| Popis: |
The genetic diversity of common commercial livestock has diminished precipitously due to intensive selection by agribusiness. Rare and/or heritage breeds of domestic livestock are thought to be of low commercial value, yet such breeds contain unique genes that impart valuable traits including disease and parasite resistance, efficient feed conversion, high fecundity, and unique food and fiber qualities. These irreplaceable genetics can be preserved by the establishment of a comprehensive germplasm preservation program whereby the complete genetics of a given unimproved breed can be reestablished in a single generation as needed. We describe and demonstrate here the successful preservation of germplasm from the Tennessee Myotonic (TM) goat breed, and the resulting initiation of a comprehensive germplasm cryolibrary of heritage livestock breeds. Cycling mature TM does (n = 18) were synchronized (PGF2α, 7.5–10 mg i.m.), superovulated (FSH, 50–40–30 mg bid i.m., decreasing over 3 days), and bred by natural service. Embryos were collected surgically from the uterus on Day 7 and good-excellent grade embryos were cryopreserved using a conventional multi-step freezing protocol and stored in LN2. Semen from mature TM bucks (n = 15) was collected biweekly (AV and teaser) and processed using a conventional slow cooling/LN2 plunge protocol. For each animal, a primary cell culture, derived from skin biopsy, was propagated (3 passages) and frozen, and blood (serum, plasma) was collected and cryobanked. A total of 242 embryos, representing 25 sire/dam pedigrees, and 1140 straws of semen were cryobanked. Embryo viability was confirmed by surgical transfer of thawed embryos (2 embryos into each of 2 does) resulting in the birth of 1 healthy buck. Semen viability was assessed by microscopy (30–50% motility; 10–55% live by fluorescence staining) and by AI with frozen-thawed semen (pregnancies confirmed by ultrasound). This report documents and validates the utility of contemporaneous cryopreservation methods to successfully establish a cryolibrary of germplasm from rare breeds of livestock. This strategy affords long term safe storage of viable germplasm with the capability for rapid and accurate reestablishment of the breed genetics if/when needed. Moreover, such storage provides material for assessment of quantitative genetic diversity and for testing of breed disease susceptibility/resistance should that be warranted in the future. This work was supported by and in partnership with SVF Foundation. |
