title: Effect of different packages and freezing/thawing protocols on fertility of ram semen.
abstract: A field trial was performed in order to evaluate the effect on fertility of different straw types, freezing protocols (one- or two-step) and thawing procedures (35 degrees C and 70 degrees C) using frozen-thawed ram semen. A total of 791 Norwegian Crossbred ewes were artificially inseminated during natural oestrus with semen collected from nine mature and proven Norwegian Crossbred rams. A milk-based extender was used for dilution. The ewes were allocated into one of the following three groups based on the different straw types and thawing temperatures: medium straw (0.5 ml) thawed at 35 degrees C for 20 s (Med35), medium straw thawed at 70 degrees C for 8 s (Med70) and mini straw (0.25 ml) thawed at 35 degrees C for 15 s (Mini35). The semen to be frozen in mini straws was re-concentrated by centrifugation. Sperm number in each insemination dose was approximately 200 x 10(6) spermatozoa. The fertility results [as 25-day non-return rate (NRR)] for Med35, Med70 and Mini35 were 53.1%, 50.8% and 58.3%, respectively, and the lambing rates 49.8%, 46.8% and 53.8%, respectively. No significant main effects were seen for straw type/thawing temperature (p = 0.17), ram (p = 0.06) or age of the ewe (p = 0.18) on NRR or lambing rates (p = 0.19, p = 0.16 and p = 0.27, respectively). Both NRR and lambing rate differed significantly among farms (p < 0.0001).
authors.affiliation: Team Semin, Oslo, Norway.
authors.forename: A B
authors.initials: AB
authors.lastname: Nordstoga
authors.forename: L
authors.initials: L
authors.lastname: Söderquist
authors.forename: T
authors.initials: T
authors.lastname: Adnøy
authors.forename: H
authors.initials: H
authors.lastname: Paulenz
mesh_terms: D000818:Animals; D015925:Cryopreservation / Q000295:instrumentation / Q000379:methods / Q000662:veterinary*; D005260:Female; D005298:Fertility / Q000502:physiology*; D006358:Hot Temperature; D007315:Insemination, Artificial / Q000662:veterinary; D008297:Male; D011247:Pregnancy; D012661:Semen / Q000502:physiology*; D012662:Semen Preservation / Q000295:instrumentation / Q000379:methods / Q000662:veterinary*; D012756:Sheep; D013696:Temperature; D013997:Time Factors