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Incidence of retained placenta and the consequences on milk production and reproductive efficiency of Holstein cows
Retained placenta (RP) promotes delay in uterine involution and resumption of ovarian activity, besides increasing risk of uterine infections, being the major reason for low fertility of dairy cows. This study aimed to evaluate the effects of parity and calving season in RP incidence, in milk production and in calving to conception interval (CCI), as well as RP effects on these variables. Data were collected at a farm located in Rio Paranaíba city, Minas Gerais state, Brazil during 2012. The herd was composed by 700 Holstein dairy cows producing 32 Kg of milk production per day. Calving of 291 cows was registered during the experiment period. To diagnose RP occurrence, cows were observed during calving, and immediately after calving, and those cows that had not eliminated all of placenta until 12 hours after fetal expulsion was considered with RP. The effects of parity and calving season on RP incidence were analyzed by logistic regression, and the effects of parity, calving season and RP occurrence on milk production and on CCI duration were evaluated by analysis of variance, both using SAS program. The incidence of RP in this herd was 13.75% (40/291). The RP incidence was not affected by parity and calving season, however there was a tendency (P = 0.066) of lowest incidence of RP for calving that had occurred during winter. The effects of parity, calving season and RP occurrence on milk production adjusted to 305 days of lactation were not verified (P > 0.05). CCI duration was influenced (P = 0.007) by parity, cows with three or more lactations had higher interval from parturition to conception. The effects of calving season (P = 0.001) and RP occurrence (P = 0.043) were also detected on CCI duration. Calving that had occurred during summer resulted in significant increase on CCI (263.00 ± 107.70) compare to winter (121.02 ± 60.64). Cows that developed RP had an interval from parturition to conception longer than cows without RP (139.64 ± 73.83 vs. 166.30 ± 95.90). The efficacy of RP treatment implemented by the farm could justify the absence of detectable effects of RP occurrence on milk production; however it was not enough to overcome the negative effects of RP on Holstein cows fertility.
Keywords: placenta, postpartum, bovine