THE DOUBLE CROSS

Press, Volume LXXXII, Issue 24983, 18 September 1946, Page 9

THE DOUBLE CROSS

A new technique is being developed in the United States for breeding meat animals, and has already attracted considerable attention in the United Kingdom. Some time ago American maize breeders found that they could overcome the disadvantages of loss of vigour in closely in-bred strains by resorting to what they call a double cross. Four strains were selected for close in-breeding to fix the desired characteristics. In the end. strains A and B. and strains C and D were crossed, and finally strains AB and CD were crossed. The double-cross maize gave a yield about 25 per cent, higher than single strains selected for yield. The Americans are now testing the system on pigs to see how it will work with livestock. They have started with a number of distinct families and inbred very closely. When the inbreeding and, of course, heavy culling, have gone on for 10 or 12 generations, they will produce flrst-crpss boars and first-cross sows and cross them again. They have not gone far enough to have proved the worth of the system, but enough has been accomplished to lead Dr. John Hammond, probably the leading authority in the world on breeding for meat production, to believe that a considerably more efficient pig is well on the way.