Professor Peter H. Brooks, Head of School of Biological Sciences at the University of Plymouth, UK, was invited to give a review paper on the latest research into feeding fibre to pregnant sows at 2008 Manitoba Swine Seminar.

He explained that there are three main reasons why we need to re-evaluate our attitude to the diets we use to feed gestating sows:

1. Confinement housing of gestating sows is becoming unacceptable to consumers in many parts of the world. As a consequence, producers are looking for cost-effective housing solutions that permit group housing of sows without the attendant problem of aggression associated with competition for food.
2. The nutritional requirements of the gestating sow have been the subject of a great deal of research in the last 50 years. However, diets formulated to meet the nutritional needs of gestating sows generally do not satisfy their behaviour and welfare needs, and
3. Changes in world trade and the increasing demand for land-based products for bio-ethanol production are increasing the cost of traditional feed ingredients and will increase the need to seek non-conventional feed sources that will meet the animal's requirements at an acceptable cost.

Professor Brooks went on to explain that he had been asked to address the subject of 'Fibre for gestating sows' in his paper. "A more appropriate title might be 'high satiety' diets for sows," he said, "because fibre is only one of the elements that we will need to consider in what may need to be a radical rethink of our approach to housing and feeding the pregnant sow."

Welfare Legislation in the UK and Europe

Discussing the current welfare legislation in the UK and Europe, Professor Brooks highlighted that changes in European Welfare legislation require that gestating sows are provided with both manipulable substrates and a diet that will satisfy their hunger. As a result, diets for gestating sows are being formulated with increased levels of fibre and alternative housing and feeding strategies are being devised that will better satisfy their behavioural and welfare needs.

He considered some of the issues underpinning these legislative changes and the ways in which producers and nutritionists can use the information to produce better diets and feeding strategies for gestating sows.

Sow Nutrition and Behaviour

Firstly, on sow nutrition and behaviour, Professor Brooks explained feeding motivation in sows fed a low-density diet ad libitum, contrasting this with a high-density diet fed ad libitum and finally, with a restricted quantity of a high density diet.

In reviewing published data on feeding high fibre diets to sows, he said "There is now irrefutable evidence that increasing the fibre content of diets can reduce stereotypical behaviour, because the sow's motivation to feed and forage is reduced. However, merely increasing the fibre content of the diet does not necessarily prevent stereotypical behaviour in the way that increasing feed (energy) intake does."

Definitions for Dietary Fibre

"At the heart of this problem is our difficulty in describing what we mean by 'fibre'," he said.

Professor Brooks explained that a number of different methods are used to measure and describe fibre in feed ingredients: crude fibre, neutral detergent fibre, acid detergent fibre and non-starch polysaccharides (soluble and insoluble).

He went on to distinguish between fibre in the diet and that provided by foraging, noting that sows can utilise a considerable proportion of the fibre in straw, the favoured bedding used in the UK. They consume up to two kilos daily, or a similar quantity of grass silage provided in racks.

Practicalities of Feeding Pregnant Sows Ad Lib

"There would be considerable advantages for producers if sows could be fed high-fibre diets ad libitum. Such an approach would enable sows to be group housed in relatively cheap structures and without the investment in Electronic Sow Feeders," said Professor Brooks.

On a practical point, he added that the use of materials like silages and root crops does require some changes to storage capacity and materials handling facilities but this could be achieved fairly easily on units using liquid feeding, as used for around one-quarter of sows in Europe. He conceded that supplementary feeding of bulky materials to dry fed sows poses greater problems, but the use of racks or ad lib feeders to supply sows housed in yards can be achieved satisfactorily.

"With the increasing costs of traditional feed inputs, many producers are looking at alternative home grown materials that could be used to substitute for grains and the use of totally grain free diets is not unknown," Professor Brooks said.

Considering the effects of high-fibre diets on sow performance, he concluded, on balance, that there are unlikely to be any adverse effect and that in some circumstances, there may be an advantage. He did warn, however, about an increased likelihood of mycotoxins.

There is little data on the effects of feeding high-fibre diets to sows on effluent. Sows on high-fibre diets tend to drink less and so urine output is lower than with high-energy diets. Currently, there is little information on the effect of fibrous diets on the mineral content of effluent.

Conclusions

"That behaviour and welfare are affected by diet and can be improved by providing less energy dense diets is now irrefutable. However, because of the number of different combinations of fibre source that have been used and the lack of a universally agreed descriptor for the functional elements of fibre it is still difficult to give unequivocal advice," said Professor Brooks.

It appears that hind gut fermentation rather than physical bulk is the main determinant of satiety although factors such as water holding capacity and viscosity may have a modulating role.

He added that there appears to be sufficient evidence to support a recommendation that diets should contain around 350 g fermentable non-starch polysaccharide per kg to elicit beneficial effects on behaviour.

Professor Brooks considered it feasible that careful selection of both feed materials and feeding method may make the ad libitum feeding of sows a practical proposition.

He predicted that gestation housing and feeding systems in the future will be less uniform than they have had over the last 30 years as producers seek different solutions, according to their situation and availability of feed raw materials.

In this context and given the financial pressures on cereal grains and oilseeds, we may well see novel systems developed that use alternative home-grown feeds such as silages and root crops together with more fuel and food industry co-products, concluded Professor Brooks.

Further Reading

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You can view Professor Brooks' paper by clicking here.

March 2009