Liquid molasses interacts with buffers to affect ruminal fermentation, milk fatty acid profile, and milk fat synthesis in dairy cows fed high-concentrate diets

摘要

We aimed to evaluate the effects of feeding sugarcaneliquid molasses (LM) with or without a commercialbuffer mix (BFM) on ruminal fermentation parameters,milk fatty acid (FA) profile, and milk yield and compositionin dairy cows fed high-concentrate diets (35:65forage-to-concentrate ratio). Eight multiparous Holsteincows (4 ruminally cannulated) averaging 165 ± 12 d inmilk at the beginning of the study were randomly assignedto a replicated 4 × 4 Latin square design with a2 × 2 factorial arrangement of treatments. Each periodlasted 21 d with 14 d for diet adaptation and 7 d fordata and sample collection. Cows were fed the followingdiets: (1) no LM or BFM supplementation (CTRL),(2) LM without BFM supplementation (MOL), (3)BFM without LM supplementation (BUF), and (4)LM plus BFM supplementation (COMBO). These 4isonitrogenous and isoenergetic diets were formulatedby replacing (dry matter basis) 5% ground corn withLM, whereas BFM replaced wheat bran at 0.8% of thediet. Significant LM × BFM interactions were observedfor the duration of ruminal pH below 5.8, molar proportionof propionate, acetate-to-propionate ratio, milkproportions of trans-10 18:1 and total trans FA, andconcentration and yield of milk fat. Feeding MOL andBUF alone were effective on reducing the time thatruminal pH remained below 5.8 compared with theCTRL treatment, and the COMBO diet decreased itfurther. A similar pattern was observed for the ruminalmolar proportion of propionate. The milk proportionsof trans-10 18:1 and total trans FA dropped significantlywith BFM or LM supplementation versus cows fedCTRL, and the COMBO diet decreased these variablesfurther. Note, however, that these changes elicited bythe COMBO diet were not in the same magnitude asthose caused by MOL or BUF fed alone. The ruminalmolar proportion of acetate increased with the BUFdiet and that of butyrate increased in cows fed MOL,but mean ruminal pH was not affected by treatments.Diets with LM resulted in increased concentrations ofshort- and medium-chain FA in milk fat. The yield of3.5% fat-corrected milk increased significantly in cowsfed MOL or BUF due to the improved concentration ofmilk fat. A trend and a significant increase for energycorrectedmilk were observed with feeding MOL orBUF, respectively. Overall, inclusion of LM and BFMappears to reduce milk trans-10 18:1 FA and total transFA by modulating ruminal pH and volatile FA profilein cows fed high-concentrate diets.