Mechanisms involved in double ovulation and twinning in dairy cattle

摘要

In general, twin births have been found to have a negative impact on dairy profitability. Cows calving twins produce less milk during the subsequent lactation compared with cows calving singletons (3,21). Twinning also reduces reproductive performance by increasing average days open and services per conception during the subsequent lactation (21). Cows calving twins have greater risks for many periparturient diseases including retained placenta, metritis, displaced abomasum, ketosis, and acidurea (20,21,23). Not surprisingly, cows calving twins are culled at a greater rate than non-twinning herdmates (8). Calves that are born as twins also have increased probability of problems. There is an increased incidence of abortion, stillbirth, neonatal calf mortality, and reduced birth weight for twin compared with singleton calves (5,9,10,21). In addition, about 92 percent of heifers born twin to a bull calf are freemartins (2). These problems can lead to a reduced number of female replacement heifers.