Journal of Animal Science, Vol 69, Issue 5 2066-2072, Copyright © 1991 by American Society of Animal Science

JOURNAL ARTICLE

Effect of serum-free co-culture and synchrony of recipients on development of cultured sheep embryos to fetuses

C. E. Rexroad Jr and A. M. Powell
Beltsville Agric. Res. Center, U.S. Department of Agriculture, Beltsville, MD 20705.

The percentage of sheep embryos that continued to develop after collection and immediate transfer on d 2 after estrus was similar when phosphate-buffered saline with 10% fetal calf serum (PBSFCS, 45%), physiological saline (50%), or tissue culture medium 199 supplemented with 10% fetal calf serum (M199FCS, 47%) was used to flush embryos from oviducts. Co-culture of sheep embryos for 3 d with oviductal cells tended (P = .1) to reduce the percentage of embryos that developed to fetuses after transfer compared with those embryos transferred immediately. Tissue culture medium 199 supplemented with .3% BSA (M199BSA) was an adequate substitute for M199FCS for culture of sheep oviductal cells if tissue culture wells were pretreated with fibronectin. Estradiol in concentrations from 10 to 1,000 pg/ml and progesterone at concentrations of 1 or 10 ng/ml in M199BSA failed to stimulate embryo development during 3 d of co-culture beyond that seen in co-culture with M199FCS or M199BSA without added steroid. Transfer of sheep embyros co-cultured for 3 d in M199BSA or M199FCS to recipients synchronized with donors resulted in about 19% of the embryos developing to fetuses, whereas transfer to recipients that were in estrus 24 h after donors resulted in 33% of embryos developing to fetuses. The significant (P less than .05) improvement for delayed recipients may reflect the relatively lesser developmental rate of co-cultured embryos compared with that of embryos in vivo. Embryo development into fetuses was similar after co-culture in M199FCS or M199BSA co-cultures; therefore, serum is not required for the co-culture of sheep embryos.