Numerous aspects of the wet acidic digestion procedure,for the.ass-ay-of Cr,O, in feed and excreta samples have-been iivestigated; these included tinie "and temperature of heating, the efiects of sulphuric acid conceltration, and the waveienEths at which oit,cal densities are read' On the basis of the findings, modific"ations of the piocedure have beerr adopted.As -ihe optical densities of dichromate solutions, ,which are the .end products of'the digestion, are influenced by their sulphuric acid-molarities, jt is essential that iuch molarities be kept -relatively constant. Reading of optical densities' at 350 mtrr permits a much greatei sensitivity in theassay tian does the use of a waveleneth of M4 m1r. Standard curves with corthan does the use of a waveleneth of M4 mrr. Standard curves with correlation coefficients of 1.@0 Setween Cr,O" concentration and optical densitw were obteined consistentlv. demonstratins a hiEh deEree of predensity were obtained consistently, demonstrating a high degree of precision. When a 3-qram samnle of feed and a l-Eram sample of excreta are cision. When a 3-gram sample and a l-gram sample of excreta are Em. feed employed, follows:, . Cr"O" per gm. feed the oDserved ratro:must be corrected as C4O" per gm. excreta Corrected ratio : (observed ratio X 1.110) -0.045. This correction accounts for the background light absorption at 350 mpr attributable to the feed and excreta.The modified method was found to give comparable r'esults to the sodium fusion technique with evidence of slilht advantages over the latter.Can. J. Anim. Sci. Downloaded from pubs.aic.ca by 203.64.11.45 on 03/15/15For personal use only.

No abstract

The time required for carmine-dyed rations to pass through the digestive tracts of mink in the late stages of growth was observed in four separate experiments with the same nine groups of animals, all of which were involved in a nutritional study. Each group received a different ration; five of the rations were based on conventional moist ingredients and four were composed of dry ingredients. In a total of 502 observations the mean time of passage was 142 minutes with a range from 62 minutes to 215 minutes. No consistent sex or diet differences in passage time were demonstrated.