Feed structure and health in young pigs

Although the number of weaned piglet studies evaluating the effectiveness of coarse particles in the diet is limited, studies in growing pigs have consistently shown beneficial effects. In a study by Hedemann et al. (2005), young grower pigs (33 kg of body weight) that were fed a coarse diet of either mash or pelleted (80.1% of the particles <1000 µm, 15.6% between 1000 and 2000 µm, 2.1% between 2000 and 3500 µm, and 2.3% > 3500 µm) showed a higher relative empty stomach weight (+7%) than pigs fed a fine diet (93.6% of the particles <1000 µm, 6.4% between 1000 and 2000 µm, 0.0 % between 1000 and 2000 µm, and 0.0% > 3500 µm). In a second study (Warneboldt et al., 2016) using pigs of the same body weight class, it was shown that the pH of the content in the fundus gastric region of pigs fed a coarsely ground diet (geometric mean diameter 671 µm) was lower for the coarsely ground diet (pH of 2.5) than that of pigs fed a finely ground diet (geometric mean diameter 217 µm; pH of 5.0). In a third study from Bornhorst et. al (2013), the stomach retention time of 30-kg pigs fed a diet with either a high proportion of brown rice (containing the rice hulls) or white de-hulled rice was measured. The stomach retention time of pigs fed the brown rice was prolonged compared to the pigs fed with the de-hulled white rice. This positive effect on the stomach retention was attributed to the rice hulls that remain longer in the stomach. The longer retention of rice hulls in the stomach resulted in a lower stomach pH already 20 minutes after feeding the pigs compared to the pigs that received the de-hulled rice based diet (Fig. 2).

In practice, it may be challenging to find fibre-rich by-products (e.g. wheat bran or oat hulls) that can be coarsely ground and therefore bring feed structure or they may also be contaminated with undesired compounds (e.g. mycotoxins). If feed structure can not be accomplished by adding these fibre-rich by-products in your situation, we would need to find other kinds of feedstuffs. Protein sources should not be ground coarsely to avoid protein digestibility being impaired. Therefore, the remaining option to bring feed structure to the diet is starch-rich sources, e.g. grains. One possibility would be to add a proportion of the grains as whole grains in the mixer and then pelleting the diet. Another possibility would be grinding a small proportion of grains (like 5%) in a roller mill and then pelleting the diet. The success of this strategy will depend on the percentage of grains, either as whole grains or rolled, that will keep structure after pelleting. From the experience that we have built so far, it seems that adding 5% of rolled barley to the mixture and then pelleting the diet could be enough to exert some positive effects on the stomach retention and gut health of post-weaning piglets. In the coming years more research will be conducted on how to optimize feed structure in swine by single processing of some ingredients. The era of grinding all the ingredients in the same way probably will come to an end if we want to achieve the right balance between feed efficiency and stomach-gut health in swine.