Objective:
ARS¿ National Animal Germplasm Program (NAGP) and the Cooperator (University of Illinois), desire to enter into this Cooperative Agreement for the purpose of improving the NAGP protocol for freezing swine germplasm. The primary objective will be to test fertility levels that can be achieved when sperm concentration per 0.5ml straw is increased, an evaluation of the number of spermatozoa needed to obtain sufficient fertility levels for breed reconstitution, and by performing either a single or double inseminations. If higher sperm concentrations can be successfully cryopreserved the end result would be fewer 0.5ml straws would have to be stored per boar which would in turn decrease NAGP¿s operation costs.

Approach:
1. Semen from boars will be collected and frozen at multiple levels of concentration (cells/0.5 ml = 1 straw) ranging from 100,000,000 per straw (the current level) to 500,000,000 per straw. Based upon post-thaw evaluation an optimal concentration level will be selected for the insemination portion of the experiment. 2. Gilts will be inseminated with either 1.0 (current dosage level), 2.0 and 4.0 billion sperm per insemination. 3. Either a single or double fixed time inseminations with the three dosage levels. 4. Gilts will be checked for pregnancy at day 25, and held until day 30 and then sent to slaughter. This method allows for investigation of fertility in a terminal line market animal with full recovery for animal value and the ability to collect larger numbers of pregnant tracts from treated animals at one time. Reproductive tracts will be identified by treated animal and analyzed for pregnancy status, numbers of healthy embryos, size and weight of embryos as an indicator of potential litter size.