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Abstract
Twenty-four multiparous cows were fed diets providing WCS with 3, 6, 9, and 12% FFA. There was no difference in DMI, milk yield, milk protein percentage, lactose, or SNF. Milk fat percentage was lower for the 6% FFA diet. Intake of CP, NDF, and apparent DMD were not affected by treatment. Apparent NDF digestibility was highest for the 3 and 6% FFA and CP digestibility was highest for the 3 and 9% FFA. Intake and digestibility of ADF increased linearly with increasing dietary FFA. Concentrations of milk C6:0 decreased and milk C16:1 increased with increasing dietary FFA. Concentrations of milk C8:0, C10:0, and C12:0 exhibited a cubic response to treatment. Differences in milk fatty acid concentration and nutrient digestibility suggest changes in rumen fermentation. However, these changes did not impact production at the FFA levels fed in this experiment. Diets containing WCS with 8, 11.3, 14.7, and 18% FFA were fed to four ruminally and abomasally cannulated Holstein steers in a 4 x 4 Latin square design. There was no difference in DM, OM, or ADF intake and flow of OM and DM to the abomasum. Ruminal DM digestibility was lower for the 11.3% FFA treatment. Intake of NDF increased linearly with increasing FFA level of the diet. Digestibility of NDF, kg of NDF digested, and ADF intake and digestibility were not affected by treatment. Intake of N, flow of microbial N, and efficiencies of microbial N production responded cubically to treatment. Flow of non-microbial N was lower and microbial N flow higher for the 14.7% FFA WCS treatment compared with the other treatments. Average pH decreased linearly with increasing levels of FFA from WCS. Molar percentages of acetate, butyrate, propionate, isovalerate, and valerate were not affected by treatment. Isobutyrate concentrations decreased linearly and A:P increased linearly with increasing dietary FFA. Flow of valine to the abomasum was higher for the 11.3% FFA WCS, and lower for the 18% FFA WCS. Total AA flow, and total NEAA were not different among treatments. Total EAA flow was higher for the 11.3 % FFA WCS than the 18% FFA WCS.