224 Cattle Problems. 



as much increase in feed, abort in as large proportion to 

 number as tlie "new" cows of moderate or small yield, 

 with which the heifers are brought in and fed in dairy 

 herds. 



Abortion in the dry-feed season is, in part, explained by 

 a great reduction in the total circulation ; the cows, in 

 many cases, starving their own tissues, and becoming thin. 

 Concentrated feed, in such cases, makes the blood thicker, 

 but does not much increase its bulk; hence a reduced 

 total or quantity of blood, and a reduced quantity of it 

 conveyed in the mammary arteries to the udder. Still, 

 the over-iizt and relaxed condition of the engorged arteries 

 that supply the udder with blood, are 7tot much reduced in 

 aborting cows until after the embryos are starved to death, 

 for growth in the embryo is arrested by non-increase of 

 blood previous to the abortment. 



There are fewer cases of abortion in old cheese-factory 

 districts than in new factory districts, as in the old districts 

 and herds, aborting and other poor cows are weeded out ; 

 and feeding is much more careful — from dearly bought ex- 

 perience — than in new dairy localities, where everything 

 is new, and little experience has been had. 



Cows that have once aborted are far more liable to again 

 abort than cows that have never aborted ; as, when cows 

 once abort, they are predisposed by more or less remaining 

 relaxation from the previous distention in the udder-supply 

 arteries, to another abortment at about the same period of 

 pregnancy at which the first takes place, by an equal de- 

 gree of engorgement and an equal increase of blood the 

 next season, to that which relaxed the udder-supply arte- 

 ries the previous season. The arteries of such aborting 

 cows have not had time to recover from their relaxation 

 by the first engorgement, before the next engorging in- 

 crease of blood again relaxes them, which explains the 

 greater liability of cows to repeated than to first abortions. 



