Reproductive parameters and efficiency of inseminators in dairy farms in Portugal.

Abstract

This study was carried out to determine the reproductive efficiency indices of one of the largest dairy co-operatives of northern Portugal, using data from 1980 to 1998. Records were made available by the computerized National Recording System. Age at first calving was 32.0 +/- 6.0 months. Mean calving to first AI interval was 95.4 +/- 30.0 days, and calving to conception intervals decreased (p < 0.05) from 176.9 +/- 4.5 to 148.1 +/- 5.6 days from the first to the fourth/fifth parturitions, respectively. Calving intervals decreased (p < 0.05) from 418.1 +/- 3.4 to 392.5 +/- 7.0 days from the first to fourth/fifth parturitions, respectively. Mean non-return rates at 90 days for first inseminations was 71.7 +/- 6.5% and mean calving rates at first insemination was 51.4 +/- 8.1%. There were significant differences (p < 0.001) in the inseminators' efficiency, measured by both non-return and calving rates at first AI, with differences between the best and worst results of 13.3 and 16.1% for non-return and calving rates, respectively. The ranking of the inseminators did not coincide when their efficiency was measured by either non-return or calving rates. The mean number of inseminations per pregnancy (pregnant cows only) was 1.4 +/- 0.7 with significant (p < 0.001) differences among herds. The mean heat detection rate was 38.1 +/- 16.9%, with highly significant (p < 0.001) differences among farms (ranging from 14.2 to 60.8%). Negative (p < 0.001) correlations were found between heat detection rate and calving to first AI, calving to conception and calving intervals. The meaning of these indexes for assessment of reproductive efficiency in the studied system, is discussed.