Selection Index methodology was used to set up an aggregate index for fertility in Italian Holstein Friesian first lactation cows. Conception Rate at first service represented the breeding objective and was predicted by an index combining EBVs obtained from a multiple-trait animal model. The traits included in the multi-trait animal model were: days from calving to first insemination (DTFS), calving interval (CI), first-service 56 d non return rate (NR56), angularity (ANG) and mature equivalent milk yield at 305 d (ME305). Relative emphasis on ANG, CI, DTFS, NR56 and ME305 was 7:51:16:17:9, respectively. Using all traits as selection criteria increased accuracy of and response to selection. On average a 10% improvement in terms of Conception Rate is expected after one round of selection. Selecting on alternative indexes based on a reduced number of traits decreased the efficiency of selection up to 25%.
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume , , 01.48, 2006
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