146 RELOCATION OF SWINE GENETICS USING EMBRYO TRANSFER

Abstract

Swine production requires a stable health status that can be compromised by introduction of live animals for genetic change. Our objective was to use embryo transfer to avoid disease transmission during genetic relocation. Forty genotype-specific (GS) donor females were scheduled for 3 sessions of embryo recovery at 6-week intervals using Altrenogest (Matrix^®, Intervet, Millsboro, DE), 1250 IU of equine chorionic gonadotropin (eCG/PMSG; Sigma, St. Louis, MO) and 750 IU of human chorionic gonadotropin (hCG; Chorulon^®, Intervet). Single-sire GS matings were made 34 h after Chorulon^® injection. To accomplish single-sire transfers, color specific (CS) supplemental embryos were used to assist in maintenance of recipient pregnancy. The CS embryo donors and GS embryo recipients were synchronized with Matrix^®, P.G. 600^® (200 IU hCG, 400 IU PMSG, Intervet) and Chorulon^®. Embryos from GS donors were surgically recovered on Day 5 post-insemination, washed per IETS recommendations using a zwitterion-buffered culture medium (PorcPro E-Blast, Minitube of America, Verona, WI) and transported in a portable incubator (Minitube of America) 2.5 h to the recipient herd. Embryos were surgically transferred into –24-h asynchronous recipients within 6 to 14 h after recovery. A total of 620 embryos were recovered from 65.2% (60/92) of GS matings, and 587 (59.4%) GS and 402 (40.6%) CS embryos were transferred into 63 recipients. On average, 9.3 GS and 6.4 CS embryos were transferred per recipient (15.7). A total of 33 GS embryos were discarded before transfer. To achieve a target of 17 embryos per transfer, 59 embryo transfers required CS embryos and 4 embryo transfers were only GS embryos. Fifty-three (84.1%) recipients were confirmed pregnant by ultrasound at 35 days of gestation. Of the 40 GS donors, one was culled for genetic reasons, 6 did not give transferable embryos, and 1 gave transferable embryos but the corresponding recipient returned to estrus for a total genetic transfer rate of 80% (32/40). After 3 sessions of embryo transfer, 32/33 (97%) GS donors that produced embryos for transfer were represented by a minimum of 1 pregnant recipient at 35 days of gestation; 17/32 GS donors were represented by a single pregnancy and 15/32 by multiple pregnancies. Sera from GS donors were evaluated for porcine reproductive and respiratory syndrome (PRRSV) and porcine circovirus type 2 (PCV2) before each embryo recovery session. Serology results were negative for PRRS (0/98)) and positive for PCV2 in 27.5% (27/98) of GS donors. Embryo wash media from the last 2 washes from PCV2 positive GS donors producing embryos for transfer were pooled and evaluated for PCV2 after transfer; all samples (0/18) were negative for PCV2. In summary, zona pellucida-intact embryos were successfully used to relocate swine genetics from a donor herd into a recipient herd with no apparent health status change in the recipient herd.