LA CRIOCONSERVAZIONE DEL MATERIALE SEMINALE NELLA SPECIE GALLUS GALLUS

In the last 50 years, great changes occurred in Italy in poultry production. Local breeds were abandoned and high performing genetic hybrids spread by few industries. The globalization of poultry trade led to a worldwide loss of avian genetic resources . The indigenous breeds survived by fancy breeders, and conservation programs are required to preserve them. One of the most important step in a conservation program is to create a cryobank of genetic resources. For avian species, the most feasible way to preserve gametes is cryopreservation of semen. Researches in this field started in the late Fifties and were soon abandoned because of the bad quality of semen after freezing/thawing procedure. In 1995, Tselutin published a protocol to freeze avian semen, obtaining the same fertility rate than fresh semen. This procedure, consisting in few simple steps, was based on the initial dilution of semen and a first equilibration time at 5°C, addition of DMA as cryoprotectant and a very fast second equilibration time, then dropping semen directly in a liquid nitrogen bath to form frozen semen pellets, finally thawing at high temperature for few seconds. On the basis of Tselutin’s procedure, the aim of this thesis was to set the best conditions to cryopreserve semen of the Italian endangered local breed Mericanel della Brianza, and of the commercial Hubbard meat type strain. The four experiments described in this work focused on the study of the most performing conditions of the cryopreservation procedure for semen from the two genetic lines chosen. Semen quality of MdB and Hubbard roosters was studied soon after collection and after freezing/thawing in experiment 1 and 2. Semen quality was tested in cryopreserved semen through the evaluation of viability, motility, mitochondria status and DNA fragmentation. In vivo fertility of cryopreserved semen from Hubbard males was evaluated through heterologous in protocol 2. The sensitivity to cryopreservation of semen according to the initial quality was studied in protocol 4; viability and motility were considered to assess sperm quality.