Genetic improvement and population structure of the Nelore breed in Northern Brazil

Abstract

-The objective of this work was to evaluate the population structure and the genetic and phenotypic progress of Nelore cattle in Northern Brazil. Pedigree information concerning animals born between 1942 and 2006 were analyzed. Population structure was performed using the Endog program. Out of the 140,628 animals studied, 67.7, 14.52 and 3.18% had complete pedigree record of the first, second and third parental generation, respectively. Inbreeding and average relatedness coefficients were low: 0.2 and 0.13%, respectively. However, these parameters may have been underestimated, since information on pedigree was incomplete. The effective number of founders was 370 and the genetic contribution of 10, 50 and 448 most influent ancestors explained 13.2, 28 and 50% of the genetic variability in the population, respectively. The genetic variability for growth traits and population structure demonstrates high probability of increasing productivity through selective breeding. Moreover, management strategies to reduce the currently observed age at first calving and generation intervals are important for Nelore cattle genetic improvement.Index terms: Bos taurus indicus, effective population size, genetic parameters, genetic trends, inbreeding, pedigree analysis. Melhoramento genético e estrutura populacional da Raça Nelore na Região Norte do BrasilResumo -O objetivo deste trabalho foi avaliar a estrutura populacional e o progresso genético e fenotípico da raça Nelore na Região Norte do Brasil. Informações sobre o pedigree foram analisadas em animais nascidos entre 1942 e 2006. A estrutura populacional foi estimada utilizando-se o programa Endog. Dos 140.628 animais avaliados, 67,7% dos pais, 14,52% dos avós e 3,18% dos bisavós eram conhecidos. O coeficiente de parentesco médio e a endogamia foram, em geral, baixos: 0,13 e 0,20%, respectivamente. Contudo, esses parâmetros podem ter sido subestimados, já que as informações de pedigree eram incompletas. O número efetivo de fundadores foi de 370 e a variabilidade genética na população explicada pelos 10, 50 e 448 mais influentes ancestrais foi de 13,2, 28 e 50%, respectivamente. A existência de variabilidade genética indica possibilidade de aumento na produtividade por meio da seleção. Adicionalmente, estratégias de manejo para diminuir a idade ao primeiro parto e o intervalo de gerações são importantes para o melhoramento da raça.Termos para indexação: Bos taurus indicus, tamanho efetivo da população, parâmetros genéticos, tendência genética, endogamia, análise de pedigree.

Genetic parameters for type classification of Nelore cattle on central performance tests at pasture in Brazil

“…This implies that the positioning of the navel, prepuce, and sheath, on average, are suitable for animals at pasture (Josahkian et al 2003). E and P had mean scores of 4.19 and 3.87, respectively, in line with those described by Faria et al (2010) The initial weight on test was 232.93 kg with a mean age of 330.20 days (Table 2) and weight corrected for 365 days was 257.48 kg, higher than found by Malhado et al (2010) who obtained 229.16 kg at 365 days with Nelore animals reared at pasture in Northern Brazil and close to that seen by Yokoo et al (2010), which was adjusted for 365 days to 250.39 kg. Average final weight adjusted for 550 days was 354.71 kg, close to that described by Yokoo et al (2010) with 347.14 kg and by Koury Filho et al (2009) who reported 330.91 kg with a mean age of 523.10 days.…”

Age at first calving of Nellore cattle in the semi-arid region of northeastern Brazil using linear, threshold, censored and penalty models

“…One of the reproductive traits that is most easily obtained and routinely registered in most breeding females is age at first calving (AFC) (Malhado et al, 2010;Boligon, Albuquerque, 2011). Moreover, AFC could potentially be analyzed employing a threshold approach.…”

<b>Genetic improvement of Nellore cattle in the semi-arid region of northeastern Brazil

“…The mean age at first birth was 1418.46 ± 518.83 days (46.5 months). Slightly higher values have been reported for the Nellore breed in the northern region (47.3 months) by Malhado et al (2010) and in the northern and northeastern regions (45.14 months) by Azevêdo et al (2006). The national average for Nellore (ABCZ/EMBRAPA) is lower than the studies cited above, but it is still high at 39.54 months.…”

“…Several studies have reported antagonistic correlations between direct and maternal genetic effects in beef cattle (Giannotti et al, 2005;Gutteres et al, 2007;Sarmento et al, 2003). Malhado et al (2010) has estimated results close to zero (W205 = -0.01 and W365 = -0.03), using information on the pedigree of approximately 143,000 animals for the period from 1942 to 2006 via restricted maximum likelihood. According to Schaeffer (2004), obtaining good estimates requires data from multiple generations with appropriate associations between direct and maternal genetic effects in beef cattle.…”

“…Malhado et al (2008) have reported genetic gains of 0.049 (W205), 0.038 (W365) and 0.068 kg per year (W550) for Nellore cattle in Bahia. In the northern region, superior genetic progress has been estimated for the same breed, with gains of 0.097 (W205), 0.132 (W365) and 0.203 kg per year (W550) (Malhado et al, 2010). However, it should be noted that a study covering the hinterlands of northeastern region in the period from 1970 to 2005 reported no genetic progress in growth traits (Malhado et al, 2009).…”