Abstract
Abstract The objective of this study was to evaluate the influence of gestation length, season at calving (autumn-winter vs. spring-summer) and calf sex on birth weight and incidence of retained placenta (RP) in crossbred lactating dairy cows. A total of 187 parturitions were evaluated in a commercial dairy farm at Alto Paranaiba region, Minas Gerais, Brazil. Cows that did not release the placental membranes within the first 12 hours after calf expulsion were diagnosed with RP. At birth, calf sex was registered, and birth weight was estimated by using a weighing tape. The incidence of RP was 36.89% (69/187). The mean birth weight of the calves (41.73 kg) did not differ among the calf sexes and seasons of the year at birth (P > 0.05), but the cows with below-average gestation lengths (274.4 days) calved lighter calves. Furthermore, the season of the year at calving and calf sex had no influence on RP incidence (P > 0.05), although a higher incidence of RP was observed in cows that had shorter gestation lengths (49.44%) and calves below-average birth weights (51.76%). In conclusion, cows with shorter gestation lengths produce lighter offspring and have a high predisposition to RP.
Highlights
Retained placenta (RP) is a uterine disease that occurs in the postpartum period and affects cows more frequently than other animal species
The lactating dairy cows were kept in a semi-intensive system, with rotational grazing patterns in paddocks of tropical pasture supplemented with a concentrate during the rainy season
The average gestation length was 274.4 days, which is consistent with the gestation length of Holstein dairy cows (276 ± 6 days) reported by Vieira-Neto et al[10]
Summary
Retained placenta (RP) is a uterine disease that occurs in the postpartum period and affects cows more frequently than other animal species. Bovines have cotyledonary placenta, composed of maternal caruncles and fetal cotyledons, which produce 70 to 120 placentomes. Fetal membranes are strongly adhered to the uterus by the juxtaposition of chorionic villi to the uterus during pregnancy, allowing metabolic exchange between the mother and fetus[1]. The placental release process involves the loss of maternal-fetal adhesion that occurs after the complete maturation of the placentome, and is correlated with the reduction of cellular population in the fetal and maternal tissues[3]. The immaturity of the placentomes causes edema in the chorionic villi, which is associated with hyperemia, necrosis, and a placental inflammatory process. The whole placental tissue undergoes autolysis and gradual decomposition and becomes friable with a yellow-brown coloration and fetid odor[4]
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