Exacerbated conceptus signaling does not favor establishment of pregnancy in beef cattle

Abstract

BackgroundInsufficient production of anti-luteolytic signals by the pre-attachment embryo is considered a major cause of pregnancy failure in cattle. We tested the hypothesis that transfer of multiple blastocysts (n = 5/recipient) and progesterone (P4) supplementation amplify anti-luteolytic signaling and reduce embryonic losses in beef cattle. Cows detected in estrus (D0; n = 104) were assigned randomly to receive 150 mg of injectable long-acting P4 (iP4) or vehicle (non-iP4) on D4 and transcervical transfer of none or five, grade 1, not-frozen, in vitro-produced blastocysts, on D7. Luteal development and time of structural luteolysis were monitored by ultrasonography. Plasma P4 concentrations were determined on D4, D5 and D7, and daily between D14 and D20. Conceptus signaling was monitored by transcript abundance of interferon-stimulated gene 15 (ISG15) in peripheral blood mononuclear cells isolated on D14, D16, D18 and D20. Early embryonic mortality (EEM) was defined as the absence of ISG15 mRNA upregulation over time and/or luteal regression up to D20. Late embryonic mortality (LEM) was defined as the absence of a conceptus with a heartbeat on pregnancy diagnosis at D30 (PD30) after observing upregulation of ISG15 mRNA and extension of luteal lifespan. Pregnant cows presented conceptuses with heartbeat at PD30.ResultsOn D5, iP4-treated cows had P4 concentrations 2.07-fold greater than non-iP4 treated (P < 0.001). On D7, P4 concentrations were similar. Pregnant and LEM animals showed a progressive increase in the abundance of ISG15 from D14 to D20. iP4-treated cows detected pregnant at PD30 had 1.53-fold greater abundance of ISG15 mRNA between D14 and D20 than non-iP4 treated cows (P = 0.05). iP4 doubled the frequency of EEM while it did not affect LEM. At PD30, embryonic survival was 37.0% vs. 55.6% for iP4-treated vs. control cows. Majority of pregnant cows (71%) presented only a single viable embryo.ConclusionsA substantial proportion of cows had EEM (31%) and LEM (20%) even after transferring multiple blastocysts. This argues that mortality was due to poor uterine receptivity that could not be reversed by supplemental P4 or overcome by transferring multiple blastocysts. Further, a given uterine environment was not necessarily adequate to all embryos.

Habitat Preferences of Wild Mammalian Species around River Chenab in Sialkot, Gujrat and Gujranwala Districts, Punjab, Pakistan

“…In the initial development of Bali cattle embryos cultured for 48 h, there were 2-, 4-, 8 and 16-cell cleavage and 42% of which developed from 542 oocytes. The development of Bali cattle embryos cultured in vitro is different from that reported by Martins et al (2018) who stated that the stage of cattle embryo cell development on the second day only reaches 4-cell division. Marsico et al (2019) stated that the initial stage of embryonic development is difficult to be carried out because they involve processes that are molecularly dynamically arranged and undergo complex structural changes.…”

The incompletely fulfilled promise of embryo transfer in cattle—why aren’t pregnancy rates greater and what can we do about it?

“…Other experiments in which embryos were repeatedly transferred to cows have revealed that there are subpopulations of highly fertile females that become pregnant after all, or nearly all, ET and other subpopulations that rarely or never become pregnant ( McMillan and Donnison, 1999 ; Geary et al, 2016 ; Moraes et al, 2018 ). Further evidence for poor uterine receptivity as a cause of infertility was the finding that 14 of 37 (32.4%) recipients receiving five embryos failed to become pregnant to any embryo ( Martins et al, 2018a ). Examples of cow factors associated with poor P/ET are low body condition score ( Mapletoft et al, 1986 ; Wallace et al 2011 ), poor weight gain ( Fernandes et al, 2016 ), lactation or parity in dairy cattle ( Dochi et al, 1998 ; Hasler, 2001 ; Ferraz et al, 2016 ), temperament ( Kasimanickam et al, 2018 , 2019 ), and periparturient or postpartum disease ( Ferraz et al, 2016 ; Ribeiro et al, 2016 ; Barbosa et al, 2018 ; Estrada-Cortés et al, 2019 ).…”

Reproductive Characterization of The Bovine Lidia Called “Brava Dos Açores”

“…Under the influence of thermal stress, the duration and intensity of estrus are reduced, with a clear decrease in activity and other manifestations such as the acceptance of copulations [15]. It should, moreover, be noted that the higher incidence of anestrus and silent heats are one of the most common observations in cows exposed to high temperatures [16]. In the Azores as in the interior of the island the pastures are abundant from the end of May to the beginning of July, deliveries occur mostly in this period occurring the mating in September and October, at which point the pasture still has enough fodder to trigger estrus behavior in females.…”

“…Açores" Cattle, the weaned calf is the main source of revenue. Table 1 shows the parameters key to assess reproductive performance [16]. Reproductive efficiency has long been recognized as one of the most important aspects of a bovine holding regardless of type.…”