Indicators of uterine contractile activity in highly productive sows using supraphysiological doses of oxytocin

Abstract

The use of large doses of oxytocin to sows in the early postpartum period is indicated to normalize lactogenesis, increase immune proteins in colostrum and transitional milk, prevent postpartum complications, and increase the viability of the offspring. However, the effect of these doses of myotropic drug on the contractile activity of the uterus is not shown. The aim of the work was to study the contractile function of the uterus of highly productive sows in the early postpartum period and the peculiarities of its reaction to supraphysiological doses of oxytocin. Scientific and production experience was carried out on the basis of a large pig breeding complex. The object of the study was highly productive sows 16 hours after the completion of normal labor. The hormonal drug oxytocin was administered intra-muscularly to animals at a supraphysiological dose of 75 units. Hysterograms of uterine contractions were recorded by internal hysterography before and immediately after administration of the myotropic drug, as well as one hour after injection. On hysterograms, spontaneous contractile activity of the uterus in highly productive sows was characterized by regular, short-term contractions of the optimal amplitude. Activation of the contractile function of the myometrium occurs 5-7 minutes after injection of the drug. After administration of oxytocin, an increase in the amplitude of contraction of uterine smooth muscle cells was noted by 39.17% (p<0.05), while a longer period of contractions was recorded by 31.64%. The frequency of uterine contractions increased 2.0 times (p<0.01). The contract index was significantly 3.66 times (p<0.05) higher than that in relation to the initial level. After 1 hour after oxytocin administration, an increase in the contraction period by 5.42% was noted, with a decrease in amplitude by 37.87% (p<0.01) and the number of contractions by 49.91% (p<0.01), the contractional index decreased by 3.05 times (p<0.01) relative to the previous level. In relation to the initial level, the contract index was 20.0% higher. At the same time, an increase in the duration of contractions by 38.78% and a decrease in their amplitude by 13.53% were noted. Consequently, oxytocin at a dose of 75 ME not violate the contractile ability of the myometrium. The response of the smooth muscle cells of the uterus to the supraphysiological dose of oxytocin is maximally manifested in the first hour after the administration of the myotropic drug.