Studies on the establishment of pregnancy in the ewe

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INTRAUTERINE INSEMINATION, TRANSCERVICAL INSEMINATION AND EMBRYO TRANSFER FOR PRACTICAL BREED IMPROVEMENT IN SMALL RUMINANTS

Razvoj laparoskopske intrauterine inseminacija ovaca od najveće je važnosti za provođenje nacionalnih Programa oplodnje u Velikoj Britaniji. Ovaj se postupak razvio istovremeno s postupcima skeniranja ultrazvukom u svrhu in vivo procjene karakteristika trupa ovaca, a primjenom postupka BLUP-a (Best Linear Unbiased Prediction) u svrhu točne procjene genetskih odlika. Ovi postupci zajedno pružaju stvarnu mogućnost ubzanja stope poboljšanja genetskih odlika za ekonomski važne karakteristike krajnjih pasmina za oplodnju ovaca. Međutim laparoskopija je invazivan postupak, pa se budući napredak oslanja na razvitak alternativnih, neinvazivnih postupaka inseminacije. Prenošenje zametaka sadrži mogućnost brže reakcije na izbor (selekciju) i to većim intenzitetom izbora te smanjenjem generacijskog razmaka u ženka. Reakcija se može nadalje pojačati cijepanjem zametka. U ovaca se, međutim, rezultati ne mogu predvidjeti zbog velikog variranja superovularnih reagiranja životinja davalaca; reakcije u koza su manje promjenljive. Ovo variranje reakcija utječe na genetski probitak i to osobito u uzgoju u srodstvu.The development of laparoscopic intrauterine insemination for sheep has been essential for the implementation of national Sire Reference Schemes in the UK. This technology has developed contemporaneously with ultrasonic scanning techniques for in vivo assessment of carcass characteristics in sheep, and with the application of BLUP (Best Linear Unbiased Prediction) techniques for the accurate estimation of genetic merit. Together these techniques offer the real possibility of accelerating the rate of improvement in genetic merit for economically important characteristics in the terminal sire breeds of sheep. However,laparoscopy is an invasive procedure and future progress relies on the development of alternative, non-invasive insemination procedures. Embryo transfer has the potential to accelerate response to selection by increasing selection intensities and reducing generation intervals in females. The response may be enhanced further by embryo splitting. However, in sheep, results remain unpredictable due to the great variation in superovulatory responses of donor animals; responses in goats are less variable. This variation in response has an effect on genetic gain and especially inbreeding