7 Mixing aggression and floor type during gestation have implications for sow reproductive performance

Abstract

Abstract Aggressive behavior resulting from mixing to establish a dominance hierarchy is a welfare concern for group-housed sows. The associated stress could negatively impact reproductive performance (RP). Objectives of this study were to investigate associations between 1) mixing aggression intensity and RP within and between parities one (P1) and two (P2), and 2) aggression intensity, floor type and RP. A total of 164 gilts were followed through two parities. Gilts were mixed into stable groups of eight unfamiliar individuals four days after insemination, and housed on fully-slatted floors, either uncovered (CON; n = 84) or covered (RUB; n = 80) by a rubber slat-mat until farrowing (for both parities). Skin lesion scores (SLS) (proxy for mixing aggression intensity), were recorded 24–72 hrs post-mixing (0 = no lesions to 5 = severe lesions) on five body regions on left and right sides, and on the tail, in both parities. Total SLS was calculated for each sow. RP data were retrospectively acquired from farm records for both parities. Data were analyzed using GLMM in PROC GLIMMIX of SAS (v9.4) where 1) each parity analyzed separately, and 2) SLS in P1 used to predict RP in P2. Gilts with higher SLS in P2 had higher piglet mortality (P = 0.021) and longer cycle length (P = 0.003) in P2. Gilts with higher SLS in P1 had more non-productive days (P < 0.001) in P2. CON gilts had higher SLS than RUB gilts (P = 0.017) in P1, but not in P2 (P > 0.05). CON gilts also had more piglets born dead (P = 0.004) and tended to crush more piglets (P = 0.097) in P2. Our results confirm that mixing aggression impacts RP in the current parity negatively. They also suggest that mixing aggression experienced by gilts may have long-term negative carry-over effects on performance in subsequent parities. Use of rubber flooring appears to mitigate detrimental effects of mixing aggression, perhaps through improved sow comfort.