In vivo kinetics of oleic, linoleic, and α-linolenic acid biohydrogenation in the rumen of dairy cows

Abstract

Ruminal biohydrogenation (BH) of unsaturated fatty acids (FA) reduces absorption of essential FA and can result in formation of bioactive FA that cause milk fat depression. Rates of biohydrogenation of unsaturated FA are commonly observed using in vitro systems and are not well described in vivo. Seven ruminally cannulated cows were enrolled in a 3 × 3 Latin square design study to quantify biohydrogenation of 18:1n-9, 18:2n-6, and 18:3n-3 using a recently developed in vivo BH assay. All cows were fed a common high corn silage basal diet. Biohydrogenation was quantified using a perturbation model that consisted of a bolus dose of 200 g of an oil enriched in each unsaturated FA (oleic acid, OA = 87% 18:1n-9 sunflower oil; linoleic acid, LA = 70% 18:2n-6 safflower oil; and α-linolenic acid, ALA = 54% 18:3n-3 flaxseed oil) and 12 g of 17:0 as a marker of rumen outflow. Rumen contents were sampled before and after the bolus and enrichment of the bolused FA modeled. Using first-order kinetics to model FA disappearance, the fractional rates of disappearance of 18:1n-9 was 0.597 per hour, 18:2n-6 was 0.618 per hour, and 18:3n-3 was 0.834 per hour, similar to rates previously reported with this approach. Rumen turnover of 17:0 was 0.123 per hour, 0.065 per hour, and 0.106 per hour during the OA, LA, and ALA treatments, respectively. The extents of BH were calculated to be 82.8, 90.4, and 88.6% for 18:1n-9, 18:2n-6, and 18:3n-3, respectively. Finally, compartmental modeling was used to quantify the amount of each unsaturated FA metabolized through trans-10 and trans-11 BH pathways. The recently developed in vivo BH assay was able to predict rates of BH and provide insight into rumen metabolism of individual FA and may be useful to future investigations.

Determining Optimal Nonlinear Regression Models for Studying the Kinetics of Fatty Acid Ruminal Biohydrogenation In Vitro

“…The use of mathematical models enables accurate predictions and saves time by testing the best model with a high accuracy and low error. In most studies, nonlinear regression models are employed to examine UFA kinetics during ruminal BH. − The parameters in nonlinear models often possess a biologically meaningful interpretation, based on the units and definitions associated with them. − This interoperability renders nonlinear models valuable for gaining insights into biological processes. It should be noted that nonlinear regression models also encounter limitations.…”

“…In most studies, nonlinear regression models are employed to examine UFA kinetics during ruminal BH. 18 − 23 The parameters in nonlinear models often possess a biologically meaningful interpretation, based on the units and definitions associated with them. 24 − 26 This interoperability renders nonlinear models valuable for gaining insights into biological processes.…”