Size of Litters 115 



duction of the last four sows listed were determined by 

 Braxton and Jones,^ under the direction of the author, 

 with sows in the Purdue University herd. 



There is, apparently, as much individual variation in 

 milk-producing capacity in a herd of brood sows as there 

 is among the untested cows of an ordinary dairy herd. 

 The variation shown above ranges all the way from 

 a minimum of 3.39 pounds daily to a maximum of nearly 

 8 pounds. The average daily production of the sixteen 

 sows tested was 5.53 pounds, which, for a ten-weeks 

 suckling period, would mean an average production of 

 387 pounds of milk during the lactation period. 



It is interesting to note, in the preceding table, that 

 the sows which produced the most milk farrowed the 

 largest litters. That a high degree of correlation should 

 exist between two such intimately associated functions 

 is natural. Fertility and milk-producing capacity are 

 in reality expressions of a common function. To improve 

 the milking qualities of a herd, therefore, the prolific 

 sows should be retained. That there is sufficient oppor- 

 tunity for selection in any herd is indicated by the wide 

 variations in the individual records shown in the pre- 

 ceding table. 



The amount of milk which a sow gives is also largely 

 conditioned on her feeding during the suckling period. 

 In order to secrete a large amount of milk, she must 

 have the raw materials from which to manufacture it. 

 The ration, therefore, that is rich in milk-producing 

 properties and that is fed in liberal amounts is the one 

 which will stimulate and make possible the largest pro- 

 duction which each sow, according to her individuality 

 and breeding, is capable of. 



' Purdue Univ. thesis, 1915. 



