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Improving pig welfare - EFSA findings on the welfare of weaner and grower pigs

Improving pig welfare - EFSA findings on the welfare of weaner and grower pigs

The European Food Safety Authority (EFSA) published the new Scientific Opinion on the Welfare of Pigs on Farm in August 2022. In this article, Laura Boyle discusses some of the implications of the findings for the welfare of weaners and rearing pigs.

General recommendations in the report for pigs prior to weaning relate to their need for adequate space and enrichment and not to have their teeth clipped or their tails docked. Also to the importance of applying preventative measures to avoid the need for these procedures in the first place. Thereafter, if the procedures are deemed necessary following comprehensive assessments of the risks, the report recommends that effective and practical methods of pain relief are employed.

This brings us to weaning. An extensive literature search was carried out to identify scientific evidence reporting welfare implications of weaning age and associated welfare indicators. The results focused on vocalisations (representing acute separation stress due to removal from the mother), enteric diseases/mortality, and belly-nosing. In general, the data on weaning ages greater than 28 days were lacking (belly-nosing) and/or highly variable (enteric disease/mortality). The relationship between separation stress and weaning age was such that over the range from 7 to 35 days, every 12 days of delayed weaning halved the acute stress experienced by piglets.

The data on mortality was complicated by the fact that later weaning ages are associated with a greater probability that a pig might die before weaning. Nevertheless, the available data suggested that there is little benefit in increasing weaning age above four weeks. Very early-weaned pigs perform belly-nosing after weaning, but it was not possible to determine at what age belly-nosing is reduced to a prevalence no greater than that seen in pigs under conditions of natural weaning. Hence the EFSA report does not recommend that the current minimum weaning age of 28 days be increased and also indicates the need for more research in this area.

However, there was evidence that the welfare benefits of increasing weaning age over the range between 21 and 28 days are meaningful as a result of the increasing maturity of behavioural, digestive and immunological systems during this period. Indeed the reality on commercial farms is that pigs are often weaned during this period, i.e. younger than 28 days of age. This is allowed due to the exception in the current legislation allowing earlier weaning in specific circumstances. The EFSA report therefore recommends that this special exception be reconsidered.

The scientific opinion also outlines several detrimental effects of artificial rearing on very early weaned piglets and recommends that it should only be used as a last resort and not as a routine management practice. It suggests that other measures should be prioritised, such as selection against extreme prolificacy to reduce numbers of surplus piglets, or the use of nurse sows.

Space allowance

The literature supports that if pigs do not have enough space they cannot perform highly motivated behaviours, including exploratory/foraging, social, resting and thermoregulatory behaviours, and they cannot maintain separate dunging and lying areas. Furthermore, reduced space allowance promotes aggression and tail biting, and compromises growth. The impact on pig welfare of insufficient space to perform thermoregulatory behaviour is greater at high ambient temperatures, where no other cooling mechanisms are in place. The space required to maintain hygiene is lower in fully slatted compared to other floor types and is greater at higher ambient temperatures. The report gives the following examples of how different space allowances influence tail biting and growth rates under different environmental conditions:

  • A minimum space allowance equal to k = 0.036 (representing 0.84 m2 for a 110 kg pig) was previously recommended by EFSA (2005) for thermoneutral conditions. At this space allowance, growth rate is less compromised (estimated as 57%) and tail biting is reduced (estimated as 48% relative to a k = 0.028 (which approximates the current legal minimum space allowance).
  • A minimum space allowance equivalent to a k value of 0.047 (representing 1.10m2 for a 110kg pig), was recommended by EFSA (2005) for temperatures above 25°C or for pigs above 110kg. At this space allowance, growth rate is even less compromised (estimated as 26%) and tail biting is further reduced (estimated as 17%) relative to a k = 0.028 (which approximates the current legal minimum space allowance).

EFSA conclude that the minimum space allowance should be increased relative to the current legal requirement to improve pig welfare, reduce tail biting behaviour and increase growth rate. They did not indicate a specific space allowance, which is understandable given how the optimal space allowance changes under different environmental conditions and importantly for different floor types.

In light of moves by several European countries to either phase out or abolish fully slatted floors for pigs, there is discussion on the appropriate level of solid flooring to provide in part-slatted systems. It is clear that pigs are more comfortable lying on solid flooring and the risk of tail biting is reduced with increasing proportion of solid flooring. Maintenance of hygiene on the solid portion of the floor is important but very challenging. This is influenced by the proportion of solid to slatted flooring, the pen layout, the nature of the airflow patterns and the ambient temperature. Because of these complications, EFSA were unable to define an area or percentage of solid floor in a partly-slatted system, which reconciles the possibly conflicting requirements of pig behaviour and hygiene. Hence the recommendations are:

  • Pigs should have a solid floor area equivalent to a k value of 0.033 (equal to 0.77 m2 for a 110-kg pig) to accommodate lying behaviour (under thermoneutral conditions), with additional space for activity, feeding/drinking and elimination.
  • Further research should be carried out to: a) Validate strategies for maintaining hygiene in partly slatted pens; b) Determine the effect of different degrees of perforation of the solid floor on pig comfort; and pen hygiene.

Environmental enrichment

As we know, current EU legislation already requires that pigs must have ‘permanent access to a sufficient quantity of material to enable proper investigation and manipulation activities’ (Directive 2008/120/EC). For the 2022 Scientific Opinion, the EFSA panel experts ranked different enrichment materials in terms of attractiveness and likely efficacy in reducing tail damage based on the scientific literature and their experience with pigs in the field. The ranking was as follows:

  1. Organic materials (e.g. mushroom compost, peat, green forages and silages) or straw mixed with maize silage, stimulate more investigation and manipulation activities than
  2. long-cut straw offered as bedding,
  3. chopped straw offered as bedding,
  4. straw provided in a rack,
  5. straw pressed into a block from a dispenser that requires extensive manipulation to obtain the substrate.
  6. Destructible point-source materials provided loose on the floor or fixed on the pen walls (e.g. fresh wood, hessian sacks, jute ropes, floor toys made from natural rubber) were considered to be less attractive, as these materials become soiled and thus less interesting over time if they are not renewed regularly, and
  7. inedible point-source enrichment-objects made of plastic or metal (i.e. hanging toys, plastic hoses and chains).

Hence the expert panel considered loose organic substrates, more effective in reducing tail biting than (a) enrichment materials which are suspended from a ceiling or fixed to a wall, and (b) pressed straw blocks and dispensers that require prolonged manipulation to obtain the substrate. Wood and rubber toys are not effective unless replaced regularly to maintain novelty.

Other conclusions were that a reduction in tail biting can be achieved in undocked pigs if they are offered 20g/day of straw or similar substrate. However, quantities that are larger (e.g. up to 400g/pig/day) are more effective. Ultimately recommendations in the report are that pigs are provided with such enrichment to reduce the risk of tail biting. Other recommendations centre on the need to maintain high herd health status, good ventilation, adequate feeding space and well formulated diets.

This article first appeared in the April Pig Newsletter. For more information on the work carried out by the  Teagasc Pig Development Department, click here.