88 MANUAL OF FAMM ANIMALS 



In these cases much depended upon the opportunity. The 

 better the sire the better will be the class of dams offered and 

 hence the better the offspring, all of which leads to further 

 opportunities. Another fact in this connection well worth re- 

 membering is that imported animals are seldom fertile until 

 acclimated. In general, distance makes less difference than 

 altitude, temperature, sunlight, and food supply. 



Sterility. — One of the breeders' greatest difficulties is ste- 

 rility among animals. The causes which lead to sterility are 

 very many, some of which are well understood and are more 

 or less preventable, while others are not so well understood 

 and beyond control. If due to the male, then all the females 

 put to him will be sterile, whereas if due to the female, she alone 

 fails to breed. Some of the causes that can be easily controlled 

 are as follows : confinement and lack of exercise ; irregular 

 supply of food and lack of uniformity in conditions ; food lack- 

 ing the proper nutrients or containing too much sugar ; - animals 

 in too fat condition ; and in-and-in breeding, close breeding, ex- 

 cessive breeding; and the like. Again, the tendency to sterility 

 or lack of fertility is often hereditary. The Duchess family 

 among Shorthorns affords a good example. This family was 

 always known as "shy breeders," and this was considered one 

 of its valuable attributes. The breeders argued that this 

 diminished the numbers and kept the price very high. The 

 results were that this most excellent family of Shorthorns dis- 

 appeared because of its infertility. 



, Relative influence of parents. — No question in the breeding 

 of farm animals has given rise to more discussion than the 

 influence that each parent exerts on the offspring. As one 

 reviews the literature on the subject, he collects the following 

 ideas : the male controls the external and the female the in- 

 ternal organs of the offspring; the male controls the forward 

 and upper parts of the body and the mental qualities of the 

 offspring; that parent which has the stronger nervous and 



