Effects of increasing dietary inclusion of high oleic acid soybeans on milk production of high-producing dairy cows.

Recent research has highlighted the importance of dietary fatty acid profile of fatty acid supplements on production responses of high-producing dairy cows. Conventional soybeans contain ∼15% oleic acid and ∼50% linoleic acid whereas high oleic acid soybeans (HOSB) contain ∼70% oleic acid and ∼7% linoleic acid. We determined the effect of increasing dietary inclusion of roasted and ground HOSB on production responses of high-producing dairy cows. Twenty-four multiparous Holstein cows (mean ± SD; 50.7 ± 4.45 kg/d of milk; 122 ± 57 DIM) were randomly assigned to treatment sequences in a replicated 4 × 4 Latin square design with 21-d periods. Treatments were increasing doses of HOSB at 0%, 8%, 16%, and 24% of DM. The HOSB replaced conventional soybean meal and hulls to maintain similar diet nutrient composition (% of DM) of 27.4% to 29.4% NDF, 20.6% forage NDF, 27.5% starch, and 15.9 to 16.5% CP. Total fatty acid content of treatments was 1.65%, 3.11%, 4.52%, and 5.97% of DM, respectively. Preplanned polynomial orthogonal contrasts included the linear, quadratic, and cubic effects of increasing HOSB. Increasing dietary inclusion of HOSB linearly decreased DMI and MUN and increased yields of milk, 3.5% FCM, ECM, and milk fat, and quadratically increased milk protein. The increased response to milk fat was due to an increase in preformed milk fatty acids. Due to the increase in milk component yields and decrease in DMI, there was an increase in feed efficiency. Increasing HOSB inclusion linearly decreased plasma BUN concentration and tended to decrease plasma insulin. Increasing HOSB had no effect on BW change or BCS change. In summary, increasing dietary inclusion of HOSB up to 24% of DM increased production responses of high-producing dairy cows and did not affect body reserves.