Associations between pregnancy-associated glycoproteins and pregnancy outcomes, milk yield, parity, and clinical diseases in high-producing dairy cows

Abstract

Pregnancy-associated glycoproteins (PAG) are produced by the ruminant placenta and secreted into the maternal circulation throughout pregnancy. The extent to which circulating PAG concentrations predict pregnancy outcomes was examined herein. Also, associations between circulating PAG concentrations and various production parameters and clinical diseases were evaluated. Lactating primiparous and multiparous Holstein cows (n=345) were bred via timed artificial insemination using a standard Ovsynch protocol. Pregnancy was diagnosed by transrectal ultrasonography at d 32, 46, and 74 of gestation. Blood was harvested at d 32 to determine plasma concentrations of PAG and progesterone. Cows pregnant at d 32 that subsequently lost their pregnancy at d 46 and 74 had reduced PAG concentrations. Both artificial insemination service number and parity were associated with plasma PAG concentrations. Concentration of PAG in plasma was greater for cows pregnant from their second or later breeding than those pregnant from the first breeding postpartum, and was increased for primiparous compared with multiparous. In addition, cows with greater milk yield had increased plasma PAG concentrations. No association was detected between body condition score and plasma PAG concentrations. Cows that experienced clinical metritis, metabolic problems, or left displacement abomasum in the early postpartum period preceding breeding had greater plasma PAG concentrations than cows not experiencing these clinical diseases. Also, cows with multiple clinical diseases had increased odds of pregnancy loss when compared with cows not experiencing clinical diseases. Odds ratio testing detected a tendency in the relationship between reduced milk yield and increased pregnancy loss. Collectively, these associations illustrate one feature of the early developing placenta that may predict pregnancy outcomes in dairy cattle. It is unclear if plasma PAG are actively involved with mediating pregnancy outcomes, but modifications in circulating PAG concentrations due to pregnancy loss, milk yield, parity, and clinical disease implicate placental PAG production or PAG release as being responsive to various physiological stimuli.

Genetic and nongenetic profiling of milk pregnancy-associated glycoproteins in Holstein cattle

“…One possible explanation for the negative correlation between PAG and conception rates is that only pregnant cows were used for this correlation, whereas PAG data from nonpregnant cows were excluded. Mercadante et al (2016) detected an association between plasma PAG concentrations and AI service number and parity (fertility trait), but no significant association for body score (Mercadante et al, 2016). They also reported that the cows with greater milk yield had increased plasma PAG concentrations, whereas López-Gatius et al (2007) reported a significant negative association between milk production and PAG values when studying cow pregnancy until d 63 (López-Gatius et al, 2007).…”

“…Many reports in different species have suggested that altered fetal growth is associated with differences in postnatal growth and performance (Wu et al, 2006;Roland et al, 2012). Therefore, given the potential role of PAG on embryonic development and growth, PAG level may serve as an important early indicator of adult performance in ruminant species (Mercadante et al, 2013(Mercadante et al, , 2016.…”

Post-transfer outcomes in cultured bovine embryos supplemented with epidermal growth factor, fibroblast growth factor 2, and insulin-like growth factor 1

“…When a timed-AI protocol was implemented, P4 [87]. Pregnant cows that will maintain their pregnancy to term have greater plasma PAG concentrations at day 30 than cows that will experience late embryonic mortality [87,88]. However, cows with late fetal losses have relatively normal PAG concentrations at day 32 [87,88].…”

“…High circulating PAG concentrations may also be indicative of impending pregnancy loss compared to average PAG concentrations [89]. These increased PAG concentrations could be due to the mother overcoming placental insufficiency, ultimately destructing the fetal-placental unit and releasing the placental products into circulation [88]. Concentrations of PAG are associated with parity, AI service number, milk production, and metabolic diseases linked with pregnancy failure [88,89].…”

“…Pregnancy outcomes in dairy cattle are more profoundly reduced in cows experiencing two or more periparturient disorders [88,119,120]. Healthy dairy cows have a 51% pregnancy rate, whereas cows one case of a disease have a reduced pregnancy rate of 43% [119].…”