RESUMO
BACKGROUND: Swine production expanded in the last decades. Efforts have been made to improve meat production and to understand its relationship to pig gut microbiota. Copper (Cu) is a usual supplement to growth performance in animal production. Here, two performance studies were conducted to investigate the effects of three different sources of Cu on the microbiota of piglets. A total of 256 weaned piglets were randomly allocated into 4 treatments (10 replicates per treatment of 4 piglets per pen in Trial 1 and 8 replicates of 3 piglets per pen in Trial 2). Treatments included a control group (fed 10 mg/kg of Cu from CuSO4), a group fed at 160 mg/kg of Copper (II) sulfate (CuSO4) or tri-basic copper chloride (TBCC), and a group fed with Cu methionine hydroxy analogue chelated (Cu-MHAC) at 150, 80, and 50 mg/kg in Phases 1 (24-35 d), 2 (36-49 d), and 3 (50-70 d), respectively. At 70 d, the cecum luminal contents from one pig per pen were collected and polled for 16 S rRNA sequencing (V3/V4 regions). Parameters were analyzed in a completely randomized block design, in which each experiment was considered as a block. RESULTS: A total of 1337 Operational Taxonomic Units (OTUs) were identified. Dominance and Simpson ecological metrics were statistically different between control and treated groups (P < 0.10) showing that different Cu sources altered the gut microbiota composition with the proliferation of some bacteria that improve gut health. A high abundance of Prevotella was observed in all treatments while other genera were enriched and differentially modulated, according to the Cu source and dosage. The supplementation with Cu-MHAC can modify a group of bacteria involved in feed efficiency (FE) and short chain fatty acids (SCFA) production (Clostridium XIVa, Desulfovibrio, and Megasphera). These bacteria are also important players in the activation of ghrelin and growth hormones that were previously reported to correlate with Cu-MHAC supplementation. CONCLUSIONS: These results indicated that some genera seem to be directly affected by the Cu source offered to the animals. TBCC and Cu-MHAC (even in low doses) can promote healthy modifications in the gut bacterial composition, being a promising source of supplementation for piglets.
Assuntos
Cobre , Microbioma Gastrointestinal , Animais , Ração Animal/análise , Ceco , Cobre/farmacologia , Sulfato de Cobre/farmacologia , Dieta/veterinária , Suplementos Nutricionais/análise , SuínosRESUMO
The study examines the influence of three types of hypercaloric diets on metabolic parameters, inflammatory markers, and oxidative stress in experimental model. Male Wistar rats (n = 40) were randomized in control (C), high-sucrose (HS), high-fat (HF), and high-fat with sucrose (HFHS) for 20 weeks. Nutritional, metabolic, hormonal, and biochemical profiles, as well as histological analysis of adipose and hepatic tissues were performed. Inflammation and oxidative stress were determined. HF model caused obesity and comorbidities as glucose intolerance and arterial hypertension. In relation to hormonal and biochemical parameters, there was no significant difference between the groups. All groups showed increased deposition of fat droplets in the hepatic tissue, even though adipocyte areas were similar. Biomarkers of oxidative stress in serum and adipose tissues were similar among the groups. HF model was effective in triggering associated obesity and comorbidities in male rats, but all hypercaloric diets were unable to promote oxidative stress and inflammation.
Assuntos
Dieta da Carga de Carboidratos , Dieta Hiperlipídica , Sacarose Alimentar , Inflamação , Obesidade , Estresse Oxidativo , Animais , Masculino , Ratos , Dieta da Carga de Carboidratos/efeitos adversos , Dieta Hiperlipídica/efeitos adversos , Sacarose Alimentar/efeitos adversos , Modelos Animais de Doenças , Inflamação/etiologia , Inflamação/metabolismo , Obesidade/etiologia , Obesidade/metabolismo , Estresse Oxidativo/fisiologia , Ratos WistarRESUMO
This study aimed to compare the effects of different levels of cashew nutshell liquid (CNSL) and castor oil (CNSL-castor oil) with growth-promoting antibiotics associated with anticoccidials in broiler chickens challenged with coccidiosis. In this work, 2520 one-day-old male broiler chicks (Cobb) were randomly assigned to 84 pens, containing 30 birds each. The experimental design was completely randomized, with seven treatments: enramycin (8 ppm), virginiamycin (16.5 ppm), and tylosin (55 ppm); different doses of CNSL-castor oil (0.5, 0.75, and 1.00 kg/t); and a control diet (without additives). All treatments received semduramicin + nicarbazin (500 g/t; Aviax® Plus) from 0 to 28 d and monensin sodium (100 ppm; Elanco) from 29 to 35 days of age, when the feed was without antibiotics. The challenge was introduced at 14 days of age by inoculating broiler chickens with sporulated Eimeria tenella, Eimeria acervulina, and Eimeria maxima oocysts via oral gavage. In addition to performance parameters, intestinal contents were collected at 28 and 42 days of age for microbiota analysis by sequencing the 16s rRNA in V3 and V4 regions using the Illumina MiSeq platform. Taxonomy was assigned using the SILVA database (v. 138) with QIIME2 software (v. 2020.11). After one week of challenge, the broilers that received tylosin had a higher body weight gain (BWG) than those in the control group (p < 0.05), while the other treatments presented intermediate values. At 28 d, the BWG was lower for the control, CNSL-Castor oil 0.5 kg/t, enramycin, and virginiamycin treatments than that in the tylosin treatment. The inclusion of CNSL-Castor oil at concentrations of 0.75 and 1 kg/t acted as an intermediate treatment (p < 0.05). For alpha diversity, using the Shannon index, it was possible to observe the effect of age, with substantial diversity at 42 d. The Firmicutes phylum had the highest abundance, with values between 84.33% and 95.16% at 42 d. Tylosin showed better performance indices than other treatments. CNSL-castor oil treatments with concentrations of 0.75 and 1 kg/t showed similar results to those of enramycin and virginiamycin. Furthermore, CNSL-castor oil acted as a modulator of intestinal microbiota, reducing the abundance of pathogenic bacteria.
Assuntos
Anacardium , Coccidiose , Eimeria , Microbiota , Animais , Antibacterianos/farmacologia , Antibacterianos/uso terapêutico , Óleo de Rícino , Galinhas , Coccidiose/tratamento farmacológico , Coccidiose/veterinária , Masculino , RNA Ribossômico 16S , Tilosina/farmacologia , Tilosina/uso terapêutico , Virginiamicina/farmacologia , Virginiamicina/uso terapêuticoRESUMO
Two performance studies were conducted to investigate the effects of 3 different sources of Cu on production parameters of piglets. A total of 256 piglets weaned at 24 ± 2 d were randomly allocated into 4 treatments with 10 or 8 replicates per treatment of 4 or 3 piglets per pen in Exp. 1 and 2, respectively. The experimental period was divided into 3 feeding phases: Phase 1 (24 to 35 d), Phase 2 (36 to 49 d), and Phase 3 (50 to 70 d). Treatments included a Control group (fed 10 mg/kg of Cu from CuSO4), a group fed 160 mg/kg of either CuSO4 (CuSO4-160) or tri-basic copper chloride (TBCC), and a group fed Cu methionine hydroxy analogue chelated (Cu-MHAC) at 150, 80, and 50 mg/kg in Phases 1, 2, and 3, respectively. The methionine value of Cu-MHAC was accounted during diet formulation to achieve the same levels of methionine across treatments. Phases 1 and 2 diets contained 2,200 and 1,500 ppm of ZnO, respectively; and antibiotics were used as growth promoters. Performance parameters were analyzed as completely randomized block design, in which each experiment was considered as a block. In trial 2, blood serum and mucosal samples, from the fundic region of the stomach, were collected from 1 piglet per replicate at day 70 and tested for serum growth hormone levels (GH) and ghrelin mRNA expression, respectively. The contrast between Cu-MHAC vs. CuSO4-160 + TBCC showed that piglets fed Cu-MHAC exhibited better feed conversion ratio (FCR) in all feeding phases compared with feeding inorganic Cu (P < 0.05). Overall, feeding Cu-MHAC improved body weight (BW), BW gain, feed intake (FI), and FCR vs. Control diet fed piglets; yet, it improved BW and FCR vs. TBCC fed piglets, and improved BW, BW gain, and FI vs. CuSO4-160 fed piglets (P < 0.05). Feeding TBCC promoted similar performance than feeding CuSO4-160, regardless of age (P > 0.05). Both ghrelin expression and growth hormone serum levels were significantly increased by feeding Cu-MHAC vs. Control diet fed animals (P < 0.01). Feeding CuSO4-160 upregulated ghrelin expression vs. Control (P < 0.01) while GH serum levels and ghrelin expression did no change by feeding TBCC compared with Control diet fed animals (P > 0.05). It was concluded that feeding Cu-MHAC at the levels tested herein can improve growth performance of piglets beyond feeding 160 ppm of either CuSO4 or TBCC, which may be partially explained by the increased expression of ghrelin and GH serum levels.
Assuntos
Ração Animal/análise , Cobre/administração & dosagem , Suplementos Nutricionais/análise , Grelina/genética , Hormônio do Crescimento/sangue , Suínos/fisiologia , Animais , Peso Corporal/efeitos dos fármacos , Dieta/veterinária , Feminino , Masculino , Metionina/análogos & derivados , Metionina/química , RNA Mensageiro/genética , Distribuição Aleatória , Estômago/fisiologia , Suínos/genética , Suínos/crescimento & desenvolvimento , Desmame , Aumento de Peso/efeitos dos fármacosRESUMO
BACKGROUND: Dietary interventions in rodents can induce an excess of adipose tissue and metabolic disorders that resemble human obesity. Nevertheless, these approaches are not standardized, and the phenotypes may vary distinctly among studies. The aim of this study was to investigate the effects of different dietary interventions on nutritional, metabolic, biochemical, hormonal, and cardiovascular profiles, as well as to add to development and characterization of an experimental model of obesity. METHODS: Male Wistar rats were randomized into four groups: control diet (C), high-sugar (HS), high-fat (HF), or high-sugar and high-fat (HFHS). Weekly measurements of body weight, adiposity, area under the curve (AUC) for glucose, blood pressure (BP) and serum triglycerides, total cholesterol level, and leptin were performed. RESULTS: HF and HFHS models were led to obesity by increases in adipose tissue deposition and the adiposity index. All hypercaloric diets presented systolic BP increases. In addition, the AUC for glucose was greater in HF and HFHS than in C, and only the HF group presented hyperleptinemia. CONCLUSIONS: HF and HFHS diet approaches promote obesity and comorbidities, and thus represent a useful tool for studying human obesity-related disorders. By contrast, the HS model did not prove to be a good model of obesity.
Assuntos
Fenômenos Fisiológicos da Nutrição Animal , Gorduras na Dieta , Açúcares da Dieta , Obesidade/etiologia , Adiposidade , Ração Animal , Animais , Biomarcadores/sangue , Glicemia/metabolismo , Pressão Sanguínea , Colesterol/sangue , Modelos Animais de Doenças , Ingestão de Energia , Nível de Saúde , Leptina/sangue , Masculino , Valor Nutritivo , Obesidade/metabolismo , Obesidade/fisiopatologia , Ratos Wistar , Fatores de Tempo , Triglicerídeos/sangue , Aumento de PesoRESUMO
This study evaluated the nutritional levels, apparent digestibility coefficients, and faecal characteristics of dogs fed with four by-products from bovine slaughter: testicles, residue sirloin steak, trachea, and liver. Ingredients were processed and packed in tins for heat treatment in autoclaves. For the digestibility and faeces quality, ingredients were mixed with a reference diet (commercial food) in the proportion of 30g kg-1 test ingredient and 70g kg-1 reference diet (as dry matter). Ten adult dogs were distributed in double Latin block squares (5x5) with five treatments and five periods, totalling ten repetitions per treatment. The residue sirloin steak presented the highest levels of essential (414.2g kg-1 of dry matter) and non-essential (399.0g kg-1 of dry matter) amino acids in tested ingredients. No differences (P>0.05) were observed in apparent digestibility coefficients of dry matter - ADCDM (907g kg-1), ADCOM (930g kg-1), ADCCP (841g kg-1), ADCAEE (954g kg-1) values, and DE (5069kcal kg-1) and ME (4781kcal kg-1) values between testicle, residue sirloin steak, and liver. The trachea presented lower digestibility and energy values (digestible and metabolizable) than the other ingredients. This lower trachea digestibility resulted in higher faecal volume for natural and dry matter (P0.05) in faecal score between ingredients. Ingredients tested in this study can be used in feeds for adult dogs; however, their nutritional levels and digestibility values should be considered for correct diet balance.
Foram avaliados os níveis nutricionais, coeficientes de digestibilidade aparente e características das fezes de cães alimentados com quatro ingredientes provenientes do abate de bovinos: testículo, apara de contra filé, traqueia e fígado. Os ingredientes foram processados e acondicionados em latas para tratamento térmico em autoclaves. Para o teste de digestibilidade e características das fezes os ingredientes foram misturados a uma dieta referência (alimento comercial) na proporção de 30g kg-1 do ingrediente teste e 70g kg-1 da dieta referência (base matéria seca). Dez cães adultos foram distribuídos em delineamento quadrado latino duplo (5x5), com cinco tratamentos e cinco períodos, totalizando dez repetições por tratamento. A apara de contra filé apresentou os maiores níveis de aminoácidos essenciais (414,2g kg-1 de matéria seca) e não essenciais (399,0g kg-1 de matéria seca) entre os alimentos avaliados. Não houve diferença (P>0,05) nos valores do coeficiente de digestibilidade aparente para matéria seca - MS (907g kg-1), MO (930g kg-1), PB (841g kg-1), EEA (954g kg-1), e os valores de ED (5069kcal kg-1) e EM (4781kcal kg-1) entre testículo, apara de contra filé e fígado. A traqueia apresentou os menores valores de digestibilidade e energia (digestível e metabolizável) entre os alimentos testados. A menor digestibilidade da traqueia resultou em maior volume de fezes na matéria natural e seca (P0,05) no escore fecal entre os alimentos. Os ingredientes avaliados no presente estudo podem ser utilizados na alimentação de cães adultos, porém deve-se considerar os seus níveis nutricionais e os valores de digestibilidade para o correto balanceamento das rações.
Assuntos
Animais , Cães , Carne Vermelha/análise , Digestão , Fenômenos Fisiológicos da Nutrição Animal , Bovinos , Fezes , Ração Animal/análiseRESUMO
This study evaluated the nutritional levels, apparent digestibility coefficients, and faecal characteristics of dogs fed with four by-products from bovine slaughter: testicles, residue sirloin steak, trachea, and liver. Ingredients were processed and packed in tins for heat treatment in autoclaves. For the digestibility and faeces quality, ingredients were mixed with a reference diet (commercial food) in the proportion of 30g kg-1 test ingredient and 70g kg-1 reference diet (as dry matter). Ten adult dogs were distributed in double Latin block squares (5x5) with five treatments and five periods, totalling ten repetitions per treatment. The residue sirloin steak presented the highest levels of essential (414.2g kg-1 of dry matter) and non-essential (399.0g kg-1 of dry matter) amino acids in tested ingredients. No differences (P>0.05) were observed in apparent digestibility coefficients of dry matter - ADCDM (907g kg-1), ADCOM (930g kg-1), ADCCP (841g kg-1), ADCAEE (954g kg-1) values, and DE (5069kcal kg-1) and ME (4781kcal kg-1) values between testicle, residue sirloin steak, and liver. The trachea presented lower digestibility and energy values (digestible and metabolizable) than the other ingredients. This lower trachea digestibility resulted in higher faecal volume for natural and dry matter (P<0.05). There was no difference (P>0.05) in faecal score between ingredients. Ingredients tested in this study can be used in feeds for adult dogs; however, their nutritional levels and digestibility values should be considered for correct diet balance.(AU)
Foram avaliados os níveis nutricionais, coeficientes de digestibilidade aparente e características das fezes de cães alimentados com quatro ingredientes provenientes do abate de bovinos: testículo, apara de contra filé, traqueia e fígado. Os ingredientes foram processados e acondicionados em latas para tratamento térmico em autoclaves. Para o teste de digestibilidade e características das fezes os ingredientes foram misturados a uma dieta referência (alimento comercial) na proporção de 30g kg-1 do ingrediente teste e 70g kg-1 da dieta referência (base matéria seca). Dez cães adultos foram distribuídos em delineamento quadrado latino duplo (5x5), com cinco tratamentos e cinco períodos, totalizando dez repetições por tratamento. A apara de contra filé apresentou os maiores níveis de aminoácidos essenciais (414,2g kg-1 de matéria seca) e não essenciais (399,0g kg-1 de matéria seca) entre os alimentos avaliados. Não houve diferença (P>0,05) nos valores do coeficiente de digestibilidade aparente para matéria seca - MS (907g kg-1), MO (930g kg-1), PB (841g kg-1), EEA (954g kg-1), e os valores de ED (5069kcal kg-1) e EM (4781kcal kg-1) entre testículo, apara de contra filé e fígado. A traqueia apresentou os menores valores de digestibilidade e energia (digestível e metabolizável) entre os alimentos testados. A menor digestibilidade da traqueia resultou em maior volume de fezes na matéria natural e seca (P<0,05). Não houve diferença (P>0,05) no escore fecal entre os alimentos. Os ingredientes avaliados no presente estudo podem ser utilizados na alimentação de cães adultos, porém deve-se considerar os seus níveis nutricionais e os valores de digestibilidade para o correto balanceamento das rações.(AU)
Assuntos
Animais , Cães , Carne Vermelha/análise , Digestão , Fenômenos Fisiológicos da Nutrição Animal , Bovinos , Fezes , Ração Animal/análiseRESUMO
A avicultura brasileira atualmente ocupa o terceiro lugar, com uma produção anual de aproximadamente, 10,9 milhões de toneladas de carne de frango. Contudo, severas perdas econômicas são relatadas, devido à coccidiose em granjas de frangos de corte, matrizes e postura. As Eimerias são classificadas como protozoários, sendo que os mesmos se multiplicam nas células intestinais diminuindo a absorção de nutrientes, levando à desidratação, perda de sangue e susceptibilidade para infecção por outros micro-organismos. Com o desenvolvimento da pesquisa objetivou-se determinar os índices de produtividade zootécnica (ganho de peso, consumo de ração, conversão alimentar, taxa de mortalidade e índice de eficiência produtiva) bem como, mensurar o nível residual do Diclazuril nos tecidos de frangos de corte, comparando com os padrões internacionais de Limites Máximos de Resíduos determinados pelo Codex Alimentarius. Para a realização do estudo, utilizou-se 624 frangos de corte, onde metade do grupo foi inoculado experimentalmente com E. acervulina, E. maxima e E. tenella. O estudo foi composto por grupos tratados e não tratados com diclazuril. O uso do diclazuril expressou efeito positivo, no desempenho zootécnico das aves inoculadas artificialmente; a análise residual do medicamento apresentou um período de carência zero, sendo considerada segura para alimentação humana a carne de frangos medicados com Diclazuril.
Assuntos
Animais , Aves Domésticas/microbiologia , Doenças das Aves Domésticas/tratamento farmacológico , Coccidiose/veterinária , Eimeria/parasitologia , Coccidiose/prevenção & controleRESUMO
A avicultura brasileira atualmente ocupa o terceiro lugar, com uma produção anual de aproximadamente, 10,9 milhões de toneladas de carne de frango. Contudo, severas perdas econômicas são relatadas, devido à coccidiose em granjas de frangos de corte, matrizes e postura. As Eimerias são classificadas como protozoários, sendo que os mesmos se multiplicam nas células intestinais diminuindo a absorção de nutrientes, levando à desidratação, perda de sangue e susceptibilidade para infecção por outros micro-organismos. Com o desenvolvimento da pesquisa objetivou-se determinar os índices de produtividade zootécnica (ganho de peso, consumo de ração, conversão alimentar, taxa de mortalidade e índice de eficiência produtiva) bem como, mensurar o nível residual do Diclazuril nos tecidos de frangos de corte, comparando com os padrões internacionais de Limites Máximos de Resíduos determinados pelo Codex Alimentarius. Para a realização do estudo, utilizou-se 624 frangos de corte, onde metade do grupo foi inoculado experimentalmente com E. acervulina, E. maxima e E. tenella. O estudo foi composto por grupos tratados e não tratados com diclazuril. O uso do diclazuril expressou efeito positivo, no desempenho zootécnico das aves inoculadas artificialmente; a análise residual do medicamento apresentou um período de carência zero, sendo considerada segura para alimentação humana a carne de frangos medicados com Diclazuril.(AU)
The Brazilian aviculture currently ranks third place with an annual production of approximately 10,9 million tons of chicken meat. However, severe economic losses are reported, due to coccidiosis in broiler chicken farms, breeders and posture. The Eimerias are classified as protozoa. They multiply in the intestinal cells decreasing the absorption of nutrients, leading to dehydration, blood loss and susceptibility to infection by other microorganisms. The development of research aimed to determine the levels of zootechnical productivity (weight gain, feed intake, feed conversion, mortality rate and productive efficiency index) as well measure the residual leveI of Diclazuril in broiler chicken tissues, compared to international standards for Maximum Residue limits established by the Codex Alimentarius. To conduct the study, we used 624 broilers, when half of the group had experimentally inoculated a mix of Eimerias: E. acervulina, E. maxima and E. tenella. The study consisted of treated and untreated groups with diclazuril. The use of diclazuril expressed positive effect on the zootechnical performance of artificially inoculated birds. The residual analysis of the drug had a zero waiting period, and is considered safe for human consumption the meat of chickens treated with diclazuril.(AU)
Assuntos
Animais , Aves Domésticas/microbiologia , Eimeria/parasitologia , Coccidiose/veterinária , Resíduos de Drogas/análise , Resíduos de Drogas/normas , Coccidiose/prevenção & controle , Doenças das Aves Domésticas/tratamento farmacológico , Coccidiostáticos/análiseRESUMO
Two experiments were conducted to evaluate the effects of reducing dietary crude protein (CP), based on the ideal protein concept for Nile tilapia reared in net pens. The experimental (isocaloric, isocalcium, and isophosphoric) diets were formulated to contain 270, 300, 330, and 360g kg-1 CP. In experiment 1, 4320 Nile tilapia (13.5±0.82g) were used to evaluate the performance and hematological parameters. The experimental design was completely randomized and the fish were distributed in 24 net pens (1.0m3), with four diets, six replicates, and 180 fishes per experimental unit. In experiment 2, 40 Nile tilapia (22.5±0.56g) were used to evaluate the ammonia excretion. Fish were distributed in 40 aquaria (3.0L), with one fish per aquarium (n=10). No protein reduction effect was observed in feed intake and the hematocrit and hemoglobin values. Regarding the statistic models used in the present study, difference was observed between CP values. The optimal level estimated by the quadratic equation first interception with the linear response plateau (LRP) as a response to CP changes in the diet was determined for weight gain (324.3g kg-1) and feed conversion (317.8g kg-1). After reduction in the CP levels, a linear reduction was observed in the ammonia excretion in water. Based on the ideal protein concept for Nile tilapia reared in net pens, reducing the CP levels in the diets is possible, without change in the performance and hematological parameters, and with a reduction in the levels of ammonia excretion in water, since amino acids are supplemented.
Dois experimentos foram realizados para avaliar os efeitos da redução na quantidade de proteína bruta (PB) da ração, com base no conceito de proteína ideal para tilápias do Nilo criadas em tanques-rede. As rações experimentais (isoenergéticas, isocálcicas e isofosfóricas) foram formuladas para conter 270, 300, 330 e 360g kg-1 de PB. No experimento 1, 4320 tilápias do Nilo (13.5±0.82g) foram usadas para avaliar os parâmetros de desempenho e hematológicos. O delineamento experimental foi inteiramente casualizado e os peixes foram distribuídos em 24 tanques (1.0m³), com quatro rações, seis repetições e 180 peixes por unidade experimental. No experimento 2, 40 tilápias do Nilo (22.5±0.56g) foram usadas para avaliar a excreção de amônia. Os peixes foram distribuídos em 40 aquários (3.0L), com um peixe por aquário (n=10). Nenhum efeito de redução proteica foi observado sobre o consumo de ração e os valores de hematócrito e hemoglobina. Em relação aos modelos estatísticos empregados neste estudo, uma diferença foi observada entre os valores de PB. O nível ótimo, estimado através da primeira intersecção da equação quadrática com o platô do modelo Linear Response Plateau (LRP) como resposta às variações na proteína da dieta, foi determinado para ganho em peso (324.3g kg-1 de PB) e conversão alimentar (317.8g kg-1). Após a redução nos níveis de PB, foi observada uma redução linear na excreção de amônia na água. Com base no conceito de proteína ideal para tilápias do Nilo criadas em tanques-rede, é possível reduzir os níveis de PB nas rações, sem alteração nos parâmetros de desempenho e hematológicos, e com redução nos níveis de excreção de amônia na água, mediante suplementação de aminoácidos.