Effects of replacing canola meal with extruded soybean meals on lactational performance and enteric gas emissions in dairy cows

Abstract

Mechanically extracting oil through an extrusion process increases rumen-undegraded protein content of oilseed meals. This study investigated the effects of replacement on an equal CP basis of canola meal (CM) with extruded soybean meals (ESBM) processed at 2 extruder temperatures, 149°C (LSBM) and 171°C (HSBM), on lactational performance and enteric gas emissions of dairy cows. Following a 2-wk covariate period, 45 Holstein cows averaging (±SD): 117 ± 64 DIM and 45 ± 8 kg/d milk yield (MY) were assigned to 1 of 3 treatments in a 9-wk randomized complete block design experiment. Cows were allowed the first 3 wk for adaptation to treatments and the last 6 wk were for data and sample collection. Treatments contained:13.7% CM (with 42.6% CP; CM diet), 12.1% LSBM (with 47.8% CP; LSBM diet), and 12.5% HSBM (with 46.1% CP; HSBM diet). Enteric CH₄ emission was measured using the GreenFeed system. Orthogonal contrasts were used to evaluate the effect of replacing CM with ESBM and source of ESBM (i.e., LSBM vs. HSBM). Estimated MP supply was 9% below requirements for cows fed CM whereas MP requirements of the cows were met by the ESBM diets. Dry matter intake, ECM, and ECM feed efficiency (ECM/DMI) did not differ among treatments. Milk urea N was lower and fat concentration was higher in cows fed CM compared with ESBM. When compared with ESBM, milk fat yield and milk true protein (MTP) content tended to be increased in cows fed the CM diet. In addition, MTP tended to be decreased in cows fed HSBM, compared with LSBM. Daily CH₄ emission and emission intensity and yield were not affected by diet. Ruminal molar proportions of propionate decreased, whereas molar proportions of acetate and acetate-to-propionate ratio increased, and isobutyrate and valerate tended to decrease with HSBM, compared with the LSBM diet. Total-tract digestibility of nutrients was not different between the CM and ESBM diets. When compared with cows fed the LSBM diet, apparent total-tract digestibility of DM, OM, CP, and starch were decreased in cows fed the HSBM diet. Urinary urea N excretion was greater in cows fed ESBM relative to CM, whereas fecal N excretion was increased by the HSBM diet compared with LSBM. This study indicates that substituting CM with ESBM on an equal CP basis does not alter lactational performance in dairy cows. Additionally, using ESBM produced at higher extrusion temperatures offered no apparent advantage in terms of lactational performance of dairy cows.