Gilt approachability to a human when selected for feed efficiency

Abstract Text:

As feed efficiency is becoming more of a priority to producers, our objective was to determine if divergent selection for residual feed intake (RFI) alters gilt approachability behavior. Twenty low-RFI (more feed efficient) and 20 high-RFI (less feed efficient) gilts 36 ± 5.7 kg BW from the 9^th generation of the ISU Yorkshire RFI selection lines were randomly selected and evaluated once over a 2 wk period using a human approach test (HAT). The HAT arena measured 4.9 m long x 2.4 m wide, with black corrugated plastic walls 1.2 m. The arena floor was divided into four zones; zone 1 being the position of the human, with zone 4 being the furthest from the human, containing the door and where the pigs enter the arena. Each gilt was moved from its home pen between 1300 and 1900 h into a weigh scale for 1 min. They then entered the HAT arena and their behavior was video recorded at 10 frames per sec for 10 min. The video was continuously scored by one observer for latency, duration and total number of escape attempts (defined as front two legs off the ground, possibly including a jump), freezing postures (defined as the whole body remaining still for ≥3 sec), and zone visits. Data were analyzed with PROC Glimmix and the experimental unit was the gilt. Compared to high-RFI gilts, low-RFI gilts tended to take longer to display the first escape attempt (P=0.07), tended to spend less time attempting to escape (P=0.08) and had fewer total escape attempts (P=0.02). No differences were observed between lines for latency and duration across zones, or total number of freezing postures. Compared to high-RFI, low-RFI gilts tended to spend a shorter duration within zone 1 (P=0.07), however there was no difference by genetic line for all other zones (P≥0.47). Additionally, genetic line did not impact frequency of zone visits (P≥0.26). In conclusion, low-RFI gilts tended to spend a shorter duration interacting with the human, but engaged in fewer total escape attempts compared to high-RFI gilts. These data suggest that while there are differences in approach behavior to a novel human between low- and high-RFI selection lines, selecting for improved feed efficiency did not aversely affect the pig-human interaction.

Keywords: Human-approach, Pig, Residual feed intake