28 MASS. EXPERIMENT STATION BULLETIN 449 



was mixed herd milk produced bj- the five dairy breeds of cows included in the 

 University herd. 



Composition of Mares' Milk as Compared with that of Other Species. (Arthur 

 D. Holmes, Albert F. Spelman, C. Tyson Smith, and John W. Kuzmeski.) The 

 mares' milk used in this study was produced by a Palomino and four Percheron 

 mares. All were mature, well-developed, normal animals, four to ten years old, 

 and in their first or fifth lactations. The study was inade in the spring and 26 

 samples of milk were assayed. The average values obtained lor the milk of 

 Percheron mares were: water 89.7 percent; protein 2.3 percent; reduced ascorbic 

 acid 89 mg. per liter; phosphorus 63 mg., potassium 64 mg., magnesiuna 9.0 mg., 

 and calcium 102 mg. per 100 g. These values indicate that mares' milk contains 

 more water than cow, goat, ewe, bufifalo, camel, or human milk; less protein 

 than cow, goat, ewe, buffalo, or camel milk, but more than human milk; more 

 ascorbic acid than cow, goat, or human milk; less phosphorus than cow or goat 

 milk but more than human milk; only about one-third as much potassium as 

 cow or goat milk; and less magnesium and calcium than cow or goat milk, but 

 four times as much calcium as human milk. The ratio of calcium and phosphorus 

 is considerably higher in mares' milk than in cows' or goats' milk but possibly 

 lower than in human milk. 



Apparently this paper was of service to people in widespread areas, for the 

 numerous requests for reprints rapidly exhausted the available supply. 



Stability of Reduced Ascorbic Acid in Mares' Milk. (Arthur D. Holmes and 

 Carleton P. Jones.) The milk was produced by mature Percheron mares at the 

 end of the lactation period. The samples were collected late in the fall and pas- 

 tures provided nearly all of the forage for the mares, but since the season was 

 warm and sunny, the rainfall ample, and the pasture had been closely grazed, 

 the grass was young and green. 



Fifteen samples of mares' milk with initial potencies of from 86 to 161 mg. of 

 reduced ascorbic acid per liter were stored in the dark at 10°C. They were 

 assayed at daily or longer intervals. Four samples observed for 10 days lost an 

 average of 2.5 mg. per liter daily; four samples stored 20 days lost 1.8 mg. per 

 day; two stored 28 days lost 1.3 mg. daily; and three stored for 33 daj^s lost 1.1 

 mg. per liter per day. These data show that the rate of loss of reduced ascorbic 

 acid from mares' milk is only a fraction of the rate of loss from cows' milk. 



Some Characteristics of Mares' Colostrum and Milk. (Arthur D. Holmes and 

 Harry G. Lindquist). Assays were made daily of the colostrum and early lac- 

 tation milk produced by one Palomino and three Percheron mares. The experi- 

 mental period was of fifteen days' duration for the Palomino and twenty-one days 

 for the Percherons. The pH value of the colostrum was very stable for the first 

 four days; on the fifth day it was decidedly higher; and from the fifth to the 

 twenty-first days it was quite constant. The fat content of the colostrum aver- 

 . aged 2.5 percent for the first four days of lactation; from the fifth day it decreased 

 slowly during the remainder of the experimental period. The quantity of total 

 solids in the colostrum decreased very rapidly during the first two days and there- 

 after decreased slowly. The reduced ascorbic acid was relatively low in the colos- 

 trum but increased fairly steadily from the first to the sixteenth day of lactation 

 and then decreased somewhat. At the first estrual period, which ordinarily oc- 

 curs about nine days postpartum, both the fat and ascorbic acid content of the 

 milk changed from the values obtained before or after the estrual period. All 

 the mares were bred at the first estrus. The foals of the two mares that were 

 bred late in the estrual period developed diarrhea, a condition which is not un- 

 common for the first postpartum estrus of mares. 



