Cyanogenic poisoning by spontaneous ingestion of star grass (Cynodon nlemfuensis var. nlemfuensis cv. ‘Florico’) in cattle

Intoxicação cianogênica pela ingestão espontânea de grama estrela (Cynodon nlemfuensis var. nlemfuensis cv. ‘Florico’) em bovinos

Franciéli A. Molossi Daiane Ogliari Raissa M. Morais Nathalia S. Wicpolt Edgar Gheller Luciano Weber Aldo Gava About the authors

ABSTRACT:

This study reports the epidemiological data and the clinical-pathological condition of five outbreaks of cyanogenic poisoning in cattle spontaneously ingesting star grass (Cynodon nlemfuensis Vanderyst var. nlemfuensis cv. ‘Florico’). In all outbreaks, the areas where the plant was previously fertilized with high concentrations of nitrogen and the properties adopted the silvipastoral system. The first clinical signs appeared between 10 and 15 minutes after the first introduction of cattle and were characterized by muscular tremors, dyspnea, moderate tympanism, staggering gait, forced breathing with open mouth, sternal recumbency followed by death after 15 to 30 minutes and/or recovery in a few hours after the signs started. In total, 43 cows have become ill and 18 died. Two necropsies were performed and no significant changes were found except for the presence of the plant near the esophageal sphincter region. No histological lesions were seen through microscopy. Green leaves of the star grass were collected from all properties where the outbreaks occurred and the test of the picro-sodium paper was performed, revealing red-brick coloration in 20 minutes after maceration of the leaves.

INDEX TERMS:
Cyanogenic poisoning; star grass; Cynodon nlemfuensis; hydrocyanic acid; star grass cv. Florico; cattle; toxic plants; toxicoses

RESUMO:

Descrevem-se os dados epidemiológicos e quadro clínico-patológico de cinco surtos de intoxicação cianogênica em bovinos que ingeriram espontaneamente grama estrela (Cynodon nlemfuensis Vanderyst var. nlemfuensis cv. ‘Florico’). Em todos os surtos, as áreas onde a planta se encontrava haviam sido previamente adubadas com altas concentrações de nitrogênio e as propriedades adotavam o sistema silvipastoril com Eucaliptus sp. Os primeiros sinais clínicos surgiram entre 10 e 15 minutos após a primeira introdução dos bovinos e caracterizou-se por tremores musculares, dispneia, timpanismo moderado, andar cambaleante, respiração forçada com a boca aberta, decúbito esternal seguido de morte após 15 a 30 minutos e/ou, recuperação em poucas horas após início dos sinais. No total, adoeceram 43 vacas e destas 18 morreram. Duas necropsias foram realizadas e não foram encontradas alterações significativas, exceto a presença da planta próxima a região do esfíncter esofágico. Através da microscopia não foram visualizadas lesões histológicas. Folhas verdes da grama estrela foram coletadas de todas as propriedades onde os surtos ocorreram e realizadas o teste do papel picro-sódico, o qual revelou coloração vermelho-tijolo em 20 minutos após maceração das folhas.

TERMOS DE INDEXAÇÃO:
Intoxicação cianogênica; grama estrela; Cynodon nlemfuensis; bovinos; ácido cianídrico; grama estrela cv. Florico; plantas tóxicas; toxicoses

Introduction

Grasses of the genus Cynodon, belonging to the Poaceae family, came from Africa and were introduced in North America in the mid-eighteenth century (Harlan 1970Harlan J.R. 1970. Cynodon species and their value for grazing and hay. Herbage Abstracts 40:233-238.). For more than 50 years, many breeding works have been carried out mainly at the universities of Georgia and Florida in the United States in order to better use the forage potential of this genus and to adapt it to the subtropical conditions of Southeastern United States. In Brazil, it is believed that this grass was introduced by private initiative to evaluate its behavior under Brazilian conditions; however, there are no records of how and where the genus Cynodon was introduced (Vilela & Alvim 1998Vilela D. & Alvim M.J. 1998. Manejo de pastagens do gênero Cynodon: introdução, caracterização e evolução do uso no Brasil, p.23-54. In: Peixoto A.M., Moura J.C. & Faria V.P. (Eds), XV Simpósio Sobre Manejo da Pastagem. FEALQ, Piracicaba.). There are also many doubts about the recognition of the species used.

The genus Cynodon is divided into two groups, the Bermuda grass group (Cynodon dactylon (L) Pers.), in which several hybrids are available, such as Coastal, Alicia, Callie, Tifton 44, Tifton 68, Tifton 78, Tifton 85, Coastcroos and more recently the Florakirk. In the star grass group (Cynodon nlemfuensis Vanderyst, Cynodon aethiopicus Clayton and Harlan), the most used cultivars are McCaleb, Ona, Florico and Florona (Vilela & Alvim 1998Vilela D. & Alvim M.J. 1998. Manejo de pastagens do gênero Cynodon: introdução, caracterização e evolução do uso no Brasil, p.23-54. In: Peixoto A.M., Moura J.C. & Faria V.P. (Eds), XV Simpósio Sobre Manejo da Pastagem. FEALQ, Piracicaba.). Florico (Cynodon nlemfuensis Vanderyst var.nlemfuensis cv. ‘Florico’) and Florona cultivars (Cynodon nlemfuensis Vanderyst var. nlemfuensis cv. ‘Florona’) are the most recent commercial star grass launches by the University of Florida in the USA (Mislevy et al. 1989aMislevy P., Brown W.F., Caro-Costas R., Vicente-Chandler J., Dunavin L.S., Hall D.W., Kalmbacher R.S., Overman A.J., Ruelke O.C., Sonoda R.M., Sotomayor-Rios A., Stanley Jr R.L. & Williams M.J. 1989a. ‘Florico’ stargrass. Institute of Food and Agricultural Sciences, University of Florida, Florida, p.15., 1989bMislevy P., Brown W.F., Dunavin L.S., Hall D.W., Kalmbacher R.S., Overman A.J., Ruelke O.C., Sonoda R.M., Stanley jr R.L. & Williams M.J. 1989b. Florona stargrass. Institute of Food and Agricultural Sciences, University of Florida, Florida, p.13.). Florona cultivar was collected at the Experimental Station of the University of Florida in 1974 and submitted to evaluation trials from 1975 (Mislevy et al. 1989bMislevy P., Brown W.F., Dunavin L.S., Hall D.W., Kalmbacher R.S., Overman A.J., Ruelke O.C., Sonoda R.M., Stanley jr R.L. & Williams M.J. 1989b. Florona stargrass. Institute of Food and Agricultural Sciences, University of Florida, Florida, p.13.). Florico cultivar, native to Kenya, was introduced in Puerto Rico in 1957 and later brought to Florida in 1972 (Mislevy et al. 1993aMislevy P., Brown W.F., Caro-Costas R., Vicente-Chandler J., Dunavin L.S., Hall D.W., Kalmbacher R.S., Overman A.J., Ruelke O.C., Sonoda R.M., Sotomayor-Rios A., Stanley Junior R.L. & Williams M.J. 1993a. Registration of Florico stargrass. Crop Science 33(2):358-359. <http://dx.doi.org/10.2135/cropsci1993.0011183X003300020044x>
https://doi.org/10.2135/cropsci1993.0011...
). Both cultivars were recorded in 1993 by Mislevy et al. (1993aMislevy P., Brown W.F., Caro-Costas R., Vicente-Chandler J., Dunavin L.S., Hall D.W., Kalmbacher R.S., Overman A.J., Ruelke O.C., Sonoda R.M., Sotomayor-Rios A., Stanley Junior R.L. & Williams M.J. 1993a. Registration of Florico stargrass. Crop Science 33(2):358-359. <http://dx.doi.org/10.2135/cropsci1993.0011183X003300020044x>
https://doi.org/10.2135/cropsci1993.0011...
, 1993b)Mislevy P., Brown W.F., Dunavin L.S., Hall D.W., Kalmbacher R.S., Overman A.J., Ruelke O.C., Sonoda R.M., Stanley jr R.L. & Williams M.J. 1993b. Registration of Florona stargrass. Crop Science 33(2):359-360. <http://dx.doi.org/10.2135/cropsci1993.0011183X003300020045x>
https://doi.org/10.2135/cropsci1993.0011...
. Florico cultivar can be distinguished from other star grasses of the nlemfuensis variety by its hairiness and purplish-green color (Mislevy et al. 1989aMislevy P., Brown W.F., Caro-Costas R., Vicente-Chandler J., Dunavin L.S., Hall D.W., Kalmbacher R.S., Overman A.J., Ruelke O.C., Sonoda R.M., Sotomayor-Rios A., Stanley Jr R.L. & Williams M.J. 1989a. ‘Florico’ stargrass. Institute of Food and Agricultural Sciences, University of Florida, Florida, p.15.). It presents high dry mass production and good response when it receives high levels of fertilization, but it has great potential for accumulation of cyanogenic glycosides, especially under high Nitrogen doses (N), especially during the early stages of plant development. In 16 years of testing in Ona, Florida, hydrocyanic acid (HCN) poisoning in cattle grazing in Florico grass (Mislevy et al. 1993aMislevy P., Brown W.F., Caro-Costas R., Vicente-Chandler J., Dunavin L.S., Hall D.W., Kalmbacher R.S., Overman A.J., Ruelke O.C., Sonoda R.M., Sotomayor-Rios A., Stanley Junior R.L. & Williams M.J. 1993a. Registration of Florico stargrass. Crop Science 33(2):358-359. <http://dx.doi.org/10.2135/cropsci1993.0011183X003300020044x>
https://doi.org/10.2135/cropsci1993.0011...
) was not observed. In Brazil, the presence of HCN in Florico grass was verified as a function of the age of grass cut, but the HCN dose did not exceed 109.01mg/kg (Castro 1998Castro F.G.F. 1998. Efeito da idade de corte sobre a produção, composição química bromatológica, digestibilidade in vitro da massa seca e da matéria orgânica e conteúdo de ácido cianídrico de Cynodon nlemfuënsis Vanderyst var. nlemfuënsis cv. ‘Florico’. Master’s Thesis, Universidade de São Paulo, São Paulo. 150p.). In Santa Catarina, cattle breeding in a silvopastoral system recommended by Garcia et al. (2013)Garcia R., Tonucci R.G. & Bernardino F.S. 2013. Sistema silvipastoril: uma integração árvore, pasto, animal, p.219-234. In: Reis R.A., Bernardes T.F. & Siqueira G.R. (Eds), Forragicultura ciência, tecnologia e gestão dos recursos forrageiros. Funep, Jaboticabal. have been developed and star grass is one of the grasses used. The use of this system seems to favor the accumulation of hydrocyanic acid in the plant similar to what occurs with Sorghum spp. described by Vetter & Haraszti (1977)Vetter J. & Haraszti E. 1977. Changes in the hydrogen cyanide content of Sudan grass (Sorghum sudanense) and broomcorn (Sorghum bicolor var. technicum) during the growing season. Acta Agron. Sci. Hung. 26:15-22..

In South Africa, other star grasses (C. nlemfuensis Vanderyst var. robustus, C. aethiopicus Clayton and Harlan) were also identified as cyanogenic (Kellerman et al. 1988Kellerman T.S., Coetzer J.A.W. & Naudé T.W. 1988. Haemopoietic system, p.193-213. In: Ibid. (Eds), Plant poisonings and mycotoxicoses of livestock in southern africa. Oxford University Press, Cape Town.). Most cyanogenic plants are harmless due to the low concentration of glycosides and low palatability. However, toxic grasses that are widely cultivated are highlighted due to their good acceptance by animals (Youssef & Maxie 2004Youssef S. & Maxie M.G. 2004. Nervous system, p.347-348. In: Jubb K.V.F., Kennedy P.C. & Palmer N. (Eds), Pathology of Domestic Animals. Vol.3. 5th ed. Academic Press, London.).

In Brazil, several other cyanogenic plants of animal interest have been described, such as Cnidoscolus phyllacanthus (Oliveira et al. 2008Oliveira D.M., Pimentel L.A., Araújo J.A.S., Rosane M.T.M., Dantas A.F.M. & Riet-Correa F. 2008. Intoxicação por Cnidoscolus phyllacanthus (Euphorbiaceae) em caprinos. Pesq. Vet. Bras. 28(1):36-42. <http://dx.doi.org/10.1590/S0100-736X2008000100006>
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), Manihot glaziovii (Tokarnia et al. 1994aTokarnia C.H., Döbereiner J. & Peixoto P.V. 1994a. Aspectos clínicos patológicos complementares da intoxicação por algumas plantas tóxicas brasileiras. Pesq. Vet. Bras. 14(4):111-122.) M. glaziovii Muell. Arg. (Amorim et al. 2005Amorim S.L., Medeiros R.M.T. & Riet-Correa F. 2005. Intoxicação experimental por Manihot glaziovii (Euphorbiaceae) em caprinos. Pesq. Vet. Bras. 25(3):179-187. <http://dx.doi.org/10.1590/S0100-736X2005000300009>), Manihot piauhyensis (Canella et al. 1968Canella C.F.C., Dobereiner J. & Tokarnia C.H. 1968. Intoxicação experimental pela maniçoba (Manihot glaziovii Muell. Arg.) em bovinos. Pesq. Agropec. Bras. 3:347-350.), Sorghum sudanense (Juffo et al. 2012Juffo G.D., Pavarini S.P., Wouters F., Oliveira L.G.S., Antoniassi N.A.B., Cruz C.E.F. & Driemeier D. 2012. Intoxicação espontânea por Sorghum sudanense em bovinos leiteiros no Rio Grande do Sul. Pesq. Vet. Bras. 32(3):217-220. <http://dx.doi.org/10.1590/S0100-736X2012000300006>
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), Sorghum halepense (Nobrega Junior et al. 2006Nóbrega Junior J.E., Riet-Correa F., Medeiros R.M.T. & Dantas A.F.M. 2006. Intoxicação por Sorghum halepense (Poaceae) em bovinos no semi-árido. Pesq. Vet. Bras. 26(4):201-204. <http://dx.doi.org/10.1590/S0100-736X2006000400003>
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), Passiflora foetida (Carvalho et al. 2011Carvalho F.K.L., Medeiros R.M.T., Araujo J.A.S. & Riet-Correa F. 2011. Intoxicação experimental por Passiflora foetida (Passifloraceae) em caprinos. Pesq. Vet. Bras. 31(6):477-481. <http://dx.doi.org/10.1590/S0100-736X2011000600003>
https://doi.org/10.1590/S0100-736X201100...
), Piptadenia macrocarpa (Tokarnia et al. 1994bTokarnia C.H., Peixoto P.V. & Döbereiner J. 1994b. Intoxicação experimental por Piptadenia macrocarpa (Leg. Mimosoideae) em bovinos. Pesq. Vet. Bras. 14(2/3):57-63.), Piptadenia viridiflora (Tokarnia et al. 1999Tokarnia C.H., Brito M.F., Barbosa J.D., Peixoto P.V. & Döbereiner J. 2012. Plantas cianogênicas, p.443-459. In: Ibid. (Eds), Plantas Tóxicas do Brasil para Animais de Produção. 2ª ed. Editora Helianthus, Rio de Janeiro.), Prunus sphaerocarpa (Saad & Camargo 1967Saad A.D. & Camargo W.V.A. 1967. Intoxicação cianídrica em animais domésticos. Arqs Inst. Biológico, São Paulo, 33(10):211-220.), Prunus sellowii (Gava et al. 1992Gava A., Stolf L., Neves D.S., Stolf O., Varaschim M.S. & Ferreira E.M.M. 1992. Intoxicação experimental por Prunus sellowii (Rosaceae) em bovinos. Pesq. Vet. Bras. 12:1-4.) and Tifton 68 (Gava et al. 1997Gava A., Pilati C., Cristani J., Simões J. & Simões L. 1997. Intoxicação cianogênica em bovinos alimentados com Tifton (Cynodon sp.). Anais VIII Ciclo de Atualização em Medicina Veterinária (CAMEV), Lages, SC, p.119., Galindo et al. 2017Galindo C.M., Hemckmeier D., Biondo N., Parizotto L.H., Ogliari D. & Gava A. 2017. Intoxicação espontânea e experimental por tifton 68 (Cynodon nlemfuensis Vanderyst) em bovinos. Pesq. Vet. Bras. 37(5):441-446. <http://dx.doi.org/10.1590/s0100-736x2017000500003>
https://doi.org/10.1590/s0100-736x201700...
).

The toxic principle of cyanogenic plants is the presence of cyanogenic glycosides, which through the action of intracellular plant enzymes and ruminal digestion are converted into hydrocyanic acid (HCN), one of the most known toxic compounds (Egekeze & Oehme 1980Egekeze J.O. & Oehme F.W. 1980. Cyanides and their toxicity: a literature review. Vet. Q. 2(2):104-114. <http://dx.doi.org/10.1080/01652176.1980.9693766> <PMid:22039904>
https://doi.org/10.1080/01652176.1980.96...
). HCN reversibly binds to the cytochrome c oxidase enzyme (CcOX) and disrupts oxygen transfer from red blood cells to somatic cells (Hibbs 1979Hibbs C.M. 1979. Cyanide and nitrate toxicosis of cattle. Vet. Hum. Toxicol. 21(6):401-403. <PMid:532080>, Way 1984Way J.L. 1984. Cyanide intoxication and its mechanism of antagonism. Annu. Rev. Pharmacol. Toxicol. 24(1):451-464. <http://dx.doi.org/10.1146/annurev.pa.24.040184.002315> <PMid:6428300>
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, Leavesley et al. 2008Leavesley H.B., Li L., Prabhakaran K., Borowitz J.L. & Isom G.E. 2008. Interaction of cyanide and nitric oxide with cytochrome c oxidase: implications for acute cyanide toxicity. Toxicol. Sci. 101(1):101-111. <http://dx.doi.org/10.1093/toxsci/kfm254> <PMid:17906319>
https://doi.org/10.1093/toxsci/kfm254...
). When ingested under the form of glycoside, the minimum lethal HCN dose for cattle and sheep is about 2mg/kg body weight (Radostits et al. 2002Radostits O.M., Gay C.C., Blood D.C. & Hinchcliff K.W. 2002. Doenças causadas por toxinas de plantas, fungos, cianofitas, clavibactéria e por venenos de carrapatos e animais vertebrados, p.1472-1547. In: Ibid. (Eds), Clínica Veterinária: um tratado de doenças de bovinos, ovinos, caprinos, suínos e equídeos. 9ª ed. Guanabara Koogan, Rio de Janeiro.). Signs of histotoxic anoxia resulting from cyanogenic poisoning are observed within a few minutes after plant ingestion and death occurs within a few minutes to one hour after the onset of signs. Clinical signs are characterized by dyspnoea, anxiety, salivation, muscle tremors, incoordination, staggering gait, reddish mucous membranes, depression, tachycardia, seizure, decubitus and opisthotonus in the terminal phase (Kellerman et al. 1988Kellerman T.S., Coetzer J.A.W. & Naudé T.W. 1988. Haemopoietic system, p.193-213. In: Ibid. (Eds), Plant poisonings and mycotoxicoses of livestock in southern africa. Oxford University Press, Cape Town., Radostits et al. 2002Radostits O.M., Gay C.C., Blood D.C. & Hinchcliff K.W. 2002. Doenças causadas por toxinas de plantas, fungos, cianofitas, clavibactéria e por venenos de carrapatos e animais vertebrados, p.1472-1547. In: Ibid. (Eds), Clínica Veterinária: um tratado de doenças de bovinos, ovinos, caprinos, suínos e equídeos. 9ª ed. Guanabara Koogan, Rio de Janeiro., Youssef & Maxie 2004Youssef S. & Maxie M.G. 2004. Nervous system, p.347-348. In: Jubb K.V.F., Kennedy P.C. & Palmer N. (Eds), Pathology of Domestic Animals. Vol.3. 5th ed. Academic Press, London.). No significant macro and microscopic lesions are observed. The finding of leaves of the plant in the cardic region, not yet mixed with the ruminal content (Tokarnia et al. 2012Tokarnia C.H., Brito M.F., Barbosa J.D., Peixoto P.V. & Döbereiner J. 2012. Plantas cianogênicas, p.443-459. In: Ibid. (Eds), Plantas Tóxicas do Brasil para Animais de Produção. 2ª ed. Editora Helianthus, Rio de Janeiro.), is fundamental for diagnosis.

The picrate test qualitatively evaluates the presence of HCN in plants, and is a fundamental tool for diagnosis. Slower reactions should not be disregarded, since there are cyanogenic glycosides of slower development. Treatment based on sodium nitrite and sodium thiosulphate is effective, but in most poisoning events, the timing for administration is short due to the rapid evolution of cases, but whenever possible, treatment should be performed as it is important in confirmation of diagnosis by cyanogenic plants (Tokarnia et al. 2012Tokarnia C.H., Brito M.F., Barbosa J.D., Peixoto P.V. & Döbereiner J. 2012. Plantas cianogênicas, p.443-459. In: Ibid. (Eds), Plantas Tóxicas do Brasil para Animais de Produção. 2ª ed. Editora Helianthus, Rio de Janeiro.).

The aim of the present study was to evaluate the epidemiological, clinical and pathological aspects of five outbreaks of cyanogenic poisoning by spontaneous ingestion of star grass Florico cultivar in cattle.

Materials and Methods

The collection of epidemiological data, the observation of clinical signs and the necropsy of two cows were carried out in visits to the five properties where the disease outbreak occurred. Viscera samples were collected and fixed in 10% formalin and processed for histological evaluation. Green star grass leaves were collected from all the properties where the outbreaks occurred and the picrate test described by Henrici (1926), quoted by Tokarnia et al. (2012)Tokarnia C.H., Brito M.F., Barbosa J.D., Peixoto P.V. & Döbereiner J. 2012. Plantas cianogênicas, p.443-459. In: Ibid. (Eds), Plantas Tóxicas do Brasil para Animais de Produção. 2ª ed. Editora Helianthus, Rio de Janeiro. was performed. The test consisted of a strip of white paper immersed in solution composed of 5g sodium carbonate and 0.5g picric acid dissolved in 100ml distilled water. Leaves were macerated and placed in glass jars with lid, where the paper strip was fixed, which remained freely suspended above the plant material. Glass jars were held upright and the reaction was observed for 1 hour. The intensity of the reaction to the picrate test was classified taking into account the time of appearance of the red-brick color.

Results

Five HCN poisoning outbreaks in cattle, four in Santa Catarina, in the municipalities of Água Doce (Properties 1 and 2), Santa Terezinha (Property 3) and Braço do Norte (Property 4) were diagnosed from 2015 to 2017. An outbreak occurred in Paraná, in the municipality of União da Vitória (Property 5). Epidemiological data from the five outbreaks are shown in Table 1. In four of the five properties, owners were informed that the cultivated grass was purchased from another property as being tifton specimens.

Table 1.
Data referring to outbreaks of spontaneous poisoning by Florico star grass

In all outbreaks, the areas where the plant was cultivated had been previously fertilized with high nitrogen concentrations and properties adopted the silvopastoral system with Eucalyptussp. (Fig.1). The first clinical signs appeared between 10 and 15 minutes after the first introduction of the cattle in pasture exclusively constituted of star grass Florico cultivar and was characterized by muscle tremors, dyspnea, moderate tympanism, staggering gait, forced breathing with open mouth, sternal decubitus followed by death after 15 to 30 minutes and/or recovery within a few hours after the onset of signs. Two necropsies were performed and no significant changes were found except for the presence of the plant near the esophageal sphincter region. No histological lesions were observed in the various organs.

Fig.1.
Star grass Florico cultivar, fresh and in silvopastoral system in the municipality of Santa Terezinha/SC.

In all properties, star grass Florico cultivar samples collected to perform the picrate test showed a red-brick color change in 20 minutes after maceration of leaves.

Discussion

The clinical-pathological condition observed in spontaneous poisoning by star grass Florico cultivar is in agreement with that described by other authors for cyanogenic plants (Saad & Camargo 1967Saad A.D. & Camargo W.V.A. 1967. Intoxicação cianídrica em animais domésticos. Arqs Inst. Biológico, São Paulo, 33(10):211-220., Canella et al. 1968Canella C.F.C., Dobereiner J. & Tokarnia C.H. 1968. Intoxicação experimental pela maniçoba (Manihot glaziovii Muell. Arg.) em bovinos. Pesq. Agropec. Bras. 3:347-350., Kellerman et al. 1988Kellerman T.S., Coetzer J.A.W. & Naudé T.W. 1988. Haemopoietic system, p.193-213. In: Ibid. (Eds), Plant poisonings and mycotoxicoses of livestock in southern africa. Oxford University Press, Cape Town., Gava et al. 1992Gava A., Stolf L., Neves D.S., Stolf O., Varaschim M.S. & Ferreira E.M.M. 1992. Intoxicação experimental por Prunus sellowii (Rosaceae) em bovinos. Pesq. Vet. Bras. 12:1-4., Tokarnia et al. 1994aTokarnia C.H., Döbereiner J. & Peixoto P.V. 1994a. Aspectos clínicos patológicos complementares da intoxicação por algumas plantas tóxicas brasileiras. Pesq. Vet. Bras. 14(4):111-122., 1994bTokarnia C.H., Peixoto P.V. & Döbereiner J. 1994b. Intoxicação experimental por Piptadenia macrocarpa (Leg. Mimosoideae) em bovinos. Pesq. Vet. Bras. 14(2/3):57-63., 1999Tokarnia C.H., Peixoto P.V., Brito M.F., Duarte M.D. & Brust L.A.C. 1999. Estudos experimentais com plantas cianogênicas em bovinos. Pesq. Vet. Bras. 19(2):84-90. <http://dx.doi.org/10.1590/S0100-736X1999000200006>
https://doi.org/10.1590/S0100-736X199900...
, Gava et al. 1997Gava A., Pilati C., Cristani J., Simões J. & Simões L. 1997. Intoxicação cianogênica em bovinos alimentados com Tifton (Cynodon sp.). Anais VIII Ciclo de Atualização em Medicina Veterinária (CAMEV), Lages, SC, p.119., Radostits et al. 2002Radostits O.M., Gay C.C., Blood D.C. & Hinchcliff K.W. 2002. Doenças causadas por toxinas de plantas, fungos, cianofitas, clavibactéria e por venenos de carrapatos e animais vertebrados, p.1472-1547. In: Ibid. (Eds), Clínica Veterinária: um tratado de doenças de bovinos, ovinos, caprinos, suínos e equídeos. 9ª ed. Guanabara Koogan, Rio de Janeiro., Youssef & Maxie 2004Youssef S. & Maxie M.G. 2004. Nervous system, p.347-348. In: Jubb K.V.F., Kennedy P.C. & Palmer N. (Eds), Pathology of Domestic Animals. Vol.3. 5th ed. Academic Press, London., Amorim et al. 2005Amorim S.L., Medeiros R.M.T. & Riet-Correa F. 2005. Intoxicação experimental por Manihot glaziovii (Euphorbiaceae) em caprinos. Pesq. Vet. Bras. 25(3):179-187. <http://dx.doi.org/10.1590/S0100-736X2005000300009>, Nóbrega Junior et al. 2006Nóbrega Junior J.E., Riet-Correa F., Medeiros R.M.T. & Dantas A.F.M. 2006. Intoxicação por Sorghum halepense (Poaceae) em bovinos no semi-árido. Pesq. Vet. Bras. 26(4):201-204. <http://dx.doi.org/10.1590/S0100-736X2006000400003>
https://doi.org/10.1590/S0100-736X200600...
, Riet-Correa & Méndez 2007Riet-Correa F. & Mendez M.C. 2007. Intoxicação por plantas e micotoxinas, p.177-181. In: Riet-Correa F., Schild A.L., Lemos R.A.A. & Borges J.R.J. (Eds), Doenças de Ruminantes e Eqüídeos. Vol.2. 3ª ed. Pallotti, Santa Maria., Oliveira et al. 2008Oliveira D.M., Pimentel L.A., Araújo J.A.S., Rosane M.T.M., Dantas A.F.M. & Riet-Correa F. 2008. Intoxicação por Cnidoscolus phyllacanthus (Euphorbiaceae) em caprinos. Pesq. Vet. Bras. 28(1):36-42. <http://dx.doi.org/10.1590/S0100-736X2008000100006>
https://doi.org/10.1590/S0100-736X200800...
, Carvalho et al. 2011Carvalho F.K.L., Medeiros R.M.T., Araujo J.A.S. & Riet-Correa F. 2011. Intoxicação experimental por Passiflora foetida (Passifloraceae) em caprinos. Pesq. Vet. Bras. 31(6):477-481. <http://dx.doi.org/10.1590/S0100-736X2011000600003>
https://doi.org/10.1590/S0100-736X201100...
, Juffo et al. 2012Juffo G.D., Pavarini S.P., Wouters F., Oliveira L.G.S., Antoniassi N.A.B., Cruz C.E.F. & Driemeier D. 2012. Intoxicação espontânea por Sorghum sudanense em bovinos leiteiros no Rio Grande do Sul. Pesq. Vet. Bras. 32(3):217-220. <http://dx.doi.org/10.1590/S0100-736X2012000300006>
https://doi.org/10.1590/S0100-736X201200...
, Galindo et al. 2017Galindo C.M., Hemckmeier D., Biondo N., Parizotto L.H., Ogliari D. & Gava A. 2017. Intoxicação espontânea e experimental por tifton 68 (Cynodon nlemfuensis Vanderyst) em bovinos. Pesq. Vet. Bras. 37(5):441-446. <http://dx.doi.org/10.1590/s0100-736x2017000500003>
https://doi.org/10.1590/s0100-736x201700...
).

In the present study, the majority of cows with clinical signs recovered spontaneously within a few hours. These animals probably stopped star grass consumption spontaneously due to the appearance of mild clinical signs, consuming doses lower than those consumed by animals that became seriously ill and died, or may be related to the management system adopted in properties. According to Radostits et al. (2002)Radostits O.M., Gay C.C., Blood D.C. & Hinchcliff K.W. 2002. Doenças causadas por toxinas de plantas, fungos, cianofitas, clavibactéria e por venenos de carrapatos e animais vertebrados, p.1472-1547. In: Ibid. (Eds), Clínica Veterinária: um tratado de doenças de bovinos, ovinos, caprinos, suínos e equídeos. 9ª ed. Guanabara Koogan, Rio de Janeiro., hungry animals and/or those not used to ingesting cyanogenic plants are more prone to poisoning. Studies indicate that animals in contact with cyanogenic plants can tolerate increasing HCN doses due to the increased production of the rhodanase enzyme, which is important in the organism detoxification. In the present study, all outbreaks were the first contact of cattle with the plant and morbidity ranged from 10% to 100% and mortality from 3.7% to 50%, evidencing the susceptibility of animals to poisoning.

The use of the silvopastoral system seems to show that shadow associated with excess nitrogen on star grass Florico cultivar favors the synthesis of hydrocyanic acid. Vetter & Haraszti (1977)Vetter J. & Haraszti E. 1977. Changes in the hydrogen cyanide content of Sudan grass (Sorghum sudanense) and broomcorn (Sorghum bicolor var. technicum) during the growing season. Acta Agron. Sci. Hung. 26:15-22. observed that the production of HCN in Sorghum spp. decreases gradually during its vegetative development, as the photosynthesis intensity increases, that is, the less photosynthesis the more HCN. Mislevy et al. (1993a)Mislevy P., Brown W.F., Caro-Costas R., Vicente-Chandler J., Dunavin L.S., Hall D.W., Kalmbacher R.S., Overman A.J., Ruelke O.C., Sonoda R.M., Sotomayor-Rios A., Stanley Junior R.L. & Williams M.J. 1993a. Registration of Florico stargrass. Crop Science 33(2):358-359. <http://dx.doi.org/10.2135/cropsci1993.0011183X003300020044x>
https://doi.org/10.2135/cropsci1993.0011...
reported that the hydrocyanic acid potential of Florico star grass is high under heavy N fertilization, especially during the early stages of plant development.

The response to the picrate test occurred within 20 minutes, which differs from that obtained from green Prunnus sellowii leaves, a cyanogenic plant found in the Southeastern and Southern regions of Brazil, which occurred within 3 to 5 minutes (Gava et al. 1992Gava A., Stolf L., Neves D.S., Stolf O., Varaschim M.S. & Ferreira E.M.M. 1992. Intoxicação experimental por Prunus sellowii (Rosaceae) em bovinos. Pesq. Vet. Bras. 12:1-4.). This is probably due to the fibrous character of Florico leaves, which makes it difficult to macerate them and consequently delay the reaction between the enzyme and the glycoside.

The differential diagnosis of cyanogenic poisoning should be made mainly in relation to other diseases or poisonings with super acute clinical evolution and without macroscopic and microscopic alterations, especially nitrate/nitrite poisoning. This poisoning is commonly observed in the southern region of Brazil in cattle that graze on grasses, mainly oat and ryegrass, well fertilized and under favorable climatic conditions (dry seasons followed by rains). The grazing time on these grasses is also an important data for differential diagnosis. While for poisoning with plant containing hydrocyanic acid, the grazing time is 10 to 20 minutes, nitrate/nitrite poisoning requires grazing time at least greater than one hour. Both conditions show clinical signs of respiratory difficulty and staggering gait; however, in nitrate/nitrite poisoning, there is a marked tachypnea, not observed in the same proportion in HCN poisoning. In addition, in HCN poisoning, mucous membranes are bright red and in nitrate/nitrite poisoning brown (Hibbs 1979Hibbs C.M. 1979. Cyanide and nitrate toxicosis of cattle. Vet. Hum. Toxicol. 21(6):401-403. <PMid:532080>). In these cases, it is interesting to apply the picrate test to identify HCN and/or the diphenylamine test for nitrate in pastures. Another difference is that pastures with high nitrate/nitrite content maintain their toxicity after desiccation (Jönck et al. 2013Jönck F., Gava A., Traverso S.D., Lucioli J., Furlan F.H. & Gueller E. 2013. Intoxicação espontânea e experimental por nitrato/nitrito em bovinos alimentados com Avena sativa (aveia) e/ou Lolium spp. (azevém). Pesq. Vet. Bras. 33(9):1062-1070. <http://dx.doi.org/10.1590/S0100-736X2013000900003>
https://doi.org/10.1590/S0100-736X201300...
) and grasses with HCN, such as Tifton 68, lose their toxic action after phenation (Galindo et al. 2017Galindo C.M., Hemckmeier D., Biondo N., Parizotto L.H., Ogliari D. & Gava A. 2017. Intoxicação espontânea e experimental por tifton 68 (Cynodon nlemfuensis Vanderyst) em bovinos. Pesq. Vet. Bras. 37(5):441-446. <http://dx.doi.org/10.1590/s0100-736x2017000500003>
https://doi.org/10.1590/s0100-736x201700...
).

Among the toxic plants that cause rapid death in cattle in the southern region of Brazil, Amorimia exotropica stands out in the coastal region of Santa Catarina and Rio Grande do Sul. However, it is possible to distinguish them among epidemiological aspects (Gava et al. 1998Gava A., Cristani J., Branco J.V., Neves D.S., Mondadori A.J. & Sousa R.S. 1998. Mortes súbitas em bovinos causadas pela ingestão de Mascagnia sp. (Malpighiaceae) no Estado de Santa Catarina. Pesq. Vet. Bras. 18(1):16-20. <http://dx.doi.org/10.1590/S0100-736X1998000100003>
https://doi.org/10.1590/S0100-736X199800...
, Pavarini et al. 2011Pavarini S.P., Soares M.P., Bandarra P.M., Gomes D.C., Bandinelli M.B., Cruz C.E.F. & Driemeier D. 2011. Mortes súbitas em bovinos causadas por Amorimia exotropica (Malpighiaceae) no Rio Grande do Sul. Pesq. Vet. Bras. 31(4):291-296. <http://dx.doi.org/10.1590/S0100-736X2011000400004>
https://doi.org/10.1590/S0100-736X201100...
). Urea poisoning is also included in the differential diagnosis, which also produces rapid death. Epidemiological data on the accidental access of cattle to urea and the alkalinity of the ruminal content should also be evaluated.

Conclusion

When cultivated in the shade, star grass (Cynodon nlemfuensis Vanderyst var. nlemfuensis cv. ‘Florico’) can accumulate cyanide acid and cause cyanogenic poisoning in cattle.

Acknowledgments

The first author thanks the Coordination for Improvement of Higher Education Personnel (CAPES) for the grant of the master’s degree.

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  • 1
    Part of Master’s Thesis of the first author.

Publication Dates

  • Publication in this collection
    Jan 2019

History

  • Received
    16 Aug 2018
  • Accepted
    28 Aug 2018
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