Replacement of soybean with canola improves short-term milk yield and nitrogen-use efficiency in high-producing, early-lactation Holstein cows

It has been demonstrated that canola meal (CM) is used more efficiently than soybean meal (SBM) by lactating dairy cows. This study was conducted to determine the effects of replacing SBM with CM on production performance, blood metabolites, and ruminal fermentation parameters of high producing dairy cows in early lactation. Twelve lactating Holstein cows (4 primiparous and 8 multiparous; 36 +/- 8 days in milk) were used in a 3 x 3 Latin square design with three treatments and four replicates (cows) over three 21-day periods. Cows were fed diets formulated with incremental amounts of CM as 0% (CM-0), 50% (CM-50), or 100% (CM-100) of SBM replaced by CM. Experimental diets were formulated to be isonitrogenous (16.8% crude protein) and isoenergetic (NEL = 1.65 Mcal/kg DM). Dry matter intake (23.2 kg/d), milk composition, energy-corrected milk production (34.5 kg/d), total VFA, and blood metabolites were not affected by treatment. However, cows fed CM diets produced an average 2.9 kg/d more milk than control cows (CM-0). Apparent N efficiency was greatest in cows fed CM-50. Compared with the control, crude protein digestibility and ruminal ammonia concentration were greater and lower for cows fed CM-50 or CM-100, respectively. CM can be a potential substitute for SBM in dairy cow diets as its partial or complete substitution of SMB improved the production performance and nitrogen-use efficiency.