76 EXPERIMENT STATION RECORD. 



An interesting donkey hybrid, R. I. Pocock (Nature [London], 84 {1910), 

 No. 2133, p. 329). — A description of a cross between a male dziggetai or Mon- 

 golian donkey (Equus hemionus) and a female Nubian donkey {E. asinus). The 

 hybrid resembles a pure bred African donkey. The color is gray, with legs 

 strongly barred with black, and a sharply defined black shoulder stripe and 

 black mottling at the base of the long ears. 



DAIRY FARMING— DAIEYING. 



A study of the cause of wide variation in milk production by dairy cows, 

 C. H. EcKLEs and O. E. Reed Ulissouri Sta. Racarch Bui. 2, pp. lOl-UfJ, figs. 

 2). — During the first 2 lactation periods the better of 2 Jersey cows from the 

 same sire produced 2.8 lbs. of milk and 3.9 lbs. of fat for each ix»und produced 

 by her half-sister, and an investigation was made to determine the cause of 

 this variation. In the third lactation period the 2 cows calved 3 days apart, 

 and were fed and cared for under identical conditions for 1 year. The ration 

 consisted of choice alfalfa hay, silage, and a grain mixture of corn, bran, and 

 oil meal 4:2:1. During the summer green alfalfa and green corn were also 

 fed. Both cows were kept farrow, and milk records, analysis of feeds, and 

 amounts of feed consumed are presented in tabular form. 



In the early part of the lactation period a digestion trial showed practically 

 identical results. The coeflicient for the better cow was 64.39 per cent of the 

 dry matter, and for the other 64.99 per cent. At the end of the milking period 

 a maintenance trial showed only a slight diflierence in cost of maintenance, the 

 higher requirement being with the better cow. The real cause of difference in 

 production was found to be in the amount of feed consumed above maintenance, 

 the better cow usiug for maintenance only 35 per cent of the total food con- 

 sumed and the other 55.8 per cent. After deducting the maintenance require- 

 ment one cow produced milk as economically as the other. 



In general the better cow consumed 1.7 lbs. of feed for 1 lb. consumed by the 

 other cow, and produced 2.67 lbs. of milk and 2.77 lbs. of fat for each pound 

 produced by the inferior cow. The better cow required for maintenance for 

 the entire period 1,200.8 lbs, of grain, 1,204.5 lbs. of hay, and 4,818 lbs. of 

 silage, which left available for milk production 2,223.2 lbs. of grain, 1,699.5 lbs. 

 of hay, 3,960 lbs. of silage, and 4,323 lbs. of green feed. The inferior cow 

 required for maintenance 1,065.8 lbs. of grain, 1,065.8 lbs. of hay, and 4,292.4 

 lbs. of silage, leaving available for milk production 841.2 lbs. of grain, 632.2 lbs. 

 of hay, 795.6 lbs. of ensilage, and 2,102 lbs. of green feed. The milk production 

 of the better cow was 8,522.9 lbs. of milk, containing 5.51 per cent fat, and that 

 of the other cow 3,188.9 lbs. of milk, containing 5.31 per cent fat. 



Data are also presented of 2 other cows kept for an entire lactation period 

 under conditions identical with those above described. The feed consumed dur- 

 ing the lactation year minus the estimated maintenance was the amount con- 

 sidered available for milk production, and the ratio between the food available 

 for milk production and the milk produced was practically the same with each 

 of the 4 cows. The available feed consumed and the milk solids produced were 

 also calculated in calories in order to reduce all to a common basis, and these 

 ratios were also found to agree closely in all 4 animals. 



" The main difference between profitable and unprofitable dairy cows is not to 

 be found in the coefficient of digestion, or in the amount of food required for 

 maintenance. A superior dairy cow is simply one with a large capacity for 

 using food above the maintenance requirement and one that uses this available 

 food for milk production." 



