EFFORTS TO INCREASE FOOD RESOURCES 



The most extensive use of crossbreeding is made in Den- 

 mark. Danish bacon has an enviable reputation. It is sold 

 in England in competition w^ith the best from British farms. 

 About one-third of this bacon from Denmark is produced 

 by mating the English Yorkshire with the Danish Land- 

 race. Purebreds only are used. Each farmer buys his breeding 

 stock from breeders who are approved by the government. 

 While English and American breeders have spent their 

 principal efforts in producing animals for the show ring, 

 Danish farmers have developed a system whereby a pound 

 of pork is produced from a little more than three pounds 

 of feed. Careful tests of this have been made at the leading 

 swine stations. At Elsesminde the Landrace has averaged 

 3.79 pounds of feed for 1 pound of gain and the Yorkshire 

 3.69 pounds. The crossbreds have averaged 3-23 pounds 

 or 13.6 per cent less. 



In the Breeder s Gazette there is a report by Casement 

 giving the results obtained on his farm where Duroc-Jersey 

 and Poland-China sows were both mated with Yorkshire 

 boars. Many such cross matings were made and hundreds 

 of pigs raised. The crossbred pigs are compared with 

 purebred litters from other sows of the same breeds as the 

 dams. There were, in round numbers, 10 per cent fewer 

 pigs dead at birth, 30 per cent more alive at time of wean- 

 ing, and 5 per cent more raised to market, of the crossbreds 

 than of the purebreds. No figures are given for Yorkshire 

 purebreds, so that the figures are not directly comparable 

 to the Danish results; but they indicate clearly that there is 

 value from crossbreeding in viability and longevity as well 

 as in economy of gain. 



The most critical evidence for hybrid vigor in domestic 

 animals is furnished by Roberts and Laible at the Illinois 

 Experiment Station. A purebred Duroc-Jersey sow was 

 mated in the same period of heat to a purebred boar of the 

 same breed and also to a purebred Poland-China. Six of 



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