title: Use of sex-sorted sperm in lactating dairy cows upon estrus detection or following timed artificial insemination.
abstract: The present study evaluated the use of sex-sorted sperm upon estrus detection (ED) or following timed artificial insemination (TAI) in lactating dairy cows. Additionally, the effect of the presence of a corpus luteum (CL) at the beginning of the TAI protocol was verified. Cows (539 crossbred Gir × Holstein and 87 Holstein) were classified according to the presence or absence of CL by ultrasonography exam. Cows with a CL were randomly assigned into one of two groups (CL-ED/AI or CL-TAI), and cows without a CL (NoCL-TAI) received TAI. Cows from the CL-ED/AI group received 500mg of cloprostenol intramuscularly and were inseminated 12h after ED in the following five days. Cows from the TAI groups (CL or NoCL) received TAI. Cows receiving CL-ED/AI had a lower (P<0.0001) service rate (45.1%, 101/224) than TAI groups (CL-TAI=94.2%, 180/191 and NoCL-TAI=97.2%, 205/211). However, cows receiving AI upon ED (CL-ED/AI=31.7%, 32/101) presented higher (P=0.03) pregnancy per AI (P/AI) than cows bred following TAI (CL-TAI=19.4%, 35/180 and NoCL-TAI=23.9%, 49/205). Despite the lower P/AI, cows receiving TAI presented greater (P=0.07) proportion of pregnant cows at the end of the reproductive program (CL-TAI=18.3%, 35/191 and NoCL-TAI=23.2%, 49/211) than those inseminated upon ED (14.3%, 32/224). There was no effect (P=0.45) of the presence of a CL at the beginning of the synchronization protocol on P/AI. Thus, the use of TAI programs, regardless of the presence of CL in the beginning of the synchronization protocol, increases the service and pregnancy rates but reduces the P/AI when compared to the use of sex-sorted sperm upon ED.
authors.affiliation: Departamento de Reprodução Animal, FMVZ-USP, Rua Prof. Orlando Marques de Paiva 87, CEP 05508-000, São Paulo, SP, Brazil. Electronic address: mfsvt@yahoo.com.
authors.forename: M F
authors.initials: MF
authors.lastname: Sá Filho
authors.forename: M F
authors.initials: MF
authors.lastname: Mendanha
authors.forename: R V
authors.initials: RV
authors.lastname: Sala
authors.forename: F J
authors.initials: FJ
authors.lastname: Carvalho
authors.forename: L H C
authors.initials: LH
authors.lastname: Guimarães
authors.forename: P S
authors.initials: PS
authors.lastname: Baruselli
mesh_terms: D000818:Animals; D002417:Cattle; D003612:Dairying; D004972:Estrus Detection; D004973:Estrus Synchronization; D005260:Female; D007315:Insemination, Artificial / Q000662:veterinary*; D007774:Lactation; D008297:Male; D011247:Pregnancy; D018873:Pregnancy Rate; D012743:Sex Preselection / Q000379:methods / Q000662:veterinary*; D013094:Spermatozoa / Q000166:cytology*
keywords: Dairy cows; Reproduction; Reproductive performance; Synchronization of ovulation