Effects of Removing Cows from Chronic Oxytocin use During Lactation

Abstract

The objectives of this study were to investigate the effect of discontinuation of chronic oxytocin supplementation on lactating dairy cows and to determine if there was a difference between methods of discontinuation. The study was conducted on a commercial dairy in central New York milking over 1,200 cows, with more than 80 cows being supplemented with oxytocin prior to the start of the study. Seventy-seven cows receiving supplemental oxytocin were enrolled in the study and randomly assigned to one of four treatment groups: 1) abrupt discontinuation; 2) abrupt discontinuation with a needle stick at the normal time of oxytocin injection; 3) graduated decrease in oxytocin dose; and 4) a control group that was only monitored. Total milk weight, milk in the first two minutes, total milking time, and bimodality of milk flow were measured at every milking for 12 milkings before and after the initiation of the treatment protocol. Non-parametric paired analysis was used within treatment group before and after initiation of treatment, and non-paired analysis was used to analyze differences between treatment groups. Other than the control group, all experimental groups showed a significant decrease in milk production per milking (P<0.005), ranging from 2.8-7.4 lb (1.3-3.4 kg) per milking per cow. None of the cows ceased lactating. There were no significant differences in milk produced in the first two minutes, total milking time, or the number of bimodal milk flows in any of the groups (P>0.09). No significant differences (P>0.11) in the change in milk production per milking or milk produced in the first two minutes were found between the group that underwent graduated discontinuation of oxytocin and the group abruptly removed from oxytocin supplementation without sham injection. These results show that dairy producers can stop supplementing cows with exogenous oxytocin in the parlor by either abrupt discontinuation or a weaning protocol with a loss of milk similar to that gained from oxytocin supplementation, and cows will not cease to lactate.