Controlled breeding of dairy heifers
Observations over a five year period
DOI:
https://doi.org/10.21423/bovine-vol0no21p146-149Keywords:
artificial insemination, reproductive management, conception rates, reproduction, cowsAbstract
Over a five year period from 1979 to 1983, 191 Holstein-Friesian heifers were artificially inseminated at present times following estrus synchronization with two injections of prostaglandin analogue 11 days apart. The heifers were not selected prior to synchronization and no heat detection methods were used. Overall conception rates for the five year period were 59.8% on timed inseminations; however, the pregnancy rates ranged from 50% in Years 3 and 5 to 76.2% in Year 4. The average interval from first to last calving for groups of heifers which conceived to synchronized insemination was 19 days. There was no significant difference in conception rates between heifers that were greater than 16 months of age and those less than 16 months old.