[Studies of the methods used for the determination of the digestibility of crude fats in calves].
An investigation was made of methods used for the exact determination of the crude content and crude extract of faeces. The following methods were examined: (1) Following treatment with hydrochloric acid a 1:1 mixture of ether and petroleum ether was used. (2) Following hydrolysis with hydrochloric acid extraction with ether was carried out immediately from the aqueous phases. (3) The analysis was carried out with Folch's solvent. A 1:1 mixture of methanol and chloroform was used. (4) The faeces were dried with infrared lamps and crude fat extraction was carried out with Folch's solvent. A 1:1 mixture of methanol and chloroform was used. (5) The faeces were dried with infrared lamps and extraction with ether was done in a Soxhlet apparatus. Nearly identical results were obtained with methods 1 and 2 or 3 and 4 in determining the content of crude extract, the acid number and the percentage proportion of fatty acids. Essential differences were found between methods 1 and 2 and methods 3 and 4. The most reliable results were obtained by using method (2). Method (5) was found to be most suitable for large-scale testing. Values for the content of crude extract in the faeces were somewhat lower (0.78%-1.2%) when determined by method (5). These variations were not significant statistically. (P greater than 5%). No significant differences were observed between methods (2) and (5). It was thus established that method (5) is best suited for estimating the crude extract of the faces. The faeces of calves were found to contain a high proportion of unsaponifiable matter. This proportion was subtracted from the percentage of crude extract and the amount of faecal crude fat was thus estimated. Very small but statistically significant differences were found by converting digestibility data of crude extract into those of crude fat. Hence, for future work the most appropriate method appears to be the estimation of the crude extract in feedingstuffs.
D000818:Animals; D002417:Cattle / Q000378:metabolism*; D004041:Dietary Fats / Q000378:metabolism*; D004063:Digestion; D005243:Feces / Q000032:analysis; D008055:Lipids / Q000032:analysis; D008722:Methods
D004041:Dietary Fats; D008055:Lipids
Methodische Untersuchungen zur genauen Bestimmung der Verdaulichkeit des Rohfettes bei Kälbern