Endogamia na raça Gir

• Main Author: Reis Filho, João Cruz
• Publication Date: 2006
• Format: Master thesis
• Language: por
• Source: LOCUS Repositório Institucional da UFV
• Download full: http://locus.ufv.br/handle/123456789/4698
• topic: Endogamia; Melhoramento genético animal; Raça Gir; Bovino de leite; Inbreeding; Animal breeding; Gyr cattle; Dairy cattle; CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA::GENETICA E MELHORAMENTO DOS ANIMAIS DOMESTICOS

The pedigree and production database of Gyr cattle selected for milk production, stored at Embrapa had been employed in this research work. There were studied population s genetic structure, inbreeding effects on productive and reproductive traits and a comparative genetic evaluation regarding a complete and selected genetic basis. The ENDOG program has used 27,610 animals to obtain the individual coefficients of inbreeding (F) and average relatedness (CR), the effective number of animals (Ne), founders (fe) and ancestors (fa) and generation intervals (IG). The average F and AR coefficients of population were 2.82 % and 2.10 %, respectively. The Ne ranged from 16.1 to 125.3 for complete generations. The estimated fe and fa were, respectively, 146 and 75, with only 28 ancestors being the source of 50 % of the populations genes. The total IG was 8.41 years, being higher for males than for females. Data from 24,045 lactations ended between 1960 and 2004, from 8,879 cows distributed in 26 herds, were used for verifying the effects of inbreeding over the productive traits: productions of milk (PL), fat (PGOR), protein (PPRO), lactosis (PLAC), total solids (PSOL) and length of lactation (DLAC); and reproductive traits: age at first calving (ID1P) and calving interval (INTP). The variance and regression analysis used SAS procedures. The variance analysis for productive traits and calving intervals considered as fixed effects the herd, year-season of calving, generation class (CG) nested in herd, inbreeding class (CF) and age of the cow at calving, as covariate, with linear and quadratic terms. For age at first calving there were considered in the model the fixed effects of herd-year of birth, birth season, CF and CG-herd. The productive traits were affected (p<0.05) by all sources of variation. The age of the cow at calving and birth season did not affect (p>0.05) the calving interval and age at first calving, respectively. A regression study of the traits, adjusted for others variation sources, was carried out considering the average inbreeding coefficient of each class, weighted by the number of observations of the class. The linear and quadratic regression terms were significant (p<0.01) for productive traits, in which the higher production levels were associated to inbreeding coefficients between 10 and 12 %. Only the linear regression term was significant (p<0.05) for ID1P. The proposed regression model did not explain INTP. The genetic evaluation for milk production was performed by MTDFREML system, applying the production database plus information of cow s parents and two different pedigree structures. The complete genetic basis (BGC) considered all available information and the selected genetic basis (BGS) used a subset with only pedigree information of progeny test bulls. The employment of BGS, on average, underestimated the breeding values. High Pearson and Spearman correlations between predicted breeding values by the utilization of both genetics basis were obtained. However, the selection of different animals based on of the genetic basis could reduce the genetic gains, mainly in males, which are more influenced by relative s information.