The production of mixed-species Bos taurus-Bos indicus twin calves

Bos taurus-Bos indicus twin calves were produced by transferring Day 6–8 Bos indicus or Bos taurus embryos to previously inseminated Bos taurus or Bos indicus cows. Embryos were transferred to 112 recipients of which 64 (57.1%) were diagnosed as pregnant by rectal palpation at 7–8 weeks gestation. Twin foetuses were diagnosed in 38 (65.5%) of 58 cows in which the location and number of foetuses was recorded. Substantial foetal losses occurred after 7–8 weeks and only 44 cows calved giving 21 sets of twins and 23 singletons. Six of the single calves were from transferred embryos. The duration of gestation of the twin pregnancies (282 days) was similar to that of single Bos taurus pregnancies (282 days for Jerseys and 286 days for Friesians) and 14 days shorter than single Bos indicus pregnancies (296 days). Consequently Bos indicus members of mixed-species twins were premature at birth and required intensive care to ensure their survival.