For Pigs, Size Really Does Matter

By Bernard Peet, Pork Industry Consultant, Lacombe, Canada. Pigs in intensive production systems rely on us to provide for all their needs, whether this be related to space, temperature, light, feed or water.
calendar icon 20 June 2003
clock icon 7 minute read

Spring 2003
by Bernard Peet
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It therefore follows that we need to fully understand the pigs requirements in order to optimize conditions for reproduction and growth. However, the systems we use are, by necessity, a compromise between the level of performance we can achieve and the cost of the facility. For example, as we give growing pigs more pen space, growth rate increases but at a certain point the cost of the extra space outweighs the value of the extra growth. Conversely, if we reduce space too much, growth rate falls dramatically and the cost of the lost performance exceeds the saving in building costs.

The space a pig requires relates partly to its size and hence the area it takes up when its lying down and also to group size, pen shape, layout and position of feeders and drinkers. Other aspects of pen and equipment design should also take into account the pigs dimensions at any particular weight, for example the height of the drinker or width of a feeder space. Unfortunately, what I see on farms often demonstrates a lack of understanding among barn and equipment designers of the pigs requirements and in particular its dimensions. I want to show some examples of where this is detrimental to the pig, but more importantly, provide some guidelines that can be used in practice. In future articles I will look at other important aspects of pen design.

So, if size does matter to the pig and may sometimes be a matter of life or death where do we get the critical dimensions from? During the 1980s Dr Jim Bruce, at the Centre for Rural Buildings in Scotland, developed a set of prediction equations based on body dimensions of pigs at various weights. He defined the total area a pig takes up when fully recumbent is its weight to the power 0.66 multiplied by 0.047. Of course, pigs dont always lie fully stretched out and often lie against each other. They may also lie on their sternum taking up less than half the space of a recumbent pig. Therefore we can use the equation Weight (kg) 0.67 x 0.03 to calculate the space required in a fully slatted pen as shown in Fig. 1.

This area is about two-thirds of the area taken by a fully recumbent pig. We must also remember that this is ‘available’ space, not total pen space, so excludes area taken up by feeders or other equipment. In part-slatted pens we may need an additional 20-25% more space depending on the size of the slatted area and in bedded systems 30-50% more. During hot conditions, where possible, we should increase space per pig because they prefer to lie away from each other.

The tip of this piglet drinker is only a couple of inches off the floor,
making it impossible to use.

Drinker height is something I see wrong more often than right. With regular bite or nipple drinkers (which should be angled downwards at 45-60 from the horizontal) pigs prefer to drink with their heads angled slightly upwards, which means that the tip of the drinker should be at shoulder height. This also minimizes water wastage, Dr Bruce defined shoulder height as 16 x Wt0.33 - this will give it in centimetres as shown in Table 1. The table also shows shoulder width for pigs from 5kg to 130kg. This dimension should be taken into account when determining the width of a feeder space or trough length for liquid feeding systems. We normally used 1.1 times shoulder width for each feeding space.

Table 1: Shoulder width and height dimensions for pigs
Weight (kg) Shoulder width (cm) Shoulder height (cm)
5 10.9 27.2
10 13.7 34.2
20 17.2 43.0
30 19.7 49.2
40 21.6 54.1
50 23.3 58.2
60 24.7 61.8
70 26.0 65.0
80 27.2 67.9
90 28.3 70.6
100 29.3 73.1
110 30.2 75.5
120 31.1 77.7
130 31.9 79.7

Dimensions of nursery and finishing pigs are also important to avoid pigs being trapped especially in feed troughs or gates and pen divisions. Any gap or opening must either be small enough to stop a pig getting its head through or large enough for it to get it in and out again easily. These critical dimensions will vary with size of pig so we cannot use a ‘one size fits all’ approach. I recently saw an example where nursery pigs were drowned in a liquid feeding trough because dimensions of the trough dividers were incorrect. Situations like this are completely avoidable by utilizing pig dimensions.

This sow is forced to lie with her head on the trough
as the stall is too short.

In breeding, gestation and farrowing areas dimensions are just as important, particularly as sows and boars are getting larger. Selection for lean, fast growing pigs has resulted in a much larger mature body weight. This means that by the time a sow reaches about fourth parity she will be considerably bigger than a sow of 10 or 20 years ago. Consequently, stalls and crates should be longer and wider than we have been used to.

A 2.1m (7ft) farrowing crate, which used to be the standard, is now completely inadequate and at worst may lead to severe welfare problems with bigger sows. The 2.25m (7ft 6ins) crate now being used in most new barns will eventually have to be increased to 2.4m/8ft as is used in Europe. Again, when we talk about length we need to measure ‘available’ length which will depend on the design and height of both the trough and the rear bars.

Many other aspects of crate design are crucial to sow and piglet performance, in particular height of the bottom rails which affects teat accessibility, rear bar design (some cause vulva damage) and presence of bolts or sharp edges which may cause injury. Most of the problems experienced could be avoided by utilizing pig dimensions at the design stage.

Flooring is also a critical part of the farrowing pen and researchers at CRB in Scotland measured piglets feet and compared them with the dimensions of slatted floor panels used in the industry. Many of these led to injury and the CRB work was instrumental in defining standards for such floors leading to much better products.

Finally, consider the male of the species. Higher mature body weights for sows and boars means that many boar pens used for service do not allow good courtship behaviour and sometimes extreme difficulty in mounting. Minimum length of any side of the pen should be 2.5m (8ft 3ins) and ideally more to achieve an effective service.

If we are going to continue to improve the productivity and efficiency of pig production we will have to understand much better how to meet the pigs needs and yet, in many cases, existing knowledge, such as that shown above, is not being applied. Next time I’ll look at how we can improve pen design by taking pig behaviour into account.

First published by Alberta Pork in their Spring 2003 Western Hog Journal.

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By Bernard Peet, BSc - June 2003
Consultants to the International Pig Industry
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