Feed efficiency effects on barrow and gilt behavioral reactivity to novel stimuli tests

Abstract

Increasing feed efficiency is an important goal for improving sustainable pork production and profitability for producers. To study feed efficiency, genetic selection based on residual feed intake (RFI) was used to create 2 divergent lines. Low-RFI pigs consume less feed for equal weight gain compared to their less efficient, high-RFI counterparts. Therefore, our objective was to assess how a pig's behavioral reactivity toward fear-eliciting stimuli related to RFI selection and improvement of feed efficiency. In this study, behavioral reactivity of pigs divergently selected for RFI was evaluated using human approach (HAT) and novel object (NOT) tests. Forty low-RFI and 40 high-RFI barrows and gilts (n = 20 for each genetic line; 101 ± 9 d old) from ninthgeneration Yorkshire RFI selection lines were randomly selected and evaluated once using HAT and once using NOT over a 2-wk period utilizing a crossover experimental design. Each pig was individually tested within a 4.9 × 2.4 m test arena for 10 min; behavior was evaluated using live and video observations. The test arena floor was divided into 4 zones; zone 1 being oral, nasal, and/or facial contact with the human (HAT) or orange traffic cone (NOT) and zone 4 being furthest from the human or cone and included the point where the pig entered the arena. During both HAT and NOT, low-RFI pigs entered zone 1 less frequently compared to high-RFI pigs (P ≤ 0.03). During NOT, low-RFI pigs changed head orientation more frequently (P = 0.001) but attempted to escape less frequently (low-RFI = 0.97 ± 0.21 vs. high-RFI = 2.08 ± 0.38; P = 0.0002) and spent 2% less time attempting to escape compared to high-RFI pigs (P = 0.04). Different barrow and gilt responses were observed during HAT and NOT. During HAT, barrows spent 2% more time within zone 1 (P = 0.03), crossed fewer zone lines (P < 0.0001), changed head orientation less frequently (P = 0.002), and froze less frequently compared to gilts (P = 0.02). However, during NOT, barrows froze more frequently (P = 0.0007) and spent 2% longer freezing (P = 0.05). When the behavior and RFI relationship was examined using odds ratios, decreasing RFI by 1 kg/d decreased the odds of freezing by 4 times but increased the odds of attempting to escape by 5.26 times during NOT (P ≤ 0.04). These results suggest that divergent selection for RFI resulted in subtle behavioral reactivity differences and did not impact swine welfare with respect to responses to fear-eliciting stimuli. ABSTRACT: Increasing feed efficiency is an important goal for improving sustainable pork production and profitability for producers. To study feed efficiency, genetic selection based on residual feed intake (RFI) was used to create 2 divergent lines. Low-RFI pigs consume less feed for equal weight gain compared to their less efficient, high-RFI counterparts. Therefore, our objective was to assess how a pig's behavioral reactivity toward fear-eliciting stimuli related to RFI selection and improvement of feed efficiency. In this study, behavioral reactivit...

The genetic basis of feed efficiency in swine divergently selected for residual feed intake

“…During both tests, Low RFI pigs spent less time touching the novel object or person (P ≤ 0.03) than High RFI pigs (Colpoys et al, 2015). Collectively, the subtle differences between Low and High RFI line pigs did not impact animal welfare in terms of response to fear-eliciting stimuli and suggest that Low RFI pigs may be less reactive to new and fear-eliciting stimuli (Colpoys et al, 2015).…”

“…During the human approach test, Low RFI barrows also tried to escape the area fewer times than High RFI barrows (P = 0.001). In G9, the Low RFI pigs changed their head orientation more frequently (P = 0.001), tried to escape the area fewer times (P = 0.0002), and spent 2% less time attempting to escape (P = 0.04) during the novel object test than High RFI pigs (Colpoys et al, 2015). During both tests, Low RFI pigs spent less time touching the novel object or person (P ≤ 0.03) than High RFI pigs (Colpoys et al, 2015).…”

“…In G9, the Low RFI pigs changed their head orientation more frequently (P = 0.001), tried to escape the area fewer times (P = 0.0002), and spent 2% less time attempting to escape (P = 0.04) during the novel object test than High RFI pigs (Colpoys et al, 2015). During both tests, Low RFI pigs spent less time touching the novel object or person (P ≤ 0.03) than High RFI pigs (Colpoys et al, 2015). Collectively, the subtle differences between Low and High RFI line pigs did not impact animal welfare in terms of response to fear-eliciting stimuli and suggest that Low RFI pigs may be less reactive to new and fear-eliciting stimuli (Colpoys et al, 2015).…”

“…In G8 and G9, pigs from the Low and High RFI lines were subjected to two tests (human approach and novel object tests) to measure behavioral reactivity to novel, feareliciting stimuli (Colpoys et al, 2014;Colpoys et al, 2015). In G8 and for both tests, barrows from the Low RFI line were observed to have fewer head movements (P ≤ 0.02), defecate less frequently (P ≤ 0.03), freeze in place for shorter amounts of time (P = 0.05), freeze less frequently (P < 0.0001), cross fewer zones (test area was split into 4 zones based on distance from novel object, P < 0.0001), and took longer (48 to 52 seconds) to approach the novel object (P ≤ 0.04) compared to High RFI barrows (Colpoys et al, 2014).…”

“…Selection for lower RFI has also been reported to have limited negative impacts on meat quality , response to fear-eliciting stimuli and welfare (Colpoys et al, 2014;Colpoys et al, 2015), reproduction , and immune response (Mpetile et al, 2015), including response to porcine reproductive and respiratory virus (Dunkelberger et al, 2015). Additionally, various metabolic mechanisms have been found to contribute to the increased efficiency of the Low RFI line within the ISU selection project, including decreased degradation of protein , less reactive oxygen species production by mitochondrion in muscle and liver tissues , and increased energy and nutrient digestibility .…”