intensive methods or winter grain feeding with low producing cows. 

 The value of pasture for dairy cows has been underestimated." 



A bibliography of related literature is given. 



Labor requirements of dairy farms as influenced by milking machines, 

 H. N. Humphrey {V. S. Dept. Agr. Bui. 423 {1916), pp. 17, figs. 3).— This is a 

 study of the milking machine as a factor in the organization of the dairy farm. 

 The data were obtained from 109 dairy farms in New York, representative of 

 the intensive type of dairy farm, and from 160 dairy farms in Ohio, Michigan, 

 and Illinois, representative of a mixed type of farm wherein dairying is com- 

 bined with general farming. In each of the localities studied a number of 

 mechanical milking machines was found. 



The author summarizes the results of his studies as follows : 



" The time saved by the use of the mechanical milker increases with Increase 

 in the size of the herd. With herds of 15 cows or less the average time re- 

 quired to milk a cow by hand is a fraction over 7 minutes ; by machine a frac- 

 tion under 5 minutes. With herds of over 50 cows it takes slightly under 

 7 minutes to milk a cow by hand and but 4.15 minutes by machine. With herds 

 of over 50 cows one man with a machine milks on the average about 28 cows 

 per milking as against 17 where the milking is done by hand. 



" With Increase in the size of the herd the cost per cow of hand milking 

 changes very little, while the cost per cow of machine milking decreases rap- 

 idly. With herds of 15 cows or less the average cost of milking per cow by 

 hand is $10.91 per year as against $10.45 in herds of 50 or more. With herds 

 of 15 cows or less the average cost of milking per cow by machine is $11.77 

 per year as against $7.34 for herds of 50 or over. 



"Although with the average small herd of 15 cows or less it costs more per 

 cow to milk by machine than by hand, it does not follow that the machine is 

 necessarily an improfitable investment on all farms on which such small herds 

 are kept. On 32 farms having herds of 15 cows or less the use of the mechan- 

 ical milker was found to effect an annual saving in hired labor of $2.63 per cow 

 through the dropping of hands who had been kept primarily to do the milking." 



Statistical weighting for age of advanced registry cows, C. W. Holdaway 

 (Amer. Nat, 50 (1916), No. 599, pp. 676-687, figs. 2).— Results are given of a 

 study made for the purpose of determining whether the records of the various 

 breed associations are consistent with their standards, and whether these stand- 

 ards can be used as a basis for weighting cows of different ages. Using 7-day 

 records secured from the Holstein-Friesian Blue Book data are tabulated of 

 9,639 A. R. O. record female progeny of the Holstein bull, Paul De Kol, No. 

 14,634. From this population correlation coefficients were worked out, and 

 ciirves were plotted for milk and fat production, showing (1) the requirements 

 of the Holstein-Friesian Association, (2) the mean of the population, (3) the 

 plus deviation from the mean, and (4) what the requirements ought to be ac- 

 cording to the performance of the cows studied. 



From an inspection of the curves of milk production the author points out 

 " that the official requirements weight animals of an age from 18 to 21 months 

 too heavily. The curve indicates that they are entitled to a reduction as great 

 as for any other age. For the purpose of discouraging such early breeding, 

 however, the requirements for this particular class should be prohibitive and 

 they are. The production increases up to at least 6 years of age instead of 5, 

 which the Holstein-Friesian Association requirements set as the maximum age 



