Evaluation of in vitro DMD, total gas and CH ₄ production, and ruminal fermentation parameters of by-product feed ingredients

This study evaluated 10 by-product feeds as potential energy sources (Exp. 1) and 20 as protein sources (Exp. 2) to examine dry matter disappearance (DMD), total gas (GP), methane (CH ₄ ) production, and rumen fermentation. Two batch culture experiments (randomized complete block designs) were conducted. Gas samples were collected at eight time points over 48 h for GP and CH ₄ determination, with DMD, pH, volatile fatty acids, and ammonia nitrogen also determined. Data were analyzed using PROC Mixed in SAS. A variety of by-products (meals, extracts, screenings, hulls, bran, or DDGS) were derived from canola, corn, flax, hemp, oat, pea, potato, quinoa, soybean, sunflower, and wheat. By-product affected ( P < 0.01) all variables (except total GP mL g ⁻¹ DMD basis). Potato starch (Exp. 1) and pea screenings (Exp. 2) had the highest (mean 87.8%) DMD, whereas hemp was lowest. Potato starch and pea hulls had the highest overall CH ₄ , with hemp lowest in Exp. 1. In Exp. 2, hemp products and red osier dogwood (ROD) had the lowest CH ₄ . Overall, hemp and ROD had the lowest CH ₄ , but reduced DMD, suggesting that animal performance may be negatively affected. However, this study examined by-products in isolation; thus, further assessment in formulated diets is required.