title: Effect of short- and long-term heat stress on the conception risk of dairy cows under natural service and artificial insemination breeding programs.
abstract: The objectives of this retrospective study were to examine the effect of heat stress on natural service and artificial insemination (AI) breeding methods. We investigated the influence of short- and long-term heat stress on the conception risk (CR) of dairy cows bred by natural service or by AI with frozen-thawed or fresh semen. In addition, the relationship between breeding method and parity was determined. Cows bred by AI with frozen-thawed semen exposed to long-term heat stress (mean temperature-humidity index ≥73 in the period 21d before breeding) were 63% less likely to get pregnant compared with cows not exposed to heat stress. Cows bred by AI with fresh semen were 80% less likely to get pregnant during periods of short-term heat stress than during periods without heat stress. Furthermore, multiparous cows bred by AI with frozen-thawed or fresh semen were 22 and 67% less likely to get pregnant, respectively, than primiparous cows. No influence of heat stress or parity was noted on the CR of cows bred by natural service. The present study indicates that the likelihood of dairy cows becoming pregnant is reduced by short- and long-term heat stress depending on the type of semen employed. In particular, CR of cows inseminated with fresh semen is negatively affected by short-term heat stress and CR of cows inseminated with frozen-thawed semen is negatively affected by long-term heat stress.
authors.affiliation: Clinic for Animal Reproduction, Faculty of Veterinary Medicine, Freie Universität Berlin, Koenigsweg 65, 14163 Berlin, Germany.
authors.forename: L-K
authors.initials: LK
authors.lastname: Schüller
authors.affiliation: Clinic for Animal Reproduction, Faculty of Veterinary Medicine, Freie Universität Berlin, Koenigsweg 65, 14163 Berlin, Germany.
authors.forename: O
authors.initials: O
authors.lastname: Burfeind
authors.affiliation: Clinic for Animal Reproduction, Faculty of Veterinary Medicine, Freie Universität Berlin, Koenigsweg 65, 14163 Berlin, Germany. Electronic address: w.heuwieser@fu-berlin.de.
authors.forename: W
authors.initials: W
authors.lastname: Heuwieser
mesh_terms: D000818:Animals; D001947:Breeding / Q000379:methods* / Q000592:standards; D002417:Cattle / Q000502:physiology*; D003612:Dairying / Q000379:methods* / Q000592:standards; D005260:Female; D005306:Fertilization / Q000502:physiology*; D006358:Hot Temperature; D006813:Humidity; D007315:Insemination, Artificial / Q000662:veterinary; D010298:Parity; D011247:Pregnancy; D012189:Retrospective Studies; D012306:Risk; D012661:Semen; D012662:Semen Preservation / Q000662:veterinary; D013312:Stress, Physiological / Q000502:physiology*
keywords: artificial insemination; conception risk; dairy cow; heat stress; natural service