Всероссийский научно-исследовательский институт физиологии, биохимии и питания животных – филиал Федерального государственного бюджетного научного учреждения «Федеральный научный центр животноводства – ВИЖ имени академика Л.К. Эрнста»
ABSTRACT. The aim was to study the blood supply to the udder and the contractile response of mioepitelium and alveoli during inhibition of milk ejection, caused by the violation of milking stereotype.The trial was performed on 5 cows of Black-and-White breed by method of periods. The cows in control period were milked by his own milkmaid and in experience period they milked by "alien" milkmaid. Registration of milk ejection was carried out using bucket meter sensors. Blood supply to the udder was assessed by electromagnetic flowmetry. To assess the dynamics of the contractile activity of mioepitelium and alveoli, 3 indicators of blood supply to the udder were determined: 1) a length of the period from the beginning of udder stimulation until the sharp increase in the mammary blood flow rate (MBF), 2) the duration of the period of increased blood supply to the udder, 3) the increase in the MBF for the milking period from baseline (average and maximum). It is found that the breach of milking stereotype leads to a shift in the dynamics of milk ejection, accompanied by activation of the sympathetic-adrenal system. At the same time, two-peak lactation curve was a more sharply manifested, and the yield of single milking and intensity of udder blood supply were reduced. Changing the stereotype milking caused an increase in the duration of the latent period of milk ejection by 20% and decrease in the duration of the period of the alveoli contractile activity by 26%. The control values of the maximum and average alveolar contraction amplitude during milking were 1.99±0.13 and 1.0±0.08 conv. units respectively. Violation of milking stereotype resulted in a reduction of these indicators, maximum up to 1.28±0.10, average up to 0.50±0.06 conv. units (P<0.001). In the experiment period, the intensity of the alveoli contraction, estimated by increase in blood supply to the udder for period of increased MBF values, was 47% (P<0.001) of control. Along with lengthening of the latent period of milk ejection, in the experiment there was an increase in the length of the period of removal of the first portion of cisternal milk. This fact indicates that the action of the inhibitory factor not only increases the tone of the teat sphincter but also delays the onset of milk ejection. Changing the dynamic parameters of blood supply to the udder during braking reflex of milk ejection is seen as the result of the later and less intensive reduction of mioepitelium and contraction of the alveoli. It is found that a violation of the parameters of milk withdrawal during inhibition of milk ejection reflex is due to a decrease in the intensity of movement of the alveolar milk in the cisternal department of udder. It is assumed that under inhibition of milk ejection, there is an infringement of milk movement from the alveoli into a duct system, due to decreased contractile response of mioepitelium and alveoli, and through the system of milk ducts and teats of the udder. It is shown that the process of reducing the contractile activity of alveolar complex is due to a decrease in alveolar contraction amplitude and shortening the period of their compression and subsequent expansion.
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