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Development of an in vitro assay to determine the intestinal digestion of lipids in ruminants.

J. R. Vinyard




Development of an in vitro assay to determine the intestinal digestion of lipids in ruminants.
J. R. Vinyard*1, E. Sarmikasoglou1, S. L. Bennett1, J. Arce-Cordero1, G. Aines2, K. Estes2, C. Zimmerman2, A. P. Faciola1. 1Department of Animal Sciences, University of Florida Gainesville, FL, 2Balchem Corporation New Hampton, NY.

The objective of this study was to develop an in vitro assay to determine the extent of intestinal digestion of corn oil (CO), canola oil (CA), and beef tallow (BT) via manipulation of incubation length and concentrations of lipase, bile, and calcium within a buffer solution. The buffer solution (0.5 M KH2PO4) was raised to a pH of 7.6 using 5% NaOH and made to volume using distilled water. Unless otherwise stated, 0.5 g of each lipid source were incubated separately and in triplicate, with triplicate runs for each treatment in 40 mL of KH2PO4 for 24 h with pancreatin (ENZ), bovine bile, and CaCl2 included at 8 g/L, 2.5 g/L, and 10 mM, respectively. Individually, concentrations of ENZ, bile, and CaCl2, as well as incubation length were tested (Table 1). Free glycerol (GLY) and fatty acid (FFA) concentrations were measured using colorimetric assays as determinants of digestibility. Data were analyzed as a completely randomized block design, with run used as block, using the Glimmix procedure of SAS. For each lipid source, GLY increased with increasing ENZ; however, FFA was lowest at 0 g/L ENZ but was similar at 6, 8, and 10 g/L. Both GLY and FFA were greater for 2.5 and 5 g/L of bile than for 0 g/L for each lipid source. Calcium concentration did not affect GLY or FFA for either CO or CA; however, GLY and FFA for BT were greater when calcium was included at 5 and 10 mM than at 0 mM. For all fat sources, GLY and FFA increased after 1 h until 12 h, but did not increase from 12 to 24 h. These results indicate that GLY and FFA can be used as determinants of lipid digestibility when lipid source is incubated for at least 12 h in a buffer solution containing 8 g/L ENZ, 2.5 g/L bile, and 5 mM.Table 1. Levels of each variable used to develop a representative assay for determining in vitro lipid intestinal digestibility

Pancreatin0, 6, 8, and 10 g/L
Bile0, 2.5, and 5 g/L
Calcium0, 5, and 10 mM
Incubation Length1, 3, 6, 9, 12, and 24 h

Keywords: digestibility, free fatty acid, glycerol.

Biography: Originally born in Carmel, IN; I studied animal sciences at Purdue University and obtained my B.S. in 2016 and pursued my Master's in ruminant nutrition at the University of Idaho. In Idaho I studied beef cattle nutrition and metabolism with focuses in forage and nitrogen utilization. From there I chose to continue my education at the University of Florida where I am pursuing my Ph.D. and studying lipid metabolism in dairy cattle.