Post-weaning social and cognitive performance of piglets raised pre-weaning either in a complex multi-suckling group housing system or in a conventional system with a crated sow

Abstract

We studied the social and cognitive performance of piglets raised pre-weaning either in a conventional system with a sow in a farrowing crate (FC) or in a multi-suckling (MS) system in which 5 sows and their piglets could interact in a more physically enriched and spacious environment. After weaning at 4 weeks of age, 8 groups of 4 litter-mates per pre-weaning housing treatment were studied under equal and enriched post-weaning housing conditions. From each pen, one pair consisting of a dominant and a submissive pig was selected, based on a feed competition test (FCT) 2 weeks post-weaning. This pair was used in an informed forager test (IFT) which measured aspects of spatial learning and foraging strategies in a competitive context. During individual training, submissive (informed) pigs learned to remember a bait location in a testing arena with 8 buckets (the same bucket was baited in a search visit and a subsequent relocation visit), whereas dominant (non-informed) pigs always found the bait in a random bucket (search visits only). After learning their task, the informed pigs' individual search visit was followed by a pairwise relocation visit in which they were accompanied by the non-informed pig. Effects of pre-weaning housing treatment were not distinctly present regarding the occurrence of aggression in the FCT and the learning performance during individual training in the IFT. During paired visits, informed and non-informed pigs changed their behaviour in response to being tested pairwise instead of individually, but MS and FC pigs showed few distinct behavioural differences.

Keywords: Cognitive development; Group housing; Informed forager test; Multi-suckling system; Pigs; Social development.

Fig. 1

Layout of the multi-suckling system. The system has 5 farrowing pens (A—with piglet nest, sow feeder, drinkers and anti-crushing devices) connected to a communal area with a lying area (B—with 2 drinkers), feeding area (C—with 5 sow feeding places surrounded by a piglet area with piglet feeders) and a dunging area (D)

Fig. 2

Layout of the testing room (7.4 × 6.3 m) used for the informed forager test. A = the area where the pigs entered the testing room, B = the start box, C = the testing arena, which contained 4 crosses (60 cm high) with 2 buckets (black circles) per cross and D = the waiting area for the litter-mates that did not participate in the test, containing 2 toys and a hessian sack. Dotted lines represent guillotine doors, and angled solid lines represent hinged doors. The dashed area in the back represents a drainage area

Fig. 3

Latency to reach the baited bucket for informed pigs during the relocation visits of the first 9 testing days (18 trials) of phase 1 of the informed forager test. The informed pigs had to find a baited bucket in the ‘search’ visit and relocate the same baited bucket during the ‘relocation’ visit. Pigs were housed pre-weaning either in a multi-suckling (MS) system with 5 sows and their piglets, or with a sow housed in a farrowing crate (FC) and only litter-mates

Fig. 4

Percentage of trials in which the informed pig (I) (a, b) and non-informed (NI) pigs (c, d, e) ate from the baited bucket, plotted against behaviours of the non-informed pigs