Residual milk yield as affected by dose and time of injection of oxytocin

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Abstract
Summary A study was made, using Holstein cows, of the relationship between (1) the dose of oxytocin administered; (2) the time between milking and intravenous (i.v.) injection and (3) the time between injection and withdrawal of residual milk. Effectiveness of each dose for removal of residual milk was expressed as the percentage of residual milk in the quarter which was withdrawn by a test milking. The total amount of milk in the quarter was determined by giving a large dose of oxytocin and a second test milking, which then indicated the volume of milk missed by each combination of dose and delay times. It was found that delay before injection had no consistent influence on the effectiveness of the test dose; however, an increased delay after injection required an increase in the test dose for removal of a constant percentage of residual milk. The mean dose required for 75% removal increased from 6·3 mu/kg bodyweight to 57 mu/kg bodyweight as the time from injection to removal of residual milk increased from 5 to 30 min. The doses which produced removal of 75% of the residual milk in at least 50% of the quarters tested were 5, 10 and 40 i.u. for delays between injection and removal of residual milk of 5, 15 and 30 min respectively.