Parâmetros e tendências da produção de leite em bubalinos da raça Murrah no Brasil

Abstract

RESUMO -Objetivou-se estimar os parâmetros e avaliar as tendências genética e fenotípica para a produção de leite ajustada aos 305 dias em bubalinos da raça Murrah nascidos no período de 1982 a 2003. Os parâmetros e os valores genéticos foram estimados por meio do aplicativo MTDFREML. A tendência genética foi estimada pela regressão dos valores genéticos sobre o ano de nascimento, por duas metodologias: 1) regressão linear; 2) regressão por meio de polinômios articulados utilizando-se a função de alisamento spline. A herdabilidade e a repetibilidade estimadas foram de 0,20 e 0,36, respectivamente. As tendências (regressão linear) fenotípica e genética foram significativas e iguais a 32,86 e 0,85 kg/ano, respectivamente. O ganho genético foi positivo, constatando-se instabilidade na tendência genética no decorrer dos anos, com períodos de ganhos e outros de perdas genéticas. A maior parte do ganho observado em alguns períodos resultou de melhorias nas condições ambientais. Palavras-chave: búfalos, ganho genético, herdabilidade, polinômios articulados, seleção Genetic and phenotypic parameters for milk production of Murrah buffaloesABSTRACT -This study aimed to estimate genetic and phenotypic parameters and trends for adjusted 305 days milk yield of Murrah buffaloes, which were born from 1982 to 2003. Variance components, genetic parameters and breeding values were obtained using the MTDFREML program. Genetic trends were estimated by regression of breeding values on birth year of the animals by two methodologies: 1) linear regression and 2) articulated polynomial regression using a spline smoothing function. Heritability and repeatability estimates were 0.20 and 0.36, respectively. Phenotypic and genetic trends (by linear regression) were significant and equal to 32.86 and 0.85 kg/year, respectively. The genetic trend was positive but very unstable during the period. Most of the gain observed was due to environmental improvements.

Genetic Parameter Estimates for Production and Reproduction Traits in Dairy Buffaloes

“…Similar results have been reported in studies conducted in Brazil, with estimates ranging from 0.20 to 0.25 (TONHATI et al, 2000a;MALHADO et al, 2007;RODRIGUES et al, 2010;SENO et al, 2010;ASPILCUETA-BORQUIS et al, 2012). In contrast, Rosati and Van Vleck (2002), studying an Italian buffalo population, estimated a heritability of 0.14 for MY.…”

“…Moderate heritabilities for milk yield (MY), ranging from 0.20 to 0.25, have been reported for buffaloes (MALHADO et al, 2007;ASPILCUETA-BORQUIS et al, 2010;RODRIGUES et al, 2010;SENO et al, 2010). These results suggest there is sufficient additive genetic variation to respond to selective breeding.…”

Editing and modeling of milk production data for genetic evaluation of Murrah buffaloes

“…These results confirm those reported in other studies that found heritabilities ranging from 0.20 to 0.25 (Malhado et al, 2007;Rodrigues et al, 2010;Tonhati et al, 2013). The repeatability of the models was low, preventing to predict future productions in the first lactations.…”

“…The repeatability of the models was low, preventing to predict future productions in the first lactations. Similar or higher estimates of repeatability were found by Ramos et al (2013) The heritabilities of the models MP270 (0.22) and MP305 (0.23) were similar to those found in the literature for buffaloes with adjustments for 270 days (Malhado et al, 2007;Rodrigues et al, 2010) and for 305 days (Aspilcueta-Borquis et al, 2010).…”

Variabilidade genética na raça bubalina Mediterrânea avaliada por meio de análise de pedigree

“…In spite of the world buffalo population has increased by approximately 18 million over the past 10 years, showing annual increase about 1.13% (KUMAR & SINGH, 2010), in Brazil the buffalo population has undergone major expansion, perhaps surprisingly, with higher growth than cattle population in recent years (MALHADO et al, 2007).…”