MILK PRODUCTION 421 



That age influences production is potent to everyone 

 conversant with dairying. During the first years of lacta- 

 tion, general experience has shown that the milk yields, 

 though advancing from year to year toward maximum, 

 are lower than maximum, and that when the meridian 

 of vigor is passed, they gradually decline. The time re- 

 quired to reach maximum yields and to maintain them, 

 varies with such influences as individual vigor, based upon 

 individual or breed inheritance, care and management. 



In nearly all instances maternity is a pre-requisite to 

 milk production in any degree, and in all instances, it is 

 a pre-requisite to the same under normal conditions. Uni- 

 formity in the quantity of the milk flow cannot be main- 

 tained for any considerable period. 



The largest milk yields are obtained during the weeks 

 which follow the first week or two subsequently to parturi- 

 tion. They then gradually decrease, howsoever suitable 

 for milk production the food may be, until finally they 

 cease entirely. The duration of the period of lactation is 

 influenced by several conditions and may be greatly pro- 

 longed but it cannot be maintained indefinitely in the 

 absence of the renewing influence of maternity. ( See p. 429. ) 



Exercise, in so far as it tends to maintain normal vigor, 

 is favorable to increase in the amount of milk given. 

 When, however, it draws upon the energies beyond the 

 necessity mentioned, it tends proportionately to reduce 

 milk yields. Cows in milk do not call for much exercise 

 when kept under proper sanitary conditions. Every step 

 taken in pastures when grazing beyond actual health re- 

 quirements, tells so far adversely on milk production. 

 When given it should always be gentle in character. 



Discomfort to cows during the period of lactation 

 may arise from many sources. Prominent among these 

 are: (i) Exposure to the extent of producing unrest 

 whether from cold or heat; (2) irritating influences such 

 as lice, mange and flies; (3) irregularity in feeding, water- 

 ing or milking and (4) disturbance of equilibrium in the ner- 



