Use of intramuscular oxytocin injections to measure milk output in nondairy sheep, and its effect on milk composition

Abstract

This paper describes a double Latin square design experiment to determine the effect of various doses of oxytocin injected intramuscularly in nondairy ewes on the induction of milk ejection and milk composition. Eight New Zealand Romney ewes without experience as dairy sheep were injected intravenously with 1 IU synthetic oxytocin and machine-milked to empty their udders. After 4 h, the procedure was repeated using 0, 1, 5, or 10 IU oxytocin in I mL sterile saline solution, this time injected intramuscularly. All doses of oxytocin significantly (P<0.01) increased the amount of milk at the second milking, and there was no difference between 1, 5, and 10 IU. Only the 10 IU treatment affected the composition of the milk: fat concentration was increased from an average of 5.2 to 6.4% (P<0.05). It was concluded that 1 IU of oxytocin injected intramuscularly is adequate to obtain milk withdrawal and that the composition of the milk is not affected provided the dose injected is <5 IU.