Size of Litters 113 



perfect development of the pigs. In the same way, 

 a balanced ration may be fed in such stingy portions 

 that the pigs are not fully developed. 



The effect of a diet of straight corn, in comparison with 

 a balanced ration, on the birth weight of pigs is strikingly 

 shown in experiments conducted at the Iowa Experiment 

 Station, the results of which have already been noted 

 in Chapter III, page 42. Yearling sows fed corn alone 

 during the winter produced pigs averaging 1.85 pounds 

 at birth, while another similar lot fed a ration of corn and 

 meat-meal, containing sufficient lime and protein, pro- 

 duced pigs which weighed, on the average, 2.42 pounds. 

 The average birth weight of pigs from gilts fed corn alone 

 at the same station was 1.74 pounds, while pigs from 

 another lot of gilts in the same experiment fed corn and 

 alfalfa hay weighed, on an average, 2.29 pounds. In- 

 adequate foetal nourishment is, no doubt, the funda- 

 mental cause of the runt pig. 



The pigs in abnormally large litters are ordinarily not 

 so well developed as are those in normal-sized litters. 

 (See Table XXV.) This, it seems reasonable to suppose, 

 is due to the inability of the foetal membranes to accommo- 

 date and properly nourish the extra number. As a rule, 

 sows which bring forth two litters a year, also, do not 

 produce as large pigs as they do when farrowing after a 

 six-months rest which is probably the result of deficient 

 nourishment. 



MILK PRODUCTION OF SOWS 



The amount of milk which a sow gives determines her 

 ability to raise a large litter of pigs, and is, therefore, 

 of first importance in determining her real value as a 

 breeder. In every herd a few sows are always better 



I 



