210 Cattle Problems. 



its rapidity, because the circulation in the walls of the re- 

 laxed arteries cannot thicken the artery walls or restore 

 their contractile powers as much in ten months, as they are 

 thinned and weakened in only that number of days, when 

 a large increase in yield is very rapidly made. Hence 

 the greater liability of " new" or strange cows — the feed- 

 ing being as strange to them as they are to the situation — 

 to udder-supply artery engorgement, and to abortion, 

 which results from relaxation of the artery walls, and the 

 loss of their contractile power. Accordingly, it is no 

 matter for surprise to find that over 60 per centf of the 

 Aborting cows in the New York dairy counties are re- 

 moved from one farm to another ; in other words, they 

 are brought into dairy herds from non-dairy farms and 

 small herds. The large and rapid increase in yield by 

 these new cows leads to great and rapid engorgement of 

 their udder-supply arteries; thinning down the artery 

 walls and relaxing them in many cows, and thus leading 

 to embryo starvation and resulting abortments. 



Heifers that abort are included in the new or stranger 

 cow class, because from not being milked, nor their udders 

 emptied, they are even more liable to udder-supply artery 

 engorgement and relaxation, than cows that are regularly 

 milked, and have their milk-glands relieved of disten- 

 tion. 



The only safe rate of increasing yield, is a very gradual 

 rate say 1 2 per cent average increase yearly ; this increases 

 yield 60 per cent by the eighth year of age, while it is 

 probably quite safe to say that the rate of increase in Neth- 

 erland or Dutch cows has not averaged i per cent in- 

 crease yearly, for the past sixty years. 



It is the very rapid increase in feed and artery-blood, 

 above their previous quantity of feed and blood, resulting 



t See Dr. W. II. CarmaltV lieport to New York State Agricultural Society, 

 ISliO. 



