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Biomedical subjects

M H Stevenson

Publications and source records attributed to M H Stevenson.

At least 19 recordsLinked to original sources
PubMed1995

Detection of irradiated chicken meat by analysis of lipid extracts for 2-substituted cyclobutanones using an enzyme linked immunosorbent assay.

The means to detect the irradiation of food has been investigated for many years. In recent times radiolytic products, termed 2-alkylcyclobutanones (2-CBs), have been identified as excellent markers of irradiation in lipid-containing foods. An ELISA test was developed, which was capable of detecting a number of these compounds in irradiated chicken meat. A polyclonal antiserum was raised to a 2-CB containing a terminal carboxyl group conjugated to a carrier protein. This antiserum was highly specific for cyclobutanones containing C10 and C12 side chains. During assay validation the limit of detection of the assay was calculated to be 0.064 microgram of 2-CB per gram of fat, within- and between-assay variations ranged from 6.7 to 18%. During experimental studies, chicken meat irradiated at doses ranging from 2.5 to 10 kGy were assayed and correctly identified as being treated. Quantitative comparisons between the ELISA and GC-MS revealed a good correlation (r2 = 0.93) between the two methodologies in concentrations of 2-CB detected in irradiated samples.

Animals↗
PubMed1995

Irradiation-induced off-odour in chicken and its possible control.

1. Volatiles isolated from irradiated raw chicken were analysed by gas chromatography (GC) in conjunction with olfactory assessment of the effluent carrier gas to locate compounds with strong smells. 2. Sixteen odours of differing intensities were registered, some, but not others, coinciding with recognisable GC peaks. Identifications were made on the basis of retention data, mass spectrometric information and odour quality agreement. 3. Dimethyltrisulphide was found to be the most potent and obnoxious compound (foul gas, sulphurous), followed by cis-3- and trans-6-nonenals (soapy), oct-1-en-3-one (mushroom) and bis(methylthio-)methane (foul). With the exception of oct-1-en-3-one, none of these compounds has been reported before in irradiated raw chicken. 4. alpha-Tocopherol and ascorbic acid induce stability in tissues in vivo and post mortem. Chickens were reared on diets supplemented with high concentrations (800 mg/kg food) of each of these vitamins. Yields of irradiation volatiles from the tissues of these birds were very much reduced, compared to yields from similar tissues from birds fed unsupplemented diets. 5. Concomitantly with the reduced yield of volatiles, less odour was associated with the samples when analysed by GC-olfactory analysis. 6. The use of enhanced concentrations of the two vitamins in combination in the diet of poultry may provide a means of controlling development of off-odour in irradiated raw chicken, thus improving acceptability to the consumer.

Animal Feed↗
PubMed1987

Withdrawal of zinc oxide-containing diets from mature, female domestic fowl: effects on laying performance and the weights of selected tissues.

1. Two hundred and sixteen laying hens of two strains were given diets containing ZnO to provide 0, 0.5, 0.75, 1.00, 1.25, 1.50, 2.00, 3.00 or 4.00 g added Zn/kg. These diets were given ad libitum for 5 consecutive 28-d periods. All hens subsequently received the control diet with no added ZnO for 5 weeks. 2. Four hens from each treatment were killed 0, 1 and 5 weeks after substitution of the ZnO-supplemented diets by the control diet. 3. The adverse effects of the ZnO-containing diets on body weight, food intake, egg production, pancreas, gizzard, oviduct and ovary weights/kg body weight were reversed by removal of the ZnO from the diets. 4. Five weeks after withdrawal egg production of the group which had received the diet with the highest concentration of added ZnO was only 50% of that of the control birds. 5. The beneficial effect of the added ZnO on internal egg quality was not maintained after withdrawal of the ZnO-containing diets.

Animals↗
PubMed1987

Withdrawal of zinc oxide-containing diets from mature, female domestic fowl: effects on selected tissue mineral contents.

1. Two hundred and sixteen laying hens of two strains were given diets containing ZnO to provide 0, 0.5, 0.75, 1.00, 1.25, 1.50, 2.00, 3.00 or 4.00 g added Zn/kg. These diets were offered ad libitum for 5 consecutive 28-d periods. All hens were subsequently offered the control diet with no added ZnO for 5 weeks. 2. Four hens from each treatment were killed 0, 1 and 5 weeks after substitution of the ZnO-supplemented diets by the control diet. 3. Dietary addition of ZnO significantly increased liver, kidneys, pancreas and gizzard Zn contents but this effect was rapidly reversed on removal of the ZnO-containing diets. 4. Hepatic and renal Fe contents were significantly depressed by dietary ZnO but after substitution of these diets by the control diet the values were comparable to that of the controls. 5. Liver Cu content declined significantly as dietary ZnO concentration increased but there was a return towards normal after ZnO withdrawal. Renal, pancreatic and gizzard Cu contents showed quadratic responses to added ZnO. 6. After ZnO withdrawal for 5 weeks, pancreas Cu contents declined linearly, whereas renal and gizzard Cu values were similar for all treatments. 7. Overall the long-term feeding of ZnO-supplemented diets followed by a period of withdrawal of the ZnO supplement had no detrimental effects on tissue mineral contents.

Animals↗
PubMed1986

Effects of short- and long-term feeding of zinc oxide-supplemented diets on the mature, female domestic fowl with special reference to tissue mineral content.

1. In Expt 1, the effects on laying hens of diets supplemented with zinc oxide providing up to 20 g added zinc/kg were compared. In Expt 2 the diets contained up to 6 g added Zn/kg. 2. In both experiments, food intake, body-weight, egg number, and liver, oviduct and ovary weights/kg body-weight were significantly reduced by added ZnO; gizzard weight/kg body-weight was significantly increased. In Expt 2, pancreas weight was significantly reduced by added ZnO. 3. Liver, kidney and pancreatic Zn and iron concentrations were significantly elevated in both experiments. 4. In both experiments, liver, kidneys and pancreatic copper concentrations gave quadratic responses to added ZnO.

Animals↗
PubMed1986

Comparison of the effects of feeding diets supplemented with zinc oxide or zinc acetate on the performance and tissue mineral content of mature female fowls.

An experiment is reported in which zinc, as acetate or oxide, was fed to laying hens for 10 weeks at concentrations equivalent to 1, 2, 3, 4 and 5 g added Zn/kg diet. Both concentration and form of Zn additive significantly reduced food, water and Zn intakes, egg production and body weight, the acetate having a greater detrimental effect than the oxide at equivalent added Zn inclusion. Zinc acetate depressed the fresh weight/kg body weight of the kidneys, ovary and oviduct to a greater extent than the corresponding oxide treatments. Concentration, but not form of additive, significantly reduced liver and pancreas weights and liver lipid concentration, while spleen and gizzard weights showed increases. Overall, the additives significantly increased the Zn and Fe concentrations of the liver, kidneys, pancreas and gizzard. Zinc concentrations of liver, pancreas and gizzard and Fe concentrations of liver were consistently higher for the acetate-fed birds. Liver, pancreas and gizzard Cu concentrations significantly declined as inclusion rate of Zn increased.

Acetates↗
PubMed1985

Effects of diets of varying energy concentrations on the growth and carcase composition of geese.

Two hundred and eighty eight-d-old goslings were allocated at random to one of 18 groups, each group comprising 8 of each sex. Three starter and three grower diets (both 11, 12, 13 MJ AME/kg) were fed and were combined in a factorial design to give 9 treatments. The starter diets were given for 4 weeks and the grower diets from weeks 5 to 9 inclusive. Body weight was unaffected by treatment, but the males were significantly heavier than the females. Food intake declined significantly as the dietary energy concentration increased. The efficiency of food utilisation of birds fed on the starter diet with the lowest energy concentration was significantly less than that of birds fed on the other diets. Birds fed on the grower diet with the highest energy concentration gave significantly better FCE than those fed on the other diets. There was no evidence to suggest that the treatments had any significant effect on carcase components and chemical composition of the geese. Oleic acid was significantly depressed and linoleic acid concentration increased as the energy concentration of the diets increased. However, this may reflect the higher fat concentrations in the diets with the higher energy concentrations.

Animal Feed↗
PubMed1984

Comparison of dietary hydrated copper sulphate, dietary zinc oxide and a direct method for inducing a moult in laying hens.

The experiment lasted for seven 28-d periods. Laying hens of two breeds were allocated to 10 treatments. For the first 28-d period all birds were offered the control diet and then the following dietary treatments applied: a control group not moulted, one group moulted traditionally, 4 groups moulted using CuSO4- and 4 using ZnO-containing diets. After the moulting treatments the hens were offered the control diet for the remainder of period 2 and for a further five 28-d periods. The treatments applied during period 2 significantly reduced food intake, body weight, egg number, total egg weight and efficiency of food conversion. On returning to the control diet, there were no significant differences in cumulative food intake (periods 3 to 7). Body weight had returned to the same value as the control group by the end of period 3. Dietary treatments significantly reduced the efficiency of food utilisation during periods 3 to 7 and 1 to 7 inclusive. For periods 1 to 7 inclusive the birds force-moulted using CuSO4 and ZnO gave on average greater egg numbers and total egg weights than those moulted traditionally. The Haugh unit score was significantly improved after moulting. Egg Zn concentrations were increased by the 14-d ZnO treatments. The use of a diet containing CuSO4 (2 g added Cu/kg for 7 d) was as effective as one containing ZnO (20 g added Zn/kg for 14 d) and both were superior to a traditional force-moulting technique.

Animals↗
PubMed1983

The effects of dietary intake and of dietary concentration of copper sulphate on the laying domestic fowl: effects on laying performance and tissue mineral contents.

Sixty white hybrid (Shaver 288) laying hens were subjected to three main dietary regimens for 5 d: ad libitum feeding of control and CuSO4-supplemented diets, force-feeding these same diets to the same intake as that of the ad libitum control diet and pair-feeding the control CuSO4-free diet to intakes equivalent to those of supplemented diets. Final body weight of the force-fed birds was significantly greater than of the other groups. Egg number and weight were significantly reduced as food intake decreased. Liver weight per unit body weight was significantly increased and oviduct and ovary weights/kg body weight were significantly reduced by force-feeding. As food intake decreased kidney and gizzard weights per unit body weight were significantly increased. The concentrations and total contents of Cu and Zn in liver were significantly increased in the ad libitum and force-fed groups. Force-feeding CuSO4-supplemented diets, which eliminated difference in food intake, confirmed that CuSO4 per se affected tissue weights and mineral concentrations as distinct from effects due to the reduced food intake associated with increasing dietary CuSO4.

Animals↗
PubMed1983

The effects of dietary intake and of dietary concentration of copper sulphate on the laying domestic fowl: effects on some aspects of lipid, carbohydrate and amino acid metabolism.

These investigations were carried out to determine whether the effects of feeding CuSO4-supplemented diets on metabolism in the laying hen were due directly to the dietary CuSO4 content or indirectly to the effects of CuSO4 on food consumption. In experiment 1, 144 hens were given CuSO4-supplemented diets ad libitum for 48 d. Food consumption decreased as the dietary CuSO4 content increased and this was associated with decreases in blood plasma lipid, 17 beta-oestradiol and liver lipid concentrations and hepatic lipogenic enzyme activities. In experiment 2, 60 laying hens were subjected to three dietary regimens in an attempt to differentiate between the effects of reduced food consumption and dietary CuSO4 per se. Control and CuSO4-supplemented diets were fed ad libitum, or the CuSO4-containing diets were force-fed to the same intake as the ad libitum control diet, or the control diet was pair-fed to the same intakes as the CuSO4-supplemented diets. Liver lipid concentrations were significantly decreased in the ad libitum and pair-fed groups at the lowest intake. Plasma 17 beta-oestradiol concentration was decreased in ad libitum and force-fed birds given diets with 1,000 mg added Cu/kg. Lipogenic enzyme activities were reduced in the ad libitum and pair-fed groups and increased in the force-fed birds. The results indicate that CuSO4 per se directly affected circulating 17 beta-oestradiol, and hence reproductive physiology, and that the quantity of food consumed influenced the rate of hepatic lipogenesis.

Amino Acids↗
PubMed1983

The interaction of food additives and protein content in broiler diets.

No evidence was found for an interaction between dietary crude protein content and the presence or absence of two proprietary food additives used as sources of avoparcin and zinc bacitracin. The food additives had a similar effect in increasing rate of growth resulting in significant improvements of about 2% in the food conversion ratios.

Animals↗