274 THE BREEDING OF ANIMALS 



ents or their offspring, or in permanent effects on the race 

 or breed. It might, in fact, influence all three. 



260. Influence of early pregnancy on the mother. - 

 The chief harmful effect which follows the mating of 

 immature breeding animals is a retardation or sudden 

 check to the growth of the young mother. Investigation 

 shows that the premature exercise of the breeding func- 

 tions in the young female acts in some instances as a 

 temporary inhibitor of growth. The author has for six 

 years compared the growth of immature mothers with the 

 normal growth curves of mothers mated when more 

 mature. In this investigation six Duroc Jersey sows were 

 divided into three groups. These groups of two sows 

 each were designated respectively as immature, half 

 mature and mature. The sows of the immature group 

 were bred at the beginning of puberty or at the first heat. 

 At this early period the young mother was very imma- 

 ture. The half mature sows were bred at about eighteen 

 months and the mature sows at about thirty months of 

 age. Careful records of the food consumed, the gain in 

 live weight, and increase in body measurements were made 

 of each animal in the experiment. Similar records were 

 made of the female offspring of the original sows for sev- 

 eral generations. The body measurements were taken 

 with a view to determining muscular and skeletal increase. 

 A large number of measurements was made, and these 

 clearly demonstrated the fact that the early exercise of 

 the breeding function in swine results in temporarily 

 checking the growth of the mother. The investigations 

 have progressed far enough at this time to measure also 

 the ultimate effect upon the mature mother. While 

 the observations have not yet included enough animals 

 to justify us in speaking with finality, yet it seems entirely 



