By Laura Merriman, AB Vista Swine Technical Service Nutritionist
This article will discuss the need to further understand the insoluble (IDF) and soluble (SDF) fractions of the total dietary fiber (TDF) and introduce the stimbiotic concept as a strategy to drive the microbiome to ferment fiber more effectively.
The addition of TDF is advantageous to sow and piglet production. However, there is evidence to suggest that not only TDF, but specifically SDF, can also be beneficial. Based on studies increasing the level of SDF in the gestation diet from 30 to 87 g/day (TDF = 315 g/day; Li et al., 2019) and from 60 to 90 g/day (TDF= 560-590 g/day; Sun et al., 2015), an increase was observed in lactation intake, number weaned, and weaning weights at > 65 grams of SDF per day in the lower fiber diet and at > 75 grams of SDF in the high fiber diets. According to Zhuo (2020), SDF is fermented by bacteria in the lower GI tract, resulting in high production of short-chain fatty acids (SCFAs). This has been observed in gestation studies when sugar beet pulp (SBP) was used as a high source of SDF increasing SCFA (Tan et al., 2018) and improving intestinal health (tight junctions and reduced inflammation; Shang et al., 2019). The IDF in general is more slowly fermented, causing the changes in transit time and increasing bulk density of the diet.
Figure 1. Lignin, Soluble and Insoluble NSP Content of Ingredients (AB Vista Feed Quality Service)
If the assumption is that SDF should be at least 65 g/d, then the next step would be to explore the SDF levels in available feed ingredients. In the United States, the main fiber sources such as corn, corn DDGs, sorghum, and rice bran are higher in IDF in comparison to other potential fiber sources such as SBP and soybean hulls, which would have a higher level of SDF (Figure 1). As an example, to provide the SDF intake of 60 g/day required on top of a corn, soybean meal, and DDGs diet, more than 10% SBP would be required. From a practical perspective, this is not feasible given the price and availability of SBP. It may be important to consider alternative strategies to provide the “soluble fiber component.” An illustration by Courtin (2018; Figure 2), outlines the composition of fiber in various forms. Polymeric networks of fiber are very complex and not very fermentable or soluble. However, as fiber is broken down to smaller fractions, either as polymers or oligomers, they become more fermentable and soluble. It may be possible to add a product to degrade fiber, such as a stimbiotic. The stimbiotic concept involves including a low concentration of product(s) used to signal the microbiome to ferment fiber. A stimbiotic could be used to shift IDF into smaller, more SDF fractions such as polymers or oligomers, leading to increased fiber digestion and SCFA production.
Figure 2. Composition of Fiber (Courtin, 2018)
The effect of a stimbiotic has been shown in nursery pigs through increased SCFA production as well as increased ratio of VFA:BCFA associated with an increase in fibrolytic species of microbiota and decreased protein fermentation. This was associated with a reduction in the inflammatory response as measured by TNF-α, thus supporting the effect of a stimbiotic on gut functionality (Cho et al., 2020). This strategy has also been explored using nursery piglets, which were supplemented with a stimbiotic over a control diet or offered an SDF in the form of SBP during a rotavirus challenge. (Merriman, 2021). Both the stimbiotic and SBP showed a numerical improvement in growth over the control with both treatments requiring fewer injections. However, the stimbiotic-fed animals were more efficient (17 points lower FCR than SBP treatment or 5 points benefit over control).
The application of a stimbiotic, therefore, may be an opportunity in sows to increase the fibrolytic species of the microbiota, increasing fiber digestion and increasing SCFA production, thereby acting similarly to the effect of an SDF addition.
AB Vista has produced a new reference guide that provides an introduction to the benefits of moving from conventional fiber methods to TDF analysis using Near Infrared Reflectance (NIR) technology. To receive a copy of the guide or to get a better understanding of the fiber content in your finished feed, please contact [email protected] or your technical representative. In addition, AB Vista has launched a new fiber calculator that uses average values of raw materials to calculate the dietary fiber content of finished animal feed.
Read part 1 of this three part series.
Read part 2 of this three part series.