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The objective of this study is to compare random-regression models used to describe changes in evaluation parameters for growth in Tabapuã bovine raised in the Northeast of Brazilian. The M4532-5 random-regression model was found to be best for estimating the variation and heritability of growth characteristics in the animals evaluated. Estimates of direct additive genetic variance increased with age, while the maternal additive genetic variance demonstrated growth from birth to up to nearly 420 days of age. The genetic correlations between the first four characteristics were positive with moderate to large ranges. The greatest genetic correlation was observed between birth weight and at 240 days of age (0.82). The phenotypic correlation between birth weight and other characteristics was low. The M4532-5 random-regression model with 39 parameters was found to be best for describing the growth curve of the animals evaluated providing improved selection for heavier animals when performed after weaning. The interpretation of genetic parameters to predict the growth curve of cattle may allow the selection of animals to accelerate slaughter procedures.

This study aimed to evaluate the seroprevalence and risk factors associated with Toxoplasma gondii infection in goats from micro-regions of the state of Piauí (Brazil). From six randomly selected properties, 145 goats were examined. Serum samples of the animals were analyzed by ELISA for the presence or absence of antibodies against T. gondii. Of these, 22% were seroreactive for T. gondii. Individual records were also taken for each property. These analyses showed that factors such as sex, age, water source, and presence of cats were associated with animal seropositivity. In addition, there was also a positive correlation (p > 0.04) between animal sex and T. gondii contamination. The presence of cats in the facilities and animal pasture fields appeared to be a risk factor for the contamination of goats in the assessed properties (p > 0.03). The parasite Toxoplasma gondii is present in the goat herds of southern Piauí state, and females are more likely to be contaminated.

Article history Due to the increasing importance of cryptosporidiosis in animal productivity, this study was carried out to investigate the occurrence of Cryptosporidium spp. and its association with animal weight development and fecal consistency in crossbred Nellore cattle. Thus, fecal samples of 30 cattle were collected biweekly, and their growth was accompanied by weighing animals from birth to 210 days of age (June 2014 to May 2015). The modified Ritchie and Ziehl-Neelsen techniques were used to screen for the presence of Cryptosporidium spp. oocysts. The chi-square, Fisher exact, Tukey and Spearman's correlation tests were used for statistical analysis. Oocysts of Cryptosporidium spp. were found in 69 (16.43%) of the 420 samples of cattle feces, and these parasitized animals presented a mean weight gain (4.76 kg) lower than that of non-parasitized individuals (10.58 kg) (p<0.05). The presence of this protozoan was detected in diarrhea and pasty stools (81.78%), indicating an association of the parasite with persistent diarrheal episodes (p<0.001). Among the bovines examined in this study, a higher occurrence of Cryptosporidium spp. was observed in lean diarrheic calves, which presented lower weight gain and poor productive performance.

O estudo foi conduzido para avaliar a idade ao primeiro parto (IPP) e o intervalo de partos (IDP) em fêmeas da raça Nelore utilizando 23.066 registros de IPP e IDP de fêmeas criadas em regime de pasto nos estados do Maranhão e Piauí no período de 1976 a 2012. As análises foram realizadas utilizando modelo animal uni e bicaracterísticas para IPP e IDP. As médias obtidas e os coeficientes de variação para as características de idade ao primeiro parto foram 1252,77±125 dias (41,76 meses) a 10,56%; intervalo de partos 591,729±149,91 dias (19,72 meses) a 38,74%, respectivamente. Foram estimados parâmetros genéticos em análise unicaracterística, sendo obtidos valores de herdabilidade em torno de 0,026 e 0,006 para IPP e IDP, respectivamente. A estimativa de repetibilidade para as características IDP em análise unicaracterística apresentou-se, de forma geral, com baixa magnitude 0,025. Na mesma ordem, para análise bicaracterística, as herdabilidades foram de 0,03 e 0,06 para IPP e IDP, e o coeficiente de repetibilidade estimado de 0,14, respectivamente. As correlações genéticas entre as características reprodutivas (IPP e IDP) observadas neste trabalho foram iguais a 0,06. O desempenho reprodutivo do rebanho estudado, para as condições de clima tropical, pode ser considerado satisfatório, estando em acordo com os parâmetros encontrados por outros autores em diferentes regiões.

Características termorreguladoras de ovinos da raça Dorper criados em condições climáticas de Meio-Norte do Brasil Thermoregulatory characteristics of Dorper sheep reared in climatic conditions in the Mid-North region of Brazil

SUMMARY:Thepurpose of thisreview isto show the increase in number of researches on covariance components and genetic evaluation using random regression models (RRM) for growth traits of Nellore cattle. Random regression models (RRM), also known as infinite-dimension models have been used to estimate variance components and genetic parameters for weight of beef cattle. In addition, those models are a standard alternative for genetic analyses of longitudinal data, however, the availibility of computational resources for performing genetic evaluations widely is an obstacle. Traits related to animal growth are adopted as selection criteria in beef cattle breeding programs, because the remuneration of cattle breeders is made based on the weight of carcasses. In recent years, RRM have been adopted as standard procedure in relation to the analysis of longitudinal data in animal breeding.Keywords: Genetic evaluation. Longitudinal data. Nellore cattle. APLICAÇÃO DE MODELOS DE REGRESSÃO ALEATÓRIA PARA CARACTERÍSTICAS DE CRESCIMENTO DA RAÇA NELORE NO BRASILRESUMO: Objetivou-se com esta revisão de literatura compilar informações sob a avaliação genética utilizando modelos de regressão aleatória (MRA) para características de crescimento em bovinos da raça Nelore. Os modelos de regressão aleatória (MRA), denominados modelos de dimensão infinita, estão sendo utilizados para estimar os componentes de variância e parâmetros genéticos de pesos de bovinos de corte. Os MRA têm se tornado uma alternativa padrão para análises genéticas de dados longitudinais, onde um dos entraves destes modelos está relacionado à disponibilidade de memória e tempo computacional para a realização de avaliações genéticas em larga escala. Características relacionadas ao crescimento animal são adotadas em programas de melhoramento genético de bovinos de corte como critérios de seleção, pelo fato da remuneração, dos produtores, ser feita com base no peso das carcaças. Nos últimos anos, os MRA têm sido adotados como procedimento padrão para análise de dados longitudinais em melhoramento genético animal.Palavras-chave: Avaliação genética. Dados longitudinais. Nelore.

The purpose of this review is to show the increase in number of researches on covariance components and genetic evaluation using random regression models (RRM) for growth traits of Nellore cattle. Random regression models, also known as infinite-dimension models have been used to estimate variance components and genetic parameters for weight of beef cattle. In addition, those models are a standard alternative for genetic analyses of longitudinal data, however, the availibility of computational resources for performing genetic evaluations widely is an obstacle. Traits related to animal growth are adopted as selection criteria in beef cattle breeding programs, because the remuneration of cattle breeders is made based on the weight of carcasses. In recent years, RRM have been adopted as standard procedure in relation to the analysis of longitudinal data in animal breeding.