Effects of Supplementation of Ionized or Chelated Water-Soluble Mineral Mixture on the Live Performance, Nutrient Digestibility, Blood Profile, Egg Quality, and Excreta Microbiota of Laying Hens

In total, 216 Hy-Line brown laying hens (40-week-old), were used in a 5-week experiment to evaluate the effects of ionized or chelated water-soluble mineral mixture supplementation on live performance, nutrient digestibility, blood characteristics, egg quality, and excreta microbiota. Layers were randomly assigned to one of three dietary treatments with 12 replicates of six adjacent cages each. The dietary treatments consisted of: 1) CON (basal diet + normal tap water), 2) T1 (CON+0.5% ionized mineral mixture in tap water, pH 3.0); and 3) T2 (CON+ 0.5% chelated mineral mixture in tap water, pH 3.0). Egg production tended to increase in week 1, week 3 and week 4 in the birds supplemented with T1 and T2 diet compared with CON. Moreover, the dietary supplementation of water-soluble mineral mixture improved (p=0.02) eggshell thickness in week 4 and tended to improve in week 5 of the experimental period in T2 hens compared with CON. The layers fed the T1 diet presented higher (p 0.05) Ca digestibility than CON hens, while the T2 diet promoted a numerical increase in Ca digestibility. Blood calcium concentration increased (p 0.05) with T1 and T2 treatments compared with CON. The laying hens fed the T1 and T2 diets tended to present lower Salmonella and E. coli counts isolated from excreta compared with CON. In conclusion, ionized and chelated mineral mixtures had a positive impact on production performance and eggshell quality, improved Ca digestibility and blood Ca level.

Effects of Supplementation of Ionized or Chelated Water-Soluble Mineral Mixture on the Live Performance, Nutrient Digestibility, Blood Profile, Egg Quality, and Excreta Microbiota of Laying Hens

In total, 216 Hy-Line brown laying hens (40-week-old), were used in a 5-week experiment to evaluate the effects of ionized or chelated water-soluble mineral mixture supplementation on live performance, nutrient digestibility, blood characteristics, egg quality, and excreta microbiota. Layers were randomly assigned to one of three dietary treatments with 12 replicates of six adjacent cages each. The dietary treatments consisted of: 1) CON (basal diet + normal tap water), 2) T1 (CON+0.5% ionized mineral mixture in tap water, pH 3.0); and 3) T2 (CON+ 0.5% chelated mineral mixture in tap water, pH 3.0). Egg production tended to increase in week 1, week 3 and week 4 in the birds supplemented with T1 and T2 diet compared with CON. Moreover, the dietary supplementation of water-soluble mineral mixture improved (p=0.02) eggshell thickness in week 4 and tended to improve in week 5 of the experimental period in T2 hens compared with CON. The layers fed the T1 diet presented higher (p 0.05) Ca digestibility than CON hens, while the T2 diet promoted a numerical increase in Ca digestibility. Blood calcium concentration increased (p 0.05) with T1 and T2 treatments compared with CON. The laying hens fed the T1 and T2 diets tended to present lower Salmonella and E. coli counts isolated from excreta compared with CON. In conclusion, ionized and chelated mineral mixtures had a positive impact on production performance and eggshell quality, improved Ca digestibility and blood Ca level.(AU)

MÉTODOS ALTERNATIVOS DE MISTURA NA PRODUÇÃO DE RAÇÃO

O estudo tem como objetivo avaliar técnicas alternativas utilizadas por produtores para preparar misturas de rações e suplementos minerais em suas propriedades, ao invés de adquiri-las prontas comercialmente. Foram analisadas misturas feitas com betoneira de construção civil, tambor metálico disposto excentricamente em cavalete, misturador Y e utilizando pá e enxada sobre lona plástica. A formulação da ração trabalhada teve composição básica com milho moído, farelo de soja, fosfato bicálcico, calcário calcítico e sulfato de manganês, este último utilizado como marcador, quantificado após coleta de amostras de 100g por meio de absorção atômica do elemento manganês. Para cada técnica foi utilizado um tratamento, sendo coletadas 10 amostras para análise e cálculo do coeficiente de variação (CV) que foi a medida utilizada para avaliar a homogeneidade da mistura final. Dentro das técnicas avaliadas, a utilização da pá e enxada obteve CV de 8,28 apresentando melhor resultado, sem diferença estatística com a betoneira que obteve 8,38 de CV, seguido pelo tambor excêntrico com 11,98 e o misturador Y com coeficiente de variação igual a 12,37. No entanto, todas as técnicas podem ser consideradas para o preparo de rações, uma vez que a literatura cita CV entre 10 a 15% como normais para misturadores convencionais. Apenas não devem ser utilizadas para preparo de rações com medicamentos por estarem acima dos 5% exigidos pela Instrução Normativa número 14 do Ministério da Agricultura Pecuária e Abastecimento.

The study aims to evaluate alternative techniques used by producers to prepare mixtures of feed and mineral supplements on their properties, instead of purchasing them commercially ready. Mixtures made with civil construction mixer, metallic drum arranged eccentrically on easel, Y mixer and using shovel and hoe on plastic canvas were analyzed. The formulation of the processed feed had a basic composition with ground corn, soybean meal, dicalcium phosphate, limestone and manganese sulfate, the latter used as a marker, quantified after collecting 100g samples by means of atomic absorption of the manganese element. For each technique, a treatment was used, and 10 samples were collected for analysis and calculation of the coefficient of variation (CV), which was the measure used to assess the homogeneity of the final mixture. Within the techniques evaluated, the use of the shovel and hoe obtained a CV of 8.28, showing the best result, with no statistical difference with the mixer that obtained 8.38 CV, followed by the eccentric drum with 11.98 and the Y mixer with a variation equal to 12.37. However, all techniques can be considered for the preparation of feed, since the literature mentions CV between 10 to 15% as normal for conventional mixers. They should not only be used to prepare rations with medications because they are above the 5% required by Normative Instruction number 14 of the Ministry of Agriculture, Livestock and Supply.

Sensitivity of salad greens (Lactuca sativa L. and Eruca sativa Mill.) exposed to crude extracts of toxic and non-toxic cyanobacteria / Sensibilidade de hortaliças (Lactuca sativa L. e Eruca sativa Mill.) à exposição de extratos brutos de cianobactéria tóxica e não tóxica

We evaluated the effect of crude extracts of the microcystin-producing (MC+) cyanobacteria Microcystis aeruginosa on seed germination and initial development of lettuce and arugula, at concentrations between 0.5 μg.L–1 and 100 μg.L–1 of MC-LR equivalent, and compared it to crude extracts of the same species without the toxin (MC–). Crude extracts of the cyanobacteria with MC (+) and without MC (–) caused different effects on seed germination and initial development of the salad green seedlings, lettuce being more sensitive to both extracts when compared to arugula. Crude extracts of M. aeruginosa (MC+) caused more evident effects on seed germination and initial development of both species of salad greens than MC–. Concentrations of 75 μg.L–1 and 100 μg.L–1 of MC–LR equivalent induced a greater occurrence of abnormal seedlings in lettuce, due to necrosis of the radicle and shortening of this organ in normal seedlings, as well as the reduction in total chlorophyll content and increase in the activity of the antioxidant enzyme peroxidase (POD). The MCextract caused no harmful effects to seed germination and initial development of seedlings of arugula. However, in lettuce, it caused elevation of POD enzyme activity, decrease in seed germination at concentrations of 75 μg.L–1 (MC-75) and 100 μg.L–1 (MC-100), and shortening of the radicle length, suggesting that other compounds present in the cyanobacteria extracts contributed to this result. Crude extracts of M. aeruginosa (MC–) may contain other compounds, besides the cyanotoxins, capable of causing inhibitory or stimulatory effects on seed germination and initial development of salad green seedlings. Arugula was more sensitive to the crude extracts of M. aeruginosa (MC+) and (MC–) and to other possible compounds produced by the cyanobacteria.(AU)

Analisamos os efeitos de extratos brutos da cianobactéria M. aeruginosa, produtora de microcistinas (MC+), na germinação de sementes e no desenvolvimento de plântulas de alface e rúcula, em concentrações de 0,5 a 100 μg.L–1de MC–LR equivalente e comparamos com extrato brutos da mesma espécie sem a toxina (MC–). Extratos brutos de cianobactérias com MC (+) e sem MC (–) causaram efeitos diferentes na germinação de sementes e desenvolvimento de plântulas de hortaliças, sendo que a alface apresentou maior sensibilidade a ambos os extratos comparando-se com a rúcula. Extratos brutos de M. aeruginosa (MC+) causaram efeitos mais evidentes sobre a germinação de sementes e desenvolvimento de plântulas de hortaliças do que os (MC–). Concentrações de 75 e 100 μg.L–1 de MC–LR equivalente induziram maior ocorrência de plântulas anormais na alface devido ao aparecimento de necrose na radícula e seu encurtamento nas plântulas normais, bem como a redução no teor de clorofila total e aumento na atividade da enzima antioxidante peroxidase (POD). O extrato (MC–) não provocou efeitos inibitórios na germinação de sementes e desenvolvimento de plântulas para a rúcula, no entanto, provocou elevação da atividade da enzima POD, redução na germinação de sementes nas concentrações de 75 e 100 μg.L–1, e no comprimento da radícula na alface, sugerindo a ação de outros compostos presentes nos extratos da cianobactéria. Extratos brutos de M. aeruginosa (MC–) podem conter outros compostos além de cianotoxinas capazes de provocar efeitos inibitórios ou estimulatórios na germinação de sementes e no desenvolvimento de plântulas de hortaliças. A rúcula apresentou menor sensibilidade aos extratos brutos de M. aeruginosa (MC+) e (MC–) e outros possíveis compostos produzidos por estas cianobactérias.(AU)

The effect of cryodevice and cryoprotectant concentration on buffalo oocytes vitrified at MII stage

Vitrification is a common method for cryopreservation of gametes and embryos. Although successful oocyte vitrification has been achieved in several animal species, subsequent progress is still limited especially in buffalo. To improve the effectiveness of vitrification of buffalo oocytes, two experiments were conducted. The first experiment evaluated the effect of cryodevices on viability and maturation of vitrified, matured buffalo oocytes. The in vitro matured oocytes were divided into two groups, the first was vitrified using conventional French straws, while the other was vitrified using Cryotops. There was a significant reduction in the morphologically normal oocytes after vitrification with both methods. Maturation rates of vitrified thawed buffalo oocytes were significantly higher in Cryotops than straws. The survival rate after vitrification was similar for both straws and Cryotops. The percentages of viable oocytes were significantly lower in straw than in controls. The second experiment evaluated the effect of two concentrations of cryoprotectants on the vitrification of in vitro matured buffalo oocytes. Mixtures of DMSO and EG as cryoprotectant (CPA) solutions were prepared in TCM-199 with two concentrations of cryoprotectants. The first concentration was 6 M V2 (3 M E.G + 3 M DMSO), and the second concentration was 7 M V2 (3.5 M DMSO + 3.5 M EG). Each concentration of cryoprotectants was added in two steps, with the first step having half the concentration of the second (and final) concentration. The survival rate after vitrification was similar for both concentration (6 M and 7 M) groups. The maturation rates of vitrified thawed buffalo oocytes were significantly higher in 7 M concentration than in the 6 M group. In conclusion, the survivability and meiotic competence of buffalo oocytes improved with vitrification at higher concentration of cryoprotectants and using cryotops.

The effect of cryodevice and cryoprotectant concentration on buffalo oocytes vitrified at MII stage

Vitrification is a common method for cryopreservation of gametes and embryos. Although successful oocyte vitrification has been achieved in several animal species, subsequent progress is still limited especially in buffalo. To improve the effectiveness of vitrification of buffalo oocytes, two experiments were conducted. The first experiment evaluated the effect of cryodevices on viability and maturation of vitrified, matured buffalo oocytes. The in vitro matured oocytes were divided into two groups, the first was vitrified using conventional French straws, while the other was vitrified using Cryotops. There was a significant reduction in the morphologically normal oocytes after vitrification with both methods. Maturation rates of vitrified thawed buffalo oocytes were significantly higher in Cryotops than straws. The survival rate after vitrification was similar for both straws and Cryotops. The percentages of viable oocytes were significantly lower in straw than in controls. The second experiment evaluated the effect of two concentrations of cryoprotectants on the vitrification of in vitro matured buffalo oocytes. Mixtures of DMSO and EG as cryoprotectant (CPA) solutions were prepared in TCM-199 with two concentrations of cryoprotectants. The first concentration was 6 M V2 (3 M E.G + 3 M DMSO), and the second concentration was 7 M V2 (3.5 M DMSO + 3.5 M EG). Each concentration of cryoprotectants was added in two steps, with the first step having half the concentration of the second (and final) concentration. The survival rate after vitrification was similar for both concentration (6 M and 7 M) groups. The maturation rates of vitrified thawed buffalo oocytes were significantly higher in 7 M concentration than in the 6 M group. In conclusion, the survivability and meiotic competence of buffalo oocytes improved with vitrification at higher concentration of cryoprotectants and using cryotops.(AU)

UTILIZAÇÃO DE SUBPRODUTOS DA INDÚSTRIA DO ÓLEO DE SOJA E BIODIESEL E SUAS MISTURAS EM DIFERENTES PROPORÇÕES NA ALIMENTAÇÃO DE FRANGOS DE CORTE

A presente tese foi desenvolvida com objetivo de avaliar a utilização dos subprodutos do processamento do óleo de soja (OS) (óleo ácido de soja -OAS, lecitina - LEC) e do biodiesel (glicerol - GLI) na alimentação de frangos de corte. Dois estudos foram conduzidos para determinar EMA destes subprodutos e suas combinações. Foram usados 390 frangos de corte machos com 21 d para cada experimento distribuídos em um delineamento experimental inteiramente casualizado com arranjo fatorial com 4 fontes de gordura e 3 níveis de inclusão mais uma dieta basal sem suplementação de gordura. Cada experimento foi composto por 13 tratamentos dietéticos com 6 repetições de 5 aves por repetição. No primeiro ensaio foi usado: OAS, GLI e LEC, bem como uma mistura contendo 85% OAS, 10% GLI e 5% LEC (MIS). As proporções das fontes de energia na mistura foram semelhantes à encontrada no óleo de soja bruto. No segundo ensaio foi usado quatro diferentes misturas destas fontes de energia sendo elas: 85% OAS e 10% GLI; 80% OAS e 15% GLI; 75% OAS e 20% GLI e 70% OAS e 25% GLI, em todas as misturas estabeleceu-se 5% LEC. Os tratamentos dietéticos foram formados pela adição de cada fonte energética suplementar aos níveis de 0% (100% da dieta basal (DB), 2% (98% DB + 2% fonte de energia), 4% (96% DB + 4% fonte de energia) ou 6% (94% DB + 6% fonte de energia). Nos dois ensaios foi realizado coleta total de excretas por 72h. Aos 28 dias de idade no final do período experimental um frango por repetição foi abatido para coleta do fígado e coleta de sangue para análise de glicerol e triglicérides plasmático e enzima hepática glicerol quinase. Para os dois experimentos houve diferença estatística entre as fontes energéticas (P<0,05). No primeiro ensaio a mistura das três fontes (85:10:5) mostrou melhor valor de EMA, no entanto no segundo experimento a mistura de 80% OAS 15% GLI e 5% LEC apresentou melhor valor quando comparado as demais misturas. Para a concentração de glicerol e triglicerídeos plasmático, assim como para a atividade da enzima glicerol quinase, houve interação entre as fontes e o nível de inclusão (P<0,05). A medida que aumentou o nível de inclusão aumentou-se a concentração de glicerol no plasma e diminuiu a atividade da enzima, no entanto, isto não foi suficiente para saturar a enzima. Em conclusão, os tratamentos mostraram que a mistura de subprodutos do óleo de soja e do biodiesel podem ser usadas como fontes energéticas em dietas de frangos de corte sem acarretar problemas no metabolismo normal do glicerol.

This thesis was carried out to evaluate the utilization of soybean oil (SO) (acidulated soap stock - ASS, lecithin - LEC) and biodiesel (glycerol - GLY) in broiler feeds. Two studies were conducted to determine AME these byproducts and their combinations. At total of 390 21-d-old male broilers were utilized for each experiment distributed in a completely randomized design with factorial arrangement of 4 fat sources and 3 levels of inclusion plus the basal diet without any fat source. Each study contained 13 dietary treatments with 6 replicates of 5 chickens per replicate. In the first experiment, the fat sources used were OAS, GLY and, LEC as well as a mixture (MIX) containing 85%, 10% and 5% respectively. The proportions of energy sources in the mix were similar to that found in crude soybean oil. In the second experiment, it was used four different mixtures of these energy sources, which are, 85% ASS: 10% GLY; 80% ASS: 15% GLY; 75% ASS: 20% GLY and 70% ASS: 25% GLY in all mixtures was fixed 5% LEC. The experimental treatments consisted of addition of each supplemental fat source at the levels of 0% (100% of basal diet (BD)), 2% (98% BD + 2% fat source), 4% (96% BD + 4% fat source) or 6% (94% BD + 6% fat source). The total excreta collection was conducted for 72h. At 28 days of age, the end of the study period one chicken by repetition was slaughtered to collect the liver and blood collection for analysis of plasmatic glycerol and triglycerides and the liver was used for analysis of glycerol kinase enzyme. For both experiments was observed statistical difference between energy sources (P <0.05) in the first experiment the mixture of the three sources (85:10: 5) showed best value of AME, however, in the second experiment the mixture of 80% OAS GLI 15% and 5% LEC showed better value when compared to the other mixtures. For the concentration of plasma glycerol and triglycerides, as well as the activity of the enzyme glycerol kinase, there was an interaction between the sources and the inclusion level (P <0.05). As we increased the level of inclusion increased the concentration of glycerol in plasma and decreased enzyme activity, however, this was not enough to saturate the enzyme. In conclusion, the treatment showed that the mixture of soybean oil and biodiesel by-products could be used as energy sources in broiler diets without causing problems in the normal metabolism of the glycerol.

MISTURAS VITAMÍNICAS NA REGENERAÇÃO DO MARACUJAZEIRO AMARELO (Passiflora edulis f. flavicarpa Deg.)

Cotyledons were used as explants in order to test the effect of different vitamin mixtures and BAP concentrations on yellow passion fruit (Passiflora edulis f. flavicarpa Deg.) in vitro direct organogenesis. They basal medium was constituted of MS salts, supplemented with 1 and 2mg. img SRC="http:/img/fbpe/cr/v32n2/a09img01.gif"> -1 of BAP (6-benzilaminopurina). Vitamin mixtures MS and B5 were tested. Every assay was done with 60 explants. The data were analyzed by Tukey's test. The medium supplemented with B5 vitaminic complex induced an increase of the capacity of cotyledons to regenerate in the presence of both BAP concentrations, as well for the number of explants with buds as for the number of buds per explant. The analysis of ploidy level of regenerated plants showed a number of chromosomes apparently normal and typical for this specie (2n=18).

Cotilédones obtidos a partir de sementes germinadas in vitro foram usados como explantes com o objetivo de avaliar o efeito de dois complexos vitamínicos e de duas concentrações de 6-benzilaminopurina (BAP) na organogênese direta do maracujá amarelo (Passiflora edulis f. flavicarpa Deg.). Empregou-se o meio Murashige & Skoog (1962) suplementado com as vitaminas MS ou B5 (vitaminas de GAMBORG et al., 1968) e 1 ou 2 mg. img SRC="http:/img/fbpe/cr/v32n2/a09img01.gif"> -1 de BAP. Foram testados quatro tratamentos, sendo cada um constituído de 60 explantes. O experimento foi inteiramente casualizado, com dez repetições. Os dados, analisados pelo teste de Tukey, demonstraram que os meios de cultura suplementados com o complexo vitamínico B5 induziram gemas em mais de 70% dos explantes, obtendo-se até 8 brotos por explante, com um enraizamento superior a 90%. A análise de ploidia das plantas regeneradas indicou um número aparentemente normal de cromossomos típicos dessa espécie (2n=18)

MISTURAS VITAMÍNICAS NA REGENERAÇÃO DO MARACUJAZEIRO AMARELO (Passiflora edulis f. flavicarpa Deg.)

Cotyledons were used as explants in order to test the effect of different vitamin mixtures and BAP concentrations on yellow passion fruit (Passiflora edulis f. flavicarpa Deg.) in vitro direct organogenesis. They basal medium was constituted of MS salts, supplemented with 1 and 2mg. img SRC="http:/img/fbpe/cr/v32n2/a09img01.gif"> -1 of BAP (6-benzilaminopurina). Vitamin mixtures MS and B5 were tested. Every assay was done with 60 explants. The data were analyzed by Tukey's test. The medium supplemented with B5 vitaminic complex induced an increase of the capacity of cotyledons to regenerate in the presence of both BAP concentrations, as well for the number of explants with buds as for the number of buds per explant. The analysis of ploidy level of regenerated plants showed a number of chromosomes apparently normal and typical for this specie (2n=18).

Cotilédones obtidos a partir de sementes germinadas in vitro foram usados como explantes com o objetivo de avaliar o efeito de dois complexos vitamínicos e de duas concentrações de 6-benzilaminopurina (BAP) na organogênese direta do maracujá amarelo (Passiflora edulis f. flavicarpa Deg.). Empregou-se o meio Murashige & Skoog (1962) suplementado com as vitaminas MS ou B5 (vitaminas de GAMBORG et al., 1968) e 1 ou 2 mg. img SRC="http:/img/fbpe/cr/v32n2/a09img01.gif"> -1 de BAP. Foram testados quatro tratamentos, sendo cada um constituído de 60 explantes. O experimento foi inteiramente casualizado, com dez repetições. Os dados, analisados pelo teste de Tukey, demonstraram que os meios de cultura suplementados com o complexo vitamínico B5 induziram gemas em mais de 70% dos explantes, obtendo-se até 8 brotos por explante, com um enraizamento superior a 90%. A análise de ploidia das plantas regeneradas indicou um número aparentemente normal de cromossomos típicos dessa espécie (2n=18)

Evaluation of the generalized likelihood ratio test of hypotheses on the genetic control of continuous traits / Avaliação da razão de verossimilhança generalizada em teste de hipóteses sobre o controle genético de características contínuas

Studies of genetic control in plants are carried out to characterize genetic effects and detect the existence of a major gene and/or genes of minor effects (polygenes). If the trait of interest is continuous, the likelihood can be constructed based on a model with mixtures of normal densities. Once exact tests are not evident with such models, the likelihood ratio test is generally used, using the chi-square approximation. This work aimed at evaluating such test statistic using computer simulation. Data sets were simulated using generations typical in plant studies, under two conditions of null hypothesis, without a major gene, and without polygenes. The power of the test was evaluated with both types of genes present. Different sample sizes and values of heritability were considered. Results showed that, although the empirical densities of the test statistic departed significantly from a chi-square distribution, under null hypotheses, there was a reasonable control of type I error, with a significance level of 5%. The power of the test was generally high to detect polygenes and major genes. Power is low to detect a major gene only when it explains a low fraction of genetic variation.

Estudos de herança genética em plantas são realizados para caracterizar os efeitos genéticos e verificar a existência de um gene de efeito maior e/ou de genes de pequeno efeito (poligenes). Quando a característica de interesse é contínua, a verossimilhança é baseada em modelos de misturas de densidades normais. Uma vez que não há testes exatos evidentes para julgar a existência de um gene de efeito maior, a razão de verossimilhança generalizada é em geral utilizada, considerando a aproximação de qui-quadrado. Este trabalho objetivou avaliar esta estatística de teste através de simulação em computador. Dados foram simulados, considerando particularidades de genealogia típicas de tais estudos, e duas condições sob a hipótese de nulidade, ou seja, sem a presença de um gene de efeito maior e sem a presença de genes de pequeno efeito (poligenes), para avaliar o controle do erro tipo I. O poder do teste foi avaliado com ambos presentes. No processo de simulação, foram variados o tamanho de amostra e valores do coeficiente de herdabilidade. Resultados indicaram que, embora a distribuição empírica da razão de verossimilhança tenha se desviado significativamente da distribuição de qui-quadrado, houve controle do erro tipo I, considerando um nível de significância nominal de 5%. O poder é elevado para detectar poligenes e gene de efeito maior, em geral. O poder é baixo para detectar ge

Evaluation of the generalized likelihood ratio test of hypotheses on the genetic control of continuous traits / Avaliação da razão de verossimilhança generalizada em teste de hipóteses sobre o controle genético de características contínuas

Studies of genetic control in plants are carried out to characterize genetic effects and detect the existence of a major gene and/or genes of minor effects (polygenes). If the trait of interest is continuous, the likelihood can be constructed based on a model with mixtures of normal densities. Once exact tests are not evident with such models, the likelihood ratio test is generally used, using the chi-square approximation. This work aimed at evaluating such test statistic using computer simulation. Data sets were simulated using generations typical in plant studies, under two conditions of null hypothesis, without a major gene, and without polygenes. The power of the test was evaluated with both types of genes present. Different sample sizes and values of heritability were considered. Results showed that, although the empirical densities of the test statistic departed significantly from a chi-square distribution, under null hypotheses, there was a reasonable control of type I error, with a significance level of 5%. The power of the test was generally high to detect polygenes and major genes. Power is low to detect a major gene only when it explains a low fraction of genetic variation.

Estudos de herança genética em plantas são realizados para caracterizar os efeitos genéticos e verificar a existência de um gene de efeito maior e/ou de genes de pequeno efeito (poligenes). Quando a característica de interesse é contínua, a verossimilhança é baseada em modelos de misturas de densidades normais. Uma vez que não há testes exatos evidentes para julgar a existência de um gene de efeito maior, a razão de verossimilhança generalizada é em geral utilizada, considerando a aproximação de qui-quadrado. Este trabalho objetivou avaliar esta estatística de teste através de simulação em computador. Dados foram simulados, considerando particularidades de genealogia típicas de tais estudos, e duas condições sob a hipótese de nulidade, ou seja, sem a presença de um gene de efeito maior e sem a presença de genes de pequeno efeito (poligenes), para avaliar o controle do erro tipo I. O poder do teste foi avaliado com ambos presentes. No processo de simulação, foram variados o tamanho de amostra e valores do coeficiente de herdabilidade. Resultados indicaram que, embora a distribuição empírica da razão de verossimilhança tenha se desviado significativamente da distribuição de qui-quadrado, houve controle do erro tipo I, considerando um nível de significância nominal de 5%. O poder é elevado para detectar poligenes e gene de efeito maior, em geral. O poder é baixo para detectar ge