The occurrence of twin calving in Holstein Friesian cattle is 3–5%. Reproductive problems found before and after the time of calving lead to serious economic losses. The authors’ aim was to form a compilation of data regarding the cause and effects of twin calving on dairy cows by comparing the reproductive performance of cows before and after calving twins vs. single calves and also analyzing the milk production of dairy cows both before and after twin calving. Cows that would have twins became pregnant earlier, probably because of their better health and fertility, with shorter gestations and calving interval. However, after calving, cows that had twins showed poorer reproductive performance. The results show that twin-calving cows had better condition prior to calving, resulting in an earlier successful twin calving. However, the economic losses during parturition, metabolic disorders of the cow, and low vitality of the twin calves, coupled with the decreased fertility and elevated culling rate in cows after twinning, may discourage breeding twins in dairy cattle
