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Unformatted text preview: Effects of Amount and Source of Fat on the Rates of Lipolysis and Biohydrogenation of Fatty Acids in Ruminal Contents 1 T. M. Beam,* ,2 T. C. Jenkins,* P. J. Moate,† R. A. Kohn,‡ and D. L. Palmquist§ *Department of Animal and Veterinary Sciences Clemson University, Clemson, SC 29634 †School of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA 19348 ‡Department of Animal and Avian Sciences, University of Maryland, College Park 20742 §Department of Animal Sciences, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster, 44691 ABSTRACT Because the percentage loss of unsaturated fatty acids across the rumen has varied considerably in previ- ous in vivo studies, we conducted five experiments to identify potential factors that might affect the in vitro rates of lipid lipolysis and biohydrogenation in ruminal contents. The factors examined included the amount of fat added to the substrate, the source of added fat, the diet fed to the donor fistulated cow, and the time of collection of inoculum from the donor cow. Lipolysis and biohydrogenation were expressed as the rates of disappearance of neutral lipid and unsaturated fatty acids, respectively, from the culture contents over time using a first-order model. The rate of lipolysis of soy- bean oil declined from 44%/h to less than 30%/h as the percentage of soybean oil in the culture substrate increased from 2 to 10%. The overall rate of biohydro- genation of C 18:2 was 14.3%/h, but declined 1.2 %/h for each percentage unit increase in C 18:2 added to the sub- strate. Compared with C 18:2 , the rates of biohydrogena- tion of C 18:1 were generally lower (averaged 3.6 %/h) for all fat sources. The rate of biohydrogenation of C 18:2 in soybean oil was not affected by the amount of grain or fat fed to the donor cow, or the time after feeding that ruminal inoculum was collected. Based on these find- ings, high linoleic acid concentrations in the diet would possibly reduce biohydrogenation and increase the post- ruminal flow of this unsaturated fatty acid. Also, lipoly- sis may vary considerably due to amount and source of lipid added to the diet, but this has little influence on Received February 15, 2000. Accepted June 11, 2000. Corresponding author: T. C. Jenkins; e-mail: tjenkins@clem- son.edu. 1 Technical Contribution Number 4514 of the South Carolina Ag- ricultural Experiment Station, Clemson University. Partial financial support was provided by the Fats and Proteins Research Foundation. 2 Present address: 3470 Bethlehem Road, Blackstock, SC 29014. 2000 J Dairy Sci 83:2564–2573 2564 the initial disappearance rates of linoleic or oleic acids from ruminal contents....
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This note was uploaded on 09/19/2011 for the course ANS 5446 taught by Professor Brown during the Spring '08 term at University of Florida.
- Spring '08