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

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.

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