BUREAU OF ANIMAL INDUSTRY. 215 



All heifers produced by approved dams will be reared to maturity, 

 when they will be tried out at the pail. Their milk production in 

 connection with their general conformation and breeding power will 

 then determine their value to the project. The bull calves are being 

 reared, and at 8 to 12 months old will be divided into three classes — • 

 reserved, approved, and rejected. xVll bull calves rejected will be 

 sold for slaughter, those approved will be sold to breeders in the 

 usual way, and those reserved will be kept for use on the circuit. 



The cows on tlie circuit are largely the same as last year except 

 some heifers that have matured and a few cows that were purchased 

 in the East. Four cows purchased in New York and Pennsylvania 

 have been added to the experiment station herd. 



Three heifers of the same breeding have also recently been pur- 

 chased for one of the herds in the circuit. They are all in their first 

 period of lactation and give indications of proving to be good 

 producers. 



During the past year there has been much inquiry and a rapidly 

 increased demand for Shorthorns that will milk profitably. The co- 

 operators have had no females and few bulls to sell. The majority 

 of buyers are demanding milk records and apparently becoming 

 more discriminating in their selection of breeding animals. 



ANIMAL BREEDING INVESTIGATIONS. 



During the past year the breeding experiments which have been 

 under way at the Bureau Experiment Station at Bethesda, Md., 

 were continued and valuable data are being obtained. 



The results of the zebra hybrid breeding work have been fully 

 described in an article submitted for publication in the Twenty-sixth 

 Annual Report of the Bureau. 



The inbreeding experiments are making satisfactory progress. 

 Data have been obtained from about 5.000 guinea pigs during the 

 past year. Complete results of the work can not be reported until 

 later. A race of polydactylous guinea pigs has been established by 

 selecting sports having this peculiarity for foundation stock. 



The results obtained from the rat-breeding work have verified 

 Mendel's law of heredity so far as coat color is concerned. 



POULTRY INVESTIGATIONS. 

 MAINE WORK. 



The detailed intensive study of inheritance of ogg production or 

 fecundity in the domestic fowl in cooperation with the Maine Experi- 

 ment Station has gone forward satisfactorily during the year. By 

 the plan of selection now being practiced it has been possible to isolate 

 from the flock strains or "blood lines" which are breeding true to 

 definite standards of egg production. There are now being propa- 

 gated {a) lines having a high winter egg production, (h) lines having 

 a medium degree of winter productiveness, and (e) lines of low 

 winter production. The results which have been obtained in this 

 work are of a definite character and are believed to be of fundamental 

 significance, not only in relation to breeding for egg production, 

 but also in relation to the broader problem or breeding animals for 



