The backtest in pigs revisited—Inter-situational behaviour and animal classification
Publication Type: |
Journal Article |
Year of Publication: |
2017 |
Authors: |
Manuela Zebunke, Gerd Nürnberg, Nina Melzer, Birger Puppe |
Publication/Journal: |
Applied Animal Behaviour Science |
Keywords: |
backtest, behaviour tests, classification, coping, personality, pigs |
ISBN: |
0168-1591 |
Abstract:
Since the introduction of the backtest for the early detection of coping strategies in piglets by Hessing in the 1990s, this behavioural test has been intensively investigated with ambiguous results. One possible explanation for this lack of consistency might be the different classification methods used in many studies, so the first aim of this research was to investigate the inter-situational consistency of backtest behaviour in a set of 120 piglets. Through a correlation analysis, we related backtest behaviour with behaviours in other test situations (mixing/dominance; group testing: human approach test (HAT), novel object test (NOT), open door test (ODT); and individual testing: open field test (OFT)). Second, in a larger number of piglets (n = 3555), we investigated four different classification methods that use different parameters (latency, duration, and frequency) and different test repetitions (1, 2, 3, and 4). We then tested the effect of classifying the animals according to each method and analysing their distribution across categories and the variance in the behavioural data using the 120-piglet dataset (category analysis). Finally, we validated the results of the category analysis with the results of the correlation analysis. The correlation analysis revealed weak (dominance: rS < 0.18) to moderately strong (group and individual testing: rS < 0.38) relationships between the backtest behaviour and the behaviour during the other tests, and some correlations reached significance, especially with the HAT and the OFT (locomotion, exploration and object contact). The investigation of different classification methods showed that more than half of the tested classifications were impracticable in our sample due to a very low number of piglets in the outlying categories representing the high (HR) and low reactive (LR) animals. Nevertheless, differences between the backtest categories depended on the classification method used, and the best fit between the category and the correlation analysis was reached with the classification method using the latency and duration parameters of four backtest repetitions (LD1234). Our results regarding the inter-situational consistency in the backtest behaviour of piglets indicate a coping disposition that is environmentally modulated, i.e., the piglets prefer a certain coping style, but this is shapeable by proximate factors that are determined via environmental or situational issues such as individual experience and age, social conditions, or the behavioural test situation. This result is consistent with a previous study of intra-situational behaviour, in which the backtest behaviour of piglets seemed to be more than just noise or random but also less than a fixed strategy as originally hypothesized. The results also show that correlation analysis is related to category analysis, but in the case of a category analysis, care must be taken during animal classification. Nevertheless, the backtest could be a useful method for investigating individual adaptations to the different challenges of a farm environment.