Effect of embryo age and stage on pregnancy rates from demi-embryos

Abstract

Goat embryos are apparently more fragile compared to their counterpart sheep and cattle embryos. Embryos of the blastocyst to nearly hatched late blastocyst stages were obtained from superovulated New Zealand Angora donors. These stages appear hardier for splitting than morula stages. Embryos were bisected using a twin needle system in conjunction with a micro-surgical cutting blade (knife). If an embryo was cut fully through, it was either replaced into a separate zona or the same zona. If the embryo was only cut partly through, it was left in its original zona. The demi-embryos were surgically transferred to progesterone synchronized recipients. All recipients were scanned ultrasonically at eight weeks. Demi-embryos in separate zonae resulted in 77.8% embryo survival (79) compared to 75.0% (34) for demi-embryos cut completely through and placed in the same zona. Survival rate was 54.0% (1426) for demi-embryos cut 90% through the inner cell mass and left in the same zona. Of 128 control embryos, 47 foeti (36.7%) were scanned at eight weeks compared to 23 foeti from 39 split embryos (59.0%; P < 0.2). Commercially, this embryo splitting system is consistently reliable and gentle for goat embryos. The system is more efficient when the demi-embryos are left within the same zona (5 to 8 min. per embryo); however, fewer offspring may result due to fusion of the embryo halves.