2.1. Animal studies
Embryo transfer methods and their outcomes for the
pure bred Cheviot and Suffolk animals used in this study
have been reported in detail previously [5]. Briefly, 4-yr-old
donor ewes provided embryos 6 d after artificial insemination
while recipients were 4 to 6 yr; all ewes were
multiparous. Standard commercial embryo transfer techniques
were used to generate 4 treatments groups SinS
(Suffolk embryo in Suffolk dam; large genotype control),
CinC (Cheviot embryo in Cheviot dam; small genotype
control), SinC (Suffolk embryo in Cheviot dam), and CinS
(Cheviot embryo in Suffolk dam). From the previously
mentioned transfers, we had 16 Cheviot ewes carrying 7
Cheviot and 9 Suffolk single embryos, and 16 Suffolk ewes
carrying 9 Cheviot and 7 Suffolk single embryos with which
to perform our studies.
All subsequent experiments were approved by the
University of Auckland Animal Ethics Committee. Ewes
were acclimatized to a full ration concentrate feed (3%–4%
of body weight per day, UniC, Dunstan, Hamilton, New
Zealand) and indoor individual pens for 10 d before experiments
were started. Body condition score within breed
ranged between 3 and 4 at feedlot entry. In-house