Eficiência reprodutiva e produtiva em rebanhos leiteiros comerciais monitorados por sistema informatizado
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Data
2002-06-01
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Editor
Sociedade Brasileira de Zootecnia
Resumo
O estudo foi conduzido com os objetivos de analisar o desempenho produtivo e algumas medidas de eficiência reprodutiva de 1877 vacas provenientes de quatro grupos genéticos Holandês ¾ Zebu e estimar os parâmetros genéticos pertinentes. Os animais pertenciam a três rebanhos comerciais que foram monitorados pelo Sistema Computacional de Informação DAISY (The Dairy Information System), durante período de 1989 a 1998. Para consistência dos dados, formação dos arquivos e análises preliminares foram usados os procedimentos disponíveis no SAS (Statistical Analysis System), enquanto os componentes de (co)variância foram estimados pelo método de máxima verossimilhança restrita livre de derivada (MTDFREML), sob um modelo animal. Os efeitos de grupo genético e ano do parto foram significativos sobre a idade da vaca ao primeiro parto (IPC), intervalo parto - primeiro serviço (PP1S), duração da lactação(DL), produção total de leite (PT) e produção de leite por dia de intervalo de parto (PLIEP). As estimativas de herdabilidade (h²) para as características reprodutivas ficaram próximas de zero, evidenciando grande dependência do manejo oferecido aos rebanhos, enquanto o valor de 0,28 para a h² da PT mostrou variância genética aditiva média. A correlação genética entre PT e DL de 0,81 pode ser considerada de alta magnitude.
The objectives of this work were to evaluate the productive and reproductive efficiencies and also the genetics parameters for traits considered, using data from 1877 crossbreed cows (Holstein x Zebu) from four genetics groups. The cows belonged to three commercial dairy herds monitored from 1989 to 1998 by the Dairy Information System (DAISY). The data were processed using the procedure available in SAS (Statistical Analysis System), while genetic parameters on productive and reproductive traits were estimated by the multiple trait derivative-free restricted maximum likelihood method (MTDFREML). Effects of genetic group and calving year were significant for age at first calving (AFC), interval from calving to first service (ICFS), lactation length (LL), milk production (MY) and milk production per day of calving interval (MYCI). The estimates of heritability (h²) for all reproductive traits were near zero in agreement with others studies indicating that these traits are mostly determined by management practices. The h² estimates for milk yield (MY) were 0.28, this means that the additive genetic variance is middle. The genetic correlations (r g) between MY and LL of 0.81 could be considered high.
The objectives of this work were to evaluate the productive and reproductive efficiencies and also the genetics parameters for traits considered, using data from 1877 crossbreed cows (Holstein x Zebu) from four genetics groups. The cows belonged to three commercial dairy herds monitored from 1989 to 1998 by the Dairy Information System (DAISY). The data were processed using the procedure available in SAS (Statistical Analysis System), while genetic parameters on productive and reproductive traits were estimated by the multiple trait derivative-free restricted maximum likelihood method (MTDFREML). Effects of genetic group and calving year were significant for age at first calving (AFC), interval from calving to first service (ICFS), lactation length (LL), milk production (MY) and milk production per day of calving interval (MYCI). The estimates of heritability (h²) for all reproductive traits were near zero in agreement with others studies indicating that these traits are mostly determined by management practices. The h² estimates for milk yield (MY) were 0.28, this means that the additive genetic variance is middle. The genetic correlations (r g) between MY and LL of 0.81 could be considered high.
Descrição
Palavras-chave
Aspectos genéticos e de ambiente, Gado de leite, Vacas cruzadas, Genetic parameters, Dairy cattle, Crossbreed cows
Como citar
Revista Brasileira de Zootecnia. Sociedade Brasileira de Zootecnia, v. 31, n. 3, p. 1362-1366, 2002.