Agrifood Research Reports 55

The objectives of this study were to determine the selection potential (genetic variation) of sow efficiency traits (prolificacy, longevity), to understand the co-responses (genetic correlations) among sow efficiency traits and other economically important traits (performance, carcass quality, and meat quality), and determine the feasibility of developing breeding value estimates for sow efficiency traits. To meet the objectives, five separate studies were carried out. The prolificacy traits evaluated were total number of piglets born, number of piglets born alive, number of piglets weaned, number of stillborn piglets, percent of stillborn piglets, number of piglets dead during suckling, percent of dead piglets during suckling, gestation length, age at first farrowing, and farrowing interval. The studied longevity traits were lifetime prolificacy (number of piglets per sow’s lifetime), length of productive life, and leg conformation (overall leg action, and six symptoms of leg weakness). The results showed that the sow efficiency traits are generally lowly heritable. The only exceptions are buck kneed on fore legs (conformation trait), age at first farrowing and gestation length, which are moderately heritable. Among leg conformation traits, there was a strong favorable genetic correlation between buck-kneed on the fore legs and overall leg action, whereas no clear genetic association were found between the other leg conformation traits. Moreover, the overall leg action was favorably correlated with length of productive life, indicating that the selection for leg conformation will improve sow longevity through indirect selection. The results showed further that length of productive life and lifetime prolificacy are genetically favorably associated with litter size and farrowing interval. The most substantial unfavorable correlation among sow efficiency traits exists between litter size and piglet mortality. The current results indicated clearly that the selection only for number of piglets born (totally or alive) will lead to increased piglet mortality. Therefore, the selection should be simultaneously for litter size and piglet mortality. In general, there was a tendency for sow efficiency traits to be favorably correlated with performance traits, and unfavorably with carcass lean and fat percentages, whereas there was no clear association between sow efficiency and meat quality. Accuracy of estimated breeding values may be improved