Novel object test can detect marginal differences in environmental enrichment in pigs
Introduction
At present research is being conducted to develop animal-based monitoring schemes for on-farm welfare assessment at the European level (Blokhuis et al., 2003, Butterworth, 2005, Velarde and Geers, 2007). As part of this work a semi-automated novel object test was developed to measure the level of environmental enrichment and/or the level of positive welfare (positive emotions) in the pigs. When play would indicate ‘having fun’ (Spinka et al., 2001) the exploration of a novel object, i.e. object play, could, perhaps, be used to measure the pigs’ residual need (i.e. their remaining motivation) to explore/play. If so, we would expect an inverse relationship between the interaction with the novel object and the level of enrichment in the pen.
The level of enrichment is known to have an effect on both play behaviour and on redirected activities (e.g. Wood-Gush and Vestergaard, 1991; Fraser et al., 1991; for a review see Bracke et al., 2006). For example, barren housed pigs were less active, showed less explorative and play behaviour and spent more time on oral activities directed at pen mates than pigs from enriched housing (Bolhuis, 2004, Bolhuis et al., 2005).
When pigs in barren housing tend to redirect their exploratory behaviour, for example to the tails of other pigs (Van Putten, 1969, Fraser, 1987, Schroder-Petersen and Simonsen, 2001), this tendency could perhaps also be detected with a novel object test. In fact, this test has been shown to be able to differentiate widely different levels of enrichment. Comparing pigs in a semi-natural environment, furnished (family) pen, open-fronted straw pen and Danish partly slatted pen, Stolba and Woodgush (1981) have shown that over an 80 min observation period the pigs’ interaction with a novel object (car tire) decreased with increasing environmental complexity. They found that pigs in more intensive systems were more interested in the car tyre immediately after introduction and that their interest was maintained for a longer period of time.
One aspect of the (further) development of the test concerned showing that it would be sensitive to much smaller differences in enrichment compared to those studied by Stolba and Woodgush (1981). A second aspect of the test concerned the ‘hope’ that a good measure of enrichment should be animal-based and preferably even be able to detect levels of enrichment that would not be directly observable (e.g. because the enrichment had been provided early in the morning, before the auditor has arrived on the farm; see also Bracke, in press-a). A final aspect of the test concerned feasibility: for on-farm application the novel object test should be feasible within a limited time frame and within a limited budget. To this end automated recording could be beneficial.
This paper reports on two experiments where a semi-automated novel object (rope) test was applied in barren pig pens treated with marginal changes in environmental enrichment, namely the provision of a jerrycan (canister), the provision of some sawdust and the removal of the metal chain standardly provided to the pigs, in order to examine whether the test could detect different levels of exposure to enrichment and/or different levels of the pigs’ motivation to interact with enrichment materials. A further objective, especially of the second 2 × 2 factorial study, was to examine interactions between the provision of sawdust and the removal of the metal chain, as part of (on-going) validation work of an assumption underlying previous modelling work (namely that interactions between enrichment materials are ignored until they have been confirmed in scientific studies; see Bracke, in press-b).
The objectives of the experiments, therefore, were to examine whether (semi-)automated recording can work in a feasible way on commercial farms, to test the sensitivity of the novel object test in relation to selected marginal changes in environmental enrichment, and to (re-)examine the enrichment value of ‘jerrycan’, ‘sawdust’ and ‘metal chain’.
Section snippets
Modelling background
What constituted marginal enrichment was determined on the basis of previous modelling work, where a model, called RICHPIG, had been constructed to specifically assess the value of enrichment materials for pigs (expressed on a scale from 0 to 10) based on available scientific information collected in a database (Bracke et al., 2006, Bracke et al., in press-a, Bracke et al., in press-b). First, a jerrycan (empty plastic canister, size: 20 cm × 30 cm × 40 cm) was selected, as, especially when a jerrycan
Jerrycan experiment
In Experiment 1a a significant effect of time was found in that the predicted mean values for the first half hour were higher compared to the second and third half hour (12.82a, 7.36b and 5.75b, respectively, where different superscripts differed significantly, F = 20.50, P < 0.001). There were no further noteworthy effects found in the Split plot analysis or on intercepts and slopes of the time-series regression lines.
Fig. 1, however, shows that on each of the seven recorded time points the mean
Discussion and conclusions
The objectives of the work were to examine the effects of marginal changes in environmental enrichment on the novel object test, which involved the introduction of a novel piece of rope into a pen with pigs, and recording the number interactions with the rope (AMI) at several time points after introduction of the rope.
As to the methodology of the experiments several points must be noted. First, the novel object test was used to examine relatively short-term effects of changes in enrichment.
Acknowledgements
Many thanks to Johan Zonderland and Petra Lenskens for contributing ideas. Thanks also to the farmers and stockmen for their hospitality.
The jerrycan experiment was part of the Welfare Quality research project which has been co-financed by the European Commission, within the 6th Framework Programme, contract No. FOOD-CT-2004-506508. The text represents the authors’ views and does not necessarily represent a position of the Commission who will not be liable for the use made of such information.
References (28)
- et al.
Behavioural development of pigs with different coping characteristics in barren and substrate-enriched housing conditions
Appl. Anim. Behav. Sci.
(2005) - et al.
Formalised review of environmental enrichment for pigs in relation to political decision making
Appl. Anim. Behav. Sci.
(2006) - et al.
Effect of straw on the behaviour of growing pigs
Appl. Anim. Behav. Sci.
(1991) - et al.
Tail biting in pigs
Vet. J.
(2001) - et al.
A systematic approach towards developing environmental enrichment for pigs
Appl. Anim. Behav. Sci.
(2003) - et al.
The seeking of novelty and its relation to play
Anim. Behav.
(1991) - Anonymous, 1993. Genstat 5 Release 3 Reference Manual, 1993. Oxford University Press, Oxford, 796...
- et al.
Environmental enrichment of intensive pig housing using spent mushroom compost
Anim. Sci.
(2001) - et al.
Measuring and monitoring animal welfare: transparency in the food product quality chain
Anim. Welfare
(2003) - Bolhuis, J.E., 2004. Personalities in pigs, individual characteristics and coping with environmental challenges. PhD...
Expert opinion regarding environmental enrichment materials for pigs
Anim. Welfare
Cited by (21)
Factors of potential influence on different behavioural tests in fattening pigs
2020, Applied Animal Behaviour ScienceCitation Excerpt :But some former studies have criticised the test-retest reliability of these tests (Miller et al., 2006), hypothesising a potential influence of age on the results of the tests (Czycholl et al., 2016). Furthermore, behavioural tests are sensitive to marginal changes in the environment (Bracke and Spoolder, 2008), which means that there could always be an influence of the environment on the results so that it remains questionable as to whether these tests could really be used to compare the reactions in the tests of animals in different housing environments and at different ages as generalised tests objectively, without considering potential influencing factors. Therefore, the present study aimed at analysing factors of potential influence on the NOT, the FHAT, the VHAT and the HART to draw conclusions about factors that should be considered while using behavioural tests as welfare assessment tools and to get deeper insights about the practicability and comparability of these tests in welfare assessment protocols.
Chains as proper enrichment for intensively-farmed pigs?
2018, Advances in Pig WelfareTail biting
2018, Advances in Pig WelfareBoredom-like states in mink and their behavioural correlates: A replicate study
2017, Applied Animal Behaviour ScienceInfluence of enrichment material and herbal compounds in the behaviour and performance of growing pigs
2017, Applied Animal Behaviour ScienceCitation Excerpt :Furthermore, redirected behaviour to other pen mates such as tail biting, ear chewing or belly-nosing was also significantly lower in the animals reared in an enriched environment as previously reported (De Jong et al., 1998; Jensen et al., 2010; Petersen et al., 1995). Moreover, pigs reared in enriched environments spent more time active than pigs reared in barren conditions in agreement with previous results (Beattie et al., 1995; Bolhuis et al., 2005; Bracke and Spoolder, 2008). However, the activity of EEHC was not enhanced, and presented similar levels to HC and CG.
Can tail damage outbreaks in the pig be predicted by behavioural change?
2016, Veterinary Journal