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Objective estrus traits consisted of vulva redness, vulva width, length of estrus, and age at puberty. Growth and composition traits included puberty weight, d to 114 kg, 10th rib backfat and LM area at 114 kg and at puberty. Subjective structural conformation traits were muscle mass, rib width, front leg side view, rear leg side view, front legs front view, rear legs rear view, and locomotion. First litter sow traits included if a gilt farrowed (STAY), age at first farrowing (AFF), total number born (TNB), and weaning-to-conception interval (WCI). Variance components were estimated using an animal model with AIREMLF90 for linear traits and THRGIBBS1F90 for categorical traits. Heritability estimates for STAY, AFF, and TNB were 0.14, 0.22, and 0.02, respectively.
Genetic correlations between length of estrus, the standing reflex traits, and age at puberty with STAY were 0.34, 0.34 to 0.74, and -0.27, respectively, and with AFF were -0.11, -0.04 to -0.41, and 0.76, respectively.
Days to 114 kg had genetic associations with STAY, AFF, and TNB of 0.52, -0.25, and -0.08, respectively. Backfat at 114 kg had genetic correlations with STAY, AFF, and TNB of -0.29, 0.14, and 0.47, respectively. Vulva redness and TNB were negatively correlated phenotypically (r = -0.14) and genetically (r = -0.53). Associations between structural conformation traits with STAY, AFF, TNB, and WCI were generally low to moderate and favorable. Selection for longer length of estrus, stronger standing reflex, or younger age at puberty would increase the proportion of gilts that farrow and reduce age at first farrowing.
Knauer MT, Cassady JP, Newcom DW, See MT; Phenotypic and Genetic Correlations between Gilt Estrus, Puberty, Growth, Composition, and Structural Conformation Traits with First Litter Reproductive Measures; J Anim Sci. 2010 Dec 10. [Epub ahead of print]
