Growth predictability models in Mangalarga marchador horses / Modelos de previsibilidade de crescimento em cavalos Mangalarga marchador

This study evaluated the suitability of the Brody, logistic, and quadratic response plateau models to describe chest and cannon girth data obtained cross-sectionally in Mangalarga Marchador horses, in order to select the best model and predict the growth and maturity of males and females of this breed. Data were collected from 230 horses aged 6 to 176 months, divided by sex and age (16 age classes). The studied models were compared according to each quality evaluator by computing the adjusted coefficient of determination (R²adj) and residual standard deviation (RSD) with R statistical software. The chest girths obtained by the models ranged from 172.06 (males) to 181.50 cm (females) (Brody), 172.51 (males) to 181.89 cm (females) (logistic), and 177.67 (males) to 183.09 cm (females) (plateau). For cannon girth, the values were 18.18 (females) to 19.33 cm (males) (Brody), 18.11 (females) to 19.41 cm (males) (logistic), and 18.70 (females) to 19.40 cm (males) (plateau). The logistic model was best suited to describe the growth in chest girth of male and female Mangalarga Marchador horses. For cannon girth growth, the model best suited for males was the logistic model, and the one best suited for females was the Brody model.

RESUMO: O objetivo deste estudo foi avaliar o ajuste dos modelos Brody, Logístico e Platô de resposta quadrática aos dados de perímetros torácico e de canela em equinos Mangalarga Marchador obtidos pelo método transversal, a fim de selecionar o melhor modelo e predizer sobre o crescimento e a maturidade de machos e fêmeas desta raça. Foram utilizados dados de 230 equinos de seis a 176 meses de idade que foram divididos por sexo e em 16 classes de idade. Os modelos estudados foram comparados segundo os avaliadores de qualidade: coeficiente de determinação ajustado (R²adj) e desvio padrão residual (DPR), utilizando-se o software estatístico R. Os perímetros torácicos obtidos pelos modelos variaram de 172,06 a 181,50 cm (Brody), 172,51 a 181,89 cm (Logístico) e 183,09 a 177,67 cm (Platô) para fêmeas e machos, respectivamente. Para o perímetro de canela os valores variaram de 18,18 a 19,33 cm (Brody), 18,11 a 19,41 cm (Logístico) e 18,70 a 19,40 cm (Platô) para fêmeas e machos, respectivamente. O modelo logístico é mais indicado para expressar o crescimento em perímetro torácico de machos e fêmeas da raça Mangalarga Marchador. Já para a variável perímetro de canela, o modelo mais indicado para os machos foi o modelo Logístico e para as fêmeas o modelo de Brody.

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 horses.

Growth curve for height at withers and body length of Mangalarga Marchador horses / Curva de crescimento em altura na cernelha e comprimento corporal de equinos Mangalarga Marchador

This study aimed to evaluate the logistic and quadratic response plateau models to describe the growth of Mangalarga Marchador horses to identify the model that best describes growth for the variables height at withers and body length. Data were used from 230 horses aged 6 to 176 months, divided by sex and 16 age classes. All computational work was performed using R statistical software. The logistic model was the best suited to express growth in height at withers and body length of male and female Mangalarga Marchadors aged 6 to 176 months. This allowed creating a table of reference values for these measurements over time based on the confidence interval of the model parameters. Estimates of height at withers obtained by the logistic model ranged from 144 to 154 cm in adult males and from 143 to 151 cm in adult females. For body length, values ranged from 146 to 156 cm in adult males and 143 to 156 cm in adult females. Females achieved stability in both height at withers and body length at earlier ages than did males.(AU)

O objetivo deste estudo foi avaliar os modelos logístico e platô de resposta quadrática na descrição do crescimento de equinos da raça Mangalarga Marchador identificando o que melhor descreve o crescimento das variáveis altura de cernelha e comprimento corporal. Foram utilizados dados de 230 equinos de 6 a 176 meses de idade que foram divididos por sexo e em 16 classes de idade. Toda a parte computacional envolvida foi realizada utilizando-se o software estatístico R. O modelo logístico foi o mais indicado para expressar o crescimento em altura na cernelha e comprimento corporal de machos e fêmeas da raça Mangalarga Marchador. Foi criada uma tabela de valores referência para estas medidas ao longo da idade com base no intervalo de confiança dos parâmetros deste modelo. Estimativas das alturas de cernelha adultas obtidas pelo modelo logístico variaram de 144 a 154 cm nos machos e de 143 a 151 cm para fêmeas. Já em comprimento corporal os valores adultos variaram de 146 a 156 cm nos machos e 143 a 156 cm para fêmeas. As fêmeas apresentam maior precocidade do que os machos para atingir a estabilidade em ambas variáveis estudadas.(AU)