Spatial relationships of ovarian follicles and luteal structures in dairy cows subjected to ovulation synchronization: Progesterone and risks for luteolysis, ovulation, and pregnancy

Abstract

Objectives were to determine relative ovary location of follicles, GnRH-induced corpora lutea (CL), and older CL present in ovaries as part of ovulation synchronization and their associations with progesterone concentration and risk for luteolysis, ovulation, and pregnancy. Cows were exposed to a timed artificial insemination (AI) program (1 dose or 2 doses 24 h apart)-56 h after first or only dose of PGF 2α -GnRH-2-16 h-timed AI at 72 ± 3 d in milk]. Blood was collected to assess progesterone when ovarian structures were mapped in 694 cows before GnRH-1 and before and 48 h after PGF 2α and, in a subset of cows, size of CL (n = 599) and progesterone (n = 380) at 6 d after AI. Dominant follicles and CL in singleovulating cows were detected more often in right than left ovaries (follicles before GnRH-1: 60.6% right and GnRH-2: 61.2% right; and CL before GnRH-1: 58.6% right and GnRH-2: 66.4% right). Dominant follicles in single-ovulating cows before GnRH-1 tended to be ipsilateral to the CL more often than contralateral (54.8 vs. 45.2%) with co-dominant follicles identified in both ovaries (19.3%). In response to GnRH-1 or GnRH-2, more left-ovary follicles ovulated contralateral to CL (left to right, 54.7%; right to left, 34.7%) than rightovary follicles, but fewer left-ovary follicles ovulated ipsilateral to CL (left to left: 45.3%) than right-ovary follicles ovulated ipsilateral (right to right: 65.3%). Preovulatory follicles in single-ovulating cows before PGF 2α tended to be detected more often ipsilateral than contralateral to CL induced by GnRH-1 (younger CL; 56.5 vs. 43.6%), but were of equal frequency ipsilateral or contralateral to older CL present before GnRH-1. Luteolytic risk was less in cows bearing co-dominant follicles in both ovaries compared with those in either right or left ovaries. Luteolytic risk in single-ovulating cows did not differ between ovaries. Luteolytic risk was greater for cows bearing older CL (86.5%) than for cows bearing younger GnRH-1-induced CL (65.3%) or both (79.6%). Pregnancy risk at 60 d after AI was or tended to be greater in cows having both CL types compared with either younger or older CL, respectively, partly because of greater embryonic loss in the latter 2 cases. More female calves tended to be carried in right horns when conception occurred after first service, whereas the opposite greater female frequency occurred in left horns after repeat services. Right-ovary dominance is evident before and after GnRH treatment.

Effect of GnRH 7 Days Before Presynchronization With Simultaneous PGF2α and GnRH on Reproductive Outcomes in Holstein Dairy Cows

“…Another finding of the current study was a tendency for cows in ExtG to have large CL volume than Control cows. A larger CL volume might be suggestive of higher concentration of progesterone and older CL, which are more likely to regress after a single treatment of PGF 2α (36). However, progesterone and luteolysis after the second PGF 2α were not measured in the current study, and suggestions of potential differences are merely speculative.…”

Superovulatory responses based on ovarian sizes after superstimulation in Thai-Holstein crossbred dairy cows

“…During both natural and synchronized estrous cycles, ovulation occurs more frequently in the right than left ovary, varying from 54%-60% in ewes and goats and from 60%-65% in cows (Pineda, 1989;Stevenson, 2019). Similar observations have been reported in superovulation, the right ovary being 27% larger than the left side after treatment, and resulted in greater CLs and embryos yielded from the right (Palubinskas et al, 2016).…”

A lateral flow-based portable platform for determination of reproductive status of cattle

“…The reference test for all analyses performed was the dichotomized P4 concentration determined by RIA using a P4 concentration cutoff of 1 ng/mL. This cutoff was used because this is a common circulating P4 concentration value used in research or in practice to estimate the presence of a putative functional CL in cattle (Ginther et al, 2010;Stevenson, 2019).…”

“…For instance, most of the developed LFIA for P4 depend on the subjective interpretation of assay results by the user, which may lead to improper interpretation of results (Waldmann and Raud, 2016). In addition, some of the previously developed LFIA systems (Xu et al, 2016;Nakami et al, 2017) were not designed to differentiate samples within a narrow range of P4 concentrations, in particular around 1 ng/mL, which is the most commonly used cutoff to classify cows in relevant reproductive statuses (Ginther et al, 2010;Stevenson, 2019). Thus, our primary objective was to develop a system integrating a disposable fluorescence-based LFIA combined with a fluorescence portable imaging device to estimate circulating concentrations of P4.…”

“…Once developed, our objective was to validate our platform and its accuracy for differentiation of bovine plasma samples with ≥1 or <1 ng/mL of P4. This cutoff was selected because it is commonly used in research and in practice to estimate the presence of a putative functional CL in cattle (Ginther et al, 2010;Stevenson, 2019), which can be used as the sole method or as an aid to determine the reproductive status of cattle. In terms of performance, we aimed to achieve at least 90% accuracy for differentiation of cows with ≥1 or <1 ng/mL of P4, and substantial interrater agreement (i.e., kappa value of 0.61 to 0.80) with a RIA for P4 for classification of plasma samples in groups of P4 ≥1 or <1 ng/mL.…”