Abstract
Pregnancy-associated glycoproteins (PAGs) and progesterone concentrations were assessed in Holstein heifers 28 days post-insemination, following estrus synchronization with either a double prostaglandin (PG) injection or the ovsynch protocol. Animals between 15 and 20 months of age, with a 3-3.5 BCS, were randomly assigned to three groups: Heifers in the control group (n = 70) were monitored for estrus behaviour for 21 days and inseminated when detected in standing heat; Estrus of heifers in the Ovsynch group (n = 70)) was synchronized following the Ovsynch protocol, and timed artificial insemination was performed 16 h after the completion of treatment; Animals in the PG group (n = 70) received two prostaglandin-F2α injections 11 days apart, were monitored for estrus behaviour for 2-5 days following the last injection, and inseminated when in heat. Serum PAGs and progesterone concentrations were measured in pregnant heifers (control group n = 25; ovsynch group n = 22; PG group n = 21) on day 28 after artificial insemination (AI). Mean serum PAGs concentrations (OD: optical density) were similar between groups (control = 3.37 ± 0.148, Ovsynch = 3.21 ± 0.136, and PG = 3.34 ± 0.143; p > 0.05). However, serum progesterone concentrations were found to be lower in the ovsynch group (4.70 ± 0.17 ng/mL) when compared to the PG (5.34 ± 0.13 ng/mL) or the control (5.37 ± 0.08 ng/mL) groups (p < 0.001). There was no correlation between serum PAGs and progesterone levels at day 28 post-insemination, or between early pregnancy PAGs concentrations and fetal death rates. Further research, including multiple sampling time points throughout gestation, after estrus synchronization protocols is warranted, to determine if there are associated temporal changes in PAGs and progesterone profiles that could impact reproductive parameters in dairy heifers.
Highlights
Pregnancy-associated glycoproteins (PAGs) belong to the family of inactive aspartic proteinases.[1]
Verification of these same ovarian characteristics was necessary to consider that a heifer from the ovsynch group positively responded to the synchronization protocol
Colazo et al.[35] reported that 11% of the cattle ovulated before timed artificial insemination (TAI) and 15% did not respond to PGF injection after using an ovsynch protocol for estrus synchronization
Summary
Pregnancy-associated glycoproteins (PAGs) belong to the family of inactive aspartic proteinases.[1]. PAGs are produced from the stage of embryo implantation and continue throughout gestation.[6,7] PAGs are thought to be involved in maternal recognition of pregnancy.[8] Presence of PAGs in maternal circulation allows for an early diagnosis of pregnancy,[9,10] detection of late embryonic or early fetal deaths, identification of twin pregnancies, and monitoring of placental function.[11,12] early detection of non pregnant animals permitsa prompt reintoduction to appropriate reproductive management practices thereby reducing the calving interval. Factors that can affect serum PAGs concentrations are day of gestation, fetal number sire, milk production and season.[14,15,16] To the authors’ knowledge, the impact of different synchronization protocols on serum PAGs levels has not been investigated
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