Factors affecting and heterosis for growth and body size of swine raised in Thailand

Abstract

One hundred and seventy eight growing pigs with similar age (84 d) and weight including Large White (Y), Pietrain (P), crossbred Large White×Pietrain (YP), crossbred Landrace×Pietrain (LP), and Crossbred Y×LP (YLP) were used to study factors affecting growth and body size. Pigs were arranged into 10 groups according to breeds and sexes (female and castrated male). Pigs in each group were kept in 4.5 × 7.5 m2 pen in open house system. Similar feed and management were provided. All pigs were measured for body weight, body length (BL), shoulder width (SW), shoulder height (SH), hip width (HW), hip height (HH), loin depth (LD), backfat (BF) and lean percentage (Lean) at 178 d of age. Average daily gain (ADG) of individual animals was calculated from body weights changed in the study period (84 to 178 d of age). The results revealed that sex had influenced only on HH (P<0.05). Breed group had influenced on ADG and body size (P<0.01), excepted for SW. Sex and breed group interaction affected ADG, SW and SH (P<0.01). Change of BF positively associated with ADG, BL, SW, SH, HW and HH, but negatively associated with Lean (P<0.01). Results of the study indicated that BF should be considered in the prediction model for growth and body size. Heterosis level for all traits in crossbred YP was higher than crossbred YLP. These results implied that using P as sow line and mate to Y boar would produce crossbred YP which had higher ADG and larger body size compared to crossbred YLP which were produced from crossbred LP sows.