LIPIDS PRESENT IN MILK FAT 799 



reviewed the influence of food fat on the composition of milk fat. Al- 

 though ingested fat was shown to have an effect on the nature of the milk 

 lipids, its action was not immediate, and a number of days were required 

 before the effect was noted. After cottonseed oil had been included in the 

 diet of cows, the fat content of milk showed a gradual increase to the seventh 

 day, although certain components present in cottonseed oil appeared in the 

 milk as early as twelve to thirty-six hours after initiation of the diet. In 

 the case of goats, some food fat also appeared in the milk within twelve 

 hours. 520 The transfer of ingested fat to the milk has been shown to vary 

 with species; Mendel and Daniels 521 noted that several fat-soluble dyes, 

 such as Sudan III, were able to pass into the milk of animals accustomed 

 to fat diets. Thus, they appeared in the milk of rats and cats, as well as in 

 the egg of the hen, but they did not appear in the milk of the cow after they 

 had been introduced into the food. Similar results were reported by Gage 

 and Fish. 522 They concluded that, in the cow and in other herbivorous 

 animals, the milk fat is derived largely from the carbohydrates and protein 

 in the food, rather than from dietary fat. 



Contrary to this view, there is considerable evidence in the literature 

 that the secretion of milk fat is reduced in cows receiving a low-fat diet. 

 However, Menard and McCay 523 found that, under these conditions, the 

 fat content of the milk produced remained fairly constant, but that the 

 amount of the milk production was reduced. 523 ' 524 Concomitantly with 

 the fat output in the milk, reduction in the plasma fatty acid and choles- 

 terol took place. Furthermore, the milk fat was more saturated. Phos- 

 pholipid and total phosphorus were also shown to decrease under these 

 conditions. 524 The interpretation which has been offered for these and 

 similar findings is that cows which are secreting large quantities of milk fat 

 cannot synthesize the fat rapidly enough to supply the need; if the outside 

 source is removed, a decrease in fat output occurs, along with decreased 

 milk production. A fall in blood lipids also ultimately ensues. 



In addition to the effect of diet on the amount of fat in the milk, it may 

 also change its composition. Buschmann 525 reported that the addition of 

 0.4 to 1.0 kg. of oil per day per 1000 kg. body weight affected the milk 

 composition in a manner similar to that which would occur if 18% of oil 

 were added directly to the milk. Coconut oil was shown to reduce the 



620 O. C. Bowes, J. Biol. Chem., 22, 11-13 (1915). 



621 L. B. Mendel and A. L. Daniels, J. Biol. Chem., 13, 71-95 (1912). 

 522 S. H. Gage and P. A. Fish, Am. J. AnaL, 34, 1-85 (1924). 



623 L. A. Maynard and C. M. McCay, /. Nutrition, 2, 67-81 (1929). 



524 C. M. McCay and L. A. Maynard, /. Biol. Chem., 92. 273-280 (1931). 



825 A. Buschmann, Tiererndhr., }, 129-178 (1930); Chem. Abst., 25, 1558 (1931). 



