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Promoting the welfare of floor and trough-fed dry sows

by 5m Editor
28 April 2003, at 12:00am

By Stotfold Pigs. This leaflet looking at the welfare of floor and trough-fed dry sows is based on the results of work by Cambac JMA Research funded by the Ministry of Agriculture Fisheries and Food (now DEFRA) and the Meat and Livestock Commission (MLC).

Introduction

Producers who have recently changed to group housing for dry sows, and those who have more experience of them, need up-to-date information about legislation which affects them. As more producers join marketing schemes, both they and others responsible for monitoring their units need objective methods for deciding whether systems meet scheme standards. This leaflet aims to outline some of the main factors affecting sow welfare in floor-fed and trough-fed systems, and to explain what regulations apply in terms of space allowance. It concludes with a method for assessing dry sow housing on individual units, to help producers monitor their systems and make changes if necessary.

The factors listed below all have a bearing on welfare in any dry sow housing system, but the list is not exhaustive - for example, health, mixing regime, air quality and above all, quality of stockmanship will make very important contributions.

Feeding

Almost all dry sows are fed a small daily ration of high density concentrate feed. Competition for feed in floor feeding systems may have detrimental effect on subordinate sows. These rations do not allow the sow to feed to appetite so she may not be satiated. Moreover, they allow very little opportunity to root, manipulate and forage. Liquid feeding is beneficial in terms of gut fill, but liquid is drunk quickly and there is still no opportunity for foraging. Providing a bulkier diet with low nutrient density can fulfil the needs of the sow, but such diets are not yet widely available. In general, sow hunger, and the need to root, manipulate and forage are not being provided for within existing feeding systems.

Flooring

The floor of a dry sow pen should provide a clean, dry, non-slip lying area which provides physical and thermal comfort and separated from areas of high activity where feeding, drinking, dunging and urinating take place. The use of straw bedding has additional benefits for fulfilling the sows’ needs, by providing a source of environmental enrichment.

Space

Overcrowding will reduce sow welfare mainly by increasing aggressive behaviour. The space required to maintain sow comfort will vary according to feeding system, group size and pen layout. Sows need space to establish dominance relationships, particularly in floor-feeding systems where there is direct competition for food. In larger groups, a sow can move further away from a potential aggressor. The layout of a pen will also affect the way in which sows can use space – for example, aggression may arise if sows have to enter a kennelled lying area through a narrow entrance.

There are no hard and fast rules about minimum space allowances for dry sows, as the Welfare and Livestock Regulations (1994) state that a sow must be able to “turn around without difficulty at all times”. In Guidance Notes accompanying these Regulations, a minimum distance of three sow lengths between troughs is recommended if sows are standing back-to-back to feed in stalls, and a minimum of one sow length behind the feed stall is recommended when sows are feeding with their backs to a wall. These recommendations are for guidance only, and the largest sow using the system must be considered when estimating space allowance.

Recreation

Recreation refers to any activity not directly related to eating the ration provided, drinking, urinating and defecating. The role of recreation in contributing to sow welfare is not trivial. One of the major criticisms of stall and tether systems was their barren nature, as indicated by much higher levels of repetitive or stereotyped behaviour. This indicates that the sows’ needs were not provided for in close confinement systems. Behaviour which does not have any obvious function, such as manipulating straw, may reflect a need to forage, or may be the first stages of nest building in a sow approaching farrowing. While social contact will take place as a result of competition for food, other non-aggressive contact may be very important to sows in maintaining group stability. A good dry sow housing system should provide an interesting environment which allows for the expression of a wide range of behaviours.

Social contact

Pigs are social animals, and in small groups a relatively stable dominance hierarchy will develop. Once established, this is better described as an avoidance order, as sows lower in the hierarchy tend to retreat from dominant sows. Much social interaction, and most aggressive interactions, take place at feeding. Low-ranking sows can experience difficulty in gaining access to food, especially if floor-fed over a limited area. The nature of social contact is affected by group size. In small stable groups (10 or less) an established avoidance order can be maintained. In very large dynamic groups, stable sub-groups can be maintained. Levels of sow welfare are probably lowest in dynamic groups of intermediate size (roughly 10-40 sows), although having a boar present may help to minimise aggression in intermediate groups. The upper limit for a group of sows to form a stable avoidance order is not known.

Sow welfare in specific systems

The layout and management of dry sow housing systems is determined largely by the feeding system, hence systems are grouped according to feeding method. Those indoor systems involving simultaneous feeding are outlined below. For detailed information on costs and sample layouts readers are referred to the Pig Welfare Advisory Group Leaflets, references PB3083 to PB3092 inclusive. (DEFRA Publications, Admail 6000, London SW1A 2XX. Tel: 08459 556000).

Floor feeding

Sows Floor Feeding on Straw
  • Groups of sows can be fed manually, or semi-automatically using dump or spin feeders. Sows can forage for food and the hierarchy is maintained through social contact.
  • Dump and spin feeding involves filling dispensers suspended above the group via an auger. Once or twice a day food is dropped onto the floor, either falling in a circle from the dispenser (dump feeding) or being thrown out over a larger area (spin feeding).
  • If access to food is restricted (for example, by dump feeders dispensing feed near walls or corners, or space allowance being low at feeding) access to food may be difficult for some lower-ranking sows, and social contact may consist largely of aggressive interactions at feeding.
  • Providing an undisturbed lying area may be difficult if food is dropped onto the bedded area.
  • Sow welfare is enhanced in floor feeding systems if group size is low, groups are stable, space allowance at feeding is generous, and a separate lying area is provided.
  • As well as leading to social instability, the use of larger groups makes it more difficult to match sows by size and condition.

Trough feeding

Sows Trough Feeding
  • Trough feeding systems range from those providing no barriers (which are rare) to those with locking feed stalls which separate and protect the sow at feeding. Providing some protection at feeding reduces aggression.
  • Partial barriers and free access stalls do not provide complete protection, but aggression and changing of feed places can be minimised by the use of “fixing” sows to trough spaces, or by liquid feeding.
  • To “fix” sows to individual spaces, feed is delivered by auger to each feeding place at a rate which should allow the slowest feeding sow to eat, while “fixing” faster eating sows to their feed place to await the next trickle of food.
  • Liquid feeding allows ration to be consumed quickly, and there is no benefit in changing feed place, as any time away from the trough reduces the time available to drink the communal ration.
  • Some trough feeding systems (for example, cubicle systems and some free-access stall systems) offer a combination of lying and feeding area. However, ability to turn round without difficulty at all times must be taken into account.
  • As with floor feeding, the use of small stable groups helps to minimise aggression and allows matching of sows for size and condition.

Simple conversions

  • A simple conversion involves converting an existing stall and tether system to group housing. Interest in these conversions has arisen as result of the ban on close confinement housing. In effect, these provide free-access feeding stalls with limited extra lying space outside the stall area.
  • They can work successfully, but ease of removal/addition of sows, ensuring simultaneous feeding, and complying with the Regulations in terms of space allowance all need to be considered when converting a building not originally designed to house sows in groups.

Assessing sow welfare in specific systems

It is possible to draw conclusions about, for example, protection at feeding being beneficial for sow welfare, but this does not help producers to assess their own systems. For example, a producer who has opted for floor feeding wants to identify strengths and weaknesses in his or her system, and is not helped by general comparisons with other systems.

  • The methods given at the end of this leaflet can be used to monitor sow welfare of stable groups of dry sows which have not been recently mixed, are housed indoors and are simultaneously fed. It is based on observation of 32 groups of sows and is designed as a practical tool for use on farm to indicate whether there may be a problem which requires further investigation.
  • While mean levels are referred to throughout, observation of a system will also help to identify individuals with a problem.
  • In trough-fed group housing systems, quick settling times are generally associated with lower levels of aggression and skin damage, and are considered to contribute to sow welfare.
  • Focusing on an acceptable settling time is not possible for floor feeding systems, since this can be very variable as sows forage to obtain all of the ration available. Although floor-fed sows tend to take longer to settle, it should still be possible to achieve acceptably low levels of aggression and skin damage.

A quick and easy method to assess welfare

The combination of measures described on the following pages can be very useful when assessing either floor or trough feeding systems. This observation method can be repeated at regular intervals to ascertain whether sow welfare is improving or declining. It can also be used to monitor the effects of any changes made to a dry sow housing system.

A quick and easy method to assess sow welfare in floor-fed systems

Observation method
The hour immediately post-feed is a period of active sow behaviour.
Observations are based on:

  • aggressive interactions at feeding
  • body condition
  • skin lesions
  • time to settle after feeding
Agression at feeding
Count every aggressive interaction observed during the hour post-feed.
Aggressive encounters include:
  • head swings
  • pushes
  • fights
  • chases
  • bites
  • vulva bites
(combination of interactions lasting for at least five seconds)

Body condition
Body condition should be taken for all the sows in the usual fashion on a scale of 1 (very thin) to 5 (over-fat), with a score of 3 being the optimum.

Skin lesions
Skin lesions are measured on a 0–5 scale for the following areas of the body:
  • head and shoulders
  • rear
  • flank
  • vulva

A score of one represents one recent (pink or bleeding) cut/scratch, whereas five represents five or more recent cuts/scratches. Add the four scores to obtain a total per sow.

Settling times
Settling times for sows that are floor-fed can be much longer than those seen in other systems (approximately 2% settled in floor-fed systems one hour post-feed). However, acceptable levels of aggression, skin lesions and body condition should still be achieved.

Definitions of categories
Use the categories below to assess the overall success of the system.
Aggression¹ Average skin lesions/sow Body condition
Very good <1 0 – 2 all scores 3 throughout pregnancy
Good 1 - 2 3 – 5 most scores 3, stable through pregnancy
Adequate 2 – 3 6 – 9 most scores 3, variable throughout pregnancy
Poor 3 – 4 10 –14 most scores greater or less than 3,variable throughout pregnancy
Very poor >4 15 – 20 most scores greater or less than 3, falling throughout pregnancy
¹ interactions per sow per hour

A quick and easy method to assess sow welfare in trough-fed systems

Observation method
The hour immediately post-feed is a period of active sow behaviour.
Observations are based on:

  • aggressive interactions at feeding
  • skin lesions
  • body condition
  • time to settle after feeding
Agression at feeding
Count every aggressive interaction observed during the hour post-feed.
Aggressive encounters include:
  • head swings
  • chases
  • pushes
  • bites
  • fights
  • vulva bites
(combination of interactions lasting for at least five seconds)

Body condition
Body condition should be taken for all the sows in the usual fashion on a scale of 1 (very thin) to 5 (over-fat), with a score of 3 being the optimum.

Skin lesions
Skin lesions are measured on a 0–5 scale for the following areas of the body:

  • head and shoulders
  • rear
  • flank
  • vulva

A score of one represents one recent (pink or bleeding) cut/scratch, whereas five represents five or more recent cuts/scratches. Add the four scores to obtain a total per sow.

Settling times
The number of sows lying in the whole group should be counted one hour after feeding.

Definitions of categories Use the categories below to assess the overall success of the system.
Aggression¹ Settling time Av. skin lesions/sow Body condition
Very good <1 majority settled 1 hour after feeding 0 – 2 all scores 3 throughout pregnancy
Good 1 – 2 at least 75% settled 1 hour after feeding 3 – 5 most scores 3, stable through pregnancy
Adequate 2 – 3 at least half settled 1 hour after feeding 6 – 9 most scores 3, variable throughout pregnancy
Poor 3 – 4 less than half settled 1 hour after feeding 10 –14 most scores greater or less than 3, variable throughout pregnancy
Very poor >4 never more than 25% settled 1 hour after feeding 15 – 20 most scores greater or less than 3, falling throughout pregnancy
¹interactions per sow per hour

This leaflet is based on the results of work by Cambac JMA Research and was funded by the Ministry of Agriculture Fisheries and Food and the Meat and Livestock Commission.

Source: Stotfold Pigs - Reprinted here April 2003


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