It is recommended that the period of postpartum in cow must evolve to allow the female reproductive function be initiated as soon as possible after parturition. The use of prostaglandin analogues can lead to acceleration of uterine involution, and the reduction of the birth interval-1 estrus, number of services / conception , service period and calving interval. In this sense, the objective of this study is to evaluate the effect of synthetic analogue of PGF2a(cloprostenol sodium) on uterine involution in postpartum Nellore cows as well as verify their relationship with the plasma concentration of 13,14-dihydro-15-keto Prostaglandin F2a(PGFM - metabolite of PGF2 ALFA) , progesterone, and gene expression of FP receptor in the uterus at different times postpartum. To do so, will be used 24 pluriparous Nelore cows pregnant with body condition score greater than 3.0. Only will be included in the experiment the animals that have had normal parturition. After parturition, the animals will be divided into two treatment groups: CON (control; Nmínimo = 12) that will receive 2 ml of saline IM on days 1 and 4 postpartum (day 0 = parturition); and TRA (treated; Nmínimo = 12) that will receive 2 mL of cloprostenol as the same way. Gynecological examinations will be conducted on days 1, 7, 14, 21, 28, 35 and 42, in which will be evaluated for uterine involution (score 1-3) via rectal palpation and uterine discharge and staining of the mucosa via vaginoscopy, accumulation of uterine fluid (score 0-3) and resumption of postpartum ovarian activity (presence of a dominant follicle and corpus luteum) in B mode ultrasound. Blood samples will be taken for determination of plasma progesterone and PGFM at each examination and transrectal ultrasound. To evaluate the gene expression of FP receptor in the uterus during the postpartum period, samples will be collected by uterine biopsy tissue on days 1, 7, 14, 28 and 42 postpartum. The results achieved in this study will contribute for a better understanding of the physiological mechanisms, and endocrine gene in postpartum zebu, collaborating to achieve the desirable objective of economic exploitation of a partirition / cow / year.
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