Physiological background From the physiological perspective, heat stress affects the ani- mal on various levels: a heat stress dependent reduction of the trans-epithelial electric resistance (TEER), which measures the integrity of the intestinal barrier, was not only shown by in vit- ro data for cell cultures, but also results in vivo in growing pigs. The weaker the intestinal barrier, the easier it is for pathogens to invade the organism, eliciting infections and provoking in- flammatory processes as an immune response. The more en- ergy a sow needs to allocate for immune responses, the less energy can be utilised for growth of foetuses. In addition, re- duced sow performance can also be linked to morphological changes of the small intestine, as shown by a team led by Sa- rah C. Pearce at Iowa State University in 2015, who reported a tendency for smaller villus height and thus a diminished absorptive capacity in the gut of heat-stressed pigs. Consequently, impaired nutrient uptake can reduce the pro- duction and impair the quality of a sow’s milk, which in turn will negatively affect piglet growth during lactation and their weaning weight.
Fibre for heat-stressed animals With respect to a reduced feed intake and impaired nutrient absorption by heat-stressed sows, the status quo feeding strategy is to provide a high-energy concentrated feed dense
in nutrients and keep the proportion of undigestible fibre as low as possible. Paradoxically, the opposite strategy of including considera- ble amounts of fibre will be highly beneficial for the animals: the reason is that the usual strategy focuses on impaired nu- trient absorption only, whereas the fibre strategy focuses on gut integrity and health and optimises the nutrient absorp- tion as a corollary effect. However, the quality of the fibre source is important. Recommendations for fibre supply under heat stress condi- tions consider the reduction of soluble fibre that results in ex- cessive fermentation. Wheat bran, soybean hulls or sugar beet pulp contain high amounts of soluble fibre with addi- tionally high proportions of fibre-bound protein that sup- ports unfavourable protein fermentation in the large intes- tine. The supplementation of a concentrated fibre source, such as lignocellulose, can provide insoluble fibre.
Lignocellulose: Quality matters Compared to basic lignocellulose products, which consist of 100% insoluble and non-fermentable fibres and mainly pro- vide a physical effect in the gastrointestinal tract supporting passage rate, eubiotic lignocellulose represents a synergistic combination of both insoluble non-fermentable and insolu- ble fermentable dietary fibre. Non-fermentable parts have
Close up of the lignocellulose product. ▶PIG PROGRESS | Volume 36, No. 7, 2020 23
PHOTO: AGROMED
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