Selection and Breeding for Improved Feed Efficiency Alters Gilt Behavioral Responsiveness to a Novel Object

Abstract Text: As feed efficiency is becoming more of a priority, our objective was to determine if divergent selection for residual feed intake (RFI) altered gilt approach and fear 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 ISU Yorkshire RFI selection lines were randomly selected. Gilts were evaluated once over a 2 wk period using a novel object test (NOT). Individual gilts were moved from the home pen into a weigh scale for 1 min. Gilts then entered the NOT arena (4.9 m long x 2.4 m wide with black corrugated plastic walls 1.2 m high) and their behavior was video recorded for 10 min. All testing occurred between 1300 and 1900 h. The video was watched continuously by one trained observer for latency, frequency, and duration of novel object touches (defined as oral, nasal, and/or facial interaction with the novel object, an orange traffic cone), frequency of escape attempts (defined as front two legs off the ground, possibly including a jump), and frequency and duration of freezing postures (defined as the whole body remaining still for ≥3 sec). Data were analyzed using the Glimmix procedure of SAS and the model included the fixed effect of genetic line, the covariate of gilt age, and pig as the experimental unit. Compared to high-, low-RFI gilts tended to take longer to first touch the object (P=0.06) and touched the object fewer times (P=0.0001); however, there was no observed difference between lines in duration of time spent touching the object (P=0.14). Low-RFI gilts attempted to escape fewer total times compared to high-RFI gilts (P=0.001). No difference was observed in frequency or duration of freezing (P≥0.14). In conclusion, low-RFI gilts interacted with the novel object fewer times, 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 object between low- and high-RFI selection lines, selecting for improved feed efficiency (low-RFI) may have resulted in calmer, less fearful gilts.

Keywords: Approach, Fear, Residual feed intake