The Survivability of Twins From Pregnancy Diagnosis to Calving and the Effects Twin Pregnancies Have on Milk Production, Culling, and Gestation Length in Holstein Dairy Cattle

Abstract

It is a common belief among dairymen and practitioners that the abortion rate is higher in cows with twin pregnancies than with single pregnancies. In this prospective study, 5493 cows on 14 California dairies were followed from pregnancy diagnosis to subsequent abortion or calving. There were 196 bicornual (3.57%) and 74 unicornual (1.35%) twins diagnosed. The incidence of twins was independent of days open, but was not independent of parity or days pregnant at diagnosis. Cows with unicornual twin pregnancies had higher peak milk production than cows diagnosed with single pregnancies, and when stratified by parity, this difference was maintained in second and greater lactations. However when stratifed by dairy, the difference was not significant between cows diagnosed with singles and cows diagnosed with twins. First lactation cows diagnosed with bicornual twin pregnancies had a reduced 305 day mature equivalent milk production in comparison to those diagnosed with single pregnancies.