title: Early postpartum administration of equine chorionic gonadotropin to dairy cows calved during the hot season: Effects on fertility after first artificial insemination.
abstract: Heat stress reduces fertility of high-producing dairy cows, and early administration of equine chorionic gonadotropin (eCG) may improve it. Here, 401 heat-stressed, high-producing dairy cows on a single commercial farm were given eCG (500 UI, n = 214) or saline (n = 187) on days 11-17 after calving, and the effects on fertility after the first artificial insemination (AI) were assessed. On post-partum day 96.34 ± 9.88, all cows were inseminated after a "double short Cosynch" synchronization protocol. Ovarian activity and uterine status were checked by ultrasound on the day of eCG administration and every 7 days thereafter for a total of 3 weeks; checks were also performed during synchronization, and 7 days after AI. On post-partum day 30, cytobrush uterine cytology was performed to check for subclinical endometritis. Pregnancy status was checked on days 30 and 60 after AI. The eCG and control groups did not differ significantly in terms of average lactations per cow (2.33 ± 1.34), days in milk at first AI (96.33 ± 9.88), average milk yield at AI (41.38 ± 7.74 L), or the particular inseminator or bull used for AI. The eCG and control groups showed increasing ovarian activity with time, with approximately 75% of cows in both groups showing a corpus luteum at the beginning of the synchronization protocol. On post-partum day 30, 17.4% of eCG cows and 22.9% of control cows showed subclinical endometritis. Cows treated with eCG showed a tendency toward lower hyperecogenic intraluminal content (16.8 vs. 21.4%, P = 0.15), but ovarian activity during the synchronization protocol was similar between eCG and control groups, with 91% of animals in both groups showing luteolysis after prostaglandin application and 88% showing ovulation after the last administration of gonadotropin-releasing hormone. Fertility was similar between the two groups at both time points after AI (30 days, 34.9 vs. 31.8%; 60 days, 30.6 vs. 28.5%; P > 0.2). These results suggest that early postpartum eCG administration does not improve fertility of heat-stressed dairy cows as long as 60 days after AI. Other strategies may be more effective at mitigating the ability of post-partum heat stress to reduce fertility of high-producing dairy cows.
authors.affiliation: TRIALVET S.L., C/ Encina 22, Cabanillas de la Sierra, 28721, Madrid, Spain. Electronic address: rpatron@trialvet.com.
authors.forename: R
authors.initials: R
authors.lastname: Patron-Collantes
authors.affiliation: Dpto. Ciencia Animal, Universitat de Lleida and Agrotecnio center, Av. Rovira Roure 191, Lleida, Spain. Electronic address: irenelh@ca.udl.cat.
authors.forename: I
authors.initials: I
authors.lastname: Lopez-Helguera
authors.affiliation: School of Veterinary Medicine and Zootechnics, Faculty of Agricultural Sciences, University of Cuenca, Avda. Doce de Octubre, Cuenca, Ecuador; Dpto. Reproducción Animal (INIA), Avda. Puerta de Hierro s/n, 28040, Madrid, Spain. Electronic address: jose.pesantez@ucuenca.edu.ec.
authors.forename: J L
authors.initials: JL
authors.lastname: Pesantez-Pacheco
authors.affiliation: Cowvet SL, Avda. País Valenciano 6, 5, 46117, Betera, Valencia, Spain; Granja SAT More, Camino Alcublas, C/ Porta Celi s/n, 46117, Bétere, Valencia, Spain. Electronic address: cowvetsl@gmail.com.
authors.forename: F
authors.initials: F
authors.lastname: Sebastian
authors.affiliation: Granja SAT More, Camino Alcublas, C/ Porta Celi s/n, 46117, Bétere, Valencia, Spain. Electronic address: migvetf@gmail.com.
authors.forename: M
authors.initials: M
authors.lastname: Fernández
authors.affiliation: VAPL S.L., C/Antoni Figueras 20, Tona, 08551, Barcelona, Spain. Electronic address: octavi.vaplslp@gmail.com.
authors.forename: O
authors.initials: O
authors.lastname: Fargas
authors.affiliation: Dpto. Reproducción Animal (INIA), Avda. Puerta de Hierro s/n, 28040, Madrid, Spain. Electronic address: astiz.susana@inia.es.
authors.forename: S
authors.initials: S
authors.lastname: Astiz
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D006063:Chorionic Gonadotropin / Q000008:administration & dosage / Q000494:pharmacology*; D004973:Estrus Synchronization; D005260:Female; D005298:Fertility / Q000187:drug effects*; D006358:Hot Temperature; D036801:Parturition / Q000502:physiology*; D049590:Postpartum Period; D011247:Pregnancy; D012621:Seasons
chemical_list: D006063:Chorionic Gonadotropin
keywords: Cyclicity; Double Ovsynch; Heat stress; Postpartum; Timed AI; eCG