Individual inbreeding coefficients (F) were estimated for 27 610 animals of Gyr Dairy Cattle and distributed in 29 classes (CF). Despite the low values of the average F (2.82%), 60% of the population is inbred, a percent considered worrying. Records of 24 405 lactations from 8,879 cows were used to evaluate the effect of inbreeding on milk yield traits (MYT) and total solids, length of lactation (LL), age at first calving (AFC) and calving interval. CF affected all traits. In the weighted regression analysis of average F for each CF, linear and quadratic effects were significant for MYT. Increase in MYT and LL were observed until 10 and 12% of F, followed by a decrease after these levels. There was a significant linear increase of 0.55 days in the AFC at each percent of increase in F. Calving interval was not explained by regression models.
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume , , 01.77, 2006
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