Imagine this clinical scenario: a commercial pig farmer client asks for your advice on reducing the incidence of tail biting following a recent outbreak that led to infection, euthanasia and financial loss. You are aware that routine tail docking is illegal in the UK and have read about straw-based enrichment as a potential factor to help prevent the problem.
You decide to consult the literature to explore whether straw-based enrichment can be used successfully as an intervention to reduce tail-biting injuries in weaner to finisher pigs housed in indoor farming systems.
You are aware that routine tail docking is illegal in the UK and have read about straw-based enrichment as a potential factor to help prevent the problem
Three papers were reviewed: two randomised controlled trials (Larsen et al., 2018; Veit et al., 2016) and one non-randomised controlled trial (Haigh et al., 2019).
Sample sizes ranged from 721 to 1,624 animals. Males and females with docked and undocked tails were studied. The pigs were a minimum of two weeks old and weighed at least 30kg. Breeds included:
- Pigs bred from terminal line Pig Improvement Company, born from Large White x Landrace sows
- Pigs bred from Danavl Yorkshire x Danaval Landrace sows inseminated with Danaval Duroc semen
- Pietrain x [Large White x Landrace]
Outcomes studied included lesions on the tail, ear, head, shoulders and flank; tail loss; and behavioural observations.
Limitations of the evidence
Limitations of the evidence included prior routine tail docking, which could have affected tail biting occurrence and severity; competition for nutrition, which could have influenced behaviour; inconsistent and large scoring intervals that could have permitted interim healing; lack of a control group; observers not being blinded to treatment group assignment; and allocation to treatment groups not being randomised.
A low number of observations and statistical analysis that included other impacting factors were also limitations of the papers. Subjective measures were exclusively used in all papers.
Summary of the findings
Two of the papers found that straw-based enrichment reduced the incidence of tail biting (Larsen et al., 2018; Veit et al., 2016), whereas one paper did not find evidence that straw-based enrichment reduced tail biting (Haigh et al., 2019).
Veit et al. (2016) found that straw-based enrichments reduced the incidences of tail biting in comparison to the control group. At the end of rearing, piglets of all batches had lost their tails to the greatest extent in the control group (48.7 percent), followed by the alfalfa hay group (45.2 percent) and the dried corn silage group (41.3 percent). The study had a strong design, moderate population size and regular scoring completed by the same person, reducing subjectivity. However, the scoring chart itself was vague, which could have impacted the accuracy of the results.
At the end of rearing, piglets of all batches had lost their tails to the greatest extent in the control group, followed by the alfalfa hay group and the dried corn silage group
Larsen et al. (2018) found providing 150g of straw per pig was an effective preventative measure against tail damage, as the study showed that tail damage was more than twice as likely to develop in pens with no straw provided. However, routine tail docking and reducing stocking density were found to be more effective measures against tail damage. The study provided a strong level of evidence due to its design, the number of observations and the presence of a control group. It should be noted that this study focused solely on the effectiveness of straw as a preventative measure and did not assess the ability of straw to stop or reduce tail-biting outbreaks once they had started.
There is moderate evidence for straw-based enrichment as a successful preventative measure to reduce tail biting. However, it should be noted that there are several triggers for tail biting, therefore enrichment will not eliminate all incidences. Implementing good husbandry measures, such as reducing stocking density, alongside straw-based enrichment can enhance the effectiveness of the treatment.
There is moderate evidence for straw-based enrichment as a successful preventative measure to reduce tail biting. However, […] there are several triggers for tail biting, therefore enrichment will not eliminate all incidences
Further research into the factors that influence tail biting during rearing – the stage when the most tail damage has been observed – would be valuable.
The application of evidence into practice should take into account multiple factors, not limited to individual clinical expertise, patient’s circumstances, owner’s values, the individual case in front of you, the availability of therapies and resources, and the country, location or clinic where you work.
Knowledge Summaries are a resource to help reinforce or inform decision making. They do not override the responsibility or judgement of the practitioner to do what is best for the animal in their care.