K. Stelwagen et al., CONTINUOUS VERSUS SINGLE DRAINAGE OF MILK FROM THE BOVINE MAMMARY-GLAND DURING A 24-HOUR PERIOD, Experimental physiology, 81(1), 1996, pp. 141-149
Five primiparous and five multiparous cows were used to determine if m
ammary cisternal storage of milk during a 24 h period of milk accumula
tion limited milk secretion. In addition, we investigated if there is
a parity effect for the capacity of the mammary cisternal compartment
to hold a 24 h accumulation of milk secretion, and studied the movemen
t of milk from the alveolar compartment into the cisternal compartment
. All cows were fitted with catheters in all teats in order to collect
cisternal and alveolar milk fractions separately. For a 24 h period o
f milk accumulation, the milk was drained once (after 24 h) from one s
ide of the udder (OD), and continuously from the other side of the udd
er (CD). There was no significant parity effect for cisternal, alveola
r and total milk volumes at 24 h. Therefore, data from primi- and mult
iparous cows were pooled for subsequent analyses. Cisternal milk volum
e from CD glands was higher than that from OD glands (P < 0.01), indic
ating that cisternal storage of milk in the mammary gland may be limit
ing to milk secretion during 24 h milking intervals. Alveolar volumes
did not differ between OD and CD, but, as a result of the higher ciste
rnal milk volume, total milk volume was highest in the CD glands (P =
0.05). Movement of milk from the alveolar into the cisternal compartme
nt was intermittent. Moreover, analyses of the slopes of individual mi
lk accumulation profiles of the first 6 h of accumulation revealed tha
t the cisternal compartment starts filling immediately following milki
ng, although the rate of filling is relatively low until 7-8 h postmil
king.