Effect of high-oleic acid whole, heated soybeans or extruded soybean meal on production performance, milk fatty acid composition, and enteric methane emission in dairy cows

Abstract Text: The objective of this study was to investigate the effect of 3 soybean sources differing in fatty acid profile and processing method on productivity, milk composition, and enteric CH₄ emission in lactating dairy cows. The soybean sources were: extruded conventional soybean meal (SBM; 48% CP and 8.7% ether extract; 22% oleic acid), extruded Plenish^® (DuPont Pioneer, Johnston, IA), a high-oleic acid variety SBM (51.4% and 8.4%, respectively; 75% oleic acid), and whole, heated Plenish® soybeans (40.0% and 20.2%, respectively). The study involved 15 Holstein cows (54 ± 8.3 days in milk) in a replicated 3 x 3 Latin square design experiment with 3, 28-d periods. The inclusion rate of the 3 soybean sources in the diet was (all data are on DM basis): 17.1, 17.1, and 7.4%, diets CESBM, PESBM, and WHPSB, respectively, providing 1.4 to 1.5% soybean oil. The rest of the dietary ingredients were: corn silage, 41%; alfalfa haylage, 16%; grass hay/straw mix, 4%; ground corn grain, 10%; cottonseed hulls, 4%; molasses, 4.9%; and a mineral/vitamin premix, 3%. The WHPSB diet also contained 9.7% solvent-extracted SBM. The diets had similar content of CP (17.0-17.6%), NDF (31.0-32.0%), ether extract (3.8-4.0%), and NE_l (1.53-1.54 Mcal/kg). Compared with CESBM, the Plenish^® diets tended to increase (P = 0.09) DMI (27.1, 27.8, and 27.8 kg/d, CESBM, PESBM, and WHPSB, respectively). Milk yield was not affected (P ≥ 0.10) by treatment (average of 42.2 kg/d; SEM = 1.41). The Plenish^® diets increased (P < 0.01) milk fat content (3.55, 3.74, and 3.76%, respectively). Feed efficiency was decreased (P < 0.001) by the Plenish® diets, compared with CESBM (1.50-1.51 vs. 1.57 kg/kg, respectively). Treatments had no effect (P ≥ 0.13) on enteric CH₄ (average of 463 g/d, SEM = 29.7) or CO₂ (average of 12,113 g/d, SEM = 241.5) emissions and methane emission yield (16.6 to 17.2 g/kg DMI). Diets had a marked effect on milk fatty acid profile. Generally, the Plenish^® diets increased (P ≤ 0.01) mono-unsaturated and cis-9 18:1 and decreased (P ≤ 0.01) poly-unsaturated, total trans-, and conjugated linoleic fatty acids concentrations in milk fat. In this study, compared with conventional extruded SBM, the Plenish^® soybean treatments had no effect on milk yield, increased milk fat concentration, decreased feed efficiency, and modified milk fatty acid profile in a manner expected from the greater concentration of oleic acid in Plenish^®soybean oil.

Keywords: high-oleic acid soybean, milk fatty acid, methane, dairy cow