The relationship of body length to economically important swine production and carcass traits

A total of 1,062 purebred Duroc pigs of 168 litters by 14 sires provided data from five farrowing seasons at Ames Plantation (November, 1968, through November, 1969). Analyses were conducted to determine the phenotypic and genetic relationships of body length and various productivity and carcass traits and to estimate heritability of body length in order to assess the possible effectiveness of including this trait in a selection program,

Phenotypic correlations among individual traits indicate that heavier weaning pigs reach 200 pounds at an earlier age, are longer and have less backfat and higher muscle scores than lighter weaning pigs. Body length was significantly (P < .01) correlated with backfat (r = -.318). Also, pigs born with higher nipple counts tend to be longer at 200 pounds than pigs with fewer nipples.

Phenotypically, dam body length was not significantly related to any litter production traits with the exception of litter average body length. Longer dams tended to produce longer litters at 200 pounds than shorter dams. Litter size at birth accounted for 60 percent of the variation in litter birth weight while litter size at weaning accounted for 79 percent of the variation in litter weaning weight.

Genetic correlations among litter traits were very erratic with many of the standard errors larger than the estimates. Heritability estimates obtained from paternal half-sib correlations for litter averages of days to 200, body length and backfat were 0.51 ± 0.29, 0.51 ± 0.28 and 0,11 ± 0.18, respectively. The estimate of heritability of litter average body length computed by intra-sire regression of offspring on dam was 0.06 ± 0.01 which was interpreted as a possible consequence of appreciable maternal influence on body length.

These data indicate that increasing dam body length would not significantly influence any pre-weaning or weaning traits.