Effect of the Ratio Lignin to Cellulose (adf-adl) on Caecal Fermentation, Gut Morphology and Performance of Rabbits around Weaning

The effect of the lignin:cellulose ratio (LCR) on intestinal morphology and microbial activity should be described. A pelleted feed was given ad libitum (CF 17.0 %; CP 15.4%; CL 3.4% DM). Supplementation of Arbocel (23.2% ADL and 71.1% ADF in DM) and Vitacel (0.1% ADL and 80.5% ADF in DM; Rettenmaier GmbH. Germany) in alternating parts (0-2-4-6-8% each) was practiced. Therefore the amount of ADF increased slightly in the 5 feeds, while the lignin level (as a result of Arbocel addition) increased from 3.5 to 5.7 % in DM, and the LCR increased (0.26/ 0.30/ 0.32/ 0.34/ 0.40). Fifty females were divided in five feeding groups with 10 mothers and 8.1 suckling animals per doe. After the 28 day suckling period 200 weaned rabbits were divided into five groups, following the feeding group of their mothers. At day 12 after weaning caecum samples from 20 healthy animals of each group were taken and histological parameters resp. volatile fatty acids (VFA) were analyzed. Neither mortality or morbidity measured from 29 to 40 d old differed among the five groups, while the feed intake and growth was reduced. When the LCR increased the total concentration of VFA in caecum linearly decreased, while the VFA molar proportions were slightly modified. For an increased LCR we detected a decreased in caecal crypt depth (222/ 236/ 192/ 150/ 142 μm). To describe the physiological potential in a complete feed the lignin and cellulose content seemed not sufficient. If the lignin content was 5% (DM) in feed and LCR over 0.4 the microbial activity would decreased and the caecal mucosa would be reduced.