Fiber in Animal Nutrition

Fiber in Poultry Nutrition 44 interesting as well is the increased number of short chain fatty acids. These fatty acids are known to inhibit the growth of patho- genic bacteria in the gut such as E. coli . The positive impact of insoluble CFC on the microbiota has been confirmed by Branton et al. (1997) in their challenge trial in broilers. They were able to observe a positive impact of insoluble CFC on the necrotic enteritis scenario, which is known to be related to Clostridium perfringens. 3.5 Performance It has been observed in a couple of indepen- dent trials that insoluble fibers have a positive impact on performance. Depending on the species an improved carcass yield, a better laying percentage, an improved feed conversi- on or a better weight gain have been reported. This positive impact on performance is valid especially for the insoluble CFC. Insoluble fibers have a positive impact on the digestion as mentioned in the ISA fee- ding guidelines. This impact on digestion is most probably the reason for the better performance. What is the mode of action behind this positive impact on digestion? Svihus and Denstadli (2010) summarize in their review article that insoluble fiber will prolong the retention time of the digesta in the gizzard which may improve the efficacy of exogenous enzymes. Due to the prolonged retention time there is more time for enzyme – substrate interaction. The same should be valid if we have a closer look at protein digestion. The first step of protein digestion is the acid hydrolysis in the gizzard. Yokhana et al. (2014) observed a signifi- cantly increased activity of the enzymes that are involved in the protein digestion in layer pullets due to the inclusion of 1.5% insolu- ble CFC. The results are shown in table 18. They tested a crude fiber concentrate that contained significant amounts of bark. This version was far less efficient. Similar results concerning the activity of proteolytic enzymes have been observed by Boguslawska (2005). These results additionally help to explain the improved protein digestion when using insoluble CFC. Indeed Farran and his group evaluated the effect of insoluble CFC on the protein digestibility in 2 week old broilers. They observed an improved protein digestion by 5.5% as shown in table 19. In a further trial the same research group used thirty six 55 week old dubbed Hy-Line roosters to evaluate the effect of the insoluble Control Mixed fiber Insoluble Fiber* Enzyme activity/organ/min -1 Pepsin 224.0 a 269.0 ab 327.0 b General proteolytic 195.9 a 207.5 a 338.9 b Trypsin 594.5 a 572.6 a 778.5 b Dipepdidase 355.2 a 481.5 b 405.1 ab Aminopeptidase 1650.5 a 2026.0 ab 1952.5 b Table 18: Effect of two different fiber sources on growth and digestive enzymes (Yokhana et al., 2014) *Arbocel a, b different superscript letters in a row indicate significant differences between means (p<0.05) © ERLING Verlag