92 THE BREEDING OF ANIMALS 



litters from the fully mature sows has been six and five- 

 tenths. 



The sows used in this experiment were all of the same 

 breeding, and received the same care, and the food, shelter 

 and all other conditions have been similar. The differ- 

 ences observed then must be due to the factor of age. 

 It will be observed that there is a marked difference 

 between the size of the litters of the immature sows and 

 the older ones. The litters of the older sows are materi- 

 ally larger than from the immature sows. 



The highest fertility in swine is not reached until the 

 mother is at or near maturity. It may not always be 

 profitable for the swine-breeder to delay breeding sows 

 until full maturity, but it is apparent that when the breed- 

 ing herd is composed of older sows, a smaller number 

 need be maintained for the production of the pigs needed 

 in a given system of farm management. 



Interesting statistics have been compiled by George 

 M. Rommel 1 from the records of the American Poland- 

 China Record Association, which have an important 

 bearing on this point. These statistics include the breed- 

 ing records of 6145 sows recorded in 1902. There were 

 examined the breeding records of 2010 one-year old sows. 

 The litters of 1520 one-year-old sows, or seventy-five per 

 cent, ranged from five to eight pigs. 



The average litter of 2047 two-year-old sows numbered 

 seven and five-tenths. The number in each litter of 

 1483 sows, or seventy-two per cent, ranged from six to 

 nine pigs. 



The average number of pigs in the litters of 1157 

 three-year-old sows was seven and nine-tenths. The 

 average litter recorded for 606 four-year-old sows was 



1 American Breeders' Association, Report 19. 



