64 THE BREEDING OF ANIMALS 



shortest in the cow and sheep, being in these species 

 usually from twelve to twenty-four hours. 1 Mares come 

 in heat seven or nine days after foaling. Bred at this 

 time the mare is more certain to conceive. Dimon, 2 

 an experienced horseman, says that there is no regular 

 period for the return of heat in mares. If mares are well 

 fed they may come in heat at any season, but are more 

 generally in heat in the spring and fall. 3 If the mare 

 fails to become pregnant when bred on the ninth day 

 after foaling, she will usually be in heat twenty-one days 

 thereafter. Heat persists for five days and recurs every 

 twenty-one days. 4 Heat recurs in the cow three or four 

 weeks after parturition and recurs every twenty-one days. 

 The heat period recurs in sheep from seventeen to twenty- 

 five days. 



In the sow the heat period will be observed three 

 days after delivery and usually not again until the 

 pigs are weaned. Heat again recurs three or four days 

 after weaning the pigs and every twenty-one days there- 

 after. 



63. Effect of ration on recurrence of oestrum. The 

 recurrence of the oestrum after delivery of the young is 

 often influenced by the character of the ration. At the 

 Wisconsin 5 Experiment Station, Hart, McCollum, Steen- 

 bock and Humphrey found that pregnant cows fed on an 

 exclusive corn ration came in heat in four to six weeks 

 after the first calf. When the cows were fed a ration 



1 Weber, "Untersuchung fiber die Brunst des Rindes," Arch, 

 f. Wissensch. u. Prakt. Tierheilk., 37 Bd., 1911. 



2 Dimon, "American Horses and Horse Breeding." 



3 Reynolds, "The Breeding and Management of Draught 

 Horses." 



4 Curtis, "Cattle, Horses, Sheep and Swine." 

 6 Wisconsin Exp. Station, Bui. No. 17. 



