Effect of acid detergent lignin concentration for diets formulated to be similar in NDF content on energy utilization in lactating Jersey cows

Lignin is a polyphenolic polymer that is an important factor in limiting fiber digestibility by ruminants. The objective of the current study was to evaluate lignin's impacts on whole animal energy utilization in diets similar in NDF content. A low lignin (LoLig) diet was formulated to contain 32.5% NDF (DM basis) and 9.59% lignin (NDF basis) and the high lignin (HiLig) diet was formulated to contain 31.0% NDF (DM basis) and 13.3% lignin (NDF basis). These diets were randomly assigned and fed to 12 late-lactation (214 ± 14.9 DIM) multiparous Jersey cows (435 ± 13.9 kg) in a 2-period crossover design. Cows fed the LoLig treatment consumed more DM than cows on the HiLig diet (19.9 vs. 18.7 ± 0.645 kg/d) while the LoLig diet was concurrently of a greater gross energy concentration (4.27 vs. 4.23 ± 0.03 Mcal/kg). As expected, increasing the concentration of lignin resulted in a reduction in total-tract NDF digestibility (45.5 vs. 40.4 ± 0.742%). Increasing lignin also resulted in a reduction in the digestibility of starch (97.7 vs. 96.3 ± 0.420) and CP (65.0 vs. 60.0 ± 0.829). Lignin also decreased the concentration of digestible energy (2.83 vs. 2.63 ± 0.04 Mcal/kg) and metabolizable energy (2.52 vs. 2.36 ± 0.05 Mcal/kg) but the concentration of net energy of lactation was similar (1.81 vs. 1.75 ± 0.06 Mcal/kg. Increasing the concentration of lignin also reduced yields of energy-corrected milk (33.7 vs. 30.0 ± 0.838 kg/d), milk protein (1.00 vs. 0.843 ± 0.027 kg/d), and milk fat (1.30 vs. 1.19 ± 0.058 kg/d). Decreasing the dietary lignin concentration did not affect daily methane emissions, averaging 391 ± 29.6 L/d. Results of this study indicate feeding a diet greater in lignin decreases the digestibility of nutrients and provides less energy for production responses and that energy supplied from digestible NDF may be less than predicted by some nutrition models.