Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 22, 2002
Publication Date: September 1, 2002
Citation: Cassady, J.P., Young, L.D., Leymaster, K.A. 2002. Heterosis and recombination effects on pig reproductive traits. Journal of Animal Science. 80:2303-2315. Interpretive Summary: Estimates of genetic effects on reproductive traits of pigs are useful to evaluate breeds and to develop efficient crossbreeding systems. Reproductive traits of gilts were influenced by breed of gilt, but seldom by breed of dam or maternal grandam. Landrace, Large White, Yorkshire, and Chester White gilts were more productive carrying crossbred rather than purebred litters, but the opposite situation tended to occur for Duroc, Hampshire, Pietrain, and Spot gilts. Crossbred gilts were younger at puberty, weighed more at farrowing, and produced larger, heavier litters to weaning than purebred gilts. Gilts raised by purebred or crossbred dams had similar levels of performance. Relative to gilts by purebred parents, new allelic combinations among genes exist in gilts by crossbred sires and dams. New combinations had few significant effects on reproductive traits, but effects tended to be favorable for white breeds that are widely used by the industry to produce F1 gilts. Continued use of white crossbred gilts in terminal crossbreeding systems is recommended.
Technical Abstract: The objective was to estimate heterosis and recombination effects on pig reproductive traits in two different four-breed composite populations. Breeds included Yorkshire, Landrace, Large White, and Chester White in Experiment 1 (Exp1) and Duroc, Hampshire, Pietrain, and Spot in Experiment 2 (Exp2). Data were recorded on purebred pigs, two-breed cross pigs, and pigs from generations F1 through F6, where F1 pigs were the first generation of a four-breed cross. Litter traits were considered a trait of the gilt. There were 868 first parity litters in Exp1 and 865 in Exp2. Direct heterosis significantly increased sow weight at 110 d of gestation and litter weight at 14 and 28 d (weaning) in both experiments. Direct heterosis significantly increased number of nipples, weight at puberty, lactation weight loss, litter size, and litter birth weight in Exp2. Gestation length in Exp1 and age at puberty in Exp1 and Exp2 were significantly decreased by direct heterosis. Maternal heterosis significantly increased age at puberty in Exp2 and decreased sow weight at 110 d of gestation in Exp1. Recombination significantly increased sow weight at 110 d of gestation and tended to increase total number born and litter birth weight in Exp1. Recombination significantly decreased age at puberty in Exp2. Maternal heterosis and recombination effects had a sampling correlation of -0.90. Therefore, maternal heterosis and recombination effects were summed and their net effect was tested. This net effect tended to increase number of nipples, lactation weight loss, and litter birth weight and significantly increased number of fully formed pigs in Exp1. Direct, maternal, and litter heterosis and recombination effects significantly influenced reproductive traits.