The aim of the present study was to investigate genetic parameters for racing time in Thoroughbred horses racing at distances between 1000 and 1600 m subdivided into 100-m intervals. The data provided by TURFETOTAL Ltda comprised races that occurred in the Gávea and Cidade Jardim race tracks over a period of 11 years (1992-2002) and consisted of 32,145 races and 238,890 time records. The variance components necessary to obtain the heritability and repeatability estimates of the traits studied were estimated with the MTDFREML program, and animal age at race (3 years old or younger, 4, 5 and older than 5 years), sex (male and female), number of races (1-32,145), and postposition at start (1-11) as fixed effects, and animal and permanent environmental random effects were included in a one-trait animal model. Males were significantly superior to females at all distances. Excluding the 1100 m distance, animals 4 years of age were significantly faster than the mean of the other ages for all distances analysed. Horses older than 5 years showed a significantly lower performance than the mean of the other ages for all distances analysed, except for the 1100 m. Postpositions one and two did not differ significantly from one another for any of the distances analysed. These two inner positions both together varied from the other positions depending on race length. The components of additive genetic and permanent environmental variance varied in a similar way, tending to decrease with increasing racing distance, and the other temporary environmental variance almost doubled from 1000 to 1600 m. As was the case for the additive genetic and environmental variances, heritability and repeatability estimates tended to decrease with increasing distance, indicating that selection based on racing time will be less successful when the racing distance increases.

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Effects of transforming a normally distributed variable into its inverse on parameters of the distribution using Monte Carlo techniquesABSTRACT -Four simulation studies were conducted to verify the distribution of the inverse of variables with normal distribution, relatively to variances, averages, truncation points and sample sizes. The variables simulated were GMD, with normal distribution and representing average daily gain, and DIAS defined as a multiple of the inverse of GMD and representing days to reach a fixed body weight. The SAS ® (1990) system was used, for simulation of the data, and for subsequent analysis of the results in all studies. The standard deviations simulated for GMD significantly affected DIAS sampling averages. The regression analyses showed a reduction on the mean and in the standard deviation of DIAS as a function of the increase in the average of GMD. Including a truncation point at about 10 to 25% of the mean value reduced the mean of GMD and increased the mean of DIAS when the coefficient of variation of GMD was above 25%. Size of the groups did not significantly affect averages of GMD or DIAS. Standard deviation and CV of GMD increased with the increase on group size. Due to the dependence between the average and the standard deviation and the variation observed in the standard deviations of DIAS as a function of group size, the use of DIAS as selection criteria may reduce the accuracy of the genetic evaluation. Therefore, in order to substitute GMD by DIAS, it is necessary the use of a method of analysis robust enough to eliminate the heterogeneity of variance.

ResumoObjetivou-se padronizar medidas ultra-sonográficas do músculo longissimus dorsi de 12 eqüinos da raça Puro-sangue Árabe submetidos a treinamento aeróbico por 90 dias, com alimentação suplementada ou não com creatina monoidratada, a fim de verificar se estas mensurações poderiam auxiliar programas de treinamento com animais desta raça, e se a creatina alteraria as medidas ultra-sonográficas. A suplementação consistiu na administração diária de 75g desta substância, misturada à ração durante os 90 dias de treinamento. Para determinar as quantidades diárias da ração comercial fornecida, os animais tiveram o peso corpóreo e o escore corporal avaliados mensalmente. O condicionamento físico foi realizado em esteira rolante de alto desempenho e a intensidade do treinamento foi estipulada mediante o cálculo da V LAC 4 (velocidade na qual o lactato sanguíneo atinge 4mmol/L) determinada mensalmente para cada animal. Estabeleceu-se a intensidade do esforço físico individual, em 80% do limiar aeróbico. Os animais foram avaliados por meio de exames ultra-sonográficos, mensurando-se a área, largura, profundidade de corte transversal e camada de gordura do músculo longissimus dorsi ao final dos oito meses de inatividade e após 30, 60 e 90 dias de treinamento. Os resultados da ultra-sonografia revelaram que o treinamento aeróbico associado ou não à suplementação com creatina causou hipertrofia do músculo longissimus dorsi e redução da camada de gordura. O treinamento aeróbico associado à suplementação prolongada com creatina levou ao aumento da medida de profundidade do músculo longissimus dorsi.Palavras-chave: longissimus dorsi; ultra-sonografia; treinamento aeróbico; eqüino. AbstractThe goal of this study was to standardize ultrassonographic measurements of the longissimus dorsi muscle in twelve Arabian horses submitted to an aerobic training for 90 days, with feed supplemented or not with monohydrated creatine, in order to find out if these measurements could help training programs of this breed of horses. Another point was to find out if creatine supplementation does enhance ultrassonographic measurements. The creatine supplementation was carried out by daily administration of 75g of this substance, for 90 training days. To determine the daily administration of the commercial ration supplied, the animals had the corporeal height and the corporeal score monthly considered. The conditioning physical program was conducted in a treadmill and the training protocol was adjusted after V LAC 4 (velocity in which the lactato blood reachs 4mmol/ L) determination which was set monthly for each horse. The intensity of effort was determined as 80% of the aerobic threshold of each horse. The animals were ultrassonographically examined measurement of the area, width of transversal cut, depth of transversal cut and fat layer of the longissimus dorsi muscle on each groups at end of eight months of inactivity and after 30, 60 and 90 training days. The ultrassonographical results showed that, the aerobic training associated or not to cr...

RESUMO -Foram simuladas nove populações, cada uma com cinco replicações da variável ganho médio diário (GMD1) com distribuição normal e média 100, variando o tamanho dos grupos e os desvios-padrão. Cada replicação foi dividida de modo a formar grupos que representariam grupos de contemporâneos (GC) e de progênie dentro de GC. Cada GC tinha dez pais.Obtiveram-se três conjuntos: o conjunto 1 com 1.000 grupos de contemporâneos (GC), cada um com 100 observações e dez observações por pai; o conjunto 2, com 2.500 GC, 40 observações e quatro observações por pai; e o conjunto 3, com 5.000 GC, 20 observações e dois filhos por pai. Em cada população, gerou-se GMD1, a qual foi transformada em outra variável, da seguinte forma: DIAS1 = 100/GMD1. Calcularam-se para cada pai, dentro de cada GC, as contribuições de cada GC ao valor de cada pai, para GMD1 (C x ) e DIAS1 (C y ). Os efeitos do máximo e da média de DIAS1 no grupo sobre o valor absoluto de Cy foram significativos, mas o R 2 foi baixo (máximo de 16%). O mínimo de DIAS1 não influenciou o valor de C y . O máximo e o mínimo de GMD1 sobre C x foram significativos, mas os R 2 foram muito baixos (máximo de 2%). A média não influenciou C x . Em grupos de contemporâneos com um animal com valor de GMD muito baixo, o valor de DIAS desse animal será relativamente muito mais alto, o que afetará a média do grupo e os valores de todos os animais do grupo. Esse efeito se refletirá na avaliação de seus pais e será mais uma importante fonte de erros na avaliação genética do rebanho. Assim, a utilização de DIAS em substituição ao GMD como critério de seleção para o melhoramento de bovinos é contra-indicada, pois deverá reduzir a possibilidade de ganho genético para crescimento.Palavras-chave: critérios de seleção, ganho de peso médio diário, heterogeneidade de variâncias Effect of outliers in contemporary groups on breeding value predictionABSTRACT -Nine populations, with five replications each, were simulated for average daily gain (GMD1) assuming normal distribution, average 100, and different group sizes as well as standard deviations. Each replication was divided into three different sets of contemporary (CG) and progeny groups. The first set (I) was formed by 1,000 contemporary groups, 100 observations each and 10 progenies/sire. The second set (II) included 2,500 CG, 40 observations and 4 progenies/sire. The third set (III) consisted of 5,000 CG, 20 observations and two progenies/sire. The number of records per group and sire and the number of sires per group varied within the same set. In each population, GMD1 was transformed by DIAS1=100/GMD1. The contribution of CG to sire breeding value predictions were calculated for GMD1 (C x ) and DIAS1 (C y ). The maximum and the average of DIAS1 effects on C y absolute value were significant, but the R 2 were low (maximum of 16%). The minimum value of DIAS1 has not influenced C y . The maximum and the minimum of GMD1 on C x were significant, but the R 2 were very low (maximum 2%). The GMD1 average has not affected C x . The effect of t...