THE BREEDING OF HORSES 



109 



days after the first service, and to return them each week there- 

 after for at least one month. 



Barrenness in mares. — It often happens that mares are 

 served normally, yet fail to conceive. Some of the causes of this 

 difficulty are readily 

 understood and eas- 

 ily prevented, while 

 others are not so 

 well known and are 

 perhaps beyond the 

 control of breeders. 

 Mares that are not 

 served till late in 

 life are often diffi- 

 cult to impregnate 

 at the first time. 

 This is often noticed 

 in mares that have 

 spent a good part of 

 a lifetime at hard 

 work. In such cases 

 it is due perhaps to 

 the long inactivity 

 of the generative organs. An excess of rich and stimulating foods 

 is a common cause of non-breeding; and the dangers attend- 

 ing parturition are more than trebled in the case of fat animals. 

 Milk-fever never occurs in mares that are kept actually at work 

 and are in only moderate flesh at the time of foaling. On the 

 other hand, barrenness may be due to poor feeding and hard 

 work, the system being weakened by the lack of suflScient 

 nutrition. Undue sexual excitement at the most active stage 

 of heat is often responsible for the mare not conceiving. In 

 addition to these, there is a long line of causes of barrenness in 

 mares over which the breeder has little or no control, such as 



Fig. 46. — Aeab Hobsb used as a Polo Pont. 



