Submitted to: World Congress of Genetics Applied in Livestock Production
Publication Type: Proceedings
Publication Acceptance Date: April 4, 2002
Publication Date: August 20, 2002
Citation: ECHTERNKAMP, S.E., THALLMAN, R.M., KAPPES, S.M., GREGORY, K.E. INCREASED TWINNING AND COW PRODUCTIVITY IN BEEF CATTLE SELECTED FOR OVULATION AND TWINNING RATE. PROCEEDINGS OF 7TH WORLD CONGRESS OF GENETICS APPLIED IN LIVESTOCK PRODUCTION. 2002. SESSION 08, REPRODUCTION. CD-ROM COMMUNICATION NO. 08-12 Technical Abstract: Since 1981, cattle have been selected for fraternal twin births using estimated breeding values for twinning calculated from repeated measurements of ovulation rate in all heifer progeny starting at about 12 months of age, from twinning rate in the selected females, and from progeny testing and subsequent assortive mating of progeny proven sires. Twinning rate increased from 4% in 1984 to 52% in 2001, an increase of 3% per year, as a result of an increase in the frequency of twin and triplet ovulations. Although a twin/multiple ovulation is the first and limiting prerequisite for multiple births in cattle, fetal mortality was increased (P < 0.01) with twin and, especially, triplet fetuses. Single-born calves were heavier (P < 0.01) than twin or triplet calves at birth (48.7±0.3, vs 37.6±0.3 or 30.5±1.3 kg, respectively) and at 200 days of age (256.9±1.4 vs 222.4±1.4 or 210.6±7.0 kg, respectively). Perinatal survival differed (P < 0.01) among the three birth groups (94.0±0.6, 86.0±0.6 and 73.6±2.6%, respectively), but mortality rate postnatally was similar among the three birth groups. Twin and triplet births increased (P < 0.01) cow productivity (total weaning weight / cow calving) at weaning 55.6 and 71.3%, respectively, compare with a single birth.