Maternal performance of Duroc, Hampshire and Landrace backcross gilts fed normal and high fiber diets during postweaning growth.

Duroc (DDDY), Hampshire (HHHY) and Landrace (LLLY) backcross gilts produced from matings of purebred sires and sixth or seventh parity F1 Duroc-Yorkshire, Hampshire-Yorkshire or Landrace-Yorkshire sows were fed and libitum either a high fiber (8.8% crude fiber, 2,910 kcal metabolizable energy (ME/kg) or normal fiber (3.9% crude fiber, 3,428 kcal ME/kg) diet during the postweaning growth period (70 to 170 d of age). A sample of 176 gilts was assigned randomly to one of three groups and exposed to purebred Yorkshire boars. All pregnant gilts were retained and exposed to boars for three additional production cycles. Sows failing to farrow were retained and returned to breeding with their contemporaries. Maternal performance, litter sizes at birth and weaning, pig weights, total litter weights and sow productivity index through four farrowings were not affected by postweaning dietary treatment of gilts. Interactions of nutritional regimen with either backcross type or exposure number were nonsignificant. Performances of the backcross types did differ. The DDDY had larger litter sizes at birth and weaning than HHHY or LLLY (12.0 vs 10.9 and 10.3 at birth and 9.6 vs 8.6 and 8.6 at weaning, respectively). Individual pig weights were similar at weaning among sow backcrosses. Therefore, DDDY females weaned heavier litters due to more pigs per litter and had higher sow productivity indices. Additionally, HHHY had a higher lactational weight loss and greater breeding and gestation weight gains than DDDY or LLLY. Sow feed consumption during lactation did not differ among backcrosses. Backcross type did interact statistically with sow group and exposure for several variables. Most significant interactions were due to differences in relative performance rather than absolute rank.