Development of an Extraction Method for Branched Chain Volatile Fatty Acid in a Supplement and Concentrate Meal

Antoinette Foliart
Undergraduate (Animal Sciences – Nutrition)
Dr. Jeffrey Firkins
Animal Sciences

Isobutyrate, isovalerate, and 2-methylbutyrate are branched chain volatile fatty acids (BCVFA) which are products derived from protein degradation that are necessary for cellulolytic bacterial growth. Previous research indicates increased feed efficiency in cattle with the addition of BCVFA by helping to stimulate fiber degradation. However, BCVFA can dissipate which would decrease the palatability of the diet and BCVFA supply to animals unless a binding process is used to prevent BCVFA loss. To determine the quantities of each BCVFA present in feed or BCVFA supplement products, extraction methods are used. The objective of this study was to establish a method for extraction and verification of BCVFA in feed and supplements. An isobutyrate supplement (S) and a concentrate meal (CM), which contained all 3 BCVFA supplements, was utilized in the experiment. A low (L, 2g S:100mL, 5g CM:100mL), medium (M, 4g S:100mL, 10g CM:100mL) and high (H, 8g S:100mL, 20g CM:100mL) ratio of supplement or meal to dH2O was extracted at 24h to determine the ideal ratio for complete extraction. Additionally, M ratio was used for samples at 0, 1, 2, 4, 8, and 24h for S and CM to establish the minimum time needed for full extraction. The BCVFA concentration of the extraction liquid was determined using gas chromatography. Data were analyzed with SAS (v9.4) using PROC GLM with the fixed effect of time or ratio on mmol/g of BCVFA extracted. The effect of ratio was found to be insignificant (P>0.23) at the 24h time point for mmol/g of total BCVFA in both CM and S. Time increased (P<0.01) mmol/g of BCVFA from CM and S. The mmol/g at 24h was greater (P<0.10) than 0, 1, 2, 4h sample for S and CM, but the 24h sample was not different (P>0.37) from the 8h time point. Therefore, soaking for a minimum of 8 hours with low, medium, or high ratio obtained maximum extraction in both CM and S. This method can be applied to test supplements for dissipation of BCVFA and determine the BCVFA supply in diets provided to cattle.