54 Effect of clinical endometritis on the follicle growth dynamics, oocyte recovery, oocyte quality, and in vitro developmental competence of oocytes using ovum pickup in Sahiwal cattle

Abstract

Sahiwal cattle is the premium quality milk breed of cattle in Pakistan. Uterine infections often lead to culling of valuable animals from a herd, resulting in genetic drain. The genetic potential of problematic females could be reaped by in vitro embryo production. The objective of the present study was to evaluate the effect of clinical endometritis on follicle growth dynamics, recovery, quality, and in vitro developmental competence of oocytes using ovum pickup (OPU) in Sahiwal cattle. The animals, 5–7 years of age, third or fourth parity, and 160 to 170 days in milk (DIM), were inspected for any discharge at the vulva or inside the vagina. Then, B-mode ultrasonography was performed to measure the diameter of cervix and to examine the uterus for the presence of pus. The animals (n = 12) were divided into 2 groups: (1) healthy (n = 6), and (2) clinical endometritis (n = 6), based on the presence or absence of pus at the vulva or in the vagina. The first OPU was performed after 7 days of dominant follicle puncture and subsequently repeated OPUs (54 and 50), after every 7 days over 9 OPU sessions, were performed in the healthy group and clinical endometritis group, respectively. Follicles were aspirated using transvaginal ultrasound–guided needle. Viable COCs were considered for further processing only and were placed in the 100-µL droplets of BO-IVM medium and incubated at 37°C, 5% CO₂, and 95% humidity for 24 h. Nuclear maturation was estimated by staining the oocytes with Hoechst 33342. Frozen semen from the same Sahiwal bull was thawed and processed for IVF throughout the study. Sperm were prepared using swim-up protocol. Sperm and COCs were co-incubated in 100-µL droplets of BO-IVF for 18 h. Finally, presumptive zygotes were cultured in 100-µL drops of BO-IVC medium at 37°C, 5% CO₂, 5% O₂, and 95% humidity for a period of 7 days. Cleavage rate and blastocyst rate were recorded on Day 2 and 7 following IVF, respectively. The data were analysed using the GLIMMIX procedure of SAS (SAS Institute Inc.). The results revealed that the number of medium-sized follicle (1.32 ± 0.11 vs. 0.56 ± 0.11) and total follicles (9.14 ± 0.70 vs. 6.58 ± 0.72) were higher (P < 0.05) in the healthy group than in the clinical endometritis group, respectively. Similarly, the number of oocytes recovered (5.05 ± 0.39 vs. 2.78 ± 0.41), viable oocytes (2.87 ± 0.25 vs. 1.46 ± 0.26), COCs with grade AB, having minimum of 2 cumulus cell layers and homogeneous cytoplasm, (33 vs. 20%) and nuclear maturation (68 vs. 55%) were also higher (P < 0.05) in the healthy group than in the clinical endometritis group, respectively. However, cleavage rate (55 vs. 46%) and blastocyst rate (29 vs. 26%) did not differ (P > 0.05) between the groups. In conclusion, clinical endometritis has a negative effect on follicle growth dynamics, oocyte recovery, oocyte quality, and nuclear maturation; however, the developmental competence of COCs is not compromised by it.