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|Title:||Isolation and Characterization of Blood Lipoproteins From Dairy Cows Fed Control or High Grain Diets (Lactation, Feeding, Lipids)|
|Author(s):||Grummer, Ric Robert|
|Department / Program:||Dairy Science|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Subject(s):||Agriculture, Animal Culture and Nutrition|
|Abstract:||Lipoproteins from the plasma of three non-lactating Holstein cows were isolated using either preparative ultracentrifugation or gel filtration chromatography. Lipoprotein classes obtained by ultracentrifugation were very low density plus chylomicrons, low density, high density(,1), and high density. These lipoprotein classes were applied individually to an agarose gel column in order to determine at what volume they eluted in comparison to lipoproteins that were separated after applying total bovine lipoproteins to the column.Three major peaks corresponding to very low density lipoproteins plus chylomicrons, low density, and high density lipoproteins resulted after gel filtration of total lipoproteins. Very low density lipoproteins plus chylomicrons, obtained by ultracentrifugation, eluted as a single peak as did low density and high density lipoproteins. However, high density lipoproteins 1 eluted as two peaks. The first peak eluted at the same volume as low density lipoproteins while the second peak eluted at a volume similar to that of the ascending slope of the high density lipoprotein peak. Results from disc polyacrylamide gel electrophoresis, immunoelectrophoresis, and double immunodiffusion of lipoprotein fractions, and SDS polyacrylamide gel electrophoresis of their apoproteins, indicated that high density lipoproteins 1 are a mixture of low and high density lipoproteins rather than a unique class of lipoproteins.
Gel filtration was employed as the lipoprotein isolation technique in an experiment in which six multiparous Holstein cows ranging from 7 to 19 weeks into lactation were used in a single reversal design to determine the effects of high grain feeding on lipoprotein concentration and composition in blood. Milk yields from cows fed the high grain diet were similar to those for control cows, however, milk fat yield was reduced 26.9%. Plasma lipoprotein concentrations and lipoprotein triglyceride, phospholipid, cholesterol, and cholesterol ester contents were not altered due to treatment. High grain feeding resulted in increased lipoprotein cholesterol ester octadecadienoic acid content and decreased phospholipid octadecaenoic acid content. It is unlikely that these differences caused an alteration in lipoprotein metabolism or were responsible for milk fat depression in dairy cows receiving high grain diets.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1984.
|Date Available in IDEALS:||2014-12-16|