Efficient utilization of Fat

By Dr Sanjib kumar Pratihar, G.M.Technical Rnk Agro & Chemicals Pvt. Ltd.

Fat composition will influence overall fat utilization because different components are digested with varying efficiency. It is generally recognized that following digestion, micelle formation is an important prerequisite to absorption. Micelles are complexes of bile salts, fatty acids, some monoglyceride and perhaps glycerol. The conjugation of bile salts with fatty acids is an essential prerequisite for transportation to and absorption through the microvilli of the small intestine. Polar unsaturated fatty acids and monoglyceride readily form this important association. However, micelles themselves have the ability to solubulise non-polar compounds such as saturated fatty acids. Fat absorption is, therefore, dependent upon there being an adequate supply of bile salts and an appropriate ratio of Saturated fatty acids (SAFA): Unsaturated Fatty acids (USFA).

•       Main factor affecting the Metabolizable energy value (MEV) of fats is digestibility which in turn is dependent on the carbon chain length and degree of saturation of the constituent fatty acids (Renner and Hill, 1961a; Leeson and Summers, 1976; Waldroup, et.al.; 1955; Leeson and Summers,2005).

•       The relationship between degree of saturation to digestibility and absorption of Fat has been suggested and pointed out by many researchers, past and present.

•       Researchers found out that Animal Fat and Palm oil samples consistently had the lowest MEV

•       While blends  with balanced Saturated fatty acids (SAFA) and Unsaturated fatty acids (USFA) ratio had best digestibility

•       Oleic acid (C18:1)-MUFA (MONO UNSATURATED FATTY ACID) plays a more direct role in the absorption process, either in the lumen or in the mucosa cells, to facilitate the increased absorption of SAFA (Young and Garrett, 1963).

•       The Vegetable Fats with high PUFA content with high degrees of ME, are well absorbed and utilized as a source of energy by the bird (Young and Artman, 1961).

•       A synergistic effect occurs when the Blended fats are having at least 20-25% of saturated fatty acids, providing a higher ME level to the blend.

•       By increasing the level of unsaturation, digestibility and ME of Blended fats from different sources were improved up to an optimum value when the U/S ratio was 2.5 (Ketels and De Groote, 1989).

•       Increase in dietary PUFA improves ME by lowering the amount of heat produced during metabolism (Dvorin, et al., 1998).

•       All established Blended fat suppliers often blend various sources of fats and oils to attain a specific U/S ratio and thus produce a product with superior ME, (Sibbald, et al., 1960; Sibbald, et al., 1962; Young, et al., 1963; Lewis and Payne, 1966; Leeson and Summers, 1976).

•       Surprisingly, the ME of the blends is higher than expected from the arithmetic mean of the ME of constituent parts (Lewis and Payne, 1966; Leeson and Summers, 1976).

• Factors decreasing metabolizable energy value –

1.        ME values can be reduced by the presence of damaged fats, for example, dimeric or polymerized fatty acids.

2.        Tallow has very low (PUFA) levels with high (SAFA) content. These fats have wide variation not only in MEV, but also in chemical characteristics.

3.        Positional Distribution of Fatty acids in the glycerol molecule. During digestion, triglycerides are hydrolyzed by the action of pancreatic lipase at Sn-1 and Sn-3 positions. 

     The difference in digestibility of Animal fat and Vegetable fat is also attributed to the fact that animal fats consists of high proportions of saturated fatty acids (SAFA) in Sn-1 and Sn-3 positions (Meng et.al.2004).(Sibbald and Kramer-1977) reported that 73% to 81% Palmitic and stearic acids in beef tallow are located at Sn-1 and Sn-3 positions

4.        Wide variation in chemical composition of fat - processing, mixing ratio, fat sources and dilution

5.        When blending oil or fat products in any region, feed stocks should be analyzed by chemical and biological means. .

6.        MOISTURE: 1-1.5% Max.; IMPURITIES: lower; UNSAPONIFIABLES, such as Sterol, pigments and hydrocarbon can’t be saponified after treatment with caustic soda Higher their percentage, Lower the energetic value of the oil or fat.

In all fairness, it is safe to state that Blended fat with right proportions of fatty acids and quality is the right choice of added fat in poultry/animal diet plan.