Background: The large animal species such as cattle, buffaloes and horses are monotocous with one or sometimes two newborns per birth whereas small farm animal species such as sheep, goats and pigs are usually polytocous animals are highly prolific and especially pigs often produce a dozen newborns at each farrowing. Cattle usually produce only one calf per gestation resulting from ovulation of a single follicle. The most common form of twinning in cattle occurs due to multiple ovulations which may produce dizygotic twins. The twin births in dairy cattle often negatively impacts the reproduction, production, health and reduces the productive lifespan of cows. Therefore, there is a great interest to know the multiple ovulations and multiple births to reduce the twinning rate in dairy cattle herds.
Objective: This review updates the status of multiple births and its impact and consequences on production of dairy cattle and goats.
Materials and Methods: The related literatures on the multiple births in cattle and goats have been reviewed for which the search was carried out in Google Scholar, PubMed, CrossRef, Banglajol and also the online daily newspapers.
Results: Although multiple births with up to quadruplets have been reported from different countries, the prevalence of twin births are commonly reported in dairy cattle. The prevalence of twinning rates are varied widely in different breeds like twin calving in Holstein Friesian cattle is 3 to 5%, 5.6% Spanish dairy herd and 3.9% in Iranian Holsteins, whereas triplet and quadruplet births represent 0.015% and 0.004% of the total births, respectively. Twin calving shorten gestation length, increased dystocia, stillbirths, decrease birth weight, perinatal calf mortality, retained placenta, decrease milk production, increases the occurrence of metabolic diseases, reduced conception rate, increased calving interval, shorten the productive lifespan of the dam and increases overall culling rate. Two strategies- the transfer of a single embryo produced in vitro and follicular drainage of co-dominant follicles at AI have been suggested to prevent twin pregnancies.
Conclusion: Multiple births in dairy cattle is not desirable due to negative effects on both cows that calve twins and calves born as twins that result in economic losses in dairy herds. Regardless of the direct effect of multiple births on health and fertility, reducing the occurrence of multiple ovulations to decrease the risk of twin births is desirable to mitigate the negative consequences of twinning in dairy cattle. The estimated losses due to twinning range between US$ 59 to 161 per twin pregnancy and attempting manual embryo reduction decreased the economic losses of a twin pregnancy by US $ 23 to 45. Bangladesh scientists discovered a new technique to produce twin calves but the future research on this aspect need to consider the negative effects of twin births in cattle.
