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British Poultry Science Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/cbps20
Reduced selenium status in chicks given diets low in Sulphur‐containing amino acids and containing Sodium Nitroprusside as a source of cyanide E. A. Elzubeir
a b
& R. H. Davis
a
a
Wye College , University of London , Wye, Ashford, Kent, TN25 5AH, England b
Institute of Animal Production , University of Khartoum , PO Box 32, Khartoum North, Sudan Published online: 08 Nov 2007.
To cite this article: E. A. Elzubeir & R. H. Davis (1990) Reduced selenium status in chicks given diets low in Sulphur‐containing amino acids and containing Sodium Nitroprusside as a source of cyanide, British Poultry Science, 31:3, 539-544, DOI: 10.1080/00071669008417285 To link to this article: http://dx.doi.org/10.1080/00071669008417285
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden.
Downloaded by [University of Montana] at 08:00 03 April 2015
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British Poultry Science (1990) 31: 539-544
REDUCED SELENIUM STATUS IN CHICKS GIVEN DIETS LOW IN SULPHUR-CONTAINING AMINO ACIDS AND CONTAINING SODIUM NITROPRUSSIDE AS A SOURCE OF CYANIDE E. A. ELZUBEIR1 AND R. H. DAVIS Wye College (University of London), Wye, Ashford, Kent, TN25 5AH, England
Downloaded by [University of Montana] at 08:00 03 April 2015
Received for publication 18th May 1989
Abstract 1. Two experiments were carried out to study the effect of dietary cyanide, given in the form of sodium nitroprusside (SNP), on the growth and selenium status of chicks fed on diets low in sulphurcontaining amino acids. 2. In experiment 1, SNP (0.3g/kg) depressed growth rate and food intake when included in diets low in total sulphur-containing amino acids. It also reduced plasma and liver glutathione peroxidase activity (GSH-Px) and kidney selenium concentration. These latter variables also showed increases in response to supplements of selenium of 0.1 and 0.2 mg selenium/kg (as sodium selenite) although growth was not affected. 3. In experiment 2, SNP did not affect growth when reduced to 0.1g/kg in diets low both in methionine and total sulphur-containing amino acids. It did, however, reduce plasma GSH-Px activity, which again increased in response to similar dietary supplements of selenium. 4. It is concluded that dietary cyanide effectively increases the requirement for selenium and could induce deficiency in diets only marginally adequate in selenium, particularly when the supply of sulphur-containing amino acids was marginal or inadequate.
INTRODUCTION
The best understood biological role for selenium is as a component of glutathione peroxidase (glutathione:hydrogen peroxide oxidoreductase, EC 1.11.1.9, GSH-Px), important in removing peroxide from biological systems. However, it is only one of several components involved in protection against oxidative damage and neither normal nor sufficient activity can be unambigu1 Present address: Institute of Animal Production, University of Khartoum, PO Box 32, Khartoum North, Sudan. 539
Downloaded by [University of Montana] at 08:00 03 April 2015
540
E. A. ELZUBEIR AND R. H. DAVIS
ously defined. Despite these uncertainties GSH-Px activity has been used as an indicator of selenium status many times. Alteration in activity should have biological significance; in particular depression of activity should give cause for concern, pointing to possible selenium deficiency. Jensen (1975) observed that minerals that counteract selenium toxicity can also induce deficiency if included in diets marginal in selenium content. Because it is now well established that dietary sources of cyanide, both natural and synthetic, can alleviate selenium toxicity (see Elzubeir and Davis, 1988a for references) it is possible that they too might induce deficiency. Evidence to support this suggestion was first provided by Rudert and Lewis (1978), who found that administering potassium cyanide to pregnant ewes led to increased nutritional myopathy among their offspring. Palmer and Olson (1981) added cyanide to the drinking water of rats fed on low selenium diets and found depressed GSH-Px activity; however, the effects were rather small and inconsistent and the authors doubted if there could be any practical biological significance. More detailed studies by Beilstein and Whanger (1984) showed that cyanide in drinking water increased urinary selenium excretion by rats and decreased both GSH-Px activity and selenium content in all tissues examined except testes. In chicks, Elzubeir and Davis (1988a) found that cyanide, offered in the diet in the form of sodium nitroprusside (SNP), decreased GSH-Px activity in the liver when low to normal amounts of selenium were fed but plasma GSH-Px activity was not affected. Methionine was added to the diet in that trial at a concentration designed to ensure adequacy of methionine and total sulphur-containing amino acids. Methionine provides methyl groups for the formation of the methylated selenium compounds that are excretory forms of the element; also, the sulphur-containing amino acids are the ultimate sources of the sulphur used to detoxify cyanide to thiocyanate, its major excretion product. There are, therefore, at least two points where methionine intake could affect the interaction between cyanide and selenium. Consequently two further experiments in which the dietary concentration of methionine has been reduced have been carried out. In the first, the amount of SNP was the same as had been used previously and which was known to reduce growth. In the second, SNP was reduced to a concentration that had not affected growth with a diet adequate in sulphurcontaining amino acids. In this way it was hoped to obtain additional information on both the effect of a dietary source of cyanide on selenium status and the value of GSH-Px activity as an index of chronic cyanide toxicity.
METHODS AND MATERIALS
Two experiments were carried out using male chicks of a commercial laying strain (Hisex). The procedures used were the same as those reported previously, both for the conduct of feeding trials and for the measurements of GSH-Px activity and tissue selenium content (Elzubeir and Davis, 1988a). Apart from alterations to the methionine supplementation, the same basal diet was also used, thereby providing continuity with the previous studies. The diet
Downloaded by [University of Montana] at 08:00 03 April 2015
DIETARY CYANIDE AND SELENIUM STATUS
541
consisted of cassava, soyabean meal (440 g/kg crude protein) and maize oil at 463, 400 and 100 g/kg respectively, the remainder consisting of vitamins and minerals. Thus, almost all the protein was derived from soyabean meal and methionine would be the limiting amino acid. A preliminary experiment had shown that sequential growth responses were obtained to methionine supplements of 2 and 4 g/kg (Elzubeir, 1986). The selenium content had been shown, by analysis, to be 0*15 mg/kg, sufficient to meet requirements. SNP was the dietary source of cyanide. Cyanide is released from this compound within the digestive tract of the chicken, particularly in the crop but also in the small intestine (Craston and Davis, unpublished). For the first experiment a DL-methionine supplement of 2 g/kg was included in the basal diet so that, by calculation, it was adequate in methionine but low in total sulphur-containing amino acids (calculated contents, 5.0 and 8.1 g/kg, respectively). Six experimental diets were formulated in which 3 concentrations of selenium supplementation were compared, 0-0, 0-1 and 0-2 mg selenium/kg (as sodium selenite), each with and without SNP at 0-3 g/kgEach diet was offered ad libitum to 4 individually caged chicks, according to a factorial randomised block design, from 14 to 38 days of age. In the second experiment there were again 6 diets, identical to those used in the first experiment except that no DL-methionine was added and the concentration of SNP was reduced to 0-1 g/kg; the diets were calculated to be low in methionine as well as total sulphur-containing amino acids. Each diet was offered ad libitum to 6 individually caged chicks, according to a factorial randomised block design from 14 to 50 days of age. In addition to measuring the performance of all birds, plasma and liver GSH-Px activity and kidney selenium concentration were measured for all birds in 2 blocks of the first experiment and plasma GSH-Px activity and liver selenium content for all birds in 3 blocks of the second experiment. Kidney selenium concentration had not been measured in the previous experiments and has frequently been found to be the tissue having the highest concentration.
RESULTS
The results for experiments 1 and 2 are given in Table 1. Although factorial analysis of variance was carried out only information for individual treatments is given. Results for the individual factors, selenium concentration and presence or absence of SNP, are apparent from consideration of individual treatments. Dietary selenium concentration did not significantly affect growth rate or food intake in either experiment, with or without simultaneous inclusion of SNP. With respect to SNP, growth rate and food intake were significantly lower at all dietary selenium concentrations in experiment 1 but differences were not significant in experiment 2 in which less SNP was included.
542
E. A. ELZUBEIR AND R. H. DAVIS TABLE 1
Growth, GSH-Px activity and tissue selenium (Experiments 1 and 2)
Downloaded by [University of Montana] at 08:00 03 April 2015
Experiment 1 Added selenium (mg/kg) 00 0-0 0-1 0-1 0-2 0-2
Experiment 2 Added selenium (mg/kg) 0-0 0-0 0-1 0-1 0-2 0-2
Weight gain1 Food intake1 GSH-Px activity2,5 Kidney selenium2 (g/bird/24 days) plasma liver (^g/g D.M.) (gAg) 404° 0-0 1002" 96-1* 74-4c 2-81"' 225 s 0-3 672* 54-2' 69-9e 2.99^ 0-0 405° 1000° 97-9* 94-9* 3-76° 242* 689* 73-9'' 53-5^ 0-3 3-06c 0-0 452° 1051" 102-1" 100-5° 3-84° 244* 677* 77-2c 74-3rf 0-3 3-37* ± S.E. 17-7 30-1 0-78 1-0 0-09 LSD (P
British Poultry Science Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/cbps20
Reduced selenium status in chicks given diets low in Sulphur‐containing amino acids and containing Sodium Nitroprusside as a source of cyanide E. A. Elzubeir
a b
& R. H. Davis
a
a
Wye College , University of London , Wye, Ashford, Kent, TN25 5AH, England b
Institute of Animal Production , University of Khartoum , PO Box 32, Khartoum North, Sudan Published online: 08 Nov 2007.
To cite this article: E. A. Elzubeir & R. H. Davis (1990) Reduced selenium status in chicks given diets low in Sulphur‐containing amino acids and containing Sodium Nitroprusside as a source of cyanide, British Poultry Science, 31:3, 539-544, DOI: 10.1080/00071669008417285 To link to this article: http://dx.doi.org/10.1080/00071669008417285
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden.
Downloaded by [University of Montana] at 08:00 03 April 2015
Terms & Conditions of access and use can be found at http://www.tandfonline.com/ page/terms-and-conditions
British Poultry Science (1990) 31: 539-544
REDUCED SELENIUM STATUS IN CHICKS GIVEN DIETS LOW IN SULPHUR-CONTAINING AMINO ACIDS AND CONTAINING SODIUM NITROPRUSSIDE AS A SOURCE OF CYANIDE E. A. ELZUBEIR1 AND R. H. DAVIS Wye College (University of London), Wye, Ashford, Kent, TN25 5AH, England
Downloaded by [University of Montana] at 08:00 03 April 2015
Received for publication 18th May 1989
Abstract 1. Two experiments were carried out to study the effect of dietary cyanide, given in the form of sodium nitroprusside (SNP), on the growth and selenium status of chicks fed on diets low in sulphurcontaining amino acids. 2. In experiment 1, SNP (0.3g/kg) depressed growth rate and food intake when included in diets low in total sulphur-containing amino acids. It also reduced plasma and liver glutathione peroxidase activity (GSH-Px) and kidney selenium concentration. These latter variables also showed increases in response to supplements of selenium of 0.1 and 0.2 mg selenium/kg (as sodium selenite) although growth was not affected. 3. In experiment 2, SNP did not affect growth when reduced to 0.1g/kg in diets low both in methionine and total sulphur-containing amino acids. It did, however, reduce plasma GSH-Px activity, which again increased in response to similar dietary supplements of selenium. 4. It is concluded that dietary cyanide effectively increases the requirement for selenium and could induce deficiency in diets only marginally adequate in selenium, particularly when the supply of sulphur-containing amino acids was marginal or inadequate.
INTRODUCTION
The best understood biological role for selenium is as a component of glutathione peroxidase (glutathione:hydrogen peroxide oxidoreductase, EC 1.11.1.9, GSH-Px), important in removing peroxide from biological systems. However, it is only one of several components involved in protection against oxidative damage and neither normal nor sufficient activity can be unambigu1 Present address: Institute of Animal Production, University of Khartoum, PO Box 32, Khartoum North, Sudan. 539
Downloaded by [University of Montana] at 08:00 03 April 2015
540
E. A. ELZUBEIR AND R. H. DAVIS
ously defined. Despite these uncertainties GSH-Px activity has been used as an indicator of selenium status many times. Alteration in activity should have biological significance; in particular depression of activity should give cause for concern, pointing to possible selenium deficiency. Jensen (1975) observed that minerals that counteract selenium toxicity can also induce deficiency if included in diets marginal in selenium content. Because it is now well established that dietary sources of cyanide, both natural and synthetic, can alleviate selenium toxicity (see Elzubeir and Davis, 1988a for references) it is possible that they too might induce deficiency. Evidence to support this suggestion was first provided by Rudert and Lewis (1978), who found that administering potassium cyanide to pregnant ewes led to increased nutritional myopathy among their offspring. Palmer and Olson (1981) added cyanide to the drinking water of rats fed on low selenium diets and found depressed GSH-Px activity; however, the effects were rather small and inconsistent and the authors doubted if there could be any practical biological significance. More detailed studies by Beilstein and Whanger (1984) showed that cyanide in drinking water increased urinary selenium excretion by rats and decreased both GSH-Px activity and selenium content in all tissues examined except testes. In chicks, Elzubeir and Davis (1988a) found that cyanide, offered in the diet in the form of sodium nitroprusside (SNP), decreased GSH-Px activity in the liver when low to normal amounts of selenium were fed but plasma GSH-Px activity was not affected. Methionine was added to the diet in that trial at a concentration designed to ensure adequacy of methionine and total sulphur-containing amino acids. Methionine provides methyl groups for the formation of the methylated selenium compounds that are excretory forms of the element; also, the sulphur-containing amino acids are the ultimate sources of the sulphur used to detoxify cyanide to thiocyanate, its major excretion product. There are, therefore, at least two points where methionine intake could affect the interaction between cyanide and selenium. Consequently two further experiments in which the dietary concentration of methionine has been reduced have been carried out. In the first, the amount of SNP was the same as had been used previously and which was known to reduce growth. In the second, SNP was reduced to a concentration that had not affected growth with a diet adequate in sulphurcontaining amino acids. In this way it was hoped to obtain additional information on both the effect of a dietary source of cyanide on selenium status and the value of GSH-Px activity as an index of chronic cyanide toxicity.
METHODS AND MATERIALS
Two experiments were carried out using male chicks of a commercial laying strain (Hisex). The procedures used were the same as those reported previously, both for the conduct of feeding trials and for the measurements of GSH-Px activity and tissue selenium content (Elzubeir and Davis, 1988a). Apart from alterations to the methionine supplementation, the same basal diet was also used, thereby providing continuity with the previous studies. The diet
Downloaded by [University of Montana] at 08:00 03 April 2015
DIETARY CYANIDE AND SELENIUM STATUS
541
consisted of cassava, soyabean meal (440 g/kg crude protein) and maize oil at 463, 400 and 100 g/kg respectively, the remainder consisting of vitamins and minerals. Thus, almost all the protein was derived from soyabean meal and methionine would be the limiting amino acid. A preliminary experiment had shown that sequential growth responses were obtained to methionine supplements of 2 and 4 g/kg (Elzubeir, 1986). The selenium content had been shown, by analysis, to be 0*15 mg/kg, sufficient to meet requirements. SNP was the dietary source of cyanide. Cyanide is released from this compound within the digestive tract of the chicken, particularly in the crop but also in the small intestine (Craston and Davis, unpublished). For the first experiment a DL-methionine supplement of 2 g/kg was included in the basal diet so that, by calculation, it was adequate in methionine but low in total sulphur-containing amino acids (calculated contents, 5.0 and 8.1 g/kg, respectively). Six experimental diets were formulated in which 3 concentrations of selenium supplementation were compared, 0-0, 0-1 and 0-2 mg selenium/kg (as sodium selenite), each with and without SNP at 0-3 g/kgEach diet was offered ad libitum to 4 individually caged chicks, according to a factorial randomised block design, from 14 to 38 days of age. In the second experiment there were again 6 diets, identical to those used in the first experiment except that no DL-methionine was added and the concentration of SNP was reduced to 0-1 g/kg; the diets were calculated to be low in methionine as well as total sulphur-containing amino acids. Each diet was offered ad libitum to 6 individually caged chicks, according to a factorial randomised block design from 14 to 50 days of age. In addition to measuring the performance of all birds, plasma and liver GSH-Px activity and kidney selenium concentration were measured for all birds in 2 blocks of the first experiment and plasma GSH-Px activity and liver selenium content for all birds in 3 blocks of the second experiment. Kidney selenium concentration had not been measured in the previous experiments and has frequently been found to be the tissue having the highest concentration.
RESULTS
The results for experiments 1 and 2 are given in Table 1. Although factorial analysis of variance was carried out only information for individual treatments is given. Results for the individual factors, selenium concentration and presence or absence of SNP, are apparent from consideration of individual treatments. Dietary selenium concentration did not significantly affect growth rate or food intake in either experiment, with or without simultaneous inclusion of SNP. With respect to SNP, growth rate and food intake were significantly lower at all dietary selenium concentrations in experiment 1 but differences were not significant in experiment 2 in which less SNP was included.
542
E. A. ELZUBEIR AND R. H. DAVIS TABLE 1
Growth, GSH-Px activity and tissue selenium (Experiments 1 and 2)
Downloaded by [University of Montana] at 08:00 03 April 2015
Experiment 1 Added selenium (mg/kg) 00 0-0 0-1 0-1 0-2 0-2
Experiment 2 Added selenium (mg/kg) 0-0 0-0 0-1 0-1 0-2 0-2
Weight gain1 Food intake1 GSH-Px activity2,5 Kidney selenium2 (g/bird/24 days) plasma liver (^g/g D.M.) (gAg) 404° 0-0 1002" 96-1* 74-4c 2-81"' 225 s 0-3 672* 54-2' 69-9e 2.99^ 0-0 405° 1000° 97-9* 94-9* 3-76° 242* 689* 73-9'' 53-5^ 0-3 3-06c 0-0 452° 1051" 102-1" 100-5° 3-84° 244* 677* 77-2c 74-3rf 0-3 3-37* ± S.E. 17-7 30-1 0-78 1-0 0-09 LSD (P
