Effects of purified lignin on in vitro rumen metabolism and growth performance of feedlot cattle

OBJECTIVE: The objectives were to assess the effects of purified lignin from wheat straw (sodium hydroxide dehydrated lignin; SHDL) on in vitro ruminal fermentation and on the growth performance of feedlot cattle. METHODS: In vitro experiments were conducted by incubating a timothy-alfalfa (50:50) forage mixture (48 h) and barley grain (24 h) with 0, 0.25, 0.5, 1.0, and 2.0 mg/mL of rumen fluid (equivalent to 0, 2, 4, 8, and 16 g SHDL/kg diet). Productions of CH(4) and total gas, volatile fatty acids, ammonia, dry matter (DM) disappearance (DMD) and digestion of neutral detergent fiber (NDF) or starch were measured. Sixty Hereford-Angus cross weaned steer calves were individually fed a typical barley silage-barley grain based total mixed ration and supplemented with SHDL at 0, 4, 8, and 16 g/kg DM for 70 (growing), 28 (transition), and 121 d (finishing) period. Cattle were slaughtered at the end of the experiment and carcass traits were assessed. RESULTS: With forage, SHDL linearly (p<0.001) reduced 48-h in vitro DMD from 54.9% to 39.2%, NDF disappearance from 34.1% to 18.6% and the acetate: propionate ratio from 2.56 to 2.41, but linearly (p<0.001) increased CH(4) production from 9.5 to 12.4 mL/100 mg DMD. With barley grain, SHDL linearly increased (p<0.001) 24-h DMD from74.6% to 84.5%, but linearly (p<0.001) reduced CH(4) production from 5.6 to 4.2 mL/100 mg DMD and NH(3) accumulation from 9.15 to 4.49 μmol/mL. Supplementation of SHDL did not affect growth, but tended (p = 0.10) to linearly reduce feed intake, and quadratically increased (p = 0.059) feed efficiency during the finishing period. Addition of SHDL also tended (p = 0.098) to linearly increase the saleable meat yield of the carcass from 52.5% to 55.7%. CONCLUSION: Purified lignin used as feed additive has potential to improve feed efficiency for finishing feedlot cattle and carcass quality.