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    Chromium (III) complexes and their relationship to the glucose tolerance factor : a thesis presented in partial fulfillment of the requirements for the degree of Master of Science in Chemistry at Massey University
    (Massey University, 1982) Cooper, Juan Anton
    Two forms of the dinicotinate complex Cr(nic)2(H2O)3OH were formed which were yellow and blue, respectively. For the yellow form the nicotinic acid ligands were coordinated via the pyridine ring nitrogen atom but this complex was biologically inactive, while for the blue form nicotinic acid was coordinated via the carboxylate group and this compound was biologically active. Only Cr(III) formed a stable carboxylate coordinated dinicotinate complex. No stable complexes were formed with Fe(III) and Mn(III) due to significant olation, even at acidic pH's, and the complexes of nicotinic acid with Cr(II), Mn(II), Co(II) and Ni(II) were all pyridine nitrogen atom coordinated and biologically inactive. Several chromium (III) complexes with amino acids possessed biological activity also, and these included the α -carboxylate coordinated species Cr(gly)n(H2O)3+6-nand Cr(glu)n(H2O)3+6-n, the bidentate coordinated Cr(gln)2(H2O)2+ complex, and the NH4OH- eluted complexes obtained when Cr(gly)2(H2O)2+ and Cr(glu)2(H2O) 2+, but not Cr(cys) 2(H2O) 2+, were eluted from a DOWEX 50W-X12 cation-exchange column (loss of the α-amino coordination was postulated to have occurred). The biologically active mixed ligand complex postulated as Cr2(nic) 4(gly) 2(OH) 2 was prepared and found to be stable at neutral pH as a result of coordination of the glycine ligands. The activity of the chromium (III) complexes in the yeast fermentation assay suggested that similar effects would be found in mammalian systems. The yeast assay system was found to be a simple, quick and reproducible method of determining biological activity. All of the active chromium (III) complexes prepared were found to be similar, in structure, to the diguanide compound 1,4-diguanidinobutane which is known to lower blood sugar levels in mammals. This similarity in structure suggested a similar function might be possessed by the complexes reported in this thesis
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    Studies on chromium-containing fractions in yeast and their relation to the proposed glucose tolerance factor : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Chemistry at Massey University, New Zealand
    (Massey University, 1981) Haylock, Steven John
    Chromium-containing fractions were isolated both from whole yeast cells and yeast extracts in attempts to isolate the glucose tolerance factor (GTF). Techniques for the isolation of chromium-containing fractions from whole yeast cells were investigated by first identifying the chromium fractions by means of chromium-51 labelling. An anionic complex was isolated from yeast cells which had been supplemented in a medium with high levels of chromium chloride. This complex was identified as a chromium-glucose complex but did not show any of the properties expected for the GTF. An isolation procedure based on ion-exchange chromatography achieved the isolation of eleven apparently discrete chromium-containing fractions from yeast extract. The activity determination of these fractions, by use of a yeast-fermentation assay, resulted in generally only the cationic fractions showing high activity levels. The origin of the isolated fractions was investigated by determining which fractions resulted from reaction with media components and those which probably resulted from association with yeast. These investigations showed that the majority of complexes formed were not synthesized by the yeast cells but were a result of reaction with media components. After these studies only two cationic fractions remained as possible candidates for the glucose tolerance factor. The cationic chromium-containing fractions from black peppercorns, sage, pork kidney powder, wheat bran and molasses were investigated. The cationic fractions obtained from these samples were identified as all having different ion-exchange elution positions and all having widely varying activities. Hence there did not appear to be a single discrete chromium-containing fraction which was capable of being identified with the glucose tolerance factor. Preincubation of chromium-deficient yeast in media containing chromium was undertaken in an attempt to demonstrate some requirement of the yeast for chromium. No such requirement could be demonstrated. On further purification of the active-cationic fractions the activity was shown to separate from the chromium but the factor causing the activity could not be identified. Collectively these results support the existence of a non-chromium containing factor, capable of increasing the rate of fermentation of yeast and hence a factor, which apart from the lack of a chromium atom, shows close similarity to the glucose tolerance factor as reported by Schwarz and Mertz.
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    Application of intraruminal chromium controlled release capsules to the measurement of herbage intake of sheep at pasture : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University
    (Massey University, 1990) Parker, Warren James
    Experimental evidence obtained since 1950 suggests that New Zealand sheep farm production and financial returns could be increased by adopting separate grazing management for ewes of different pregnancy and rearing status from 6 weeks before lambing until weaning. Progress in developing management systems for the differential allocation of pasture, favourable lambing paddocks and labour during this period has been restricted by the absence of equipment for diagnosing ewe pregnancy status and a lack of data relating pasture conditions to feed intake and ewe and lamb productivity. Accurate pregnancy diagnosis by realtime ultrasound scanning has been available to farmers since 1985, but research into ewe grazing management continues to be hampered by the absence of techniques for measuring feed intake. This thesis addressed the latter issue, first by validating controlled release capsule (CRC) technology for measuring feed intake and second by examining feed intakes of ewes differing in pregnancy and rearing status and relating intakes to productivity. A series of 11 experiments were conducted with sheep CRC to validate this technology for measurement of intake and to develop appropriate systems for using the technology in experimental situations. These studies examined: the linearity and period of Cr2O3 release; the effect of presence of capsules in the rumen on voluntary feed intake; the effect of feed type and feeding level on Cr2O3 release rate; and the accuracy of faecal Cr2O3 concentration in predicting faecal output of sheep dosed with CRC when alternative sampling regimens were applied. These experiments, conducted under both indoor feeding and outdoor grazing conditions, established that CRC released Cr2O3 into the rumen in a uniform manner once initiation of matrix extrusion had been completed 2 to 3 days after capsule insertion. The subsequent period of linear release (25 to 100 days) was found to be primarily dependent upon characteristics of the capsules controlled at manufacture (i.e. orifice diameter, matrix composition and length of pressed tablet matrix core). In comparison, environmental factors, both within and outside the sheep, had relatively small effects on the rate or linearity of Cr2O3 release. Release rate decreased by c. 4% if daily feed intake was at 0.7 maintenance compared to an ad libitum level, increased by c. 2% if hay rather than fresh pasture was consumed and decreased by 10 to 13% if capsules were placed in rumen-fistulated sheep rather than in intact animals. Adoption of feeding level below 0.6 maintenance for 4 to 7 days reduced Cr2O3 release rate and could cause capsule failure. Between-capsule variation in release rate from CRC recovered from the rumen by slaughter was low (coefficient of variation 2.0 to 6.5%). Variation between capsules within sheep was usually lower still. Voluntary herbage intake was significantly reduced if sheep were dosed with prototype CRC with inflexible wing designs. Under indoor conditions, correlations of 0.90 to 0.99 between daily faecal output derived by Cr2O3 dilution and actual faecal output for individual sheep were obtained. The correlation between estimates of mean 3-day faecal output of sheep at pasture predicted from the Cr2O3 concentration in morning and evening grab samples and from total collections was 0.87. Prediction of individual animal intakes (indoors) appeared less accurate (r = 0.74) because of variation in capsule release rate and in the animal's own ability to select and digest its diet. Group mean estimates, which are appropriate for practical grazing conditions, were usually within ± 10% of the actual value. Low diurnal variation in faecal Cr2O3 concentration (non-significant) allowed flexible faecal sampling regimens to be applied. In summary CRC were demonstrated to be superior to existing feed intake measurement techniques and to be well suited to the estimation of mean intakes of sheep, provided that suitable faecal sampling regimens were applied. A pilot study investigating the feed intakes and productivity of ewes of different pregnancy and rearing status indicated that intakes of twin-bearing ewes were reduced in comparison to those of single-bearing ewes during late pregnancy, when the two groups were grazed together under "commercial" farming conditions. During lactation, intakes exhibited a curvilinear relationship with time and were generally higher (by up to 32%) in twin-rearing ewes than in single-rearing ewes. This pattern of feed intake was less clear in a subsequent nine-week lactation study. In that trial, experimental groups comprising equal numbers of ewes rearing single or twin lambs were continuously grazed on five different pastures maintained at fixed sward surface heights (2.5, 4.0, 6.0, 7.0 and 9.0 cm). Herbage intakes by both single- and twin-rearing ewes were maximised at a sward surface height of approximately 5.0 cm (1000 to 1100 kg dry matter/ha). Lamb growth rates were not affected by sward height during the first six weeks of lactation because the ewes mobilised body reserves to maintain milk production. All ewes lost liveweight during the first 6 weeks of lactation but only the ewes on the 2.5 cm sward failed to regain lost liveweight from weeks 6 to 9 of lactation. Wool production, strength and colour were not affected by sward conditions in either the ewes or lambs over the lactation period. These results suggest that New Zealand farmers would gain little benefit from differential management of ewes post-lambing where a minimum grazing height of 5.0 cm could be maintained provided that ewes were in good condition (i.e minimum condition score 3.0) at lambing.