TYPES AND MARKET CLASSES OF LIVE STOCK 



173 



bulls to grade up the ordinary dairy cows of the country. There 

 is no good argument in behalf of keeping any except a purebred 

 dairy bull at the head of any dairy herd. No progressive dairy- 

 man will take chances in raising a heifer calf for milk purposes 

 whose sire is either a beef bull or a mongrel. The necessity 

 for using purebred sires to breed to common cows and the finan- 

 cial advantage of such a policy was pointed out in Chapter IX., 

 in which the breeding of beef cattle for the market was dis- 

 cussed. The arguments there presented apply with equal force 

 to the breeding of dairy cattle. 



Tests which strikingly illustrate the effect of a purebred 

 sire in improving a herd of scrub dairy cows have been conducted 

 at the Iowa Station* by Kildee and McCandlish. The results 

 presented in the following table show the average yearly pro- 

 duction of the original scrub cows and the greatly increased 

 ability of their daughters and granddaughters sired by good 

 purebred dairy bulls. All were fed and cared for alike, and no 

 animals were weeded out during the experiment, so that the 

 improvement secured can be credited only to the use of good 

 purebred sires: 



If the results are expressed on the percentage basis, the 

 percentage increase in production of the daughters and grand- 

 daughters over the original scrub cows may be determined. 

 The following table shows this percentage increase: 



*Iowa Buls. 165 and 188. 



