432 FEEDING FARM ANIMALS 



During the first period; viz., from two to five years, 

 there is gradual increase in milk-giving capacity. This in- 

 crease is material, frequently amounting to considerably 

 more than 50 per cent. The relatively low production dur- 

 ing this period is caused in part by the diversion of food 

 nutrients to promote increase in growth. This, however, 

 does not furnish a complete explanation, as milk produc- 

 tion increases more relatively than' weight, and it continues 

 for a time after increase in weight has ceased. It would 

 seem fair to assume, that there is increase in capacity of 

 function in the milk gland, the outcome in part at least of 

 use, on the same principle that use strengthens any other 

 organ of the body up to a certain limit. 



During the second period ; viz., from six to nine years, 

 the yields should not vary much, but toward the latter 

 portion of the same, the tendency toward declension is 

 accentuated in many instances. On the whole, however, 

 the years covered by this period are those of the most prof- 

 itable production in the cow, notwithstanding the greater 

 activity of the digestive and assimilative functions during 

 the previous period. 



During the third period; viz., from nine to 12 years, 

 the decline in production continues, although it is not rapid, 

 not nearly so marked as a rule as the increase during the 

 first period. The value of a cow in the dairy, therefore, is 

 greater during the third period than during the first. 



It is to be understood, however, that in actual ex- 

 perience, the variations may be considerable, owing to the 

 way in which a cow is fed. The machinery of digestion 

 may be driven at a rate so rapid through high feeding, 

 that the first period may prove the most profitable, and 

 that a cow's usefulness may be at an end before the close 

 of the second period. In some instances maximum produc- 

 tion may not be reached until the seventh year, in other 

 instances it is reached at five years, and yet again produc- 

 tion may be more profitable in the ninth year than in the 

 eighth. 



