junci, I920 Variation of Individual Pigs in Economy of Gain 233 



However, our main interest lies in the possibility of utilizing this factor 

 of variation, making it a definite factor in the breeder's support. Is it a 

 hereditary character ? How is it transmitted ? Can the breeder through 

 careful testing and selective mating develop or produce a strain that is 

 more economical in feeding or pure for the quality of economy in pro- 

 duction? Can he produce a line that is homozygous for this character- 

 istic? Extreme results are not to be expected, but even a moderate 

 saving, if constant, would be a marked achievement. 



In this connection a feature of Danish agricultural practice is very 

 interesting. An article^ describing it came to hand as our data were 

 being tabulated, and a brief quotation is pertinent in this connection: 



There is, however, quite another group of qualities which must be kept in mind 

 in connection with swine-breeding, but which cannot be estimated with sufficient 

 accuracy with the naked eye, namely, the quality of the bacon and the thrivingness 

 and growing energy of the pigs. 



The Experimental Laboratory has, during a long period of years, carried out ex- 

 periments with regard to the offspring of stud animals in the breeding centers which 

 afford reliable and helpful information as to the powers of transmission of qualities 

 possessed by the stud animals in regard to the qualities mentioned. It is the breeding 

 centers which supply the material for these experiments. 



The owner of each recognized breeding center is bound to supply on an average 

 two young pigs from selected sow annually to the Experiment Stations, and as there 

 are about 900 selected sows (757 Danish and 147 Yorkshire), the stations have at their 

 disposal a good deal of material. For pecuniary and other reasons they have found it 

 necessary to confine themselves to about 1,000 test animals per annum. Neverthe- 

 less, the experiments are on a big scale such as is scarcely equalled elsewhere. 



The young pigs are supplied at the age of seven or eight weeks. Each experiment 

 pen contains four full-blooded sisters and brothers. All the pens receive the same 

 food mixture in weighed proportions, and the animals themselves are weighed at 

 regular intervals. The experiments finish when the abattoir weight is reached . . . 

 The result is made use of in the selection of stud animals, those being preferred whose 

 descendants have sho-wn the highest degree of thrivingness and growth energ>' and the 

 best bacon . 



This is a good plan and doubtless characteristic of the results obtained 

 through Danish agricultural cooperative organization, though just how 

 each pen could contain four litter mates when only two pigs are sent 

 from each litter is a bit puzzling. 



Of recent years the possibility of a "register of merit " for meat animals 

 has received considerable attention. If more thorough investigation cor- 

 roborates our results and should it be found possible to develop families 

 or strains that are more economical producers, no sounder basis of pre- 

 ferment could be desired. 



If selection along this line will achieve results, we believe it desirable 

 to put the work on an individual basis from the start. The Danish plan 

 deals with pen averages which our data show to be somewhat unreliable 

 so far as indicating the true performance of the individuals concerned. 



1 MORKEBERG, Peter AUC the present position A^rD future prospects of SWINEBRBBDINC in DEN- 

 MARK. In Dept. Agr. and Tech. Instr. Ireland Jour., v. 17, no. i, p. 46-47. 1916. 



