Size of Litters 107 



there is a regular tendency, both absolutely and relatively, 

 for the number farrowed dead or immature to increase 

 with the increased size of the litter. 



BIRTH WEIGHT OF PIGS 



Generally speaking, the heaviest pigs in the litter are 

 the strongest and the smallest ones the weakest. The 

 pig that is well grown and developed at birth has an 

 advantage over his smaller litter-mate which renders 

 him a better prospect for economical pork production. 

 The average weight of pigs at birth is approximately 

 2| pounds, but they may range all the way from less than 

 \ pound to almost 5. A number of influences are sup- 

 posed to be responsible for this wide variation. Some 

 of these influences or factors are : sex, the age of the 

 mother, cross-breeding, the size of the litter, vigor of 

 the sow and boar at breeding time, and nutrition during 

 foetal development. 



Sex. 



It is generally believed that boar pigs are heavier than 

 sow pigs. It is an accepted fact that the males of colts, 

 lambs, and calves are heavier than the females. In 

 Table XXI are some figures interesting in this connec- 

 tion. In 5287 pigs farrowed in the college herds of 

 Illinois ^ and Purdue, there were 2376 boars and 2217 

 sows. The average birth weight of the boars is shown 

 in Table XXI to be 2.58 pounds, and of the sows 2.50 

 pounds, a difference in favor of the boars of only ^ 

 of a pound. 



' W. J. Carmichael, Master thesis : Univ. of 111., 1916. 



