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Composition and nutritive value of sewage-grown duckweed (Lemna minor L.) for rats
ANIMAL FEED SCIENCE AND TECHNOLOGY
Animal Feed Science and Technology 52 (1995) 339-343
ELSEVIER
Composition and nutritive value of sewage-grown duckweed (Lemna minor L. ) for rats P. HanczakowskP*,
B. Szymczykb, M. Wawrzy6skib
“Institute ofAnimal Production, Department ofAnimal Nutrition, 32-083 Bake, Poland blnstitute ofAnimal Production, Experimental Station Rossocha, 96-204 Kurzeszyn. Poland
Received 24 January 1994; accepted 14 September 1994
Abstract Gross composition and carotenoid and heavy metal content of sewage-grown duckweed were analysed. The essential amino acid pattern of its protein was also determined. The dry matter content in fresh duckweed when harvested ranged from 78 to 95 g per kg. Gross composition of duckweed grown at the sewage inlet and water outlet did not differ markedly but the former contained about 30% more carotenoid. The protein content of both samples exceeded 300 g per kg (dry matter basis). This protein was high in lysine but low in sulphur amino acids. The metal (zinc, copper, lead and cadmium) content was below harmful levels. The nutritive value of protein of duckweed grown at the sewage inlet, determined on rats using the Thomas-Mitchell balance method, was higher (33) than when grown at the water outlet (25 ). The true digestibility of both proteins was relatively low (60% and 5 I%, respectively). Keywords: Duckweed; Nutritive value, duckweed; Rat
1. Introduction
Duclcweed (Lemna minor L.) is one of the simplest flowering aquatic plants. Due to its rapid growth, especially in nutrient-laden ponds, it has been proposed for waste water treatment (Hillman and Culley, 1978 ). Being rich in protein and xanthophyll, duckweed can be succesfully used as a soybean substitute in poultry feeding as reported by Haustein ( 1990)) who found that addition of duckweed to layer diets significantly increased yolk pigmentation. * Corresponding author. 0377-8401195 / $09.50 0 1995 Elsevier Science B.V. All rights reserved SSDZO377-8401(94)00729-2
340
P. Hanczakowski et al. /Animal Feed Science and Technology 52 (I 995) 339-343
On the other hand, it is possible that waste-grown duckweed could be contaminated with heavy metals which could be harmful for animals. This experiment was undertaken to determine the composition and nutritive value of duckweed grown in a waste purification plant cleaning domestic waste from a small village (about 400 inhabitants and a small butchery) and sludge from a hen farm ( 10 000 hens). Approximate yields of such a pond is about 20 000 kg of fresh duckweed per ha per year.
2. Materials and methods Duckweed (Lemna minor L. ) was grown in a purification plant constructed by Lemna Co. (Minnesota, USA) in the Rossocha Experimental Station of the Institute of Animal Production (Central Poland). This purification plant comprised a sedimentator of solid particles, aeration pumps and an earthen pond of 3800 m* water surface area. Duckweed was manually harvested at the sewage inlet (Sample I) and at the outlet of purified water (Sample II). Both samples were dried under infra-red lamps at 55 ‘C and milled. There were three harvests: in July and September 1992 and in May 1993. The presented results are the means of these three harvests. The gross composition of dried duckweed and the content of some metals (zinc, copper, lead and cadmium) were analysed according to methods of the Association of Official Analytical Chemists ( 1990). The amino acid composition of proteins was determined using a Carlo Erba automatic analyser. The carotenoid content was determined according to Gstirner ( 1965 ) . True digestibility and biological value of proteins were assessed on rats using the Thomas-Mitchell balance method as modified by Eggum ( 1973). Net protein utilization (NPU ) was calculated on the basis of true digestibility and biological value [NPU= (TDxBV)/lOO]. The analysed duckweed was the only source of protein in the diets. Two groups of rats, one for each sample of duckweed, were used. Six male 40-day-old albino rats, each weighing about 90 g, were used in each experimental group. The adaptation period lasted for 4 days and the balance period for 5 days. Each rat received 10 g of fresh feed (9.2-9.4 g of dry matter), i.e. 1 g of protein per day. Diets also contained (g per kg): sucrose 200; soybean oil 60; cellulose (Whatman CF 11) 40; mineral 40 and vitamin 20 mixtures, the latter two according to Eggum ( 1973 ) . Wheat starch was used to complete the diet composition. 3. Results and discussion The gross composition of both samples did not differ markedly (Table 1 ), although the crude protein content of Sample I was about 30% higher than that of Sample II. Similar differences were found for zinc and lead content. Differences in copper and cadmium contents were even larger (about 50%).
P. Hanczakowski et al. /Animal Feed Science and Technology 52 (1995) 339-343 Table 1 Composition
341
of dried duckweed
Component
Dry matter (g per kg) Crude protein (gperkgDM) Ether extract (gperkgDM) Crude libre (gperkgDM) Ash (gperkgDM) Carotene (mgperkgDM) Xantophyll (mgperkgDM) Carotenoids (mgperkgDM) Zinc (mg per kg DM) Copper (mg per kg DM) Lead (mg per kg DM) Cadmium (mgperkgDM)
Duckweed
Lucernea
Sample I
Sample II
941
971
370
353
215
44
44
32
94 176
89 185
260 115
150
120
359
261
554 98 4.7 1.6
416 -I5 3.1 1.2
0.09
0.06
Toxic concentrationb
330 34 15
Recommended standard for laying hens’
50-75 5-15 30 1
“Nehring et al. ( 1970). bWeinrich et al. ( 1992). “Blair et al. (1983). DM, dry matter.
According to Porath et al. ( 1979)) dried duckweed may contain up to 40% of protein and this content greatly depends on the amount of nutrients in the water (Muztar et al., 1976). The protein content of the examined duckweed approached this limit. It was much higher than the normal protein content of dried green crops such as grass, clover (Hakansson and Malmlof, 1984) or lucerne (Nehring et al., 1970). This high protein and carotenoid content was probably due to the anatomical structure of this plant and the high contribution of leaves to its total biomass. Because Samples I and II were harvested and dried simultaneously, the higher content of all carotenoids in Sample I was probably due to the stimulating effect of some substance, probably nitrogen, present in sewage. The beneficial effect of nitrogen fertilization on carotene production in plants was found also by Mlodkowska and Mlodkowski ( 1975 ) . The zinc content of both samples was higher than that recommended for hens (Blair et al., 1983) but that of copper was low. According to McDonald et al. ( 1988), the normal content of these two elements in feed is 15-50 and 4-8 mg per kg, respectively. According to Weinrich et al. ( 1992), the contents of cadmium and lead in both samples were also much below their toxic levels. Differences in amino acid composition of proteins in both samples were negli-
342
P. Hanczakowski et al. /Animal Feed Science and Technology 52 (1995) 339-343
gible (Table 2 ). Both samples were high in lysine but low in sulphur amino acids. The composition was similar to that of other forage crops, such as luceme (Nehring et al., 1970). Dried duckweed can supply farm animals with sufficient amounts of all required amino acids except methionine. A shortage of isoleucine in the case of layers and of phenylalanine in the case of chicks may also occur. Both the true digestibility and biological value of proteins in Sample I were higher than those in Sample II but these differences were not statistically significant (Table 3 ) . The nutritive value of protein in both samples was relatively low, comparable to that of bone-meat meal (NPU= 30), but lower than that of soyTable 2 Amino acid composition and pig requirements Amino acid
Asp Thr Ser Glu Pro Gly Ala Val Ile Leu Tyr Phe His LYS CYS Met
of duckweed and luceme proteins (g per 16 g N) in comparison with poultry
Duckweed
Lucernea
Sample I
Sample II
1.9 3.9 3.4 8.9 4.3 4.4 5.3 4.8 3.9 6.3 2.6 4.8 2.6 5.1 0.8 1.4
8.1 4.3 3.8 7.5 3.8 4.9 5.9 5.0 3.8 6.7 2.6 3.8 2.8 5.0 0.9 1.4
Requirement Chicksb
laying hensc
Pigsd
4.2
3.8
3.7
3.1
5.4 4.3 1.3 2.3 4.5 2.1 5.1 1.2 1.4
3.4 3.3 5.6
4.3 5.0 7.5 6.6”
3.1 2.9 3.9 4.2’
2.0 5.0 3.6f
1.4 0.8 2.6’
5.6 1.4 4.1 3.6f
“Nehring et al. ( 1970). bNational Research Council ( 1984). ‘Blairet al. (1983). dNational Research Council ( 1988). “Tyr+Phe. fCys+Met. Table 3 Nutritive value of duckweed protein Duckweed
True digestibility
Biological value
Net protein utilization
Sample I Sample II Standard error
60 51 1.724
55 49 3.579
33 25 2.166
Differences are not statistically significant at P> 0.05.
P. Hanczakowski et al. /Animal Feed Science and Technology 52 (1995) 339-343
343
bean meal (NPU=49) found earlier in this laboratory (Carlsson and Hanczakowski, 1985 ) . This low value was due to the low digestibility of duckweed protein because its retention (biological value) was relatively high, similar to that of soya (55) and fish meal (54) found earlier in the cited experiment. The slightly higher nutritive value of protein of duckweed grown at the sewage inlet could be due to the presence of some nutritive substance in the sludge. On the basis of this experiment it can be stated that the sewage-grown duckweed could be a source of some nutrients, i.e. protein and carotenoids. Regarding its fibre and carotenoid content, duckweed could probably be used in the feeding of laying hens and cattle.
Acknowledgement
The authors are grateful to the Hydro Ltd., Kielce, Poland, for financial support.
References Association of Offtcial Analytical Chemists, 1990. Official Methods of Analysis, Vol. 1, 15th edn. Arlington, VA, 684 pp. Blair, R., Daghir, N.J., Morimoto H., Peter, V. and Taylor, T.G., 1983. International nutrition standards for poultry. Nutr. Abstr. Rev. Ser. B, 53: 669-7 13. Carlsson, R. and Hanczakowski, P., 1985. The nutritive value of mixtures of white leaf protein and food proteins. J. Sci. Food Agric., 36: 946-950. Eggum, B.O., 1973. A study of certain factors influencing protein utilization in rats and pigs. Beret. Forsoegslab. Statens Husdyrbrugsudvalg, 406: 17-30. Gstimer, F., 1965. Chemisch-physykalische Vitaminbestimmungsmethoden. F. Enke, Stuttgart, 45 PP. Hakansson, J. and Malmlof, K., 1984. The nutritive value of grass-, clover-, and pea crop meals for growing pigs. Swed. J. Agric. Res., 14: 45-51. Haustein, A., 1990. Duckweed, a useful strategy for feeding chickens: performance of layers fed with sewage-grown Lemnaceae species. Poult. Sci., 69: 1835- 1844. Hillman, W.C. and Culley, Jr., D., 1978. The uses of duckweed. Am. Sci., 66: 442-45 1. McDonald, P., Edwards, R.A. and Greenhalgh, J.F., 1988. Animal Nutrition, 4th edn. Longman, Harlow, 543 pp. Mlodkowska, I. and Mlodkowski, M., 1975. The effect of nitrates on conversion of carotene in chickens (in Polish). Acta Agrar. Silvestria Ser. Zootech., 15: 75-8 1. Muztar, A.J., Slinger, S.J. and Burton, J.H., 1976. Nutritive value of aquatic plants for chicks. Poult. Sci., 55: 1917-1921. National Research Council, 1984. Nutrient Requirements of Poultry, No. 1. National Academy of Science, Washington, DC. National Research Council, 1988. Nutrient Requirements of Swine, No. 2. National Academy of Science, Washington, DC. Nehring, K., Beyer, M. and Hoffmann, B., 1970. Futtermitteltabellenwerk. Deutscher Landwirtschaftsverlag, Berlin, 459 pp. Porath, D., Hepher, B. and Koton, A., 1979. Duckweed as an aquatic crop: evaluation of clones for aquaculture. Aquat. Bot., 7: 273-278. Weinrich, O., Koch, V., Knippel, J. and Eberhardt, W., 1992. Futtermittelrechtliche Vorschriften, Agrimedia, A. Strothe, Frankfurt, 269 pp.
Animal Feed Science and Technology 52 (1995) 339-343
ELSEVIER
Composition and nutritive value of sewage-grown duckweed (Lemna minor L. ) for rats P. HanczakowskP*,
B. Szymczykb, M. Wawrzy6skib
“Institute ofAnimal Production, Department ofAnimal Nutrition, 32-083 Bake, Poland blnstitute ofAnimal Production, Experimental Station Rossocha, 96-204 Kurzeszyn. Poland
Received 24 January 1994; accepted 14 September 1994
Abstract Gross composition and carotenoid and heavy metal content of sewage-grown duckweed were analysed. The essential amino acid pattern of its protein was also determined. The dry matter content in fresh duckweed when harvested ranged from 78 to 95 g per kg. Gross composition of duckweed grown at the sewage inlet and water outlet did not differ markedly but the former contained about 30% more carotenoid. The protein content of both samples exceeded 300 g per kg (dry matter basis). This protein was high in lysine but low in sulphur amino acids. The metal (zinc, copper, lead and cadmium) content was below harmful levels. The nutritive value of protein of duckweed grown at the sewage inlet, determined on rats using the Thomas-Mitchell balance method, was higher (33) than when grown at the water outlet (25 ). The true digestibility of both proteins was relatively low (60% and 5 I%, respectively). Keywords: Duckweed; Nutritive value, duckweed; Rat
1. Introduction
Duclcweed (Lemna minor L.) is one of the simplest flowering aquatic plants. Due to its rapid growth, especially in nutrient-laden ponds, it has been proposed for waste water treatment (Hillman and Culley, 1978 ). Being rich in protein and xanthophyll, duckweed can be succesfully used as a soybean substitute in poultry feeding as reported by Haustein ( 1990)) who found that addition of duckweed to layer diets significantly increased yolk pigmentation. * Corresponding author. 0377-8401195 / $09.50 0 1995 Elsevier Science B.V. All rights reserved SSDZO377-8401(94)00729-2
340
P. Hanczakowski et al. /Animal Feed Science and Technology 52 (I 995) 339-343
On the other hand, it is possible that waste-grown duckweed could be contaminated with heavy metals which could be harmful for animals. This experiment was undertaken to determine the composition and nutritive value of duckweed grown in a waste purification plant cleaning domestic waste from a small village (about 400 inhabitants and a small butchery) and sludge from a hen farm ( 10 000 hens). Approximate yields of such a pond is about 20 000 kg of fresh duckweed per ha per year.
2. Materials and methods Duckweed (Lemna minor L. ) was grown in a purification plant constructed by Lemna Co. (Minnesota, USA) in the Rossocha Experimental Station of the Institute of Animal Production (Central Poland). This purification plant comprised a sedimentator of solid particles, aeration pumps and an earthen pond of 3800 m* water surface area. Duckweed was manually harvested at the sewage inlet (Sample I) and at the outlet of purified water (Sample II). Both samples were dried under infra-red lamps at 55 ‘C and milled. There were three harvests: in July and September 1992 and in May 1993. The presented results are the means of these three harvests. The gross composition of dried duckweed and the content of some metals (zinc, copper, lead and cadmium) were analysed according to methods of the Association of Official Analytical Chemists ( 1990). The amino acid composition of proteins was determined using a Carlo Erba automatic analyser. The carotenoid content was determined according to Gstirner ( 1965 ) . True digestibility and biological value of proteins were assessed on rats using the Thomas-Mitchell balance method as modified by Eggum ( 1973). Net protein utilization (NPU ) was calculated on the basis of true digestibility and biological value [NPU= (TDxBV)/lOO]. The analysed duckweed was the only source of protein in the diets. Two groups of rats, one for each sample of duckweed, were used. Six male 40-day-old albino rats, each weighing about 90 g, were used in each experimental group. The adaptation period lasted for 4 days and the balance period for 5 days. Each rat received 10 g of fresh feed (9.2-9.4 g of dry matter), i.e. 1 g of protein per day. Diets also contained (g per kg): sucrose 200; soybean oil 60; cellulose (Whatman CF 11) 40; mineral 40 and vitamin 20 mixtures, the latter two according to Eggum ( 1973 ) . Wheat starch was used to complete the diet composition. 3. Results and discussion The gross composition of both samples did not differ markedly (Table 1 ), although the crude protein content of Sample I was about 30% higher than that of Sample II. Similar differences were found for zinc and lead content. Differences in copper and cadmium contents were even larger (about 50%).
P. Hanczakowski et al. /Animal Feed Science and Technology 52 (1995) 339-343 Table 1 Composition
341
of dried duckweed
Component
Dry matter (g per kg) Crude protein (gperkgDM) Ether extract (gperkgDM) Crude libre (gperkgDM) Ash (gperkgDM) Carotene (mgperkgDM) Xantophyll (mgperkgDM) Carotenoids (mgperkgDM) Zinc (mg per kg DM) Copper (mg per kg DM) Lead (mg per kg DM) Cadmium (mgperkgDM)
Duckweed
Lucernea
Sample I
Sample II
941
971
370
353
215
44
44
32
94 176
89 185
260 115
150
120
359
261
554 98 4.7 1.6
416 -I5 3.1 1.2
0.09
0.06
Toxic concentrationb
330 34 15
Recommended standard for laying hens’
50-75 5-15 30 1
“Nehring et al. ( 1970). bWeinrich et al. ( 1992). “Blair et al. (1983). DM, dry matter.
According to Porath et al. ( 1979)) dried duckweed may contain up to 40% of protein and this content greatly depends on the amount of nutrients in the water (Muztar et al., 1976). The protein content of the examined duckweed approached this limit. It was much higher than the normal protein content of dried green crops such as grass, clover (Hakansson and Malmlof, 1984) or lucerne (Nehring et al., 1970). This high protein and carotenoid content was probably due to the anatomical structure of this plant and the high contribution of leaves to its total biomass. Because Samples I and II were harvested and dried simultaneously, the higher content of all carotenoids in Sample I was probably due to the stimulating effect of some substance, probably nitrogen, present in sewage. The beneficial effect of nitrogen fertilization on carotene production in plants was found also by Mlodkowska and Mlodkowski ( 1975 ) . The zinc content of both samples was higher than that recommended for hens (Blair et al., 1983) but that of copper was low. According to McDonald et al. ( 1988), the normal content of these two elements in feed is 15-50 and 4-8 mg per kg, respectively. According to Weinrich et al. ( 1992), the contents of cadmium and lead in both samples were also much below their toxic levels. Differences in amino acid composition of proteins in both samples were negli-
342
P. Hanczakowski et al. /Animal Feed Science and Technology 52 (1995) 339-343
gible (Table 2 ). Both samples were high in lysine but low in sulphur amino acids. The composition was similar to that of other forage crops, such as luceme (Nehring et al., 1970). Dried duckweed can supply farm animals with sufficient amounts of all required amino acids except methionine. A shortage of isoleucine in the case of layers and of phenylalanine in the case of chicks may also occur. Both the true digestibility and biological value of proteins in Sample I were higher than those in Sample II but these differences were not statistically significant (Table 3 ) . The nutritive value of protein in both samples was relatively low, comparable to that of bone-meat meal (NPU= 30), but lower than that of soyTable 2 Amino acid composition and pig requirements Amino acid
Asp Thr Ser Glu Pro Gly Ala Val Ile Leu Tyr Phe His LYS CYS Met
of duckweed and luceme proteins (g per 16 g N) in comparison with poultry
Duckweed
Lucernea
Sample I
Sample II
1.9 3.9 3.4 8.9 4.3 4.4 5.3 4.8 3.9 6.3 2.6 4.8 2.6 5.1 0.8 1.4
8.1 4.3 3.8 7.5 3.8 4.9 5.9 5.0 3.8 6.7 2.6 3.8 2.8 5.0 0.9 1.4
Requirement Chicksb
laying hensc
Pigsd
4.2
3.8
3.7
3.1
5.4 4.3 1.3 2.3 4.5 2.1 5.1 1.2 1.4
3.4 3.3 5.6
4.3 5.0 7.5 6.6”
3.1 2.9 3.9 4.2’
2.0 5.0 3.6f
1.4 0.8 2.6’
5.6 1.4 4.1 3.6f
“Nehring et al. ( 1970). bNational Research Council ( 1984). ‘Blairet al. (1983). dNational Research Council ( 1988). “Tyr+Phe. fCys+Met. Table 3 Nutritive value of duckweed protein Duckweed
True digestibility
Biological value
Net protein utilization
Sample I Sample II Standard error
60 51 1.724
55 49 3.579
33 25 2.166
Differences are not statistically significant at P> 0.05.
P. Hanczakowski et al. /Animal Feed Science and Technology 52 (1995) 339-343
343
bean meal (NPU=49) found earlier in this laboratory (Carlsson and Hanczakowski, 1985 ) . This low value was due to the low digestibility of duckweed protein because its retention (biological value) was relatively high, similar to that of soya (55) and fish meal (54) found earlier in the cited experiment. The slightly higher nutritive value of protein of duckweed grown at the sewage inlet could be due to the presence of some nutritive substance in the sludge. On the basis of this experiment it can be stated that the sewage-grown duckweed could be a source of some nutrients, i.e. protein and carotenoids. Regarding its fibre and carotenoid content, duckweed could probably be used in the feeding of laying hens and cattle.
Acknowledgement
The authors are grateful to the Hydro Ltd., Kielce, Poland, for financial support.
References Association of Offtcial Analytical Chemists, 1990. Official Methods of Analysis, Vol. 1, 15th edn. Arlington, VA, 684 pp. Blair, R., Daghir, N.J., Morimoto H., Peter, V. and Taylor, T.G., 1983. International nutrition standards for poultry. Nutr. Abstr. Rev. Ser. B, 53: 669-7 13. Carlsson, R. and Hanczakowski, P., 1985. The nutritive value of mixtures of white leaf protein and food proteins. J. Sci. Food Agric., 36: 946-950. Eggum, B.O., 1973. A study of certain factors influencing protein utilization in rats and pigs. Beret. Forsoegslab. Statens Husdyrbrugsudvalg, 406: 17-30. Gstimer, F., 1965. Chemisch-physykalische Vitaminbestimmungsmethoden. F. Enke, Stuttgart, 45 PP. Hakansson, J. and Malmlof, K., 1984. The nutritive value of grass-, clover-, and pea crop meals for growing pigs. Swed. J. Agric. Res., 14: 45-51. Haustein, A., 1990. Duckweed, a useful strategy for feeding chickens: performance of layers fed with sewage-grown Lemnaceae species. Poult. Sci., 69: 1835- 1844. Hillman, W.C. and Culley, Jr., D., 1978. The uses of duckweed. Am. Sci., 66: 442-45 1. McDonald, P., Edwards, R.A. and Greenhalgh, J.F., 1988. Animal Nutrition, 4th edn. Longman, Harlow, 543 pp. Mlodkowska, I. and Mlodkowski, M., 1975. The effect of nitrates on conversion of carotene in chickens (in Polish). Acta Agrar. Silvestria Ser. Zootech., 15: 75-8 1. Muztar, A.J., Slinger, S.J. and Burton, J.H., 1976. Nutritive value of aquatic plants for chicks. Poult. Sci., 55: 1917-1921. National Research Council, 1984. Nutrient Requirements of Poultry, No. 1. National Academy of Science, Washington, DC. National Research Council, 1988. Nutrient Requirements of Swine, No. 2. National Academy of Science, Washington, DC. Nehring, K., Beyer, M. and Hoffmann, B., 1970. Futtermitteltabellenwerk. Deutscher Landwirtschaftsverlag, Berlin, 459 pp. Porath, D., Hepher, B. and Koton, A., 1979. Duckweed as an aquatic crop: evaluation of clones for aquaculture. Aquat. Bot., 7: 273-278. Weinrich, O., Koch, V., Knippel, J. and Eberhardt, W., 1992. Futtermittelrechtliche Vorschriften, Agrimedia, A. Strothe, Frankfurt, 269 pp.