Date of Award
Doctor of Philosophy
Lauren L. Christian
Data from 358 purebred, F[subscript]1, backcross, F[subscript]2, and F[subscript]3 litters of Hampshire and Landrace breeding were used to estimate direct and maternal effects, individual and maternal heterosis and epistatic recombination losses in the offspring and dam for several maternal performance traits. The same genetic parameters were estimated for various carcass traits by analysis of data collected on 500 gilt and barrow carcasses and for growth and performance traits by analysis of data collected on 125 pens of pigs. Estimates of maternal genetic effects showed that Landrace females were superior to Hampshire females for number born, number born alive, litter birth weight, adjusted 21-day litter weight and milk production at 10 days of litter age. Milk from Hampshire females was higher in percent protein at 10 days and percent solids-not-fat at 10 and 20 days of litter age. Individual heterosis was significant for number born alive and litter birth weight. Maternal heterosis and recombination loss was significant for litter birth weight;Average direct effects for performance and carcass traits for the Hampshire breed were for leaner, more efficient pigs with more loin muscle area with maternal effects in the opposite direction. Individual heterosis estimates were important for dressing percentage, average backfat, tenth rib backfat, average daily gain, daily feed consumption, lean gain per day and lean efficiency. Crossbred F[subscript]1 pigs grew faster, ate more feed and had more lean gain per day while purebred pigs were leaner and more efficient. Recombination loss estimates were significant for carcass length and approached significance for tenth rib backfat. Differences in maternal performance of reciprocal F[subscript]1 dams mated to purebred and crossbred boars were not significant. In addition, performance and carcass merit of pigs out of reciprocal F[subscript]1 dams did not differ significantly.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Thomas J. Baas
Baas, Thomas J., "Heterosis and recombination effects in Hampshire and Landrace swine " (1990). Retrospective Theses and Dissertations. 9389.