Response of Broiler Chick to Dietary Selenium

Response of Broiler Chick to Dietary Selenium W. GUENTER 1 and D. B. BRAGG Department of Poultry Science, University of British Columbia, Vancouver, British Columbia, Canada V6T 1W5 (Received for publication April 13, 1977)

Poultry Science 56:2031-2038, 1977 INTRODUCTION Selenium (Se.) was first discovered b y t h e Swedish chemist Berzelius in 1 8 1 7 as an a t o m i c e l e m e n t closely associated with sulfur and tellurium. T h e t o x i c i t y of Se. h a s b e e n k n o w n since 1 9 3 4 ( F r a n k e , 1934) when high levels of Se. in plant foodstuffs of South D a k o t a were s h o w n t o cause alkali disease in cattle a n d o t h e r livestock. T h e nutritional r e q u i r e m e n t for Se. was unsuspected until Schwarz and Foltz ( 1 9 5 7 ) observed t h a t 0.10 p p m . of Se. in t h e d i e t of vitamin E deficient rats prevented dietary liver necrosis. More recent research has demonstrated t h e i m p o r t a n c e of Se. in n u t r i t i o n and n o r m a l metabolism of chickens, t u r k e y s , pigs, cattle, sheep and o t h e r animals (Scott, 1973). T h e essentiality of selenium in t h e diet of chicks was shown by T h o m p s o n and S c o t t ( 1 9 6 9 ) . F u r t h e r m o r e it is generally accepted t h a t a d e q u a t e levels of available Se. in animal feeds is b e t w e e n 0.1 and 0.2 p p m . (National

1 Present address: Department of Animal Science, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2.

Research Council, 1971). Several r e p o r t s have appeared on t h e effect of Se. s u p p l e m e n t a t i o n of n o r m a l rations on tissue Se. residues (Arnold et al, 1 9 7 3 ; S c o t t and Cantor, 1971). S c o t t and Cantor ( 1 9 7 1 ) d e m o n s t r a t e d t h a t chicks continuously s u p p l e m e n t e d with Se. t o 4 weeks of age at 0.3 p p m . Se. (Sodium Selenite) t o a ration containing a n o r m a l level of Se. ( S o d i u m Selenite) t o a ration containing a n o r m a l level of Se. (0.17 p p m . ) t h e blood and tissue Se. c o n c e n t r a t i o n s are elevated slightly. This was due t o a " p l a t e a u effect" w h e r e b y Se. levels increased rapidly at first and t h e n very slowly in response t o increasing dietary intake of Se.. T h u s t h e chick responds similar t o t h e pig (Lindberg and L a n n e k , 1965) in retaining physiological levels of Se. a n d excreting excesses. M o s t of t h e studies r e p o r t e d o n tissue levels were concerned with dietary levels above 0.1 p p m . Se.. This s t u d y was initiated t o d e t e r m i n e changes in t h e tissue c o n c e n t r a t i o n of Se. during depletion (indicated by t h e o n s e t of exudative diathesis) and during repletion in order t o establish a measure of dietary deficiency and a d e q u a c y . Tissue levels were determined for chicks in which corresponding growth and feed efficiency d a t a were collected.

2031

Downloaded from http://ps.oxfordjournals.org/ at University of Cambridge on May 14, 2015

ABSTRACT An experiment was conducted using four hundred and eighty day-old straight run broiler chicks. The birds were divided into two groups and fed one of two depletion diets. Depletion diet 1 was low in Se (0.017 ppm.) and adequate in vitamin E (50 I.U./kg.), diet 2 was low in Se. and vitamin E. The two groups remained on these diets for 21 and 15 days respectively until the first signs of exudative diathesis (ED) appeared. During the depletion period blood and tissue samples (3 samples of 3 birds/sample) were obtained at 3 day intervals. Se. levels of 0.120, 0.107, 0.090, 0.073 and 0.041 ppm. were obtained for thigh muscle, kidney, heart muscle, liver and blood respectively at 21 days of depletion on the low Se. adequate vitamin E diet. The same tissues respectively were: 0.083, 0.180, 0.097 and 0.043 ppm. Se. at 15 days of depletion when fed the low Se.-Vit. E deficient diet. The birds fed diet 2 at 15 days of depletion were randomly allotted to 12 pens (16 birds/pen) after which one of four treatments (0, 0.02, 0.04 and 0.08 ppm. added Se. as Na2 Se0 3 ) was randomly assigned to each pen (3 pens/trt) and fed for 14 days. Triplicate pooled blood and tissue samples were obtained at 3 day intervals as during the depletion period. A significant (P<0.05) response in growth rate and feed efficiency was observed with 0.04 and 0.08 ppm. Se. supplementation. Liver and kidney responded to all dietary Se. supplementation, whereas blood and heart only responded to 0.08 ppm. supplementation. However, skeletal muscle showed no response. Zero, 24, 40 and 70% of birds fed 0, 0.02, 0.04 and 0.08 ppm. Se. respectively were protected from ED during the experiment.

2032

W. GUENTER AND D. B. BRAGG TABLE 1.— Composition of basal diet g./kg. diet

Isolated soybean protein Sucrose Torula yeast Lard* Cellulose CaHPO„-2H 2 0 CaC0 3 KH 2 P0 4 Vitamin premix** Mineral premix**

* Refined animal fat contained no antioxidants and was heated at 65°C. for 24 hours while air was bubbled through the fat to destroy residual vitamin E. This treatment did not increase rancidity as measured by peroxide value (Seier and Bragg, 1973). **Scott, M. L., et al. (1969). Vitamin premix without vitamin E, mineral premix without selenium, calcium, phosphorus and potassium.

MATERIALS AND METHODS

Six hundred and forty straight run broiler chicks hatched at the University laboratory were utilized in this study. The chicks were randomly divided into two groups of 240 (A) and 240 (B) birds each. Group A was placed on a selenium deficient (0.017 ppm.) diet (Table 1) with adequate vitamin E added to the diet (50 I.U./kg.), however Group B was given a selenium-Vit. E deficient diet (Table 1). Both groups were examined for exudative diathesis (ED) at two day intervals (occurrence of ED

RESULTS AND DISCUSSION

The blood and tissue selenium concentrations during the depletion periods are shown in Table 2 and 3. Rate of Se. depletion of tissues

TABLE 2.—Blood and tissue selenium concentration1 at various days of depletion, when fed a low Se. diet with adequate vitamin E (Group A) Fresh tissues Se. (p.p.m.) Blood

Liver

Kidney

Heart

Thigh muscle

0 3

0.104 c 0.063

6

2

1.013 c3 0.533 b 0.207^ 0.147^ 0.110 a 0.103 a 0.073 a +.097

0.820 f 0.493 e 0.217 c 0.190 b c 0.140 a b 0.117 a 0.107 a ±.022

0.543 e 0.390 d 0.167 b c 0.147abc 0.117 a b 0.100 a b 0.090 a ±.026

0.277 b 0.217 b 0.113 a 0.127 a 0.097 a 0.093 a 0.120 a ±.026

Days of depletion

12 15 18 21

Pooled SD4

0.041

1

Each value is an average of three samples expressed in ug./g. fresh tissue.

2

Samples lost due to charring during the digestion procedure.

3

Means within a column not followed by the same letter are significantly different at P<0.01.

4

Pooled error standard deviation calculated from the residual mean square (vRMS).

Downloaded from http://ps.oxfordjournals.org/ at University of Cambridge on May 14, 2015

117.0 492.5 200.0 50.0 70.0 20.7 14.8 10.0 10.0 15.0

was recorded by using wing band No's.). Tissue samples were taken from a total of 21 birds from each group (A or B) during the depletion phase. Blood samples were taken at three day intervals by cardiac puncture from three birds starting at 18 days of incubation to the time of ED occurrence. Liver, heart, kidney and thigh muscles were collected (3 samples of 3 birds/sample) from the same birds after sacrificing. All samples were stored at —20 C. until Se. analysis was performed. Birds in group B were randomly assigned to 12 pens after first occurrence of ED. Four repletion diets (0, 0.02, 0.04 and 0.08 ppm. added Se.) were fed in a random design for a period of 14 days repletion. Blood and tissue samples (3 samples of 3 birds each) were obtained at 0, 3, 6, 9 and 14 days of repletion. Birds were fed daily in order to avoid feed waste, water was supplied ad libitum. Body weights and feed consumption data were collected and calculated on weekly intervals for the repletion period. Analysis for Se. in feed, blood and tissue samples was performed according to the method described by Seier and Bragg (1973). Results were tested by analysis of variance and differences among means were determined by Duncan's multiple range test (Steel and Torrie, 1960).

SELENIUM SUPPLEMENTATION AND BROILER RESPONSE

2033

TABLE 3.—Blood and tissue Se. concentration' at various days of depletion when fed a low Se. diet (0.017 p.p.m.) deficient in vitamin E (Group B) Fresh tissues Se. (p.p.m.) Blood

Liver

Kidney

Heart

Thigh muscle

-3 0 3 6 9 12 15 Pooled S D 3

0.267c2 0.3 50C 0.327c 0.157b 0.107ab 0.077ab 0.043 a 0.033

0.547*= 0.4 50d 0.243C 0.183b 0.130ab 0.097a 0.022

1.160d 0.887c 0.44 7 b 0.270* 0.237* 0.180a 0.046

0.440c 0.397c 0.223b 0.177ab 0.140ab 0.097a 0.47

0.377« 0.297d 0.217c 0.137b 0.117ab 0.083a 0.017

1

Each value is an average of three samples expressed in Mg./ml. blood or Mg-/g. fresh tissue. Means within a column not followed by the same letter are significantly different at P<0.01. 3 Pooled error standard deviation.

2

was quite rapid; however, when vitamin E was omitted from the diet (Table 3), the first signs of exudative diathesis (ED) occurred six days (15 days of age) earlier than in the presence of vitamin E (21 days of age). Even though the tissue Se. levels at day 15 were essentially the same for both groups, vitamin E appeared to delay the visual symptoms of ED. Thompson and Scott (1969) demonstrated that vitamin E at high dietary levels (100 I.U./kg.) would completely prevent the occurrence of ED, however the level used in this trial was only sufficient to delay the onset of this condition. The first signs of ED occurred at the same whole blood Se. concentration (0.041 and 0.043 jug./ml.) independent of the presence or absence of dietary vitamin E. The delay in the appearance of ED in the presence of the vitamin further supports the dietary interaction between vitamin E and selenium. Differences in initial (0 days of depletion)

blood and liver Se. concentration were probably due to the fact that chicks in groups A and B were hatched from eggs of different flocks. Therefore, it appears that parental diet affects the blood and tissue Se levels at hatching time. Under conditions of dietary vitamin E, the liver and thigh muscle rapidly reached a depleted plateau (9 days) which apparently was maintained at the expense of the kidney and heart Se. (Table 2). However, under deficient vitamin E conditions, all tissue Se. (Table 3) reached the plateau at approximately the same time (6 to 9 days of depletion). The plateau levels in tissue were higher than the dietary levels of Se.. This suggested that a mechanism is operating to prevent further tissue depletion. The growth pattern for broilers (group B, repletion) is shown in Table 4. The low level of dietary Se. showed no adverse effect on growth during the first two weeks of depletion (Table 4, Initial wt.). The average weight of 200 g.

TABLE 4.—Average body weights of broilers during repletion ofSe. Dietary selenium (p.p.m.) Added Total 0.00 0.02 0.04 0.08

1 2

0.017 0.031 0.055 0.095 Pooled S D 1

Initial 195a2 200a 199a 207a 11.9

Average body weights (g.) 7-days 272 a 289ab 313bc 321 c 15.9

Pooled error standard deviation. Means within a column not followed by the same letter are significantly different at P<0.05.

14-days 247 a 3 54b 460c 494c 52.6

Downloaded from http://ps.oxfordjournals.org/ at University of Cambridge on May 14, 2015

Days of depletion

2034

W. GUENTER AND D. B. BRAGG TABLE 5.—Feed consumption (feed/body wt./day) of broilers fed a semi-purified diet supplemented with Se. from Na2Se03

Dietary selenium (p.p.m.) Total3 Added

0.017 0.031 0.055 0.095

0.00 0.02 0.04 0.08

Age of broilers (days) Repletion 16-22

Depletion 0-15 (g. feed/g. body wt.) 0.713 0.713 0.713 0.713

25-29

0.34 5 a ' ' 0.61lb 0.610b 0.6 20b

0.666 0.684 0.667 0.716

Means within a column not followed by the same letter are significantly different at P<0.01. Statistical comparisons were based on analysis of variance with pooled error standard deviation ± 0.046. 'Analyzed selenium value.

compares well with published body weight of commercial broiler stock fed commercial type wheat-soy broiler diets. A significant (P<0.05) growth response was observed during the first week of repletion by supplementing Se. from sodium selenite to the basal diet (Table 4). This growth response was magnified during the second week of repletion. This resulted in a significant (P<0.05) response at 0.031, 0.055 and 0.095 ppm. dietary Se. after two weeks of supplementation. Results demonstrate that a low level of dietary Se (0.031 ppm.) will support a slow rate of growth, therefore a marginal dietary selenium level may not be observed until birds become severely depleted. The decreased growth of birds fed 0.031 ppm. Se. was not a result of decreased feed consumption on a per gram per bird basis (Table 5) as was the case with the deficient birds. However, feed efficiency was reduced,

especially during the second week. The inadequacy of Se. in the diet resulted in poor feed conversion (Table 6) and was readily corrected by 0.04 ppm. Se. supplementation. Further addition of dietary Se. had no significant (P<0.05) effect on feed conversion. These results agree with Miller et al. (1972) who showed that 0.05 ppm. Se. from sodium selenite (Na 2 Se03) maintained Se. in balance with its original content in the chick. Birds fed the basal diet had a negative feed efficiency for the second week. This was due to a weight loss during this period. The apparent reason for the poor performance of the basal fed birds was the high incidence of ED (essentially 100%, Figure 1). Approximately 70-76% of the birds fed 0.031 ppm. Se. also exhibited ED symptoms. However, the higher levels of supplementation (0.04 and 0.08 ppm.) completely prevented further occurrence of ED

TABLE 6.-Feed efficiency of young broilers fed a semi-purified diet supplemented •with Se. from NaiSeOi Periods (days) Dietary Se. (p.p. m.)

Repletion

Depletion

Added

Total

0-7

0.00 0.02 0.04 0.08

0.017 0.031 0.055 0.095

1.95

8-15

16-22

23-29

2.51bl'2 2.36 a b 2.05 a 2.06 a

-6.39 c 4.33b 2.38 a 2.40*

(g. feed/g. gain)

1 2

2.05

Means within the column not followed by the same letter are significantly different at P<0.05. Statistical comparisons were based on analysis of variance with pooled error standard deviation ± 0.187.

Downloaded from http://ps.oxfordjournals.org/ at University of Cambridge on May 14, 2015

1 2

SELENIUM SUPPLEMENTATION AND BROILER RESPONSE CO 17 ppm.Se)

100

(.031 ppm.SeJ

80 .

7gt

(.055 ppm.Se)

60 40

1001

60)!

(.095 ppm.SeJ

/

33J

20

-2

4

6 8 10 Days of Repletion

12

14

within 7 and 3 days of 0.04 ppm. and 0.08 ppm. supplementation respectively. Furthermore, all birds that had shown the ED symptoms recovered from all visual symptoms. The restorative effect according to Noguchi et al. (1973) is that dietary Se. supplementation restores plasma glutathione peroxidase levels which destroys hydrogen peroxide and other peroxides in blood plasma and tissues. The patterns of blood and tissue repletion under the various dietary Se. levels are shown in Tables 7—11. There was no positive response in blood Se. for birds fed the basal, 0.02 ppm. and 0.04 ppm. dietary Se. over the 14 day repletion period (Table 7). Levels of 0.017 and 0.031

ppm. dietary Se. resulted in a decrease in blood Se.. The 0.055 ppm. level maintained the blood Se. and 0.095 ppm. dietary Se. significantly (P<0.01) increased the blood Se. within six (6) days of Se. treatment. This did not correspond with the time that the occurrence of ED subsided. However, the insignificant increase in blood Se. from 0.043 to 0.049 ppm. probably was adequate for preventing further occurrence of the disease. The mean blood levels over the 14 days of repletion period were significantly (P<0.01) different, i.e. both 0.055 and 0.095 ppm. dietary Se. resulted in a positive response. Although the blood levels responded to dietary levels, they did not in fact equilibrate with dietary Se. concentration within the present experimental period. The ratios of blood levels to dietary levels were 1.18, 0.87, 0.75 and 0.83 respectively for treatments of 0, 0.02, 0.04 and 0.08 ppm. supplemental Se.. This is contrary to the results reported by Seier and Bragg (1973) where blood levels reflected dietary levels with higher levels of dietary Se., but is similar to results reported by Scott and Thompson (1971) with dietary Se. similar to those used in this study. Contrary to the blood, the liver tissue (Table 8) responded quicker to dietary Se.. All three supplemental diets resulted in a significant (P<0.05) increase in liver Se.. The response was dependent on the dietary level supplied. The greater the dietary Se. level, the earlier the

TABLE 7.—Blood Se. levels during repletion Dietary Se. levels (jug./g.) 0.055

0.095

Pooled SD 3

0.017

0.031

0

0.0431 >2

0.043 y

0.043 x

0.043x

3

O.029£Y

0.03 2 A

0.043 B

0.049 B

0.004

XA

B

0.0 5 6 ^

0.003

(days)

(Mg./ml. of blood)

A

6

0.020

9

0.023 A

14

0.020A

Mean

0.027A

0.027 X 0.023 A

Pooled SD3

0.005

0.007

1

0.025

0.03 5

X

0.03 2

AB

X

AB

0.06 l £ y

0.004

0.041B

0.079 Y

0.006

0.041 B

0.058 C

0.007

0.008

0.007

°-

041

x

Each value/cell is an average of three replicates expressed as ;ug./ml. blood. Means within a column not followed by the same subscript are significantly different at P<0.01 X, Y and P<0.05 x, y. Means within a row not followed by the same superscript are significantly different at P<0.01, A, B, C. 3 Pooled error standard deviation. 2

Downloaded from http://ps.oxfordjournals.org/ at University of Cambridge on May 14, 2015

FIG. 1. Cumulative occurrence (%) of exudative diathesis during Se. repletion of broiler chicks.

2035

W. GUENTER AND D. B. BRAGG

2036

TABLE 8.—Liver selenium levels during repletion Dietary Se. levels (iig./g.) Pooled SD 3

0.095

0.097x

0.097x

0.097x

0.110 B

0.123 B

0.153XY

0.017

O.073 A

0.087 A

0.147BY

0.193BZ

0.013

9

0.083 A

0.107AB

0.140XY

223

0.016

14

0.09 7

A

AB

C

0.257^

0.031

Mean

0.088 A

0.111 B

0.141 C

0.185°

0.019

0.013

0.013

0.025

0.023

0.031

0

O.0971 <2

3

0.090 A

6

Pooled SD

3

0.153

0.197y

°-

zo

1

Each value/cell is an average of three replicates expressed as fig./g. fresh tissue. Means within a column not followed by the same subscript are significantly different at P<0.01, X, Y, Z, O and means within a row not followed by the same superscript are significantly different at P<0.01, A, B, C. 3 Pooled error standard deviation. 2

response was observed. The kidney (Table 9) was the most responsive tissue to dietary Se.. Within three days, a significant (P<0.01) difference was observed between the 0.095 ppm. treatment and the other treatments. By six days there was a significant difference between all treatments. The heart muscle (Table 10) was not as responsive to supplemental Se. treatment as liver and kidney. Only the highest dietary level showed a significant (P<0.01) response which only became apparent after nine days of feeding the 0.095 ppm. Se. diet.

The skeletal (thigh) muscle (Table 11) showed no response to feeding supplemental Se.. The results support the hypothesis of self-regulation of Se. accumulation in muscle. The muscle concentration in rats independent of toxic or deficient dietary levels remain the same (Harr et al., 1973). The Se. concentration in muscle of chicks fed the deficient diet was probably maintained at the expense of the other tissues. These data agree with results reported by McFarland et al. (1970) in that kidney and liver, characterized by some form of protein

TABLE 9.—Kidney selenium levels during repletion

0.017

(days)

Dietary Se. levels (Mg./g.) 0.055 0.095

0.031

0

0.180 x ' 2

0.180

3

0.150 A

6

0.126

A

0.206AB X 0.180 D

9

0.127 A

14

0.147

A

Mean

0.146 A

0.198 D

0.01

0.018

Pooled SD 1

3

X

X

0.180x

0.180x

0.210AB

0.277 B

0.036

0.240XY

0.330°z

0.017

0.197 B

0.213

0.227

I

Pooled SD 3

B

0.014

0.280x

°" ZO 0.407°

0.225 C

0.314°

0.022

0.029

0.024

Y

7

0.017

Each value/cell is an average of three replicates expressed as Mg./g. fresh tissue. Means within a column not followed by the same subscript are significantly different at P<0.01 for X, Y, Z, O and P<0.05 for x, y, z and means within a row not followed by the same superscript are significantly different at P«0.01. 3 Pooled error standard deviation. 2

Downloaded from http://ps.oxfordjournals.org/ at University of Cambridge on May 14, 2015

0.055

0.017

(days)

SELENIUM SUPPLEMENTATION AND BROILER RESPONSE

2037

TABLE 10.—Heart selenium levels during repletion Dietary Se. levels (Mg-/g-) (days)

0.017

0.031

0.097 1 -2

0

X A

3

0.100

6

0.087 A

0.097 0.110

X A

9

0.080

14

0.080 A

X

X A

o.ioo

0.110 B C X A

0.097

0.099

0.012

0.013

0.009

0.127xy

0.007

X

AB

B Z

0.012

0.113 A

0.177 B

0.013

X B

C

0.014

0.110

0.133

0.014

0.016

Each value/cell is an average of three replicates expressed as Mg./g- fresh tissue.

2

Means within a column not followed by the same subscript are significantly different at P<0.01, X, Y and Z, P<0.05, x, y, and means within a row not followed by the same superscript are significantly different at P«0.01. 3

Pooled error standard deviation.

synthesis, and being e x c r e t o r y organs generally c o n c e n t r a t e d Se. m o r e readily t h a n muscle. T h e kidney had t h e greatest ability t o c o n c e n t r a t e Se.. T h e liver c o n c e n t r a t e d Se. 2.6 fold t h a t present in t h e diet whereas t h e k i d n e y showed a 4 . 0 fold c o n c e n t r a t i o n when 0 . 0 9 5 p p m . dietary Se. was fed. Heart c o n c e n t r a t e d Se. 1.7 fold t h a t of t h e diet in 14 days. T h e ability of tissues t o c o n c e n t r a t e Se. increased as dietary Se. levels decreased. This is d e m o n s t r a t e d b y t h e fact t h a t t h e dietary Se. level increased 5.6 fold whereas t h e increases for b l o o d , liver, kidney, h e a r t muscle and skeletal muscle after 14 days of feeding increased 4.0, 2.5, 2.7, 1.5 and 1.0 fold respectively. T h e results of this s t u d y suggest t h a t b l o o d Se. levels could be a very good m o n i t o r for detecting Se. deficiency. T h e depletion d a t a

indicates t h a t b l o o d levels b e t w e e n 0 . 0 4 a n d 0.05 p p m . Se. are "critically l o w " and t h a t conditions could be right for t h e expression of ED, or a growth depression. Therefore in testing a flock of broilers suspected t o be Se. deficient, b l o o d levels will give an excellent estimate of dietary selenium levels w h e n t h e available Se. is between 0.02 t o 0.05 p p m . . S u p p l e m e n t a t i o n with Se. would replenish b l o o d and tissue levels and result in improved growth and feed efficiency in broiler flocks.

ACKNOWLEDGEMENTS T h e a u t h o r s are grateful t o Mrs. Heidi v o n der Wense for technical assistance. T h e senior a u t h o r is t h e recipient of a National Research Council Fellowship for which h e expresses his

TABLE 11.—Thigh muscle selenium levels during repletion Dietary Se. levels (Mg-/g-)

Periods (days)

0.017

0.031

0.055

0.095

0 3 6 9 14 Mean

0.083 1 ' J 0.077 0.060 0.070 0.080 0.074

0.083 0.080 0.070 0.077 0.070 0.076

0.083 0.073 0.083 0.077 0.080 0.079

0.083 0.083 0.083 0.080 0.080 0.082

1

Each value/cell is an average of three replicates expressed as Mg-/g- fresh tissue.

2

Pooled error standard deviation for the statistical analysis was ± 0.013.

Downloaded from http://ps.oxfordjournals.org/ at University of Cambridge on May 14, 2015

0.089

0.117XY

0.153

0.113

X

O.093 A

Pooled SD 3

A

X

AB

X A

Mean

1

0.110

X

X

0.097x

0.097 x A

Pooled SD 3

0.095

0.055

2038

W. GUENTER AND D. B. BRAGG

sincere gratitude. Also, support from Agriculture Canada is gratefully acknowledged. REFERENCES

Downloaded from http://ps.oxfordjournals.org/ at University of Cambridge on May 14, 2015

Arnold, R. L., O. E. Olson and C. W. Carlson, 1973. Dietary selenium and arsenic additions and their effect on tissue, egg selenium. Poultry Sci. 52:847-854. Berzelius, J. J., 1817. Sur dex metaux nouveaus (litium e t selenium). J. Schweigger. 21:1818-1823. Franke, K. W., 1934. A new toxicant occurring naturally in certain samples of plant foodstuffs. 1. Results obtained in preliminary feed trials. J. Nutr. 8:597-608. Harr, J. R., J. H. Exon, P. H. Weswig and P. D. Whanger, 1973. Relationship of dietary selenium concentration: chemical cancer induction; and tissue concentration of selenium in rats. Clin. Toxicol. 6:487-495. Lindberg, P. and N. Lanner, 1965. Retention of selenium in kidneys, liver and striated muscle after prolonged feeding of therapeutic amounts of sod i u m selenite to pigs. Acta Vet. Scand. 6:217-223. McFarland, L. Z., C. M. Winget, W. O. Wilson and C. M. Johnson, 1970. Role of selenium in neural physiology of avian species. 1. The distribution of selenium in tissue of chickens, turkeys and coturnix. Poultry Sci. 4 9 : 2 1 6 - 2 2 1 . Miller, D., J. H. Soares, Jr., P. J. Bauersfeld and S. L. Cuppett, 1972. Comparative selenium retention by chicks fed sodium selenite, selenomethionine, fish

m e a l and fish s o l u b l e s . P o u l t r y Sci. 51:1669-1673. National Research Council., 1971. Subcommittee on Selenium. Selneium in Nutrition, National Academy of Sciences, Washington, D.C. Noguchi, T., A. H. Cantor and M. L. Scott, 1973. Mode of action of selenium and vitamin E in prevention of exudative diathesis in chicks. J. Nutr. 103:1502-1511. Schwarz, K. and C. M. Foltz, 1957. Selenium as an integral part of factor 3 against dietary necrotic liver degeneration. J. Amer. Chem. Soc. 79:3292-3293. Scott, M. L., 1973. The selenium dilemma. J. Nutr. 103:803-810. Scott, M. L. and A. H. Cantor, 1971. Tissue selenium levels in chicks receiving graded amounts of dietary selenium. Fed. Proc. 30:237. Scott, M. L., M. C. Nesheim and R. J. Young, 1969. Nutrition of the chicken. M. L. Scott and Associates, Ithaca, New York, New York. Scott, M. L. and J. N. Thompson, 1971. Selenium content of feedstuffs and effects of dietary selenium levels upon tissue selenium in chicks and poults. Poultry Sci. 50:1742-1748. Seier, L. and D. B. Bragg, 1973. Influence of vitamin E and antioxidant on the response of dietary selenium by the chick and the biological activity of selenium in feed grain. Can. J. Anim. Sci. 53:371-375. Steel, R. G. D. and J. H. Torrie, 1960. Principles and Procedures of Statistics. McGraw-Hill Co. Inc. Toronto, Ontario. Thompson, J. N. and M. L. Scott, 1969. Role of selenium in the nutrition of the chick. J. Nutr. 97:335-342.