About 22% of a sow’s total feed intake is the straw provided for her bedding, though this can increase up to 30% when fresh straw is provided daily (Mansbridge and Stewart, 2012). Historically different cereal straws have been used as appropriate bedding materials for pigs. However, since pigs are inclined to eat the straw, the potential impacts on pigs’ performance and health should be considered:
- Straw is particularly poorly digested as it has a very high content of lignin, cellulose and hemi-cellulose, and other non-structural carbohydrates.
- Because straw is such a fibrous material it can create too rapid flow of the food through the intestines. In consequence the nutrients in pigs’ diet are not properly absorbed in the intestines thus reducing the digestibility of the diet.
- Pigs eating straw have a higher maintenance in energy and protein due to lower absorption of nutrients and higher endogenous losses in the gut.
Moving sows from straw bedding to a farrowing unit without straw can give rise to issues during this transition, often manifesting as constipation problems. Constipation and reduced time for intestinal transit allow the formation of endotoxins and growth of Gram-negative bacteria. Endotoxins are responsible for decreased secretion of prolactin as well as the stimulation of the immune system. This reduces milk production (agalactia) and increases the risk of mastitis. Constipation could also lead to mechanical problems, narrowing the birth channel and leading to more stillborn piglets due to longer parturition intervals.
Additionally, straw carries a possible risk for mycotoxin contamination. According to the 2014 BIOMIN Mycotoxin Survey results, 57 % of all samples were positive for deoxynivalenol with an average contamination of 804ppb. Both deoxynivalenol and zearalenone can have a big impact on performance. More than one third of samples contained the estrogenic mycotoxin zearalenone. Deoxynivaleol, also known as vomitoxin reduces feed intake and results in reduced growth. Zearalenone has an impact on the fertility of sows and therefore causes a lower number of weaned piglets per sow in a year.
Housing sows on straw thus presents certain challenges that require special attention. Some nutritional aspects can help to overcome these challenges:
- Adding highly fermentable fibers in the diet to increase the hind-gut fermentation. Better fermentation in the gut makes sows feel calmer and more satiated which prevents the voluntary intake of straw.
- Compensating for lower nutrient absorption and higher protein loses, for example by increasing these nutrients in the feed formulation.
- Regular analysis of straw for mycotoxins: Follow a good sampling protocol as mycotoxins in straw are not equally distributed and often occur in hot spots. Make use of a reliable analytical method like High Performance Liquid Chromatography (HPLC) or the latest state-of-the-art LC-MS/MS (Liquid Chromatography-Mass Spectrometry/Mass Spectrometry) technology, commercially available as Spectrum 380®, which allows the measurement of more than 380 mycotoxins and other secondary metabolites in a single analysis.
- Application of innovative and EU authorized mycotoxin risk management solutions to counteract mycotoxins.
As many consumers connect welfare of pigs with housing on straw bedding, they do not see the risks associated with this system. As the pig industry learns more about the challenges of this housing system, appropriate solutions involving management improvements and changes to diet formulation can be applied.