Samples of Antarctic krill (Euphausia superba) and Atlantic krill (Meganyctiphanes norvegica) were analysed for fluoride using a selective fluoride electrode method. Both species showed very high concentrations, a total of 1330–2400 mg F−/kg on fat free dry weight basis in raw samples whereas deep sea prawns (Pandalus borealis) showed a total of 18–91 and red feed (Calanus finmarchicus) 10–37 mg F−/kg. Sections of Antarctic krill were analyzed, and the highest concentration was found in the carapace, 4260 mg F−/kg fat free dry matter, compared with 570 and 750 mg F−/kg in raw and boiled muscle. Biological availability was measured in a chick assay, and showed fluoride in krill to be equally utilized as sodium fluoride added to the diet. Key words: krill, red feed, deep sea prawn, fluoride
Chromium(III)-oxide added to feed was determined by flame atomic absorption spectrophotometry in the same Kjeldahl digest as protein (N × 6.25). The recovery was 98.0% compared with only 40.0% using nitric/perchloric acid digestion. Samples of apparent indigestible protein in Atlantic cod (Gadus morhua) could be collected from the middle and distal part of the intestine 24 h after feeding a diet based on fillets of saithe (Pollachius virens). The level of reference substance and the apparent digestibility of protein indicated that feces samples from the rectum representing the feed could not be obtained until 72 h after the first feeding. Water-insoluble protein from the intestine and rectum accounted for 35–47% and 27%, respectively, of the total dry matter protein. Postdefecation loss of water-soluble nitrogenous components would therefore cause overestimation of protein digestibility. Chromium(III)-oxide and titanium(IV)-oxide were equivalent as external indicators. With titanium(IV)-oxide as indicator substance, calcium, iron, and zinc present in the feed were examined as internal reference substances. The gastric ratios of protein over calcium or zinc were compared with the corresponding ratios in the distal part of the intestine. The apparent protein digestibility agreed with the corresponding estimates obtained by titanium(IV)-oxide. Estimates of protein digestibility from capelin (Mallotus villosus) predating cod caught at sea using the gastrointestinal levels of calcium and zinc as internal reference substances corresponded well with estimates from experiments with cod fed whole capelin with titanium(IV)-oxide as external reference substance. The estimates indicate that samples of feces should be taken from the distal part of the intestine excluding the rectum. Because of large differences between individuals, a sufficient number of fish should be included in digestibility studies.Key words: cod, protein digestibility, digestibility indicators, feces sampling
A method for the determination of astaxanthin in free and esterified forms is based on silica gel chromatography of a lipid extract to obtain fractions of diester, monoester and free astaxanthin. The fractions are reduced with borohydride and the tetrahydroxy @-carotene is measured by ultra-violet spectrophotometry at 4.50 and 476 nm. The method has been applied to different crustacean samples and products, l o fish oils and to organs from rainbow trout. Values down to 0. I pg/g sample could be measured. The fractions were identified by thin-layer chromatography.
A method for repeated blood sampling from small as well as large fish by puncturing the duct of Cuvier is described. The method is simple and makes possible rapid sampling of relatively large volumes of blood. The method is thought to be less stressing for the fish than earlier methods described. Application of the technique to 20- and 300-g trout resulted in no deaths or apparent damage during a 1-mo observation period.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.