Curvas de crescimento de mamíferos produtores de carne pelo modelo de von Bertalanffy

The objective of this work was to evaluate how the parameterization and the application of different allometric values affect the obtention of the most adequate fit of von Bertalanffy’s model, in the description of the growth curve of meat-producing mammals (bovine, pigs, rabbits, and sheep). Among the nonlinear models, von Bertalanffy’s has been very often applied in several areas, with different parameterizations. This model has been commonly used with an allometric value of m = 2/3; however, for mammals, it is believed that this value can be m = 3/4. The analyzed data referring to the mass of meat-producing mammals according to their age were obtained from research institutions and from the literature. The results showed that von Bertalanffy’s model, with the allometric value of m = 3/4 and the used parameterization, provided better adjustments to quality evaluators. Besides, the model softened the overestimation of parameter a, giving a direct interpretation of parameter b, with the lowest values for curvature measurements, mainly for the parametric ones, and provided more reliable adjustments. Von Bertalanffy’s model can be used in the description of the growth curves of meat-producing mammals.O objetivo desde trabalho foi avaliar como a parametrização e a aplicação de diferentes valores alométricos afetam a obtenção do ajuste mais adequado do modelo de von Bertalanffy, na descrição da curva de crescimento de mamíferos produtores de carne (bovinos, porcos, coelhos e ovelhas). Entre os modelos não lineares, o de von Bertalanffy tem sido frequentemente aplicado em diversas áreas, com diferentes parametrizações. Em geral, esse modelo tem sido utilizado com um valor alométrico de m = 2/3; no entanto, para mamíferos, acredita-se que o valor possa ser m = 3/4. Os dados analisados quanto à massa dos mamíferos de corte de acordo com a sua idade foram obtidos de instituições de pesquisa e da literatura. Os resultados mostraram que o modelo de von Bertalanffy, com o valor alométrico de m = 3/4 e com a parametrização utilizada, forneceu melhores ajustes aos avaliadores de qualidade. Além disso, o modelo suavizou a superestimativa do parâmetro a, o que possibilitou interpretação direta ao parâmetro b, com menores valores das medidas de curvatura, principalmente as paramétricas, e forneceu ajustes mais confiáveis. O modelo de von Bertalanffy pode ser utilizado na descrição da curva de crescimento de mamíferos produtores de carne

Modelos lineares e não lineares para a descrição da curva de lactação da raça Girolando

The objective of this work was to compare the main linear and nonlinear models used to describe lactation curves and to evaluate the nonlinearity of the nonlinear models, in order to obtain the most adequate model to describe the lactation curves of the Girolando breed. Data from 165 lactations of 89 3/4 Holstein + 1/4 Gyr cows were used, and average yield was calculated every 20 days up to 310 days of lactation. Seventeen models of lactation curves available in the literature were compared. The selection of the best model was based on the curvature measures of Bates & Watts, the bias of Box, adjusted coefficient of determination, Akaike’s information criterion, and residual standard deviation. The linear model of Cobuci estimated a yield peak of 16.7 kg at 40 days of lactation, whereas the nonlinear model of Wood estimated a yield peak of 16.8 kg at 41 days of lactation and a persistence of 6.82. Nonlinearity measures were the most appropriate for selecting the most suitable nonlinear model for the description of lactation curves. To describe the lactation curves of the Girolando breed, the most suitable linear model is that of Cobuci and the nonlinear model is that of Wood.O objetivo deste trabalho foi comparar os principais modelos lineares e não lineares usados para descrever curvas de lactação e avaliar a não linearidade dos modelos não lineares, para obter o modelo mais adequado para a descrição das curvas de lactação da raça Girolando. Foram utilizados dados de 165 lactações de 89 vacas 3/4 Holandesas + 1/4 Gir, tendo-se calculado a produção média a cada 20 dias até 310 dias de lactação. Foram comparados 17 modelos de curvas de lactação disponíveis na literatura. A seleção do melhor modelo foi feita com base nas medidas de curvatura de Bates & Watts, no vício de Box, no coeficiente de determinação ajustado, no critério de informação de Akaike e no desvio-padrão residual. O modelo linear de Cobuci estimou um pico de produção de 16,7 kg aos 40 dias de lactação, enquanto o modelo não linear de Wood estimou um pico de produção de 16,8 kg aos 41 dias de lactação e persistência de 6,82. As medidas de não linearidade foram as mais adequadas para selecionar o modelo não linear mais adequado para a descrição das curvas de lactação. Para descrever as curvas de lactação da raça Girolando, o modelo linear mais adequado é o de Cobuci e o não linear é o de Wood

Características morfométricas de equinos da raça Mangalarga Marchador determinadas por modelos não lineares

The objective of this work was to evaluate the development of the morphometric characteristics of Mangalarga Marchador horses through nonlinear models. The transversal method was used to collect data on height at the withers (HW), body length (BL), and thoracic (TP) and cannon (CP) perimeters from 200 horses (75 males and 125 non-pregnant females), aged between 6 and 153 months. The parameters of the Brody, Gompertz, logistic, and von Bertalanffy nonlinear models were estimated using the R software. Models were compared and selected using the coefficient of determination, the residual standard deviation, and the corrected Akaike information criterion. For adult females, HW, BL, TP, and CP ranged between 146.45–148.34, 148.59–151.64, 179.07–182.88, and 18.25–18.76 cm, respectively. For males, HW, BL, and CP ranged between 148.55–151.80, 150.77–154.88, and 18.95–19.41 cm, respectively. The logistic model best expresses growth in HW for males and females, as well as in BL and CP for males, whereas the Brody model is the best predictor for HW, BL, TP, and CP for females. The increase in the values of the morphometric measurements is more rapid and homogeneous between the ages of 6 and 24 months, stabilizing at 60 months in both sexes.O objetivo deste trabalho foi avaliar o desenvolvimento de características morfométricas de equinos Mangalarga Marchador por meio de modelos não lineares. Utilizou-se o método transversal para coletar dados de altura da cernelha (AC), comprimento corporal (CC) e perímetros torácico (PT) e de canela (PC) de 200 cavalos (75 machos e 125 fêmeas não gestantes), com idade entre 6 e 153 meses. Os parâmetros dos modelos não lineares de Brody, de Gompertz, logístico e de Von Bertalanffy foram estimados com uso do programa R. A comparação e a seleção dos modelos foi realizada por meio do coeficiente de determinação, do desvio-padrão residual e do critério de informação de Akaike corrigido. Nas fêmeas adultas, AC, CC, PT e PC variaram entre 146,45–148,34, 148,59–151,64, 179,07–182,88 e 18,25–18,76 cm, respectivamente. Nos machos, AC, CC e PC variaram entre 148,55–151,80, 150,77–154,88 e 18,95–19,41 cm, respectivamente. O modelo logístico é o mais indicado para expressar o crescimento em AC em machos e fêmeas, bem como em CC e PC em machos, enquanto o de Brody é o melhor preditor de AC, CC, PT e PC em fêmeas. O aumento nos valores das medidas morfométricas é mais rápido e homogêneo entre as idades de 6 a 24 meses, e estabiliza-se aos 60 meses em ambos os sexos

Genetic characterization of Mangalarga Marchador horse

Mangalarga Marchador (MM) is the most important Brazilian horse breed, with 600 thousand animals registered. The aim of this study carry out the genetic characterization of the breed. Samples were collected from 355 horses [MM, n = 218; Andalusian n = 20; Purebred Lusitano n = 21; Sorraia (SOR) n = 16; Thoroughbred n = 21; Campolina (CAM) n = 21, and Mangalarga (MAN) n = 38] and genotyped with the SNP 70K BeadChip. Parameters were calculated, such as expected heterozygosities (He), Hardy-Weinberg equilibrium (HWE), linkage disequilibrium (r2), genetic differentiation, and principal component analysis (PCA); and haplotypes in common and population structure was assessed by Bayesian methods. The MM breed obtained reasonable He and deviations from HWE. The SOR breed had high r2, and CAM and MM had low r2. MAN and MM had a similar haplotype block. Analyses of population structure showed that, just as the other Brazilian breeds, the MM breed is not well defined, showing signs of substructure and possibly admixture. The analyses with PCA showed that Brazilian breeds clustered together, and well separated from the remaining breeds. A breeding program seeking to maximize the variability of MM and structure the breed as a more defined genetic entity should be implemented immediately.Fil: Moura Baena, Marielle. Universidade Federal de Viçosa.; BrasilFil: Caetano Souza, Felipe Amorim. Universidad Federal de Lavras.; BrasilFil: Pereira Ribeiro, Yasmin. Universidad Federal de Lavras.; BrasilFil: Diaz, Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico CONICET- La Plata. Instituto de Genética Veterinaria "Ing. Fernando Noel Dulout". Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Instituto de Genética Veterinaria; ArgentinaFil: Olivera, Leónidas Hernán. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico CONICET- La Plata. Instituto de Genética Veterinaria "Ing. Fernando Noel Dulout". Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Instituto de Genética Veterinaria; ArgentinaFil: Silva de Moura, Raquel. Universidad Federal de Lavras.; BrasilFil: Meirelles, Sarah Laguna Conceição. Universidade Federal de Lavras; Brasi

Tournaments between markers as a strategy to enhance genomic predictions.

Analysis of a large number of markers is crucial in both genome-wide association studies (GWAS) and genome-wide selection (GWS). However there are two methodological issues that restrict statistical analysis: high dimensionality (p≫n) and multicollinearity. Although there are methodologies that can be used to fit models for data with high dimensionality (eg, the Bayesian Lasso), a big problem that can occurs in this cases is that the predictive ability of the model should perform well for the individuals used to fit the model, but should not perform well for other individuals, restricting the applicability of the model. This problem can be circumvent by applying some selection methodology to reduce the number of markers (but keeping the markers associated with the phenotypic trait) before adjusting a model to predict GBVs. We revisit a tournament-based strategy between marker samples, where each sample has good statistical properties for estimation: n>p and low collinearity. Such tournaments are elaborated using multiple linear regression to eliminate markers. This method is adapted from previous works found in the literature. We used simulated data as well as real data derived from a study with SNPs in beef cattle. Tournament strategies not only circumvent the p≫n issue, but also minimize spurious associations. For real data, when we selected a few more than 20 markers, we obtained correlations greater than 0.70 between predicted Genomic Breeding Values (GBVs) and phenotypes in validation groups of a cross-validation scheme; and when we selected a larger number of markers (more than 100), the correlations exceeded 0.90, showing the efficiency in identifying relevant SNPs (or segregations) for both GWAS and GWS. In the simulation study, we obtained similar results

Nonlinear modeling growth body weight of Mangalarga Marchador horses

ABSTRACT: The analysis of the growth and development of various species has been done using the growth curves of the specific animal based on non-linear models. The objective of the current study was to evaluate the fit of the Brody, Gompertz, Logistic and von Bertalanffy models to the cross-sectional data of the live weight of the MangalargaMarchador horses to identify the best model and make accurate predictions regarding the growth and maturity in the males and females of this breed. The study involved recording the weight of 214 horses, of which 94 were males and 120 were non-pregnant females, between 6 and 153 months of age. The parameters of the model were estimated by employing the method of least squares, using the iteratively regularized Gauss-Newton method and the R software package. Comparison of the models was done based on the following criteria: coefficient of determination (R²); Residual Standard Deviation (RSD); corrected Akaike Information Criterion (AICc). The estimated weight of the adult horses by the models ranged between 431kg and 439kg for males and between 416kg and 420kg for females. The growth curves were studied using the cross-sectional data collection method. For males the von Bertalanffymodel was found to be the most effective in expressing growth, while in females the Brody model was more suitable. The MangalargaMarchador females achieve adult body weight earlier than the males

Practical procedures to body weight estimation and correction factors applied to Campolina horses

The objective of this study was to evaluate the accuracy of the following six body weight (BW) estimation methods in Campolina (CAM) horses: A - weight tape placed at three different positions on the animal’s thorax; B - Crevat and Quetelet’s formula; C - Hall’s formula; D - Hintz and Griffiths’s table; E - Santos’s table; and F - Cintra’s formula. A total of 380 CAM horses were separated according to sex, age class, and gestational stage and evaluated. To determine their accuracy, weights measured on a scale and weight estimates of the six methods were compared by paired t-test, mean prediction error (MPE), and coefficient of determination (R²), using R software. The predictive capacity of method F was lower in the 6-12 months age class, so this formula is not indicated. The BW was overestimated compared with the actual weight by methods A (with weight tape placed in position 3) and B and underestimated by method C. Methods D and E accurately estimated BW of CAM horses. Correction factors are required to accurately estimate BW in this breed using methods B and C. Method A with the weight tape placed in position 2 is the most accurate for predicting BW, including pregnant female horses, and can, therefore, be considered the most suitable method for estimating BW of CAM horse

Estimation methods and correction factors for body weight in Mangalarga Marchador horses

ABSTRACT The objective was to evaluate the accuracy of six body weight (BW) estimating methods in Mangalarga Marchador horses (MM) (n = 318): method A - tape placements at three different positions around the thoracic girth; B - Crevat and Quetelec's formula; C - Hall's formula; D - Hintz and Griffiths’ table; E - Santos’ table; and F - Cintra's formula. For additional analyses, gender, age, and gestational stage were considered. Estimated average BW was compared to the actual scale weight by the paired T test, mean predicted error, and determination coefficient. In the general population, methods A (position 3), B, and C estimated BW that were different from that of the scale. Method A, at positions 1 and 2, was more accurate in predicting the scale weight results compared with all other methods. For pregnant mares, the tape in positions 1 and 2 in method A did not differ from those of the scale. Method A in positions 1 and 2 and the table (method E) may be used to estimate the BW of males and females of different ages and/or gestational stages. To use Methods B and C, correction factors are necessary to precisely estimate the body weights in this breed

Estimation methods and correction factors for body weight in Mangalarga Marchador horses

<div><p>ABSTRACT The objective was to evaluate the accuracy of six body weight (BW) estimating methods in Mangalarga Marchador horses (MM) (n = 318): method A - tape placements at three different positions around the thoracic girth; B - Crevat and Quetelec's formula; C - Hall's formula; D - Hintz and Griffiths’ table; E - Santos’ table; and F - Cintra's formula. For additional analyses, gender, age, and gestational stage were considered. Estimated average BW was compared to the actual scale weight by the paired T test, mean predicted error, and determination coefficient. In the general population, methods A (position 3), B, and C estimated BW that were different from that of the scale. Method A, at positions 1 and 2, was more accurate in predicting the scale weight results compared with all other methods. For pregnant mares, the tape in positions 1 and 2 in method A did not differ from those of the scale. Method A in positions 1 and 2 and the table (method E) may be used to estimate the BW of males and females of different ages and/or gestational stages. To use Methods B and C, correction factors are necessary to precisely estimate the body weights in this breed.</p></div