In order to examine the rate of recovery of milk yield and composition following an extended milking interval, 20 cows were milked out with the aid of oxytocin and subjected to single intervals of either 16, 24, 32 or 40h. Cows were then milked frequently with the aid of oxytocin during the subsequent 26h. Milk secretion rate was depressed to 67 and 56% of pre-treatment (twice-daily milking) rates by the 32 and 40h treatments, and rates of recovery were slow, extending beyond 26h post-treatment. Milk fat and protein contents did not differ significantly among treatment groups while lactose content was reduced by the 32 and 40h intervals, recovering by 26h post-treatment. It was concluded that the udder is particularly sensitive to milk accumulation beyond 24h and that this leads to impairment of the ‘synthetic machinery’ in the udder. The prolonged effect on milk lactose concentrations with the longer intervals suggests that there was a sustained change in the integrity of tight junctions between secretory cells, leading to increased permeability of the mammary gland. Rates of recovery of yield and composition were relatively slow, taking >24h in spite of enhanced rates of milk removal.
Proceedings of the New Zealand Society of Animal Production, Volume 58, , 47-48, 1998
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