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Expert opinion: common indestructible materials are not proper enrichment for pigs at all

New research shows that chains and indestructible objects may reduce rather than improve pig welfare, but what alternatives do experts suggest?

27 March 2019, at 12:14p.m.

A new study, published in PLOS One and FareWellDock, investigated the impacts of current materials used as enrichment in pig pens on the welfare and health of pigs. EC Directive 2001/93 stipulates that all pigs have access to proper investigation and manipulation materials, however, this frequently consists of short metal chains with or without an indestructible object attached to the chain. To date, authorities are regarding metal chains and indestructible objects as sufficient enrichment, potentially referring to the RICHPIG model as a justification. However, subsequent research and expert opinion suggests that this is not proper enrichment and may even reduce pig welfare.

The current study aimed to assess current enrichment methods, including chains and indestructible materials, through an expert opinion survey.

The survey

  • The survey consisted of 26 questions.
  • On a scale from 0 to 10 experts specified their level of agreement with the hypothesis, and the prevalence and the welfare scores of nine indestructible enrichment materials.
  • The indestructible enrichment options to be graded by experts were as follows: branched chains, chain on the floor, hard wood, pipe, bare chain, short chain, small ball, big ball, and chain hanging too high.
  • In total 36 experts, mostly pig-welfare scientists, responded (response rate: 39 percent).

Results

  • The experts’ score for agreement with the hypothesis: that chains do not provide proper enrichment, and that adding an indestructible object to the end of the chain may even reduce rather than improve pig welfare, was only 4.6 on average (scale 0–10; n = 25).
  • Indestructible objects are less prevalent in countries that provide straw (like Sweden and the UK) and outside the EU (US).
  • Indestructible objectsare more prevalent in the Netherlands, Belgium, France and Finland, while the prevalence seems to be low in Spain.
  • Balls, wood and pipes were provided most frequently: hard wood especially in the UK (as specified in farm assurance); indestructible balls and pipes in Germany and the Netherlands.
  • Enrichment materials, ranked from high to low welfare score, were grouped in five significance levels. Branched chains scored significantly better than all other indestructible materials and its welfare score (5.1 on average) was close to the pre-defined level of acceptability (5.5 on a scale from 0, worst, to 10, best).
  • The welfare benefits of adding balls, pipes or hard wood to the metal chain were marginal, and well below what the experts considered acceptable enrichment.
  • The branched-chains design, by contrast, appears to be the most viable alternative. It involves providing a longer chain, i.e. with the free end reaching to floor level, adding ‘branches’, ie several short chains ending at the nose height of the pigs, and providing more chains per pen (ie 1 branched chain per 5 pigs).
  • Branched chains should be implemented widely and in the short term as a first step towards, and benchmark for, providing proper enrichment to intensively-farmed pigs.
This is a chain reaching to floor level where the chain may be ‘rooted’ or manipulated while lying down, and to which two short pieces of chain have been attached such that ends of a chain are available at nose height to pigs of different sizes or age groups for manipulation while standing. Note, however, that this is a presumably inferior-type of c-chain, not a recommended stainless-steel anchor-chain
This is a chain reaching to floor level where the chain may be ‘rooted’ or manipulated while lying down, and to which two short pieces of chain have been attached such that ends of a chain are available at nose height to pigs of different sizes or age groups for manipulation while standing. Note, however, that this is a presumably inferior-type of c-chain, not a recommended stainless-steel anchor-chain

© Marc BM Bracke and Paul Koene, 2019