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Effects of nutritionally balanced and stabilized flaxmeal-based diets on Eimeria tenella infections in chickens
Research Notes Effects of Nutritionally Balanced and Stabilized Flaxmeal-Based Diets on Eimeria tenella Infections in Chickens P. C. Allen,*,1 H. Danforth,* and P. A. Stitt† *USDA-Agricultural Research Service, Livestock and Poultry Sciences Institute, Parasite Biology and Epidemiology Laboratory, Beltsville, Maryland 20705; and †ENRECO, Inc., PO Box 730, Manitowoc, Wisconsin 54220 At 6 d postinfection, chickens were weighed, bled, killed, and scored for lesions. No level of dietary flaxmeal tested provided protection against weight gain depression, increased feed conversion ratios, or lesions. We concluded that these diets did not protect against E. tenella infection because levels of linolenic acid were not high enough, and the oxidative potentials were well suppressed by vitamin E and other stabilizers present.
(Key words: Eimeria tenella, n-3 fatty acids, weight gain, feed conversion, lesions) 2000 Poultry Science 79:489–492
sions, and lesion scores from E. tenella infections were assessed.
INTRODUCTION The antiparasitic activities of flaxseed and flaxseed oil are well documented. Levander and Ager (1995) showed that 12.5% dietary flaxseed supplementation significantly increased survival of mice infected with Plasmodium yoelii in a vitamin E deficient model. Allen et al. (1994, 1996, 1997) have shown that 10% flaxseed oil and 15% whole flaxseed, when added as supplements to broiler starter diets, were effective in reducing cecal lesions caused by Eimeria tenella. Such supplemented poultry feed, however, may become nutritionally unbalanced due to its high caloric content from fat, which is relatively unstable because of the ease at which its high n3 fatty acid content undergoes oxidation. Therefore, we investigated the efficacy of diets containing varying percentages of stabilized flaxmeal that were formulated to conform to nutrient values found in typical broiler starter rations. The levels of flaxseed meal tested (2 to 10%) encompassed a range reported to yield poultry egg and meat products that are acceptable in taste to the consumer. These diets were fed to chickens through 4 wk of age, and their effects on weight gains, feed conver-
MATERIALS AND METHODS Chickens and Housing Twenty day-old, Sex Sal cockerels2 were housed per brooder3 (91.4l cm long × 61.0 cm wide × 27.9 cm high) through 17 d of age. Brooder temperatures, initially at 37 C, were gradually reduced over the 2-wk period to 27 C. All 20 chicks within each brooder were then transferred to suspended wire colony cages (137.2 cm long × 76.2 cm wide × 55.9 cm high), in which room lighting was continuous, and temperature was maintained between 25 and 27 C. Birds were provided unlimited access to feed and water. The experimental protocols (AUP 97022) were approved by the Beltsville Area Animal Care and Use Committee.
Diets Four diets, containing 0, 2, 5, or 10% stabilized flaxmeal were formulated.4 They were stored in an unheated building until fed to the chickens. Formulations are listed in Table 1. We calculated that the 2, 5, or 10% flaxmeal formulations contributed 0.45, 1.11, or 2.22% n-3 fatty acids (primarily linolenic acid), respectively, to the diets. Each diet was assigned to two groups of 20 chicks each (one group per brooder or colony cage) and was fed continuously through the end of the experiment. Feed consumption was measured, and feed conversions
Received for publication September 7, 1999. Accepted for publication December 14, 1999. 1 To whom correspondence should be addressed: pallen@lpsi. barc.usda.gov. 2 Moyer’s Hatchery, Quakertown, PA 18951. 3 Brower, Houghton, IA 52631. 4 ENRECO, Inc., Manitowoc, WI 54220.
489
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on June 7, 2015
ABSTRACT Twenty Sex Sal cockerels were randomly assigned to each of eight groups; each of four nutritionally balanced diets were fed to two groups from 1 d through 4 wk of age. These diets contained 0, 2, 5, or 10% stabilized flaxseed meal that provided a calculated 0, 0.45, 1.11, or 2.22% n-3 fatty acids, primarily linolenic acid. At 3 wk of age, one group of chickens from each diet treatment was infected with Eimeria tenella and was housed in separate but similar conditions to uninfected control chickens.
490
ALLEN ET AL. TABLE 1. Compositions of flax-based diets Flaxseed meal Ingredients
0%
2%
5%
10%
(g/kg diet) 541.0 335.0 60.0 0 16.5 14.0 3.5 2.5 1.0 26.5
532.5 330.0 56.5 20.0 16.0 14.0 3.5 2.5 1.0 24.0
517.5 323.5 52.0 50.0 15.0 14.0 3.5 2.5 1.0 21.0
492.5 312.5 44.5 100.0 14.0 14.5 3.5 2.5 1.0 15.0
241 481 6,833 0 12.5 5.5 36.61
241 530 6,833 4.50 12.5 5.5 36.41
241 605 6,833 11.1 12.5 5.5 36.12
241 729 6,833 22.2 12.5 5.5 35.66
1
ENRECO, Inc., Manitoc, WI 54220. Provides trace minerals (in mg/kg diet): manganese, 50; iron, 115; copper, 10; zinc, 100; selenium, 0.10; iodine, 0.50; cobalt, 0.438. Provides fat-soluble vitamin (per kg diet): vitamin A, 6,615 IU; vitamin D, 1,654 IU; vitamin E, 22.05 IU; vitamin K, 2.425 mg. Provides water-soluble vitamins (in mg/kg diet): thiamine, 0.717; riboflavin, 5.513; pyridoxine, 1.433; niacin, 22.05; vitamin B-12, 0.02205; pantothenic acid, 17.64; biotin, 0.0882; folic acid, 0.430; choline, 132.3 (J. C. Feed Mills, Inc., Waterloo, IA 50704). 2
were determined through 17 d of age and during the 6 d of E. tenella infection.
Parasite and Dose A laboratory strain of E. tenella, obtained from a pharmaceutical company5 and maintained at the Parasite Biology and Epidemiology Laboratory over the past 5 yr through periodic passage through young chickens, was used to infect the chickens. Oocysts, purified from cecal collections and stored in 2% potassium dichromate, were freed of the dichromate through repeated centrifugation and washing with water and were adjusted to a concentration of 25,000 sporulated oocysts per 1 mL. Chickens in infected groups were each inoculated by gavage with 1 mL of the oocyst preparation.
Experimental Protocol Chickens in one group from each diet treatment were infected with E. tenella. Infected and control chickens were housed in separate, but environmentally similar, rooms. All birds were weighed immediately prior to infection and at the termination of the experiment, which occurred 6 d postinoculation. At termination, 15 chickens per group were bled and killed by cervical dislocation, and the ceca of infected chickens were scored for lesions (Johnson and Reid, 1970).
5 This strain was provided by Helen Profusjukelka, Merck Research Laboratories, Rahway, NJ 07065.
Statistical Analyses The experimental design was a randomized, complete block design; a chicken was considered the experimental unit per diet and infection treatment. Weight data were analyzed by analysis of variance using the general linear models procedure of SAS (SAS Institute, 1990) to determine main effects and interactions. Significant differences between group means were determined by Duncan’s multiple-range test (P ≤ 0.05). Lesion score data were analyzed using the Kruskal-Wallace test of the NPAR1WAY procedure of SAS (SAS Institute, 1990).
RESULTS Prior to coccidia infection, no significant differences among diet groups were observed with respect to weight gain or feed conversion (Table 2). TABLE 2. Effects of flax-based diets on body weights and feed conversions through 17 d of age (period before infection) Body weights Diet
Day 1
Day 9
Day 17
(g) 0% 2% 5% 10%
Flax Flax Flax Flax
36 35 36 36
± ± ± ±
0.51 0 0.5 0.5
60 54 53 61
± ± ± ±
1.51 1.5 1.0 0
191 190 182 190
± ± ± ±
3a 3a 3a 3a
Feed conversion (feed/gain) 1.65 1.75 1.66 1.68
a Means ± SEM. Means with no common superscript letter differ significantly (P ≤ 0.05). 1 Calculated from duplicate group weights. 2 Calculated from individual bird weights.
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on June 7, 2015
Ground corn, meal Soybean meal (47.5%) Corn gluten meal (60%) Stabilized Flaxseed Meal1 Dicalcium phosphate (18.5% P) Calcium carbonate Salt Prime Line-SW Grower Premix2 DL-Methionine (99.5%) Mineral oil Calculated composition Crude protein Crude fat Poultry ME kcal/kg n-3 Fatty acids Lysine Methionine Vitamin E, IU/kg
491
RESEARCH NOTE TABLE 3. Effects of flax-based diets and Eimeria tenella infection on weight gains, feed conversions, and lesion scores at 6 d postinoculation Start weight
Diet
End weight
Uninfected controls 0% 2% 5% 10%
Flax Flax Flax Flax
(g)
Feed conversion
Lesion score
± ± ± ±
6a 6a 5a 6a
321 332 316 326
± ± ± ±
9ab 8a 7ab 8ab
110 109 107 111
± ± ± ±
3a 3a 3a 5a
(feed/gain) 2.23 2.14 2.41 2.22
(score)
211 223 209 214
220 207 205 215
± ± ± ±
4a 4a 4a 3a
307 290 280 293
± ± ± ±
7bc 6cd 8d 6cd
86 83 75 79
± ± ± ±
4b 4b 5b 4b
2.46 2.63 2.66 2.66
3.13 3.13 3.27 3.07
0.232 0.494 0.078
0.159 0.0001 0.312
± ± ± ±
0.19a 0.16a 0.15a 0.15a
0.321 0.0001 0.597
Means ± SEM. Within columns, means with no common superscript differ significantly (P ≤ 0.05). D = diet; I = infection.
a–d 1
At 6 d postinoculation, mean weight gains of all infected groups averaged 74% of uninfected controls. Within control and infected groups, there were no significant differences in weight gain among dietary treatments (Table 3). Therefore, there were no diet × infection interactions with respect to weight gain. Feed conversion ratios of infected groups of chickens averaged 16% greater than uninfected groups (Table 3). There were no significant differences (P = 0.8231) in mean lesion scores among the infected diet groups (Table 3).
DISCUSSION Flaxseed provides a highly concentrated source (about 19%) of the n-3 fatty acid, linolenic acid. This seed has been incorporated into poultry feeds at levels up to 20% as a means of increasing the availability of n-3 fatty acids in eggs and poultry meat for human consumption (Caston et al., 1994). Levels as high as 15% have the potential to generate off-flavors and cause decreases in egg production (Aymond and Van Elswyk, 1995), and it has been shown that diets containing only 5% flaxseed are adequate for significantly increasing linolenic acid in eggs (Aymond and Van Elswyk, 1995). It was of interest, therefore, to test balanced diets containing less than 15% flaxseed to see whether they could provide protection against E. tenella infection in a manner similar to that observed in previous studies (Allen et al., 1996, 1997). Uniform growth was observed across all diet treatments until infection with E. tenella. During infection, no level of flaxmeal tested provided protection against weight gain depression, lesions, or increased feed conversion ratios. The groups that consumed the 5% flaxmeal diet underperformed to a small degree. No obvious reason for this aberration could be determined. It is hypothesized that the successes experienced by using flax oil and flaxseed supplements against E. tenella infections (Allen et al., 1996, 1997) are due to their induc-
tion of oxidative stress (Levander et al., 1993) that is detrimental to the ceca-dwelling coccidian. The oxidative stress effect is directly related to the amount of oxidizable double bonds added to the diet. It has been estimated from the calculated linolenic acid content of flaxseed (Exler and Weinrauch, 1986) that 15 and 12.5% flaxseed supplements would provide, respectively, 0.031 and 0.027 mol of double bonds/100 g feed that are available for oxidation. These diets, which contained no supplementary antioxidants, were reported to protect against cecal coccidiosis (Allen et al., 1996, 1997) and murine malaria (Levander and Ager, 1995). It is estimated that the 10% flaxmeal diet from this experiment provided only 0.022 mol of double bonds per 100 g feed. Therefore, the ineffectiveness of the current diets to protect chicks against E. tenella infection may be due to their lower levels of linolenic acid and to the amounts of linolenic acid present being well protected from potential oxidation by high concentrations of vitamin E (Table 1) and other antioxidants. In summary, the results of this experiment indicate that chickens raised on balanced diets containing up to 10% stabilized flaxmeal remain susceptible to E. tenella infection. Therefore, for flaxseed meal to be useful as an anticoccidial, it should be added at levels of 12 to 15% as a supplement to balanced diets. Such diets could be of practical use primarily as starter rations for young chicks for which E. tenella is a known problem.
ACKNOWLEDGMENTS The authors are grateful to ENRECO, Inc., Manitowoc, WI 54220, for the donation of the diets used in this study and to Certified Animal Nutritionist, Gary Boyett, Kenton, TN 38233, for providing calculated nutrient data. ARS, Beltsville employees, Ron Bilheimer, Clarence Parsons, Angela Parsons, and Beth Summers are commended for their excellent technical help.
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on June 7, 2015
E. tenellainfected 0% Flax 2% Flax 5% Flax 10% Flax Main effects (Pr > F) D1 I D×I
Gain
492
ALLEN ET AL.
REFERENCES Allen, P. C., H. Danforth, and O. A. Levander, 1994. High dietary levels of flaxseed oil and fish oil lower cecal lesion scores in broiler chickens infected with the cecal parasite Eimeria tenella. Pages 123–126 in: Proceedings of the 55th Flax Institute. The Flax Institute of the United States, Fargo, ND. Allen, P. C., H. D. Danforth, and O. A. Levander, 1996. Diets high in n-3 fatty acids reduce cecal lesion scores in chickens infected with Eimeria tenella. Poultry Sci. 75:179–185. Allen, P. C., H. D. Danforth, and O. A. Levander, 1997. Interaction of dietary flaxseed with coccidia infections in chickens. Poultry Sci. 76:822–827. Aymond, W. M., and M. E. Van Elswyk, 1995. Yolk thiobarbituric acid reactive substances and n-3 fatty acids in response to whole and ground flaxseed. Poultry Sci. 74:1388–1394. Caston, L. J., E. S. Squires, and S. Leesen, 1994. Hen performance, egg quality and sensory evaluation of eggs from SWCL hens fed dietary flax. Can. J. Anim. Sci. 74:347–353.
Johnson, J., and M. Reid, 1970. Anticoccidial drugs: Lesion scoring techniques in battery and floor pen experiments with chickens. Exp. Parasitol. 28:30–36. Exler, J., and J. L. Weihrauch, 1986. Provisional Table on the Content of Omega-3 Fatty Acids and Other Fat Components in Selected Foods. USDA, Human Nutrition Service, HNIS/ PR-103, Washington, DC. Levander, O. A., and A. L. Ager, 1995. Antimalarial effects of flaxseed and flaxseed oil. Pages 237–243 in: Flaxseed in Human Nutrition. S. C. Cunnane and L. U. Thompson, ed. AOCS Press, Champaign, IL. Levander, O. A., A. L. Ager, V. C. Morris, R. Fontela, and R. G. May, 1993. Dietary oxidant stress. Suppression of malaria by dietary oxidant stress. Pages 347–357 in: Active Oxygen, Lipid Peroxides and Antioxidants. Yagi, K., ed. CRC Press, Boca Raton, FL. SAS Institute, 1990. SAS/STAT User’s Guide, Vol. 2. SAS Institute Inc., Cary, NC. Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on June 7, 2015
(Key words: Eimeria tenella, n-3 fatty acids, weight gain, feed conversion, lesions) 2000 Poultry Science 79:489–492
sions, and lesion scores from E. tenella infections were assessed.
INTRODUCTION The antiparasitic activities of flaxseed and flaxseed oil are well documented. Levander and Ager (1995) showed that 12.5% dietary flaxseed supplementation significantly increased survival of mice infected with Plasmodium yoelii in a vitamin E deficient model. Allen et al. (1994, 1996, 1997) have shown that 10% flaxseed oil and 15% whole flaxseed, when added as supplements to broiler starter diets, were effective in reducing cecal lesions caused by Eimeria tenella. Such supplemented poultry feed, however, may become nutritionally unbalanced due to its high caloric content from fat, which is relatively unstable because of the ease at which its high n3 fatty acid content undergoes oxidation. Therefore, we investigated the efficacy of diets containing varying percentages of stabilized flaxmeal that were formulated to conform to nutrient values found in typical broiler starter rations. The levels of flaxseed meal tested (2 to 10%) encompassed a range reported to yield poultry egg and meat products that are acceptable in taste to the consumer. These diets were fed to chickens through 4 wk of age, and their effects on weight gains, feed conver-
MATERIALS AND METHODS Chickens and Housing Twenty day-old, Sex Sal cockerels2 were housed per brooder3 (91.4l cm long × 61.0 cm wide × 27.9 cm high) through 17 d of age. Brooder temperatures, initially at 37 C, were gradually reduced over the 2-wk period to 27 C. All 20 chicks within each brooder were then transferred to suspended wire colony cages (137.2 cm long × 76.2 cm wide × 55.9 cm high), in which room lighting was continuous, and temperature was maintained between 25 and 27 C. Birds were provided unlimited access to feed and water. The experimental protocols (AUP 97022) were approved by the Beltsville Area Animal Care and Use Committee.
Diets Four diets, containing 0, 2, 5, or 10% stabilized flaxmeal were formulated.4 They were stored in an unheated building until fed to the chickens. Formulations are listed in Table 1. We calculated that the 2, 5, or 10% flaxmeal formulations contributed 0.45, 1.11, or 2.22% n-3 fatty acids (primarily linolenic acid), respectively, to the diets. Each diet was assigned to two groups of 20 chicks each (one group per brooder or colony cage) and was fed continuously through the end of the experiment. Feed consumption was measured, and feed conversions
Received for publication September 7, 1999. Accepted for publication December 14, 1999. 1 To whom correspondence should be addressed: pallen@lpsi. barc.usda.gov. 2 Moyer’s Hatchery, Quakertown, PA 18951. 3 Brower, Houghton, IA 52631. 4 ENRECO, Inc., Manitowoc, WI 54220.
489
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on June 7, 2015
ABSTRACT Twenty Sex Sal cockerels were randomly assigned to each of eight groups; each of four nutritionally balanced diets were fed to two groups from 1 d through 4 wk of age. These diets contained 0, 2, 5, or 10% stabilized flaxseed meal that provided a calculated 0, 0.45, 1.11, or 2.22% n-3 fatty acids, primarily linolenic acid. At 3 wk of age, one group of chickens from each diet treatment was infected with Eimeria tenella and was housed in separate but similar conditions to uninfected control chickens.
490
ALLEN ET AL. TABLE 1. Compositions of flax-based diets Flaxseed meal Ingredients
0%
2%
5%
10%
(g/kg diet) 541.0 335.0 60.0 0 16.5 14.0 3.5 2.5 1.0 26.5
532.5 330.0 56.5 20.0 16.0 14.0 3.5 2.5 1.0 24.0
517.5 323.5 52.0 50.0 15.0 14.0 3.5 2.5 1.0 21.0
492.5 312.5 44.5 100.0 14.0 14.5 3.5 2.5 1.0 15.0
241 481 6,833 0 12.5 5.5 36.61
241 530 6,833 4.50 12.5 5.5 36.41
241 605 6,833 11.1 12.5 5.5 36.12
241 729 6,833 22.2 12.5 5.5 35.66
1
ENRECO, Inc., Manitoc, WI 54220. Provides trace minerals (in mg/kg diet): manganese, 50; iron, 115; copper, 10; zinc, 100; selenium, 0.10; iodine, 0.50; cobalt, 0.438. Provides fat-soluble vitamin (per kg diet): vitamin A, 6,615 IU; vitamin D, 1,654 IU; vitamin E, 22.05 IU; vitamin K, 2.425 mg. Provides water-soluble vitamins (in mg/kg diet): thiamine, 0.717; riboflavin, 5.513; pyridoxine, 1.433; niacin, 22.05; vitamin B-12, 0.02205; pantothenic acid, 17.64; biotin, 0.0882; folic acid, 0.430; choline, 132.3 (J. C. Feed Mills, Inc., Waterloo, IA 50704). 2
were determined through 17 d of age and during the 6 d of E. tenella infection.
Parasite and Dose A laboratory strain of E. tenella, obtained from a pharmaceutical company5 and maintained at the Parasite Biology and Epidemiology Laboratory over the past 5 yr through periodic passage through young chickens, was used to infect the chickens. Oocysts, purified from cecal collections and stored in 2% potassium dichromate, were freed of the dichromate through repeated centrifugation and washing with water and were adjusted to a concentration of 25,000 sporulated oocysts per 1 mL. Chickens in infected groups were each inoculated by gavage with 1 mL of the oocyst preparation.
Experimental Protocol Chickens in one group from each diet treatment were infected with E. tenella. Infected and control chickens were housed in separate, but environmentally similar, rooms. All birds were weighed immediately prior to infection and at the termination of the experiment, which occurred 6 d postinoculation. At termination, 15 chickens per group were bled and killed by cervical dislocation, and the ceca of infected chickens were scored for lesions (Johnson and Reid, 1970).
5 This strain was provided by Helen Profusjukelka, Merck Research Laboratories, Rahway, NJ 07065.
Statistical Analyses The experimental design was a randomized, complete block design; a chicken was considered the experimental unit per diet and infection treatment. Weight data were analyzed by analysis of variance using the general linear models procedure of SAS (SAS Institute, 1990) to determine main effects and interactions. Significant differences between group means were determined by Duncan’s multiple-range test (P ≤ 0.05). Lesion score data were analyzed using the Kruskal-Wallace test of the NPAR1WAY procedure of SAS (SAS Institute, 1990).
RESULTS Prior to coccidia infection, no significant differences among diet groups were observed with respect to weight gain or feed conversion (Table 2). TABLE 2. Effects of flax-based diets on body weights and feed conversions through 17 d of age (period before infection) Body weights Diet
Day 1
Day 9
Day 17
(g) 0% 2% 5% 10%
Flax Flax Flax Flax
36 35 36 36
± ± ± ±
0.51 0 0.5 0.5
60 54 53 61
± ± ± ±
1.51 1.5 1.0 0
191 190 182 190
± ± ± ±
3a 3a 3a 3a
Feed conversion (feed/gain) 1.65 1.75 1.66 1.68
a Means ± SEM. Means with no common superscript letter differ significantly (P ≤ 0.05). 1 Calculated from duplicate group weights. 2 Calculated from individual bird weights.
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on June 7, 2015
Ground corn, meal Soybean meal (47.5%) Corn gluten meal (60%) Stabilized Flaxseed Meal1 Dicalcium phosphate (18.5% P) Calcium carbonate Salt Prime Line-SW Grower Premix2 DL-Methionine (99.5%) Mineral oil Calculated composition Crude protein Crude fat Poultry ME kcal/kg n-3 Fatty acids Lysine Methionine Vitamin E, IU/kg
491
RESEARCH NOTE TABLE 3. Effects of flax-based diets and Eimeria tenella infection on weight gains, feed conversions, and lesion scores at 6 d postinoculation Start weight
Diet
End weight
Uninfected controls 0% 2% 5% 10%
Flax Flax Flax Flax
(g)
Feed conversion
Lesion score
± ± ± ±
6a 6a 5a 6a
321 332 316 326
± ± ± ±
9ab 8a 7ab 8ab
110 109 107 111
± ± ± ±
3a 3a 3a 5a
(feed/gain) 2.23 2.14 2.41 2.22
(score)
211 223 209 214
220 207 205 215
± ± ± ±
4a 4a 4a 3a
307 290 280 293
± ± ± ±
7bc 6cd 8d 6cd
86 83 75 79
± ± ± ±
4b 4b 5b 4b
2.46 2.63 2.66 2.66
3.13 3.13 3.27 3.07
0.232 0.494 0.078
0.159 0.0001 0.312
± ± ± ±
0.19a 0.16a 0.15a 0.15a
0.321 0.0001 0.597
Means ± SEM. Within columns, means with no common superscript differ significantly (P ≤ 0.05). D = diet; I = infection.
a–d 1
At 6 d postinoculation, mean weight gains of all infected groups averaged 74% of uninfected controls. Within control and infected groups, there were no significant differences in weight gain among dietary treatments (Table 3). Therefore, there were no diet × infection interactions with respect to weight gain. Feed conversion ratios of infected groups of chickens averaged 16% greater than uninfected groups (Table 3). There were no significant differences (P = 0.8231) in mean lesion scores among the infected diet groups (Table 3).
DISCUSSION Flaxseed provides a highly concentrated source (about 19%) of the n-3 fatty acid, linolenic acid. This seed has been incorporated into poultry feeds at levels up to 20% as a means of increasing the availability of n-3 fatty acids in eggs and poultry meat for human consumption (Caston et al., 1994). Levels as high as 15% have the potential to generate off-flavors and cause decreases in egg production (Aymond and Van Elswyk, 1995), and it has been shown that diets containing only 5% flaxseed are adequate for significantly increasing linolenic acid in eggs (Aymond and Van Elswyk, 1995). It was of interest, therefore, to test balanced diets containing less than 15% flaxseed to see whether they could provide protection against E. tenella infection in a manner similar to that observed in previous studies (Allen et al., 1996, 1997). Uniform growth was observed across all diet treatments until infection with E. tenella. During infection, no level of flaxmeal tested provided protection against weight gain depression, lesions, or increased feed conversion ratios. The groups that consumed the 5% flaxmeal diet underperformed to a small degree. No obvious reason for this aberration could be determined. It is hypothesized that the successes experienced by using flax oil and flaxseed supplements against E. tenella infections (Allen et al., 1996, 1997) are due to their induc-
tion of oxidative stress (Levander et al., 1993) that is detrimental to the ceca-dwelling coccidian. The oxidative stress effect is directly related to the amount of oxidizable double bonds added to the diet. It has been estimated from the calculated linolenic acid content of flaxseed (Exler and Weinrauch, 1986) that 15 and 12.5% flaxseed supplements would provide, respectively, 0.031 and 0.027 mol of double bonds/100 g feed that are available for oxidation. These diets, which contained no supplementary antioxidants, were reported to protect against cecal coccidiosis (Allen et al., 1996, 1997) and murine malaria (Levander and Ager, 1995). It is estimated that the 10% flaxmeal diet from this experiment provided only 0.022 mol of double bonds per 100 g feed. Therefore, the ineffectiveness of the current diets to protect chicks against E. tenella infection may be due to their lower levels of linolenic acid and to the amounts of linolenic acid present being well protected from potential oxidation by high concentrations of vitamin E (Table 1) and other antioxidants. In summary, the results of this experiment indicate that chickens raised on balanced diets containing up to 10% stabilized flaxmeal remain susceptible to E. tenella infection. Therefore, for flaxseed meal to be useful as an anticoccidial, it should be added at levels of 12 to 15% as a supplement to balanced diets. Such diets could be of practical use primarily as starter rations for young chicks for which E. tenella is a known problem.
ACKNOWLEDGMENTS The authors are grateful to ENRECO, Inc., Manitowoc, WI 54220, for the donation of the diets used in this study and to Certified Animal Nutritionist, Gary Boyett, Kenton, TN 38233, for providing calculated nutrient data. ARS, Beltsville employees, Ron Bilheimer, Clarence Parsons, Angela Parsons, and Beth Summers are commended for their excellent technical help.
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on June 7, 2015
E. tenellainfected 0% Flax 2% Flax 5% Flax 10% Flax Main effects (Pr > F) D1 I D×I
Gain
492
ALLEN ET AL.
REFERENCES Allen, P. C., H. Danforth, and O. A. Levander, 1994. High dietary levels of flaxseed oil and fish oil lower cecal lesion scores in broiler chickens infected with the cecal parasite Eimeria tenella. Pages 123–126 in: Proceedings of the 55th Flax Institute. The Flax Institute of the United States, Fargo, ND. Allen, P. C., H. D. Danforth, and O. A. Levander, 1996. Diets high in n-3 fatty acids reduce cecal lesion scores in chickens infected with Eimeria tenella. Poultry Sci. 75:179–185. Allen, P. C., H. D. Danforth, and O. A. Levander, 1997. Interaction of dietary flaxseed with coccidia infections in chickens. Poultry Sci. 76:822–827. Aymond, W. M., and M. E. Van Elswyk, 1995. Yolk thiobarbituric acid reactive substances and n-3 fatty acids in response to whole and ground flaxseed. Poultry Sci. 74:1388–1394. Caston, L. J., E. S. Squires, and S. Leesen, 1994. Hen performance, egg quality and sensory evaluation of eggs from SWCL hens fed dietary flax. Can. J. Anim. Sci. 74:347–353.
Johnson, J., and M. Reid, 1970. Anticoccidial drugs: Lesion scoring techniques in battery and floor pen experiments with chickens. Exp. Parasitol. 28:30–36. Exler, J., and J. L. Weihrauch, 1986. Provisional Table on the Content of Omega-3 Fatty Acids and Other Fat Components in Selected Foods. USDA, Human Nutrition Service, HNIS/ PR-103, Washington, DC. Levander, O. A., and A. L. Ager, 1995. Antimalarial effects of flaxseed and flaxseed oil. Pages 237–243 in: Flaxseed in Human Nutrition. S. C. Cunnane and L. U. Thompson, ed. AOCS Press, Champaign, IL. Levander, O. A., A. L. Ager, V. C. Morris, R. Fontela, and R. G. May, 1993. Dietary oxidant stress. Suppression of malaria by dietary oxidant stress. Pages 347–357 in: Active Oxygen, Lipid Peroxides and Antioxidants. Yagi, K., ed. CRC Press, Boca Raton, FL. SAS Institute, 1990. SAS/STAT User’s Guide, Vol. 2. SAS Institute Inc., Cary, NC. Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on June 7, 2015