As efforts to reduce antimicrobials in pig production continue in many regions of the globe, dietary fibre provides an interesting option for steering pigs’ gut health without antibiotics. The source of fibre in a pig’s diet is an important consideration as not all fibres are alike. Increasing research suggests that careful selection of soluble fibre, insoluble fibre and resistant starches can contribute to optimal pig health and growth as well as improved production economics.
Dietary fibre includes a vast group of complex carbohydrates that can only be fermented and utilized by specific classes of microbes in the gut of the pig. This fermentation leads to the production of specific metabolites that can be utilized by the pig. This digestive complexity has led to questions about the benefits of including fibre in the diet. However, a closer look at the types of fibre and their function within the animal suggests proper fibre inclusion in the diet can deliver benefits for pigs and producers.
Below, we consider criteria to inform inclusion of fibre in the nursery diet.
Soluble or insoluble fibre?
Both soluble and insoluble fibre influence digestive processes in the pig’s gastrointestinal tract. Soluble fibre typically serve as a base substrate for rapid fermentation of microbiota in the gut. The end-products of fermentation, primarily volatile fatty acids, are used by the pig for energy. Additionally, the stimulation of specific health-promoting bacterial groups can help reduce the risk of diarrhoea. Prebiotics are a subgroup of soluble fibres that includes purified fibres derived mainly from vegetable ingredients. Inclusion of probiotics at low levels is known to stimulate the beneficial gut microflora, supporting efforts to control diarrhoea.
In contrast, insoluble fibre is more resistant to fermentation during the digestive process and are partly excreted intact in the pig’s faeces. As insoluble fibres travel through the gut, they may bind toxins and harmful bacteria, while delivering bulking properties that prevent constipation. Feed processors play an important role in assuring the benefits of insoluble fibre make it into the feed, as particle size must be large enough to assure the beneficial binding and bulking properties of insoluble fibre sources are retained.
Resistant starch is a small portion of total starch, and acts similarly to soluble fibre. While resistant starches evade digestion by the pig’s enzymes, these starches are largely fermented in the lower parts of the gut. An optimal pig diet should include soluble and insoluble fibre as well as resistant starch. Beet pulp is an example of an ingredient rich in soluble fibre, while palm-kernel meal provides insoluble fiber. Some fibrous materials, such as wheat co-products, include a mixture of soluble and insoluble fibre. Crude fibre on its own does not provide adequate information to assess an ingredient’s benefits, therefore it’s important to consider the fibre source and fibre analysis. The inclusion levels of fibre in a feed should also be carefully considered, as nutritionists must balance optimal performance and health with specific challenges on the farm and pig genotype.
Research centre study – the fibre factor on managing diarrhoea without antibiotics
An example of how carefully selected fibre can help reduce the risk of post-weaning diarrhoea without antibiotics or zinc oxide comes from a study conducted by Trouw Nutrition researchers. Piglets weaned at 25 days of age were housed in four groups in suboptimal climate conditions that exacerbated the stressful effect of weaning.
The first group of pigs (CON-) received a nutritionally adequate diet that included low levels of zinc oxide and no antibiotics. A second group (CON+) was fed a control diet supplemented with an antibiotic. A third group (BP) received a diet containing beet pulp fibre at 7%, and a fourth (WB) group received a fibre-rich diet containing wheat bran at 11%, replacing native cereals. Pigs in all four groups had similar levels of amino acids, while the fibre groups were kept only marginally lower in net energy by adding more fat.
As expected, the study’s design simulating sub-optimal conditions characteristic of weaning stress induced a high prevalence of diarrhoea. The inclusion of fibre sources in the BP and WB groups resulted in weight gains and faecal scores comparable with pigs in the antibiotics group (CON+). Pigs in the low-fibre group (CON-) that received low levels of zinc oxide and no antibiotics scored significantly worse, showing a relative incidence of diarrhoea approximately 20% higher (Figure 1).
Commercial farm study – fibre’s role on efficient intake and improved feed economics
A Belgian farm with highly prolific sows evaluated how selected fibres support intestinal health of weaner pigs in field conditions. A total of 600 piglets weaned at three weeks of age were allotted to one of two treatments: (1) a low fibre (CON) treatment and a high-fibre feed programme. High-fibre diets included graded levels of soluble and insoluble fibres over feed phases to balance fermentability in the pig’s hindgut and intestinal bulk formation to support proper digesta flow and laxation. Due to the farm’s history of respiratory problems, all animals received therapeutic applications of doxycycline. During the first 14 days, 2.5 kg/tonne of ZnO was administered and nutritional levels of zinc were supplied for the remainder of the study. All test diets contained largely the same levels of net energy and amino acids, as well as all other nutrients to assure consistency across groups. Animals were fed test diets during the first two feed phases up to 29 days post weaning and then all pigs were fed a similar diet until the end of the nursery phase at 10 weeks of age.
Primary response parameters observed in the study were growth performance and feed costs per kg body weight. Pigs fed the fibre mixture had improved bodyweight gain at several checkpoints throughout the study and this was statistically significant during the initial four weeks post-weaning (p<0.05) and over the whole nursery period (p<0.10).
While all groups had similar feed intakes, feed was more efficiently converted into gain by animals in the fibre group (P=0.115 total period), resulting in a reduction of feeding costs of 2.7% per kilo of piglet sold. Faecal scores, reported by farm staff, were also improved by feeding the fibre mixture diet. Overall, data from this study supports earlier research that found including the right balance and quantity of dietary fibre is an efficient element for feeding programmes that aim to stabilize weaner pigs’ gut health.
Research findings suggest that including thoughtfully selected and processed sources of fibre along with high-quality protein, mineral, and energy sources can make key performance metrics easier to predict.
Author details - Neil Jaworski, Global Nutritionist at Trouw Nutrition
