title: Time of insemination relative to reaching activity threshold is associated with pregnancy risk when using sex-sorted semen for lactating Jersey cows.
abstract: The objective of this observational experiment was to determine the association between the interval from reaching activity threshold (AT) to artificial insemination (AI) with sex-sorted semen and the probability of pregnancy. Jersey cows (n = 678) from a commercial dairy herd were fitted with heat-rumination long-distance collars (SCR Ltd., Netanya, Israel) at approximately 42 ± 7 days postpartum. Cows were presynchronized with three injections of PGF2α given 14 days apart starting on Day 39 ± 3 postpartum. Cows in estrus, based on tail paint removal, after 50 ± 3 days postpartum were inseminated by one of three technicians with semen from one of six sires. Cows were examined for pregnancy at 31 ± 3 and 66 ± 3 days after insemination. Only cows inseminated in estrus and examined for pregnancy at 31 ± 3 days after AI were used in the experiment (n = 419). A subsample of cows (n = 35) were examined by ultrasound every 8 hours after reaching AT to estimate the interval from reaching AT and ovulation. The mean (± standard error of the mean) interval from reaching AT to AI was 16.9 ± 0.5 hours, whereas the interval from peak activity to AI was 9.8 ± 0.5 hours. The length of high activity among cows diagnosed in estrus was 17.3 ± 0.3 hours. The mean interval from reaching AT to ovulation was 25.7 ± 1.2 hours. There was a quadratic effect of the interval between reaching AT and AI on probabilities of pregnancy at 31 ± 3 (P = 0.07) and 66 ± 3 (P = 0.15) days after AI. Pregnancy per AI at 66 ± 3 days after AI was higher for cows inseminated between 23 and 41 hours after the onset of estrus (≤ 3 hours = 20.0%, 4-12 hours = 27.1%, 13-22 hours = 39.1%, 23-41 hours = 45.6%, and ≥ 42 = 40.0%). Insemination of lactating Jersey cows with sex-sorted semen closer to expected ovulation yielded the highest probability of pregnancy.
authors.affiliation: Department of Large Animal Clinical Sciences, University of Florida, Gainesville, Florida, USA; Department of Animal Sciences, University of Florida, Gainesville, Florida, USA.
authors.forename: Gabriel D
authors.initials: GD
authors.lastname: Bombardelli
authors.affiliation: Department of Large Animal Clinical Sciences, University of Florida, Gainesville, Florida, USA; Department of Animal Sciences, University of Florida, Gainesville, Florida, USA.
authors.forename: Henrique F
authors.initials: HF
authors.lastname: Soares
authors.affiliation: Department of Large Animal Clinical Sciences, University of Florida, Gainesville, Florida, USA; Department of Animal Sciences, University of Florida, Gainesville, Florida, USA. Electronic address: rcchebel@ufl.edu.
authors.forename: Ricardo C
authors.initials: RC
authors.lastname: Chebel
mesh_terms: D000818:Animals; D002417:Cattle; D004971:Estrus / Q000502:physiology; D005260:Female; D007315:Insemination, Artificial / Q000379:methods / Q000662:veterinary*; D007774:Lactation; D008297:Male; D010060:Ovulation; D011247:Pregnancy; D011256:Pregnancy Outcome; D018873:Pregnancy Rate; D011336:Probability; D012661:Semen / Q000502:physiology; D012743:Sex Preselection / Q000662:veterinary*; D013094:Spermatozoa / Q000502:physiology*; D013997:Time Factors
keywords: Jersey cow; Sex-sorted semen; Timing of insemination