Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: February 22, 1996
Publication Date: N/A
Technical Abstract: To assess the feasibility of increasing productivity in beef cattle by twinning, incidence of dystocia and retained placentas, calf survival, length of postpartum interval and pregnancy rate (PR) were compared between cattle producing single (S; n=3370) and twin (T; n=1014) births in the Twinning Project from 1989 to 1994. Females were mated by AI for 40 d followed by 20 d of natural service with equal numbers bred and calved in spring and fall. Type of birth affected (P<.01) both incidence (46.9 vs 20.6, T vs S) and type of dystocia; T had more malpresentations of calves (37.0 vs 4.5, T vs S) but fewer required traction (9.9 vs 16.1). First- (40.5) and second- (22.7) parity dams with S births had more (P<.01) dystocia than older dams (13.4); parity did not affect (P>.1) dystocia with T births. Incidence of retained placenta was higher for T than S births (27.9 vs 1.9%; P<.01) and in spring (March-April) than fall (August-Septemb bd of age was lower for T calves (81.0 vs 93.0 and 73.6 vs 88.8, T vs S; P<.01). The shorter (P<.01) gestation length for T (276.1 vs 283.7 d, T vs S) contributed to a longer interval from parturition to conception for T births (94.4 vs 83.7 d, T vs S; P<.01); whereas, mean conception dates differed by only 2 d (Julian date=247.9 vs 245.8, T vs S). PR was higher after a S birth than a T birth (79.0 vs 69.8; P<.01). Dystocia with a S birth decreased PR (73.9 vs 84.0 with vs without; P<.01) but had no effect after a T birth (71.8 vs 67.8, respectively; P>.1). Retained placenta did not have a significant effect on PR (73.9 vs 84.0, respectively). Even with the lower PR and calf survival, cows birthing twins wean 1.5 times more calves than cows birthing singles.