21G Qattle Problems. 



In the case of Netherland cows, the arteries have been 

 seldom, if at all, engorged, and their walls have been 

 gradually ihu-kcncd and strengthened as blood pressure in 

 their channels has increased; while the walls of many 

 American cheese-dairy and other cows \\iNz\izzn thinned 

 down by over-rapid distention, as yield has increased, be- 

 cause the increase of yield has been so rapid that the 

 arteries have not had even half time enough to thicken 

 their walls by gradual nutrition. This difference between 

 the rates of increase in yield in Netherland cows, in con- 

 trast with our American dairy cows, shows why the ar- 

 teries of the former do not become relaxed, while those of 

 the latter are relaxed by rapid engorgement. With this 

 explanation, various calculations that will confirm these 

 views may be readily made.* 



The effect of over-rapid increase in yield and artery 

 blood is to thin down the artery walls very much faster 

 than nutrition can strengthen them, thus causing the loss 

 of contractile power, which loss leads to abortion in 

 many cows. 



In the table we have estimated 12 per cent yearly, as 

 large a rate of increase as seems safe, because we had in 

 our mind the very slow rate of increase in the best dairy 

 cows found in Europe ; and in contrast therewith the 

 great number of abortions in our American dairy dis- 

 tricts, where the rate of increase in yield has been ex- 

 tremely rapid, particularly in the new cows that mainly 

 compose the herds that supply milk to new cheese fac- 

 tories. 



To illustrate tlie practice that in many cases leads to 

 abortion, suppose that in one, or in several localities, 

 from 100 to 300 cows and heifers are bought up to form 

 or to fill up herds that supply a new cheese factory with 



'^ Sue Tablo 



