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Effects and Mechanism of Aflatoxin on Variation in Shell Strength
Effects and Mechanism of Aflatoxin on Variation in Shell Strength K. W. WASHBURN, R. D. WYATT, P. L. POTTS, and G. M. LANZA Department of Poultry Science, University of Georgia, Athens, Georgia 30602 (Received for publication February 1, 1984)
1985 Poultry Science 64:1302-1305 INTRODUCTION
The increased incidence of mycotoxins in various poultry feedstuffs has stimulated an increased interest in mycotoxicological studies. The mycotoxin most often found in poultry rations is aflatoxin produced by certain strains of Aspergillus flavus. Aflatoxin as high as 100 |Ug/g diet has been reported in the diets of laying hens. This level resulted in high mortality and decreased egg production (Hamilton, 1971). The occurrence of such high levels of aflatoxin is certainly rare. However, aflatoxin may affect egg formation at much lower levels and may interact with the effects of nutritionally marginal diets (Hamilton et al, 1974) and infectious disease (Wyatt et al., 1975). The potential effects of aflatoxin on shell strength is of concern in view of the high incidence of eggs whose shells are damaged before reaching the consumer. The shell strength of eggs produced during aflatoxin feeding is uncertain. Hamilton and Garlich (1971) reported that eggs produced during aflatoxin feeding had a normal percentage shell, and Huff et al. (1975) found no significant effect of aflatoxin feeding on percentage shell or shell thickness. However, Hamilton and Garlich (1972) reported an increase in the percent shell of hens receiving aflatoxin. Potts et al. (1976) reported that aflatoxin feeding significantly depressed shell strength in certain commercial layer strains with initial poor shell strength. A number of factors, including level of aflatoxin fed, strains of birds used, methods of assessing shell strength, dietary regimens, and shell strength status of birds prior to aflatoxin
feeding may account for the uncertainty concerning the effect of aflatoxin on shell strength. In the present study the interrelationships of prior shell strength status to the effects of aflatoxin on shell strength were assessed by several methods of measuring shell strength. The mechanism of aflatoxin action on shell strength was also studied by comparing the changes in the proportions of the egg components.
MATERIALS AND METHODS
Shell strength, assessed by shell deformation, and the percent production were determined for commercial layers in production for either 8 (Trial 1) or 12 (Trial 2) months. Hens were housed singly in commercial layer cages. After discarding hens laying at a poor rate, those showing evidence of previous molt, and those in apparent poor condition, the remainder were separated into high and low shell strength groups on the basis of shell deformation. The treatments consisted of either aflatoxin mixed in the feed at 5 /Ug/g or a control standard University of Georgia layer diet. A total of 160 hens in each trial (40 high shell strength fed the diet containing aflatoxin: 40 high shell strength fed the diet with no aflatoxin; 40 low shell strength fed the diet containing aflatoxin; and 40 low shell strength fed the diet with no aflatoxin) were used. Egg shell strength was determined for two eggs from each hen prior to the initiation of aflatoxin feeding and thereafter at weekly intervals for 3 weeks. In both trials, the average
1302
Downloaded from http://ps.oxfordjournals.org/ at North Dakota State University on May 24, 2015
ABSTRACT Changes in shell strength and relative size of the egg components associated with feeding dietary aflatoxin to hens differing in shell strength were determined. Shell strength was increased in groups fed aflatoxin because the shell weight of these groups was not decreased in proportion to the decrease in total egg weight. This resulted in a greater percentage shell. The effects of aflatoxin on percentage shell was greater for hens whose initial shell strength was poorer. A consistent relationship was observed between shell strength and percentage shell of groups differing in shell strength. (Key words: aflatoxin, layers, shell strength)
AFLATOXIN AND SHELL STRENGTH
1303
TABLE 1. Effect of aflatoxin on shell strength Aflatoxin in diet
Deform ation (X 10" 2 ram)
Break strength
Specific gravity
Thickness (X 10" 2 m m )
(kg)
(Mg/g)
Trial 1 0 5
2.94* 2.79b
5.00* 5.28b
0 5
3.05* 2.89b
5.37* 5.70b
1.081* 1.083*
31.6* 32.4b
1.079* 1.080*
33.5* 34.5b
Trial 2
value of eggs collected from an individual hen for 3 days was used as the value of an individual for that week. In addition to shell deformation, which was used for separation into high and low shell strength groups, the effects of aflatoxin on the shell strength was assessed by specific gravity, shell thickness, and breaking strength. The methods used have been previously described (Potts and Washburn, 1974). At the conclusion of the 3-week experiment, two eggs from each hen in production were weighed and the contents separated from the shells that were rinsed with water and the weight determined after air drying overnight. Chalazae were removed from the yolk, excess albumen was removed, and the yolk was weighed to the nearest .1 g on a top loading balance. Percent yolk and percent shell were then calculated. Aflatoxin was produced on rice by the method of Shotwell et al. (1966) and analyzed for total aflatoxin content by the methods of Nabney and Nesbitt (1965). A weighed amount of the rice powder was added to the commercial corn-soya diet to obtain the 5 /Ug dietary aflatoxin. In the statistical analysis, mean values for the duplicate eggs obtained from individuals for a particular week were used in the analysis of variance for unequal subclass numbers (Barr and Goodnight, 1972).
strength, specific gravity, or thickness (Table 1). Those groups receiving aflatoxin laid eggs with stronger shells than did controls. This relationship was highly significant for deformation, breaking strength and thickness in Trial 1 and 2. The results in Table 2 provide an explanation for the increased shell strength in eggs from groups fed aflatoxin. The egg weights of groups receiving aflatoxin were significantly lower than that of controls. This smaller egg size was apparently due to a decrease in yolk size. However, the shell weights of the eggs from the aflatoxin and control groups were not different in either trial. The consistency in shell mass resulted in a significant increase in the percent shell of the smaller eggs laid by the aflatoxin groups.
TABLE 2. Effects of aflatoxin on weight of egg and components Aflatoxin in diet
Egg weight
(Mg/g)
Yolk weight
—
(g)
Shell weight
%
5.5* 5.7*
9.1* 9.8b
5.9* 5.9*
8.5* 8.8b
Shell
• -
Trial 1 0 5
61.6* 59.2b
19.0* 17.8b
0 5
69.6* 67.6b
22.6* 21.4b
Trial 2
RESULTS AND DISCUSSION
Shell Strength. Dietary aflatoxin at 5 jug/g did not have a detrimental effect on shell strength as assessed by deformation, breaking
a' b Superscripts (P<.05).
indicate
significant
difference
Downloaded from http://ps.oxfordjournals.org/ at North Dakota State University on May 24, 2015
a,b,Significant differences within trial (P<.05).
1304
WASHBURN ET AL.
The results of the present study support the conclusion that the feeding of aflatoxin results in an increase in the percent shell and a decrease in egg weight. It further shows that the shell strength of eggs from hens fed aflatoxin is increased and the yolk weight is decreased. These results suggest that the feeding of aflatoxin at 5 /ig/g caused a slight reduction in
yolk size, resulting in a slight decrease in egg size. Shell deposition was not affected; thus, the same amount of shell being deposited on a slightly smaller egg resulted in an increased percent shell and shell strength. The metabolism of aflatoxin occurs primarily in the liver, and the results of Garlich et al. (1973) demonstrated that feeding of high aflatoxin to layers rapidly caused liver malfunctions. As a result of the liver malfunctions, the plasma lipids and protein precursors of the yolk lipids and protein normally produced in the liver would be decreased. This would be expected to result in a decrease in volume of yolk material produced, resulting in either decreased numbers, size, or a combination of both. Huff et al. (1975) suggested that the decrease in yolk weight of aflatoxin-fed hens accounted for the decrease in egg size. This conclusion was based on the identical (5.4 g) decrease in yolk and egg weights of hens receiving a diet containing 10 /ig aflatoxin/g diet for 4 weeks. In the present study, in which the aflatoxin was 5 Mg/g. the egg weight was decreased 2.35 and 2.00 g from control levels in Trials 1 and 2, respectively. Yolk weights were reduced 1.15 and 1.20 g in Trials 1 and 2. When the egg and yolk size of groups with the largest and smallest egg size were compared, the difference in yolk size was negligible (.10 g), although the egg size of these groups differed by 3.8 g. These results indicate that, although the decrease in yolk size in hens receiving 5 /ig aflatoxin/g diet may account for some of the decrease in egg size, it does not account for all of it. Although differences in the level of dietary aflatoxin fed and number of hens used in the treatment groups probably account for most of the variation in effects on shell strength observed between different studies, the egg shell
TABLE 3. Relationship of deformatii m to percentage shell and egg weight % Shell
Deformation H
Egg weight
L
H
L
H
3.1b 3.3 b
9.9s9.1a
8.8 b 8.3 b
60.4 a 68.5 a
(X 10"2 mm) Trial 1 Trial 2
2.6 a 2.6 a
L (g) 60.6 a 68.7 a
' High (H) and low (L) group means within a trial with different superscripts are significantly different (P<.01).
Downloaded from http://ps.oxfordjournals.org/ at North Dakota State University on May 24, 2015
Comparisons of the percent shell of the high and low shell deformation groups in both trials (Table 3) show a clear relationship between shell strength and percent of the total egg that is shell. In the high and low shell strength groups (high deformation value indicates low shell strength), the difference in percent shell was obtained without a significant difference in egg weights. The studies of Stout and Buss (1976) have also shown a relationship between percent shell and shell thickness. Hamilton and Garlich (1972), in a study of the fatty liver syndrome caused by aflatoxin, reported that the shell as a percent of the egg showed a slight but statistically significant increase as a result of dietary aflatoxin at 10 /ig/g, whereas egg weight was decreased significantly. In a previous study, Hamilton and Garlich (1971) reported that aflatoxin has no significant effect on egg shell thickness or on the percent shell, although egg weights were significantly depressed. Examination of their data shows that although none of the differences were significant, the shell thickness and percent shell of the eggs from groups receiving 5 £tg aflatoxin/g diet were numerically greater than controls. In a subsequent study, Huff et al. (1975) found no significant effects of feeding aflatoxin on shell thickness or percent shell. In their study, the egg and yolk weights were decreased when aflatoxin was fed for 4 weeks at 10 /ig/g but not when fed at lower levels for the same period.
AFLATOXIN AND SHELL STRENGTH
1305
TABLE 4. Percentage increase in shell quality of high and low shell strength groups fed aflatoxin „, ,.
Trial 1 Trial 2
Shell strength
strength group
Specific gravity
Thickness
Breaking strength
Deformation
High Low High Low
101 106 102 102
102 104 104 107
106 109* 112 120*
101 116* 101 116*
'Significant (P<.05) differences between high and low shell strength groups of aflatoxin-fed groups.
REFERENCES Barr, J. A., and J. H. Goodnight, 1972. A User's Guide to the Statistical Analysis System. Raleigh, NC. Garlich, J. D., Hsi-Tang Tung, and P. B. Hamilton, 1973. The effects of short term feeding of aflatoxin on egg production and some plasma constituents of the laying hen. Poultry Sci. 52:2206-2211. Hamilton, P. B., 1971. A natural and extremely severe occurrence of aflatoxicosis in laying hens. Poultry Sci. 50:1990- 1992.
Hamilton, P. B., and J. D. Garlich, 1971. Aflatoxin as a possible cause of fatty liver syndrome in laying hens. Poultry Sci. 50:800-804. Hamilton, P. B., and J. D. Garlich, 1972. Failure of vitamin supplementation to alter the fatty liver syndrome caused by aflatoxin. Poultry Sci. 51:688-692. Hamilton, P. B., H. T. Tung, R. D. Wyatt, and W. E. Donaldson, 1974. Interaction of dietary aflatoxin with some vitamin deficiencies. Poultry Sci. 53:871-877. Huff, W. E., R. D. Wyatt, and P. B. Hamilton, 1975. Effects of dietary aflatoxin on certain egg yolk parameters. Poultry Sci. 54:2014-2018. Nabney, J., and B. F. Nesbitt, 1965. A spectrophotometric method of determining the aflatoxins. Analyst 90:155-156. Potts, P. L., and K. W. Washburn, 1974. Shell evaluation of white and brown egg strains by deformation, breaking strength, shell thickness and specific gravity. Poultry Sci. 53:1123-1128. Potts, P. L., R. D. Wyatt, and K. W. Washburn, 1976. The effect of aflatoxin on shell strength of six commercial laying strains. Poultry Sci. 55:1603. (Abstr.) Shotwell, O. L., C. W. Hesseltine, R. D. Stubblefield, and W. G. Sorenson, 1966. Production of aflatoxin on rice. Appl. Microbiol. 14:425—428. Stout, J. T., and E. G. Buss, 1976. Egg shell quality: Time or rate of shell deposition. Poultry Sci. 55:2087. (Abstr.) Wyatt, R. D., M. D. Ruff, and R. K. Page, 1975. Interaction of aflatoxin with Eimeria tenella infection and monensin in young broiler chickens. Avian Dis. 19:730-740.
Downloaded from http://ps.oxfordjournals.org/ at North Dakota State University on May 24, 2015
strength status of the hens used might also influence the results obtained. In the present study, the shell strength of the low shell strength groups (assessed by breaking strength and deformation) appeared to be affected more by the feeding of aflatoxin for 3 weeks than were those in the high shell strength groups (Table 4). In Trial 1, the interaction between high and low shell strength groups in response to aflatoxin feeding was significant for the two measures of shell strength (breaking strength and deformation) increased by the feeding of aflatoxin. A similar but nonsignificant trend was observed for specific gravity and thickness. In Trial 2 the interaction of the effects of aflatoxin feeding on shell strength of the groups differing in shell strength was significant for breaking strength and deformation.
1985 Poultry Science 64:1302-1305 INTRODUCTION
The increased incidence of mycotoxins in various poultry feedstuffs has stimulated an increased interest in mycotoxicological studies. The mycotoxin most often found in poultry rations is aflatoxin produced by certain strains of Aspergillus flavus. Aflatoxin as high as 100 |Ug/g diet has been reported in the diets of laying hens. This level resulted in high mortality and decreased egg production (Hamilton, 1971). The occurrence of such high levels of aflatoxin is certainly rare. However, aflatoxin may affect egg formation at much lower levels and may interact with the effects of nutritionally marginal diets (Hamilton et al, 1974) and infectious disease (Wyatt et al., 1975). The potential effects of aflatoxin on shell strength is of concern in view of the high incidence of eggs whose shells are damaged before reaching the consumer. The shell strength of eggs produced during aflatoxin feeding is uncertain. Hamilton and Garlich (1971) reported that eggs produced during aflatoxin feeding had a normal percentage shell, and Huff et al. (1975) found no significant effect of aflatoxin feeding on percentage shell or shell thickness. However, Hamilton and Garlich (1972) reported an increase in the percent shell of hens receiving aflatoxin. Potts et al. (1976) reported that aflatoxin feeding significantly depressed shell strength in certain commercial layer strains with initial poor shell strength. A number of factors, including level of aflatoxin fed, strains of birds used, methods of assessing shell strength, dietary regimens, and shell strength status of birds prior to aflatoxin
feeding may account for the uncertainty concerning the effect of aflatoxin on shell strength. In the present study the interrelationships of prior shell strength status to the effects of aflatoxin on shell strength were assessed by several methods of measuring shell strength. The mechanism of aflatoxin action on shell strength was also studied by comparing the changes in the proportions of the egg components.
MATERIALS AND METHODS
Shell strength, assessed by shell deformation, and the percent production were determined for commercial layers in production for either 8 (Trial 1) or 12 (Trial 2) months. Hens were housed singly in commercial layer cages. After discarding hens laying at a poor rate, those showing evidence of previous molt, and those in apparent poor condition, the remainder were separated into high and low shell strength groups on the basis of shell deformation. The treatments consisted of either aflatoxin mixed in the feed at 5 /Ug/g or a control standard University of Georgia layer diet. A total of 160 hens in each trial (40 high shell strength fed the diet containing aflatoxin: 40 high shell strength fed the diet with no aflatoxin; 40 low shell strength fed the diet containing aflatoxin; and 40 low shell strength fed the diet with no aflatoxin) were used. Egg shell strength was determined for two eggs from each hen prior to the initiation of aflatoxin feeding and thereafter at weekly intervals for 3 weeks. In both trials, the average
1302
Downloaded from http://ps.oxfordjournals.org/ at North Dakota State University on May 24, 2015
ABSTRACT Changes in shell strength and relative size of the egg components associated with feeding dietary aflatoxin to hens differing in shell strength were determined. Shell strength was increased in groups fed aflatoxin because the shell weight of these groups was not decreased in proportion to the decrease in total egg weight. This resulted in a greater percentage shell. The effects of aflatoxin on percentage shell was greater for hens whose initial shell strength was poorer. A consistent relationship was observed between shell strength and percentage shell of groups differing in shell strength. (Key words: aflatoxin, layers, shell strength)
AFLATOXIN AND SHELL STRENGTH
1303
TABLE 1. Effect of aflatoxin on shell strength Aflatoxin in diet
Deform ation (X 10" 2 ram)
Break strength
Specific gravity
Thickness (X 10" 2 m m )
(kg)
(Mg/g)
Trial 1 0 5
2.94* 2.79b
5.00* 5.28b
0 5
3.05* 2.89b
5.37* 5.70b
1.081* 1.083*
31.6* 32.4b
1.079* 1.080*
33.5* 34.5b
Trial 2
value of eggs collected from an individual hen for 3 days was used as the value of an individual for that week. In addition to shell deformation, which was used for separation into high and low shell strength groups, the effects of aflatoxin on the shell strength was assessed by specific gravity, shell thickness, and breaking strength. The methods used have been previously described (Potts and Washburn, 1974). At the conclusion of the 3-week experiment, two eggs from each hen in production were weighed and the contents separated from the shells that were rinsed with water and the weight determined after air drying overnight. Chalazae were removed from the yolk, excess albumen was removed, and the yolk was weighed to the nearest .1 g on a top loading balance. Percent yolk and percent shell were then calculated. Aflatoxin was produced on rice by the method of Shotwell et al. (1966) and analyzed for total aflatoxin content by the methods of Nabney and Nesbitt (1965). A weighed amount of the rice powder was added to the commercial corn-soya diet to obtain the 5 /Ug dietary aflatoxin. In the statistical analysis, mean values for the duplicate eggs obtained from individuals for a particular week were used in the analysis of variance for unequal subclass numbers (Barr and Goodnight, 1972).
strength, specific gravity, or thickness (Table 1). Those groups receiving aflatoxin laid eggs with stronger shells than did controls. This relationship was highly significant for deformation, breaking strength and thickness in Trial 1 and 2. The results in Table 2 provide an explanation for the increased shell strength in eggs from groups fed aflatoxin. The egg weights of groups receiving aflatoxin were significantly lower than that of controls. This smaller egg size was apparently due to a decrease in yolk size. However, the shell weights of the eggs from the aflatoxin and control groups were not different in either trial. The consistency in shell mass resulted in a significant increase in the percent shell of the smaller eggs laid by the aflatoxin groups.
TABLE 2. Effects of aflatoxin on weight of egg and components Aflatoxin in diet
Egg weight
(Mg/g)
Yolk weight
—
(g)
Shell weight
%
5.5* 5.7*
9.1* 9.8b
5.9* 5.9*
8.5* 8.8b
Shell
• -
Trial 1 0 5
61.6* 59.2b
19.0* 17.8b
0 5
69.6* 67.6b
22.6* 21.4b
Trial 2
RESULTS AND DISCUSSION
Shell Strength. Dietary aflatoxin at 5 jug/g did not have a detrimental effect on shell strength as assessed by deformation, breaking
a' b Superscripts (P<.05).
indicate
significant
difference
Downloaded from http://ps.oxfordjournals.org/ at North Dakota State University on May 24, 2015
a,b,Significant differences within trial (P<.05).
1304
WASHBURN ET AL.
The results of the present study support the conclusion that the feeding of aflatoxin results in an increase in the percent shell and a decrease in egg weight. It further shows that the shell strength of eggs from hens fed aflatoxin is increased and the yolk weight is decreased. These results suggest that the feeding of aflatoxin at 5 /ig/g caused a slight reduction in
yolk size, resulting in a slight decrease in egg size. Shell deposition was not affected; thus, the same amount of shell being deposited on a slightly smaller egg resulted in an increased percent shell and shell strength. The metabolism of aflatoxin occurs primarily in the liver, and the results of Garlich et al. (1973) demonstrated that feeding of high aflatoxin to layers rapidly caused liver malfunctions. As a result of the liver malfunctions, the plasma lipids and protein precursors of the yolk lipids and protein normally produced in the liver would be decreased. This would be expected to result in a decrease in volume of yolk material produced, resulting in either decreased numbers, size, or a combination of both. Huff et al. (1975) suggested that the decrease in yolk weight of aflatoxin-fed hens accounted for the decrease in egg size. This conclusion was based on the identical (5.4 g) decrease in yolk and egg weights of hens receiving a diet containing 10 /ig aflatoxin/g diet for 4 weeks. In the present study, in which the aflatoxin was 5 Mg/g. the egg weight was decreased 2.35 and 2.00 g from control levels in Trials 1 and 2, respectively. Yolk weights were reduced 1.15 and 1.20 g in Trials 1 and 2. When the egg and yolk size of groups with the largest and smallest egg size were compared, the difference in yolk size was negligible (.10 g), although the egg size of these groups differed by 3.8 g. These results indicate that, although the decrease in yolk size in hens receiving 5 /ig aflatoxin/g diet may account for some of the decrease in egg size, it does not account for all of it. Although differences in the level of dietary aflatoxin fed and number of hens used in the treatment groups probably account for most of the variation in effects on shell strength observed between different studies, the egg shell
TABLE 3. Relationship of deformatii m to percentage shell and egg weight % Shell
Deformation H
Egg weight
L
H
L
H
3.1b 3.3 b
9.9s9.1a
8.8 b 8.3 b
60.4 a 68.5 a
(X 10"2 mm) Trial 1 Trial 2
2.6 a 2.6 a
L (g) 60.6 a 68.7 a
' High (H) and low (L) group means within a trial with different superscripts are significantly different (P<.01).
Downloaded from http://ps.oxfordjournals.org/ at North Dakota State University on May 24, 2015
Comparisons of the percent shell of the high and low shell deformation groups in both trials (Table 3) show a clear relationship between shell strength and percent of the total egg that is shell. In the high and low shell strength groups (high deformation value indicates low shell strength), the difference in percent shell was obtained without a significant difference in egg weights. The studies of Stout and Buss (1976) have also shown a relationship between percent shell and shell thickness. Hamilton and Garlich (1972), in a study of the fatty liver syndrome caused by aflatoxin, reported that the shell as a percent of the egg showed a slight but statistically significant increase as a result of dietary aflatoxin at 10 /ig/g, whereas egg weight was decreased significantly. In a previous study, Hamilton and Garlich (1971) reported that aflatoxin has no significant effect on egg shell thickness or on the percent shell, although egg weights were significantly depressed. Examination of their data shows that although none of the differences were significant, the shell thickness and percent shell of the eggs from groups receiving 5 £tg aflatoxin/g diet were numerically greater than controls. In a subsequent study, Huff et al. (1975) found no significant effects of feeding aflatoxin on shell thickness or percent shell. In their study, the egg and yolk weights were decreased when aflatoxin was fed for 4 weeks at 10 /ig/g but not when fed at lower levels for the same period.
AFLATOXIN AND SHELL STRENGTH
1305
TABLE 4. Percentage increase in shell quality of high and low shell strength groups fed aflatoxin „, ,.
Trial 1 Trial 2
Shell strength
strength group
Specific gravity
Thickness
Breaking strength
Deformation
High Low High Low
101 106 102 102
102 104 104 107
106 109* 112 120*
101 116* 101 116*
'Significant (P<.05) differences between high and low shell strength groups of aflatoxin-fed groups.
REFERENCES Barr, J. A., and J. H. Goodnight, 1972. A User's Guide to the Statistical Analysis System. Raleigh, NC. Garlich, J. D., Hsi-Tang Tung, and P. B. Hamilton, 1973. The effects of short term feeding of aflatoxin on egg production and some plasma constituents of the laying hen. Poultry Sci. 52:2206-2211. Hamilton, P. B., 1971. A natural and extremely severe occurrence of aflatoxicosis in laying hens. Poultry Sci. 50:1990- 1992.
Hamilton, P. B., and J. D. Garlich, 1971. Aflatoxin as a possible cause of fatty liver syndrome in laying hens. Poultry Sci. 50:800-804. Hamilton, P. B., and J. D. Garlich, 1972. Failure of vitamin supplementation to alter the fatty liver syndrome caused by aflatoxin. Poultry Sci. 51:688-692. Hamilton, P. B., H. T. Tung, R. D. Wyatt, and W. E. Donaldson, 1974. Interaction of dietary aflatoxin with some vitamin deficiencies. Poultry Sci. 53:871-877. Huff, W. E., R. D. Wyatt, and P. B. Hamilton, 1975. Effects of dietary aflatoxin on certain egg yolk parameters. Poultry Sci. 54:2014-2018. Nabney, J., and B. F. Nesbitt, 1965. A spectrophotometric method of determining the aflatoxins. Analyst 90:155-156. Potts, P. L., and K. W. Washburn, 1974. Shell evaluation of white and brown egg strains by deformation, breaking strength, shell thickness and specific gravity. Poultry Sci. 53:1123-1128. Potts, P. L., R. D. Wyatt, and K. W. Washburn, 1976. The effect of aflatoxin on shell strength of six commercial laying strains. Poultry Sci. 55:1603. (Abstr.) Shotwell, O. L., C. W. Hesseltine, R. D. Stubblefield, and W. G. Sorenson, 1966. Production of aflatoxin on rice. Appl. Microbiol. 14:425—428. Stout, J. T., and E. G. Buss, 1976. Egg shell quality: Time or rate of shell deposition. Poultry Sci. 55:2087. (Abstr.) Wyatt, R. D., M. D. Ruff, and R. K. Page, 1975. Interaction of aflatoxin with Eimeria tenella infection and monensin in young broiler chickens. Avian Dis. 19:730-740.
Downloaded from http://ps.oxfordjournals.org/ at North Dakota State University on May 24, 2015
strength status of the hens used might also influence the results obtained. In the present study, the shell strength of the low shell strength groups (assessed by breaking strength and deformation) appeared to be affected more by the feeding of aflatoxin for 3 weeks than were those in the high shell strength groups (Table 4). In Trial 1, the interaction between high and low shell strength groups in response to aflatoxin feeding was significant for the two measures of shell strength (breaking strength and deformation) increased by the feeding of aflatoxin. A similar but nonsignificant trend was observed for specific gravity and thickness. In Trial 2 the interaction of the effects of aflatoxin feeding on shell strength of the groups differing in shell strength was significant for breaking strength and deformation.