Systematic Control of Genital hifedions in Herds 705 



by the permanent mating of one female with one male. 

 Whenever polygamy or polyandry is substituted, each in- 

 dividual in the group becomes exposed through sex contact 

 vs^ith each other member of the group. Genital infections 

 increase in virulence vi^ith repeated coitus. The larger a 

 group of apparently sound breeding animals, the greater 

 the danger that some one of the group harbors a highly peril- 

 ous infection. In practice a certain group of cows should 

 be assigned to a given bull and the assignment rigidly main- 

 tained. Nothing can well be more imprudent than the prac- 

 tice of shifting a sterile cow from one bull to another. 

 I have records where the breeder had used five or six 

 different herd bulls on one cow during a single year. Each 

 of the bulls thereby exposes the cow to any genital infec- 

 tions he may carry, and she in turn exposes each subsequent 

 bull to the original infections in her own organs and to any 

 which may have been deposited therein by each preceding 

 bull. It is sexual pandemonium. If the bull and the cows 

 assigned to him are rigidly maintained as a distinct unit, 

 the breeder soon knows of the fertility of the bull. If he is 

 unfertile the remedy is clear. If nearly all cows conceive 

 promptly and one is sterile after repeated coitus, she is evi- 

 dently at fault and the danger from her should be eliminated 

 promptly by overcoming the infection or by sending her to 

 slaughter. There is a false assumption that some cows will 

 not conceive to one bull, but may do so to another of equal 

 fertility. Bulls show every gradation of fertility, and a 

 cow is naturally more certain to conceive to the bull of 

 highest fertility, but the bull of low fertility should be 

 eliminated instead of used unsuccessfully upon cows and 

 later supplanting him with a highly fertile bull, in which 

 case the latter becomes exposed to the infections deposited 

 by the former. 



The permanent assignment of certain cows to a bull may 

 at times lead to the complication of several of his group 

 coming into estrum simultaneously or in rapid succession. 

 This need cause no material embarrassment. The rule 

 should be made, and supported vigorously, restricting the 



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