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.
Part of the book: Ruminants
This chapter deals with the study of extranuclear hereditary material and the possibilities of using it to maintain endangered animal breeds. The chapter characterizes mtDNA, presents its genes and their functions, while also emphasizing the hypervariable control region. It reports on the results of previous researches, referring to international publications. It sheds light on promising areas of mitogenomic research. It shows the maternal genetic background of local native varieties according to the results of the study of available country/geographical region. It deals with reasons for endangerment and the arguments for preservation of autochthonous breeds. In addition, it gives place to discuss some exciting professional concepts in rare breed preservation.
Part of the book: Landraces