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We studied the impact of such use through one of the only known concrete cases, in the Abondance cattle breed, a local breed of the French Alps, where the semen of an old bull was used to reintroduce diversity lost over time.

The motivation for using this bull, named Naïf, was to reintroduce an extinct lineage. He was born in 1977, used once from 1980 to 1993, and then used a second time from 2004 to 2009 to produce 45 and 33 offspring respectively. Using pedigrees and molecular data, we were able to study the impact of such reintroduction on genetic diversity and performance. Indeed, Naïf was genetically very original compared to the other sires used in the breed in the 2000s. In addition, he also brought diversity by reducing the average level of inbreeding in the breed because, since this line had almost disappeared, the females with which he was bred were little or not related to Naïf. However, his performance, especially in terms of milk, was that of a bull from the 1980s, and therefore much lower than that of bulls from the 2000s, due to the selection carried out during all these years. This drop in productivity could have been a brake on the reintroduction of "old" genetic diversity, but this was largely circumvented by the choice of using the semen on the best cows available during its second use. Conversely, the reintroduction of this old sire in the selection scheme of the Abondance breed allowed to improve the reproductive performances which had been degraded in the course of time because they had not been selected in the past and were negatively linked to the dairy performances. Therefore, the use of frozen semen from an old sire has proven to be an effective option to reintroduce genetic diversity in an animal breed. However, the choice of females receiving this semen is crucial to combine diversity and performance.

This example shows the interest of a cryobank which should not only be used to store semen as in a museum, but also be used in current populations for a dynamic management of their diversity. This relies on a precise characterization of the available collections, in particular with the help of molecular tools. These results could be transposed to the management of threatened wild populations in order to reintroduce genetic diversity, provided that seed freezing/thawing techniques are well mastered for these species.

Contact :

• Alicia.jacques@inrae.fr
• Michele.boichard@inrae.fr
• Gwendal.restoux@inrae.fr