Energy utilization, nitrogen balance and microbial protein supply in cattle fed Pennisetum purpureum and condensed tannins

Summary The aim of the experiment was to assess the effect of condensed tannins ( CT ) on feed intake, dry matter digestibility, nitrogen balance, supply of microbial protein to the small intestine and energy utilization in cattle fed a basal ration of Pennisetum purpureum grass. Five heifers ( Bos taurus  ×  Bos indicus ) with an average live weight of 295 ± 19 kg were allotted to five treatments consisting of increasing levels of CT (0, 1, 2, 3 and 4% CT /kg DM ) in a 5 × 5 Latin square design. Dry matter intake ( DMI ) was similar (p > 0.05) between treatments containing 0, 1, 2 and 3% of CT /kg DM and it was reduced (p < 0.05) to 4% CT (5.71 kg DM /day) with respect to that observed with 0% CT (6.65 kg DM /day). Nitrogen balance, purine derivatives excretion in urine, microbial protein synthesis and efficiency of synthesis of microbial nitrogen in the rumen were not affected (p ≥ 0.05) by the increase in the levels of condensed tannins in the ration. Energy loss as CH 4 was on average 2.7% of the gross energy consumed daily. Metabolizable energy intake was 49.06 MJ /day in cattle fed low‐quality tropical grass with a DMI of 6.27 kg/day. It is concluded that concentrations of CT between 2 and 3% of DM of ration reduced energy loss as CH 4 by 31.3% and 47.6%, respectively, without affecting intakes of dry and organic matter; however, digestibilities of dry and organic matter are negatively affected.