200 PLANT PRODUCTS 



(i) The period of lactation. Immediately after calving, 

 the milk is commonly called colostrum, when the composition 

 is very abnormal. The total amount of nitrogenous material, 

 albumen, and casein may be as high as 23 per cent., most of 

 which is albumen, the casein being comparatively small in 

 amount. Even the second milking on the first day shows 

 a distinct drop in the percentage of albumen and casein, 

 and during the first day the majority of the figures that have 

 been obtained bj^ the author show over 10 per cent, of these 

 two substances. The third day after calving brings the 

 figures down to about 6 per cent, of albumen and casein. 

 By about the seventh day the percentage of albumen and 

 casein has fallen to 4 per cent, as against 3 J per cent, in 

 ordinary milk. During the same period the milk sugar 

 undergoes a very marked increase. On the first day the 

 amount is only about i per cent., steadily rising until about 

 the fifth day, when it reaches the normal figures between 

 4 and 5 per cent. The ash is also usually high after calving. 

 From the second to the seventh week the greatest quantity 

 of milk is produced, the quantity decreasing and the qualit>; 

 improving after that. During the last two or three weeks 

 before going dry the milk is usually of very uncertain 

 composition, but as the amount is very small, little trouble 

 results. 



(2) In the spring, milk is usually at its poorest, and in 

 November at its richest. Owing to the disturbance in the 

 times of milking which occurs on Sunday, it is not infrequently 

 found that the Monday morning's milk is rather poor. The 

 difference between the morning and evening milk follows a 

 fairly regular rule, depending upon times of milking. The 

 following formula represents the change in composition, 

 which was obtained on an average of a very large number of 



experiments, E — M= 6*2, where E stands for the even- 



ing fat per cent, and M for the morning fat per cent., and 

 the e stands for the interval between the evening and morn- 

 ing periods of milking, calculated in hours. The portions 

 of milk first drawn may contain only i per cent, fat, whilst 



