AN EXPERIMENTAL COMPARISON OF EQUIVALENT TERMINAL AND ROTATIONAL CROSSBREEDING SYSTEMS IN SWINE - PIG PERFORMANCE

Eleven thousand forty-nine pigs produced from 934 litters using 262 ro tational and F-1 crossbred sows were used to study differences in pig weights, survival rates and pen average daily gain, daily feed intake, and feed conversion between pigs from equivalent three-breed rotation al and three-breed terminal crossbreeding systems using Duroc, Yorkshi re, and Landrace breeds. Pig weights at birth and 21 and 56 d and days to reach 100 kg did not differ (P > .10) between the terminal and rot ational crossbreeding systems. However, ultrasound backfat thickness o f pigs from the terminal crossbreeding system was .04 cm greater (P < .007) than that of pigs from the rotational crossbreeding system. Surv ival rate from 56 d to 100 kg was .8% greater (P < .01) for pigs from the terminal crossbreeding system than for those from the rotational c rossbreeding system. The crossbreeding system had no effect (P > .10) on survival rate at birth, from birth to 21 d, from 21 to 56 d, or fro m birth to 100 kg. Differences between the two crossbreeding systems w ere nonsignificant (P > .20) for pen average daily gain, daily feed in take, and feed conversion. Breed composition of pigs was an important source of variation (P < .01) for pig weights at birth and at 56 d. Si milarly, breed composition of the pig also affected ultrasound backfat thickness at 100 kg(P < .01), but not days required to reach 100 kg(P > .10). For survival traits, only survival rate from 56 d to 100 kg w as influenced by breed composition of the pig. Breed composition of pi gs affected daily feed intake and feed conversion (P < .01), but it ha d no effect on average daily gain during the test period. Except for 2 1-d pig weight, the average of the three rotational crosses did not ex ceed the best of the three terminal crosses produced. However, there w as no one best terminal cross for all traits.