Effect of follicle size on oocytes recovery rate, quality, and in-vitro developmental competence in Bos indicus cows

Abstract

The objective of the present study was to determine the effect of follicle size on recovery rate, quality, and in-vitro developmental competence of oocytes in Bos indicus cows. The ovaries (n = 507) of Bos indicus cows having age of 5-8 years, with mixed parity, BCS 2.75 ± 0.25, and clinically normal reproductive tracts were collected from the local abattoir. The follicles on the ovaries were divided into two groups based upon their size; 1) ≥6 mm diameter, and 2) <6 mm diameter. After initial evaluation of quality of the oocytes, the COCs were in vitro matured, fertilized, and cultured to determine the in vitro developmental competence. The oocyte recovery, quality, maturation, cleavage, 4-cell, 8-cell, and 16-cell stages were analyzed using PROC GLIMMIX procedure of SAS. However, the number of oocytes recovered per ovary was analyzed using MIXED procedure of SAS. Results revealed that the recovery of oocytes (LSM ± SEM) derived from the follicles having size <6 mm per ovary was greater (1.02 vs. 3.14 ± 0.13; P < 0. 0001). However, the percentage (n/n) recovery [69.8 (474/679) vs. 62.7% (1454/2320); P = 0.01] and grade I_+_II oocytes [68.4 (324/474) vs. 57.9% (842/1454); P < 0.0001] was greater in ≥6 mm as compared with <6 mm group, respectively. However, maturation rate did not differ [92.9 (288/310) vs. 92.2% (296/321); P = 0.98] between the groups. In contrast, cleavage rate [58.1 (180/310) vs. 47.4% (152/321); P = 0.01], the 4-cell [34.5 (107/310) vs. 18.7% (60/321); P = 0.0003], 8-cell [15.5 (48/310) vs. 7.8% (25/321); P = 0.008], and 16-cell [8.7 (27/310) vs. 2.1% (7/321); P = 0.004] stage embryos were greater in ≥6 mm group. It can be concluded that oocytes derived from follicle ≥6 mm have better in vitro developmental competence based on embryonic conversion in Bos indicus cows.

Effect of three schemes of ovum pick‐up on the follicular dynamics, gene expression, and in‐vitro developmental competence of oocytes in Sahiwal cattle

“…These findings are supported by previous studies (Gibbons et al, 1994; Hendriksen et al, 2004). The most plausible reason for the higher number of COCs with grade A and B in the TW OPU interval group might be the higher number of medium‐sized follicles (Nawaz et al, 2021; Sarwar et al, 2020) and comparatively low proportion of DFs which leads to the decrease in the level of α‐inhibin in the follicle resulting in the low incidence of atresia in the developing follicles (Guilbault et al, 1993). The proportion of COCs with grade C and D, proportion of oocytes with grade D and number of degenerated oocytes were higher in the OW and BW OPU interval groups compared with TW OPU interval group.…”

The central role of pyruvate metabolism on the epigenetic and molecular maturation of bovine cumulus-oocytes complexes

“…COCs were selected and washed three times in collection media (tissue culture medium 199 (TCM-199) with 4-(2-hydroxyethyl)-1-piperazineethanesulphonic acid (HEPES), 10% fetal bovine serum (FBS), 0.2 mM pyruvate and 1.25 mg mL -1 gentamicin). Only Grade I and II COCs (Sarwar, et al, 2020) were selected and IVM was performed in groups of 25 COCs in 90 µL droplets of maturation medium (TCM-199 with bicarbonate supplemented with 10% FBS, 0.5 mg mL1 FSH (FolltropinV; Bioniche), 100 IU mL1 human chorionic gonadotropin (hCG; Chorulon; Merck Animal Health) and 1.0 mg mL1 oestradiol ) under mineral oil at 38.5 o C with 5% CO 2 in air and high humidity.…”

“…Besides the epigenetic remodeling, oocytes must undergo a series of alterations known as oocyte molecular maturation, which includes the transcription, storage, and processing of RNAs to support the early embryonic development until the major genome activation, around 8-16 cells in bovine embryos (Graf, et al, 2014). The RNA synthesis occurs mainly during oocyte growth, persisting during oocyte maturation and ending only when chromosomes are fully condensed and become inactive (Sarwar, et al, 2020). During these processes, the cumulus cells (CC) play an essential role as they directly transfer RNAs through transzonal projections and, indirectly, influence the levels of RNA polymerase II transcripts and, consequently, the expression of other genes (Regassa, et al, 2011; Macaulay, et al, 2016).…”

Exogenous progesterone‐dependent modulation in the follicular dynamics of Bos indicus cattle undergoing repeated ovum pick‐up sessions

“…Ovum pick up (OPU) is a discreet technique which is safely been used for oocyte collection in cattle for the last 20 years (Moore & Hasler, 2017). Several factors have been investigated to improve the OPU‐IVEP efficiency in terms of oocytes' recovery and quality, and in vitro developmental competence (Merton et al., 2003) which included follicular size (Sarwar et al., 2020), corpus luteum (CL) presence (Hajarian et al., 2016) and plasma P4 concentration (Saad et al., 2019). The past studies reported low P4 plasma concentration during the growing phase of follicles resulted in low conception rates (Pursley & Martins, 2011).…”