Effects of twinning on gestation length retained placenta, and dystocia

Constraints to maximal productivity from twinning in beef cattle include in creased incidence of dystocia and retained placenta, longer postpartum inte rval, and lower conception rate. Incidence and cause(s) of the shorter gest ation length and of the increased retained placenta and dystocia associated with twinning were evaluated for 3,370 single and 1,014 twin births produc ed in a population of cattle selected for natural twin births. Gestation le ngth was shorter for twin than for single pregnancies (275.6 vs 281.3 d, P < .01) and likely contributed to the higher incidence of retained placenta associated with twin births (27.9 vs 1.9%; P < .01). Incidence of retained placenta was also higher in the spring (March-April) than in the fall (Augu st-September) calving season (18.3 vs 11.4%; P < .01). The higher incidence of dystocia with twins than with singles (46.9 vs 20.6%, P < .01) was prim arily due to abnormal presentation (37.0 vs 4.5%, respectively) of one or b oth twin calves at parturition. First- (40.5%) and second- (22.7%) parity d ams with a single birth had more(P < .01) dystocia than older dams (13.4%), whereas dystocia was not affected (P > .10) by parity with twin births. Be cause of the shorter gestation length and the increased incidence of retain ed placenta and (or) dystocia, achievement of increased productivity with t winning in cattle necessitates intensive management of twin-producing dams and their calves during the calving season. Management of the increased dys tocia can be facilitated by preparturient diagnosis of twin pregnancies, en abling timely administration of obstetrical assistance to facilitate delive ry of twin calves and to increase their neonatal survival.