Study of the function of the teat sphincter in lactating cows
Bernabé, J.; Peeters, G.
Archives Internationales de Pharmacodynamie et de Therapie 246(1): 162-164
1980
ISSN/ISBN: 0003-9780 PMID: 7192537 Document Number: 158415
In 4 cows given oxytocin infusions, milk leakage was related to teat contractions according to 1 of 3 patterns. In type 1, a milk spurt of duration 6-13 s began halfway through teat relaxation and terminated just before or at the start of contraction. In type 2, milk dripped for 8-25 s during relaxation and spurted for 1-4 s around the start of contraction. In the rare type 3, a 1-2 s spurt of milk occurred during contraction. Milk lost was collected during 5-min periods after injection of saline or noradrenaline at 160 mu g, with the teat cannulated to abolish sphincter muscle effects. Noradrenaline strongly enhanced longitudinal muscle tone but had little effect on milk loss. In another experiment isoprenaline at 3-75 mu g increased milk loss whilst noradrenaline at 10-160 mu g diminished or abolished milk loss for 2-3 min. It was concluded that sphincter muscle activity is important for milk retention and is affected by alpha - and beta -adrenoceptors.