46 SOUTHERN PORK PRODUCTION 



Work done by Carlyle 1 at the Wisconsin Station has 

 shown that there is a direct relation between the size of 

 the litter and the size of the sow, the larger sows having 

 the larger litters. The same holds true for the age, al- 

 though to a lesser extent, and the greater the age the 

 larger the litter, up to certain limits, of course. These are 

 important facts and should be kept in mind by the 

 breeder desiring large litters. 



Color of swine. The color of swine usually is of 

 secondary importance. Our pure-bred swine are more 

 or less constant in color, because this was one of the 

 easiest characters to establish in the formation of the 

 breeds. In the case of the wild types of swine, the colora- 

 tion, while fairly constant, is, as a rule, variegated for 

 protective purposes. The necessity of color protection 

 in the case of domestic swine is not present. Color in 

 swine has some value in protection from adverse climatic 

 condition. Most wild swine inhabit temperate and sub- 

 tropical climates, where sunshine tends to produce a 

 scalding on white swine. None of the wild breeds of 

 swine are light in color. 



Period of heat. When the sow gives off germ cells 

 there are certain symptoms manifested which, taken 

 collectively, indicate the period of heat. The external 

 genitals may become swollen and congested, and there 

 may be a slight discharge. The mammary glands may 

 also become slightly congested. Restlessness and change 

 of voice are also manifestations. These periods occur 

 with some degree of regularity. They first appear in the 

 gilt in subdued or premature form at about three months 

 of age. After that, they occur every twenty-one days or 



1 Bulletin 104 Wisconsin Agr. Exp. Station. 



