SEASONAL VARIATIONS IN MILK 15 



the colostrum, which is the first milk secreted in lactation, and the 

 constitution of which has been fully described. Some of its char- 

 acters are carried on into the first weeks of lactation. During the 

 first two months after deliver)- the casein and fat are increased in 

 amount. The sugar is diminished during the first month, but in- 

 creased from the eighth to the tenth. The salts increase up to the 

 third month, after which they steadily diminish.^ The changes 

 may be expressed in a general way by saying that every newly- 

 calved cow gives the richest milk the first week after calving. 

 About the second or third or fourth week the milk falls fairly 

 rapidly to the normal From this time forward the cow gradually 

 moves upwards in milk standard until near the drying period 

 (Spier). 



(3) Kind of fodder. — The nature of the diet exerts consider- 

 able influence upon the quantity and quality of the secretion.^ 

 The amount of casein is increased by a nitrogenous diet, owing 

 to the assimilation of proteid. It is possible that fat may be 

 increased in the same way but in a less degree. Food rich in 

 carbohydrates, e.g. beetroot, carrot, etc., causes an increase of 

 the amount of sugar in the milk. The value of forage is 

 determined by its yield, composition, palatability, season of the 

 year in which it may be grown, time required for it to 

 mature, and its effect upon the flavour of milk.^ 



(4) Seasonal variations. — Distinct variations according to season 

 may also occur. Richmond divides the year into four periods 

 having the following characteristics : — 



1. November, December, and January — the milk is rich, both in 

 fat and in solids not fat. 



2. February, March, and April — the solids not fat do not show 

 appreciable diminution, but the fat becomes less in quality. 



3. May, June, July, and August — the fat is low, though there is 

 a tendency to rise at the end of the period. In July and August 

 the solids not fat are below the average. 



4. September and October — an improvement in quality both 

 in fat and solids not fat is noticed. 



A period of drought tends, while diminishing the yield, to raise 



^ Text-book of Physiology. Landois & Stirling. Fourth Edition, p. 428. 



- Departmental Committee (Board of Agriculture) on Milk and Cream Regu- 

 lations (1901), p. 7. Sections 24 and 30, also footnote. 



^ Special Report after six years' investigation. New Jersey Agricultural- 

 Experiment Station (1902). See also Sixteenth Annual Report of the Bureau 

 of Animal Industry (U.SA.), 1899, pp. 450-463, on Feed and Care of the Dairy 

 Cow. 



