Effect of lactation length adjustment procedures on genetic parameter estimates for buffalo milk yield

The objectives of this study were to estimate the genetic parameters for milk yield unadjusted and adjusted for days in milk and, subsequently, to assess the influence of adjusting for days in milk on sire rank. Complete lactations from 90 or 150 days of lactation to 270 or 350 days in milk were considered in these analyses. Milk yield was adjusted for days in milk by multiplicative correction factors, or by including lactation length as a covariable in the model. Milk yields adjusted by different procedures were considered as different traits. Heritability estimates varied from 0.17 to 0.28. Genetic correlation estimates between milk yields unadjusted and adjusted for days in milk were greater than 0.82. Adjusting for days in milk affected the parameter estimates. Multiplicative correction factors produced the highest heritability estimates. More reliable breeding value estimates can be expected by including short length lactation records in the analyses and adjusting the milk yields for days in milk, regardless of the method used for the adjustment. High selection intensity coupled to the inclusion of short length lactations and adjustment with multiplicative factors can change the sire rank.

Estudo genético quantitativo do fluxo lácteo em bovinos da raça Holandesa

Parâmetros genéticos para o fluxo lácteo medido no dia do controle (FLDC) de primeiras lactações de vacas da raça Holandesa foram estimados utilizando modelos de dimensão finita (TDM) e modelos de regressão aleatória. Para os TDM foram analisadas 10 características por meio de modelos uni e bi e multi-características e de repetibilidade, que continham como aleatórios, o efeito genético aditivo e o efeito residual e, como efeitos fixos, o grupo de contemporâneos e as covariáveis idade da vaca ao parto. A variável número de dias em lactação foi incluída somente no modelo de repetibilidade. Para os MRA, foram considerados os efeitos aleatórios genético aditivo direto, de ambiente permanente e o residual. Foram considerados como efeitos fixos, o grupo de contemporâneos, os efeitos linear e quadrático da covariável idade da vaca ao parto e a curva média de lactação da população, modelada por meio de polinômios ortogonais de Legendre de quarta ordem. Os efeitos aleatórios genético aditivo e de ambiente permanente foram modelados por meio de regressão aleatória sobre polinômios ortogonais de Legendre e por meio de funções b-splines. Diferentes estruturas de variâncias residuais foram testadas, por meio de classes contendo 1, 7, 10, 20 e 43 variâncias residuais, para os MRA modelados por meio de polinômios de Legendre. Já, para os MRA modelados por funções b-splines, a estrutura residual foi considerada heterogênea, contendo 7 classes de variâncias. Os MRA foram comparados usando o teste de razão de verossimilhança, o critério de informação de Akaike e o critério de informação de Bayesiano de Schwarz. As estimativas de herdabilidade (h2) para os FLDC variaram de 0,23 a 0,32 nas análises unicaracterísticas, de 0,24 a 0,32 nas bi-características e de 0,28 a 0,37 nas multicaracterísticas. Os valores de h2 estimados variaram no decorrer da...Flow milk genetic parameters to the first lactation test-day milk yields of Holstein cattle were estimated using Test-day models (TDM) and Random regression models (RRM). Ten TDM differents traits were analyzed using uni, bi and multi-trait and repeatability animal models, that included the additive genetic as random effect and the fixed effects of contemporary group, age of cow (linear and quadratic) as covariables. The days in milk (linear) variable was included only at repeatability model. To RRM were included the additive genetic, permanent environmental and residual as random effects, the fixed effects of contemporary group, age of cow as covariable (linear and quadratic effects) and a 4th-order Legendre orthogonal polynomials of days in milk, to model the mean trend. The additive genetic and permanent environmental effects were fitted by Legendre orthogonal polynomials and b-splines functions. Different structures of residual variances were used, through the variances classes containing 1, 7, 10, 20, and e 43 residual variances, to the models fitted by Legendre orthogonal polynomials. Moreover, for the RRM fitted by b-splines-functions, the residual estructure was considered heterogeneous, having 7 variance classes. The RRM were compared by Likelihood ratio test, Bayesian and Akaike´s information criteria. The heritability estimated ranged from 0.23 to 0.32 by uni-trait analyses, from 0.24 to 0.32 by bi-traits analyses and from 0.28 to 0.37 by multi-trait analyses. The h2 estimates varied during the lactation being the highest estimate at the fourth month. The estimate obtained by the repeatability model was 0.27, and a repeatability estimate of 0.66. For the MRA fitted by Legendre orthogonal polynomials, related to the residual variance, the best model the one that deemed 7 residual classes. For the additive and permanent environmental effects, the having 3th-order... (Complete abstract click electronic access below)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Qualidade microbiológica do mel de Melipona sp. produzido na amazônia central, Parintins, AM, Brasil

Fifteen samples of honey were collected directly from the hives in different meliponary at rural and urban areas of Parintins County. Molds and yeasts were quantified by counting in Petri dishes containing potato dextrose agar (pH 3.5) and incubated for until seven days. Total and thermotolerant coliforms were quantified by the technique of multiple tube fermentation, then determining the most probable number per gram. Molds and yeasts occurred an average of 71.9 x 102 colony forming units per gram (CFU/mL). Filamentous fungi occurred in 80% samples (average of 2.8 x 102 CFU/mL), while yeasts occurred in 100% of the samples (average of 62.2 x 102 CFU/mL). Five samples (33.33%) had total coliforms and thermotolerant, and three of these were within the limits tolerated by law. Statistical analysis showed no relationship between the microbiological quality of samples and the type of environment (rural or urban) in which it was collected. The Pearson correlation coefficient (0.89, p = 0.000) demonstrated a correlation between the amounts of molds and yeasts and coliforms. The highest count of microorganisms in the beginning of the season suggests a relationship between microbiological quality and availability of flowers to bees.Quinze amostras de mel foram coletadas diretamente das colméias em diferentes meliponários nas zonas rural e urbana do município de Parintins. Bolores e leveduras foram quantificados por contagem em placas de Petri contendo Agar Batata Dextrose (pH 3,5), incubadas por até sete dias. Coliformes totais e termotolerantes foram quantificados pela técnica de fermentação em tubos múltiplos, determinando-se a seguir o número mais provável por grama. Bolores e leveduras ocorreram em média de 71,9 x 102 Unidades Formadoras de Colônias por grama (UFC/mL). Fungos filamentosos ocorreram em 80% amostras (média de 2,8 x 102 UFC/mL), enquanto leveduras ocorreram em 100% das amostras (média de 62,2 x 102 UFC/mL). Cinco amostras (33,33%) apresentaram contaminação por coliformes totais e termotolerantes, sendo que três destas encontravam-se dentro dos limites tolerados pela legislação em vigor. A análise estatística demonstrou não haver relação entre a qualidade microbiológica das amostras e o tipo de ambiente (rural ou urbano) na qual foram coletadas. O coeficiente de correlação de Pearson (0,89; p=0,000) demonstrou correlação entre os quantitativos de bolores e leveduras e coliformes. A contagem de microrganismos obtida no início da safra sugere relação entre qualidade microbiológica e disponibilidade de flores às abelhas

Characterization and polymorphism screening of IGF-I and prolactin genes in Nelore heifers

Insulin growth factor I (IGF-I) and prolactin (PRL) are peptide hormones that exert complementary effects on reproductive traits by acting on folliculogenesis. In view of the lack of information about the IGF-I and PRL genes in Bos indicus, the objective of this study was to partially characterize the promoter regions of these genes and to screen animals of different ages at first pregnancy for the presence of polymorphisms in these regions. In addition, we determined whether polymorphisms influence the regulation of the two hormone genes, evaluating their association with sexual precocity. The animals were divided into three groups according to age at first pregnancy: 1) 100 heifers considered to be sexually precocious that became pregnant at 15-16 months of age, 2) 100 heifers that became pregnant during the normal breeding season at 24 months of age, and 3) 100 heifers that did not become pregnant until 24 months of age. For the IGF-I gene, PCR-RFLP-SnaBI analysis showed the presence of genotypes AB and BB at frequencies of 0.02 and 0.98, respectively. Sequencing of the IGF-I gene fragment revealed a single nitrogen base change from cytosine to thymine, corresponding to the restriction site of SnaBI. The polymorphisms identified in the 5’-flanking region of the IGF-I gene may serve as a basis for future studies of molecular markers in cattle. For the PRL gene, PCR-RFLP-HaeIII analysis showed the presence of only one migration pattern, a finding characterizing the region studied as monomorphic. The study of other regions in the IGF-I and PRL genes might provide molecular data that can be used in the future for the selection of sexually precocious animals

The impact of heterogeneity of variances on the genetic evaluation of performance traits in Nellore cattle

The objective was to evaluate the existence of heterogeneity of variances and its impact on the genetic evaluation of ponderal performance in sires of the Nellore breed. We used records of adjusted body weights at 210 (W210), 365 (W365), and 450 (W450) days of age. Both W365 and W450 were combined by principal component analyses using the first component (PC). Average daily gain (ADG) was obtained by difference between W450 and W210. The classes of standard deviations (SD) for W210, PC, and ADG were obtained by the standardization of means of herd-year means subclasses, with positive values composing the high SD and values equal and less than zero composing the SD. The model included the fixed effects of contemporary group and age at calving as a covariate, random genetic additive, and maternal genetic (except for PC) effects, and the permanent maternal environment. Variance components were obtained by Gibbs sampling. Posterior means of heritability in analyses without considering heterogeneity of variances ranged from 0.15±0.01 to 0.31±0.01. Posterior means of genetic correlations between the two classes of SD for W210, PC, and ADG were equal to 0.85±0.04, 0.83±0.03, and 0.71±0.08, respectively. Spearman correlation to breeding values of sires for ADG as the selection intensity increased in them, and the correlations between breeding values in general analyses were more correlated with those predicted in the high DP. Therefore, when there is a higher selection intensity on the sires only for the ADG criterion, there is a significant presence of the heterogeneity of variances and impact on the genetic evaluation of the sires. Thus, for ADG, the predictions of breeding values obtained by the genetic evaluation model in which the heterogeneity of variances are not considered are more weighted by the class of greater heterogeneit