njf2009 apparent digestibility of glycerol in mink

7/27/2019 NJF2009 Apparent Digestibility of Glycerol in Mink

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Apparent digestibility of Glycerol in mink ( M u s t e l a v i s o n )

Mette Schulin-Zeuthen & Peter Sandbl Danish Fur Breeders Research Center, Herning 112C, 7500 Holstebro, Denmark

AbstractA dark and light sample of Glycerol was compared in a digestibility trial. Thelight Glycerol contained slightly more crude protein, fat, ash and salt(percentage of dry matter) and thus slightly less calculated crudecarbohydrates than the dark sample. A discrepancy was noted betweencarbohydrate content in the product sample and recovery of carbohydrates inthe diets. The apparent digestibility of carbohydrates in both samples of Glycerol was 93 %.Schulin-Zeuthen, M. & Sandbl, P. 2009. Apparent digestibility of Glycerolin mink ( Mustela vison ). NJF Seminar no. 427, Fur Animal Seminar, October13 th to 15 th, 2009. pp 4

Sammendrag En mrk og lys Glycerol blev sammenlignet i et fordjelighedsforsg. Den lyseGlycerol indeholdte en anelse mere rprotein, rfedt, raske og salt (procentaf trstof) og derfor en anelse mindre beregnet rkulhydrat end den mrkeGlycerol. Der kunne observeres en forskel i mellem kulhydratindholdet iproduktprven og genfindingen af kulhydrat i foderblandingerne. Dentilsyneladende fordjelighed af kulhydrater i begge prver af Glycerol var 93%.Schulin-Zeuthen, M. & Sandbl, P. 2009. Tilsyneladende fordjelighed af Glycerol hos mink ( Mustela vison ). NJF Seminar nr. 427, Pelsdyr Seminar,13.-15. Oktober 2009. pp 4

Keywords: Glycerol, digestibility, crude carbohydrate

IntroductionAs a coproduct from the production of biodiesel, Glycerol is an interesting potential feedingredient for farm animals. Glycerol has been examined with positive results in pigs(Lammers et al., 2008b), poultry (Dozier et al., 2008; Lammers et al., 2008a) and dairycows (Nielsen & Kristensen, 2004). Chemically, Glycerol is an alcohol, and is consideredto best fit the crude carbohydrate fraction in the diet.

The colour of Glycerol can range from almost clear to very dark brown and depends onthe concentration of pigments and other compounds originating from the feedstock usedin the production of biodiesel (Kerr et al., 2007). Further details of Glycerol are given inClausen & Sandbl, (2009).

The purpose of the trials was to measure apparent digestibility of crude carbohydrates ina light and a dark Glycerol, respectively.

Materials and methodsThe applied samples of Glycerol were produced and delivered by Elbe Fetthandel GmbH.The trials were conducted as regression designs, consisting of four groups with threeanimals in each group. Adult male mink of the colour type Brown/Glow were used. Themink were housed in metabolic cages (mod. after Jrgensen & Glem-Hansen, 1973). Thediet 1 to 4 contained increasing quantities of the Glycerol (Table 1). The diets wereconstructed so crude carbohydrate from Glycerol made up from 0 % (diet 1) to 100 %

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One animal offered diet 1 was excluded from the data analysis because of an inadequatefeed intake. Feed intake of all other animals was satisfactory and consistency of faeceswas normal.

The apparent digestibility of crude carbohydrate was 93 0.4 % and 93 0.9 % in darkand light samples of Glycerol (Figure 1). The higher SEM found in light Glycerol is causedby a higher variation between animals inside groups.

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Glycerol, dark Glycerol, light

Feed ingr edient

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Figure 1. Apparent digestibility of calculated carbohydrate content in two samples of Glycerol

The carbohydrate digestibility is corrected for the dietary content of cellulose, which isassumed to be 100 % non-digestible. Thus, diet 4 should contain 100 % of carbohydrates from Glycerol after adjustment for cellulose. However, these fractionswere 104 % for dark and 114 % for light Glycerol, indicating that either carbohydrate

concentration in Glycerol are over estimated or some carbohydrates in the mixed dietsare missing. As a diet is more complex than a single feed ingredient, it is more likely thatchemical analysis of diets containing Glycerol will result in an underestimatedconcentration of carbohydrates in the diets. Especially, two possibilities are significant:

1) in the chemical analysis, part of Glycerol could be extracted with the fat. Soy oil is thesole fat source in the diets and before addition of water exactly the same amount of soyoil is added to the diets. However, chemical analysis of the diets showed on wet basisthat crude fat content increased from diet 1 to 4. An adjustment of crude fat content tobe identical to diet 1 resulted in carbohydrate digestibilities increased to 95 0.5 % fordark and 94 1.1 % for light Glycerol. However on dry matter basis, the content of crude fat was identical for dark Glycerol-diets and varied 1 %-unit for light Glycerol-diets

suggesting that this adjustment is overcorrecting.2) Glycerol is known to be hygroscopic (i.e. absorbing moisture from the air), which forinstance can be utilised in hand lotions. By absorbing moisture from the air the dietarydry matter content would decrease resulting in a lower calculated dietary carbohydratecontent. Leaving 20 g Glycerol in a bowl exposed to air resulted in a 1 % increase inweight after 1 hour and a 1.5 % increase after 4 hours. A moisturising effect on dietsshould however be adjusted for a bidirectional loss of water. This was not examined inthis trial. As a last alternative, a forced adjustment of the calculated dietary carbohydratefractions to 100 % resulted in an unchanged carbohydrate digestibility of Glycerol on 93%.

A calculation of metabolizable energy in the two Glycerols result in 3793 kcal / kg darkGlycerol and 3730 kcal / kg light Glycerol, which is in line with the 3331 ME found in

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njf2009 apparent digestibility of glycerol in mink

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