title: Cooled semen for fixed-time artificial insemination in beef cattle.
abstract: This study evaluated the use of cooled semen in a fixed-time artificial insemination (FTAI) program compared with frozen-thawed semen to improve pregnancy rates in beef cattle. Ejaculates of three bulls were collected and divided into two treatments: (1) frozen-thawed semen and (2) cooled semen. Egg-yolk extender without glycerol was used for the cooled semen treatment. Straws (25×106spermatozoa) were submitted to cooling for preservation at 5°C for 24h, after which FTAI was performed. Nelore cows (n=838) submitted to FTAI were randomly inseminated using frozen-thawed semen or cooled semen. There was a 20% increase in the pregnancy per AI (P AI-1) using cooled semen compared with frozen-thawed semen (59.9±4.7 vs 49.4±5.0%; P<0.005). There was no difference in P AI-1among the bulls (P=0.40). The frozen-thawed semen had fewer functional spermatozoa than did the cooled semen when evaluated by sperm motility (61.7 vs 81.0%), slow thermoresistance test (41.7 vs 66.7%) and hypoosmotic swelling test (38.3 vs 53.7%; P<0.05). The percentage of sperm abnormalities did not differ between the freeze-thawing and cooling processes (18.6 vs 22.1%; P>0.05). Because there was less damage to spermatozoa and improvement in P AI-1, the use of cooled semen instead of frozen-thawed semen is an interesting approach to increase reproductive efficiency in cattle submitted to a FTAI protocol.
authors.affiliation: University of São Paulo, Piracicaba, 13418-900, Brazil.
authors.forename: Juliana C
authors.initials: JC
authors.lastname: Borges-Silva
authors.affiliation: Melhore Animal Consultoria LTDA, Jaboticabal, 14871-835, Brazil.
authors.forename: Márcio R
authors.initials: MR
authors.lastname: Silva
authors.affiliation: Ema Agropecuária Pantanal LTDA, Corumbá, 79300-006, Brazil.
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Marinho
authors.affiliation: Embrapa Pantanal, Corumbá, 79320-900, Brazil.
authors.forename: Eriklis
authors.initials: E
authors.lastname: Nogueira
authors.affiliation: Federal University of Mato Grosso do Sul, Campo Grande, 79090-900, Brazil.
authors.forename: Deiler C
authors.initials: DC
authors.lastname: Sampaio
authors.affiliation: Embrapa Pantanal, Corumbá, 79320-900, Brazil.
authors.forename: Luiz Orcírio F
authors.initials: LOF
authors.lastname: Oliveira
authors.affiliation: Embrapa Pantanal, Corumbá, 79320-900, Brazil.
authors.forename: Urbano G P
authors.initials: UGP
authors.lastname: Abreu
authors.affiliation: University of São Paulo, Piracicaba, 13418-900, Brazil.
authors.forename: Gerson B
authors.initials: GB
authors.lastname: Mourão
authors.affiliation: University of São Paulo, Piracicaba, 13418-900, Brazil.
authors.forename: Roberto
authors.initials: R
authors.lastname: Sartori
mesh_terms: D000818:Animals; D002417:Cattle; D015925:Cryopreservation / Q000662:veterinary*; D005260:Female; D007315:Insemination, Artificial / Q000662:veterinary*; D008297:Male; D011247:Pregnancy; D000069466:Red Meat; D012661:Semen; D012662:Semen Preservation / Q000662:veterinary*; D013081:Sperm Motility; D013094:Spermatozoa