Effects of ruminal inoculations with tannin-tolerant bacteria on fibre and nitrogen digestibility of lambs fed a high condensed tannin diet

Abstract

The goal of this study was to evaluate the effects of dosing unadapted lambs with tannin-tolerant bacteria to improve the digestibility of a high condensed tannin (CT) diet. During the initial phase (metabolism study), a diet containing 30% peanut skins was fed to two groups of Suffolk × Finn-Dorset ram lambs that were about three months old and weighed an average of 24.2 ± 1.4 kg. All animals received 150 ml of a culture (A 600 of 1.0) of a Gram positive rod (a close relative of Eubacterium cellulosolvens) that was able to tolerate 0.5 g/l of purified CT from Desmodium ovalifolium. The control group (7 animals) was inoculated with autoclaved bacteria. The treatment group (6 animals) was inoculated with actively growing bacteria. Inoculations were made daily during a three-week period. Dry matter intake (DMI) was 55.4 and 64.9 g/kg 0.75/day for the control and treatment group, respectively, ( P = 0.13). Digestibility of DM, crude protein (CP) and neutral detergent fibre (NDF) was similar between treatments. Crude protein intake ( P = 0.10) and CP retention ( P = 0.07) were higher for animals inoculated with live bacteria. The CP retention/CP intake ratio was also higher for animals inoculated with the live bacteria ( P = 0.07). To investigate carry-over effects on animal performance due to the bacterial inoculations after the metabolism study, the animals were kept in metabolism cages, but they received no supplemental bacteria. During a subsequent two-week period, the animals continued to receive the high CT diet. Dry matter and CP intake, as well as the feed : gain ratio, were similar between the groups of animals. Finally, for a second two-week period, the animals were fed a low CT (normal) diet without peanut skins. Dry matter intake was 92.9 and 88.6 g/kg 0.75/day for the control and treatment groups, respectively ( P = 0.14). Crude protein intake and feed : gain ratio were similar between the two groups of animals.