Animal Husbandry Investigations in 1917. 227 



This conclusion in itself is important as one of the primary 

 sbjects for which the cooperative record project was inaugu- 

 rated was to collect statistics bearing on the question as to 

 whether the proportion of males to females in cattle could be 

 influenced or controlled by the time of service relative to the 

 beginning of the period of heat. Some earlier statistics 9 ap- 

 aeared to indicate that there was a possibility of influencing 

 the sex ratio by paying attention to this point. 



The statistics analyzed in Table 8 probably prove conclu- 

 sively, that the apparent relation between these two factors, 

 which is believed by many breeders to exist and which our 

 Earlier studies appeared to indicate, was purely accidental. In 

 fact taken on its face value without regard to probable errors 

 instead of their being more females resulting from services in 

 ;arly heat, there are actual a slight access of males. 



The conclusion of the previous incomplete analysis 10 of 

 :he cooperative data is therefore substantiated, that there is no 

 significant preponderance of females when the service is early 

 in heat. 



(e) THE DECLINE IN THE NUMBER OF CONCEPTIONS AS THE 

 NUMBER OF NECESSARY SERVICES INCREASES 



This problem is an ever occurring one in the breeding op- 

 erations of any dairy herd. When shall a valuable animal be 

 sold as a non-breeder? This, of course, depends on the num- 

 ber of service trials the cow has had. Data on the time when 

 lonception took place in a large series of connected birth and 

 service records are valuable in our cooperative records. These 

 lata are shown in Table 9. 



'Pearl, R., and Parshley, H. M. Sex Studies V— Data on Sex Deter- 

 nination in Cattle. Biol. Bulletin, vol. 24, pp. 205-225, 1913. 



Pearl, R. Brief Report of Progress on Animal Husbandry Inves- 

 igations in 1914, Me. Agric. Expt. Sta. Misc. Publ. 503, pp. 1-11, 1914. 



10 Loc. Cit. 



