Vasopressin increases milk flow and milk fat concentration in the goat.
OBJECTIVE
The aim of this study was to investigate whether physiological doses of vasopressin affect milk flow and milk composition in goats.


METHODS
Six goats were given vasopressin intravenously at doses of 0.1 ng kg(-1) min(-1) (a low dose, VL), 0.3 ng kg(-1) min(-1) (a medium dose, VM) and 1.0 ng kg(-1) min(-1) (a high dose, VH), oxytocin at 10 ng kg(-1) min(-1) and 0.15 m NaCl during 90 min at random.


RESULTS
Milk flow increased from 1.3 +/- 0.2 to 3.5 +/- 1.0 g min(-1) (VL), from 1.8 +/- 0.4 to 4.3 +/- 0.6 g min(-1) (VM) and from 1.5 +/- 0.2 to 7.9 +/- 0.9 g min(-1) (VH) during the first 30-min infusions (all P < 0.001), respectively, and then declined. The response to oxytocin corresponded to that of VH. Milk fat concentration increased from 2.1 +/- 0.1 to 3.3 +/- 0.4% during VH and from 2.8 +/- 0.6 to 4.1 +/- 0.6% during oxytocin (both P < 0.001), and tended to increase during VM and VL. The mammary blood flow of four goats was studied with ultrasound during VH and oxytocin infusion. Milk flow increased from 1.8 +/- 0.4 to 4.7 +/- 1.0 g min(-1) during VH and from 1.9 +/- 0.3 to 12.4 +/- 2.4 g min(-1) during oxytocin (both P < 0.001). Mammary blood flow decreased from 262 +/- 37 to 53 +/- 7 mL min(-1) (P < 0.001) during VH, but did not change during oxytocin.


CONCLUSIONS
We conclude that vasopressin increases milk flow and milk fat concentration and suggest that vasopressin, like oxytocin, acts on the myoepithelial cells.
Olsson
K
K
Department of Animal Physiology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Malmgren
C
C
Olsson
K K
KK
Hansson
K
K
Häggström
J
J
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D005223:Fats / Q000032:analysis*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D007262:Infusions, Intravenous; D007774:Lactation / Q000187:drug effects*; D008892:Milk / Q000737:chemistry / Q000187:drug effects*; D010121:Oxytocin / Q000494:pharmacology; D012964:Sodium / Q000032:analysis; D018608:Ultrasonography, Doppler / Q000379:methods; D014667:Vasopressins / Q000008:administration & dosage / Q000494:pharmacology*
D005223:Fats; D014667:Vasopressins; D010121:Oxytocin; D012964:Sodium