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Assessing milk response to branched-chain volatile fatty acids.

K. E. Mitchell



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Assessing milk response to branched-chain volatile fatty acids.
K. E. Mitchell*1, M. T. Socha2, L. E. Moraes1, Y. Roman Garcia1, J. L. Firkins1. 1The Ohio State University Columbus, OH, 2Zinpro Corporation Eden Prairie, Minnesota.

Supplemental branched-chain volatile fatty acids (BCVFA) and valerate (i.e., “isoacids”) have improved both NDF digestibility and feed efficiency in ruminants. Cellulolytic bacteria require BCVFA to synthesize branched-chain amino acids (BCAA) and branched-chain fatty acids because they cannot uptake or synthesize BCAA de novo. Many studies provided isobutyrate (IB), 2-methylbutyrate (MB), isovalerate (IV), and valerate (V) altogether without exploring optimal combinations. Our objective was to determine a combination of isoacids that is optimal for milk production. Sixty (28 primiparous and 32 multiparous) lactating Jersey cows (106 � 54 DIM) were blocked and randomly assigned to 4 treatments: 1) control (CON) with no isoacids, 2) MB (12.3 mmol/kg DM), 3) IB+MB (12.6, and 7.7 mmol/kg DM), or 4) all 4 isoacids (7.3, 6.2, 4.2, and 5.1 mmol/kg DM IB, MB, IV, and valerate). All cows were fed CON for a 2-wk period, then randomly assigned within block to treatments for 8 wk (n = 15). Milk samples from 4 milkings per week were analyzed by DHI (Columbus, OH). Data were analyzed with PROC MIXED (v. 9.4, SAS Institute 2015) with the random effect of block and fixed effects of treatment, week, and parity. Data from the wk 2 of the study were used as a covariate, and weekly or biweekly means per cow were repeated measures. Interactions of treatment and parity (P < 0.10) were detected for fat and protein percentages. There were no differences in components for primiparous cows, whereas IB+MB increased (P < 0.09) protein percentage by 0.04 and 0.08 in multiparous cows compared with CON and MB treatments, respectively. IB+MB increased (P < 0.01) fat by 0.23 to 0.31% units compared with other treatments. Milk yield and DMI were not affected, but treatment interacted with week (P = 0.06) for ECM/DMI; IB+MB increased (P < 0.10) ECM/DMI by 0.15 (main effect means difference) compared with CON and MB, mainly during the earlier weeks of the study after which differences decreased as cows entered late lactation. The IB+MB treatment optimized feed efficiency in our study and not at the expense of BW gain. Further research is needed to optimize isoacids formulas under differing dietary conditions.

Keywords: branched-chain volatile fatty acids, feed efficiency, cellulolytic bacteria.

Biography: Kelly Mitchell is originally from Tulare, CA where she grew up around dairy cattle by following her father, Ken Mitchell a dairy veterinarian. After completing her undergraduate degree in Animal Sciences at UCD in 2015 she continued her education at UCD with Dr. Heidi Rossow and earned a MS in Animal Biology in 2017. Currently she is working towards her PhD with Dr. Jeff Firkins in The Ohio State University Nutrition program, while she also works as a research associate in the Animal Sciences Department.