A Brief Review: MagnaFat (Calcium Salts of Fatty Acids), Prilled Fatty Acids and Hydrogenated Fats

          As average milk production climbs each year, it becomes more difficult to meet early lactation energy demands of high producing cows.  Higher production levels require the cow to consume more energy to support increased milk production and maintain body condition.  This is especially important with the use of bovine somatotropin (BST).  The use of BST according to product guidelines can increase milk production by 10-15% at the onset of usage through the end of lactation.  Increased milk production at the onset of BST administration is supported by body fat mobilization to meet the increased energy requirement not provided by dietary intake.  Increasing ration energy density can help support additional milk production.  Feeding excessive amounts of grain ingredients or rumen active fats (oilseeds, tallow, grease) to improve ration energy density is undesirable.  Rumen inert fat supplements can safely increase ration energy density above the maximum feeding rates of oilseeds and tallow without altering ruminal fermentation.  The non-interference of rumen function by rumen inert fats and the increased availability of long chain fatty acids can greatly increase energy available for milk production and improved body condition.

         There are several types of commercial inert fat supplements available today.  These can be divided into three basic groups: calcium salts of fatty acids, prilled fatty acids, and hydrogenated tallow or triglyceride.  The feeding value and net energy content of these fat supplements is dependent on the fatty acid content of the supplement, and its digestibility.  Most commercial fat products are also advertised to be “rumen inert”, meaning they have little or no affect on ruminal fermentation.  This is important since ruminally active fats can have a negative influence on ruminal fermentation and animal performance (4).  A generally accepted rule is a maximum supplementation of basal feed fats at 3%, and oilseeds plus tallow at an additional 3% of ration dry matter.  Feeding rumen inert fats thereafter can safely increase ration energy density (Table1).

         Fats are digested in the rumen by the processes of hydrolyzation and hydrogenation.  Fat from plant sources and tallow or grease is mainly in the triglyceride form.  Triglyceride is a molecule of glycerol attached to three fatty acids.  In the rumen, bacteria hydrolyze triglyceride to a molecule of glycerol and three free fatty acids.  The glycerol is digested by other bacteria.  The remaining free fatty acids are hydrogenated to become mainly saturated fatty acids. Therefore, fatty acids available for absorption in the small intestine are mainly the saturated palmitic and stearic fatty acids.  To maintain high digestibility, commercial rumen inert fat supplements should contain no more than 80-85% saturated fatty acids, and at least 15% unsaturated acids. See Table 2 for MagnaFat's fatty acid analysis.

         The degree of saturation of triglyceride has an influence on its digestibility (1,2,3,4).  Highly saturated triglycerides such as hydrogenated tallow or grease products have reduced digestibility.  These products are not completely hydrolyzed in the rumen.  Since ruminants absorb fat in the form of free fatty acids, very hard or saturated triglycerides can have low actual energy contents due to their low digestibility.  Highly unsaturated fats such as yellow grease or vegetable oils can have a negative influence on ruminal fermentation.  These fats can be toxic to rumen bacteria and negatively affect fiber digestion when fed in large amounts.  They are not “rumen inert”.

         Manufacturers of dry fat products have sought to overcome these problems with various methods.  Chemical hydrogenation of tallow or grease will increase rumen inertness by increasing the level of saturation, but can also reduce digestibility (1,2,4).  Another method is to form a small bead or prill of fatty acids.  Prilled fatty acid products may become unstable and melt at higher temperatures and thus may be difficult to use with summer storage conditions.  The third method used is the formation of a calcium salt of free fatty acids.  This complex is considered inert in the rumen at the normal rumen pH range.  The calcium salt – fatty acid complex disassociates in the acidic environment of the abomasum.  The free fatty acids are then available for absorption.  Calcium salt products also contain a source of digestible calcium, which can replace some supplemental dietary calcium.

          Because of its chemical and physical properties, MAGNA FAT is highly digestible (85-87%) .  Remember, because of the unique calcium-fatty acid complex of MAGNA FAT, it can contain more unsaturated fatty acids and still be highly digestible and rumen inert.

         Calcium salt-fatty acid products such as MAGNA FAT combine the benefits of rumen inertness, superior digestibility and absorption, high ambient temperature stability, and high fat content and energy density.  Because of a unique manufacturing process, MAGNA FAT has excellent palatability and will not affect feed consumption.  It can be top-dressed and included in feed and mineral mixes.

 1.   Chandler, Paul.  1993.  Fat sources have place in diet of high producing dairy cows. 

       Feedstuffs.  February  8:12.

 2.   Davis, C. L.  1990.  Fats in animal feeds.  Milk Specialties Co., Dundee, IL.

 3.   Jenkins, T.C.  1993.  Lipid metabolism in the rumen.  J. Dairy Sci. 76:3851.

 4.   Jenkins, T.C. and B.F. Jenny.  1989.  Effect of hydrogenated fat on feed intake, nutrient

      digestion, and lactation performance of dairy cows.  J. Dairy Sci. 72:2316.