Blood parameters and body composition in fetuses from reciprocal crosses of genetically lean and obese swine.

Lines of swine previously selected for either high backfat (obese) or low backfat (lean) were investigated to determine the effect of maternal obesity and the relationship between serum parameters and body composition. Fetal weight, percentage body protein, fat, fat-free organic matter and ash, and serum concentrations of albumin, growth hormone, triiodothyronine, and cortisol were compared in fetuses from straight line and reciprocal crosses at 110 days of gestation. Fetuses from the obese line weighed less but had a greater percentage body protein, fat, and fat-free organic matter than did fetuses from the lean line. Serum concentrations of albumin and triiodothyronine were less whereas those of growth hormone were greater in fetuses from the lean line compared to fetuses from the obese line. Values for these parameters in fetuses from the reciprocal crosses were generally intermediate to those of fetuses from the lean and obese lines. Comparisons of fetuses from the reciprocal and line crosses by linear contrast showed that the observed differences were mainly due to the average genetic effect of individual fetal genotypes and not due to maternal effects. Correlations computed from the residual variance showed a positive relationship between percentage body protein, serum albumin, and triiodothyronine while percentage body fat was not correlated with any of the other traits. Serum growth hormone was negatively correlated with fetal weight. We conclude that there is no apparent maternal effect of obesity or relationship of fetal fat content with any of the other variables measured in these lines of swine at the stage of fetal development at which these determinations were made.