Environmental enrichment strategies for nursery piglets and efficacy for maintaining interest
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Context: Animals in situations of stress and constant fear exhibit unwanted behaviours for production. Pigs that are afraid of humans tend to associate any management as stressful. The use of environment enrichment for pigs may help to alleviate anxiety and fear, and hence reduce unwanted behaviours during handling. However, provision of appropriate enrichment presents challenges such as the rapid loss of interest in objects by animals. Aims: The present study evaluated the effects of different environmental enrichment strategies on the behaviour of pigs at the nursery stage, maintenance of animal interest in the enrichment objects, and their reflexes when faced with emotionally negative situations. Methods: Piglets (n = 425) were assigned in a completely randomised design with five treatments and five replicates per treatment (17 animal per replicate). The treatments employed were: control, no enriching objects in the environment; WB, wooden box with popcorn and wood shavings; PT, objects made of plastic tubing; WB and PT concurrently; and WB or PT on alternate days. Behavioural observations were made over 10 days for 8 h each day, divided into four periods of 2 h. Piglets from enriched (n = 10) and non-enriched (n = 10) environments were subjected to three fear tests (human approach, novel object and novel arena). Key results: No significant (P > 0.05) effect was found for the type of enrichment provided or strategy adopted (concurrent vs alternating) on the time piglets interacted with the enrichment objects. Animals kept in an environment with no stimulus had higher frequency (P < 0.05) of undesirable behaviours than those with enrichment, regardless of enrichment type or strategy adopted. Piglets reared without enrichment, when isolated in a new environment, had higher frequency of behaviours such as defecating, urinating and attempting escape, as well as more and longer vocalisation events (P < 0.05). Piglets reared in an enriched environment had higher frequency and duration of interaction with a new object, as well as shorter latency time for the first contact with the object (P < 0.05). Conclusions: The use of enrichment objects in the rearing environment of piglets at the nursery stage reduced undesirable behaviours, suggesting reduced fear and anxiety, and may therefore improve their psychological wellbeing. Implications: Use of enrichment objects during rearing may have implications for alleviation of chronic stress, which leads to constant release of cortisol, an immune suppressor hormone that reduces the health status of the batch and hence production indices.