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Simple Summary: The main objective of this study was to determine the influence of the recipient dairy cows' breed, lactation number, estrus condition, the type, location and volume of the corpus luteum (CL) and the time of year that the embryo transfer (ET) was performed on the pregnancy rates of a large, fresh in vitro fertilization–embryo transfer program for dairy cows in a commercial herd in China. Our results showed that heifers with a larger CL without liquid cavity in the center of the CL and ET in spring significantly enhanced the pregnancy rates in dairy cows under farm conditions in the northwest region of China. These results can help breeders to select the best recipient dairy cows and improve the efficiency of embryo transfer in China. The main objective of this study was to determine the influence of the recipient dairy cows' breed, lactation number, estrus condition, the type, location and volume of the corpus luteum (CL) and the time of year that the embryo transfer (ET) was performed on the pregnancy rates of a large, fresh in vitro fertilization–embryo transfer program for dairy cows in a commercial herd in China. The recipients were from a herd of dairy cows in Ningxia, a province in northwest China, and we statistically analyzed the data of 495 cows from 2021 to 2023. Cumulus oocyte complexes (COCS) were isolated from follicular fluid obtained through ovum pick-up (OPU) and oocytes were incubated 20–22 h for in vitro maturation (IVM). Embryos were obtained after 10–12 h of in vitro fertilization (IVF) and six days of in vitro culture (IVC). Embryos at the morula or blastocyst stage were transferred to randomly chosen recipients (n = 495). The influence of recipients' breed (Holstein or other), recipients' lactation number (heifers or cows), estrus type (natural or synchronized), CL type (homogeneous, CLhom or cavitary, CLcav), CL side (left or right), volume of the CL and season of transfer (spring, autumn or winter) on pregnancy rates were determined. The pregnancy rates were analyzed by binomial logistic regression with IBM SPSS statistics software, version 26. Pregnancy rates after ET to Holstein cows and other breeds were 43.49% and 42.68%, respectively (p > 0.05). Regarding age, pregnancy rates were 45.56% for heifers and 30.77% for cows (p < 0.05). Pregnancy rates following ET during natural and synchronized estrus were 44.41% and 41.5%, respectively (p > 0.05). Pregnancy rates with a left- or right-side CL were 40.18% and 45.65%, respectively (p > 0.05). The pregnancy rates achieved with a CLhom and CLcav were 44.44% and 39.68%, respectively (p < 0.05). The rates obtained in spring, autumn and winter were 49.26%, 46.02% and 34.64%, respectively (p < 0.05). Moreover, it was found that pregnancy rates were higher in recipients with a CL volume measuring greater than 10 cm3 compared with those with a CL volume measuring less than 10 cm3 (p < 0.05). The comparisons showed that recipients' breed, estrus type or side of the CL had no effect, but the recipients' lactation number, ET season and the type and volume of the CL have significant effects on pregnancy rates during ET. [ABSTRACT FROM AUTHOR]

Endometritis in high-yield dairy cows adversely affects lactation length, milk quality, and the economics of dairy products. Endoplasmic reticulum stress (ERS) in bovine endometrial epithelial cells (BEECs) occurs as a consequence of diverse post-natal stressors, and plays a key role in a variety of inflammatory diseases. Nuclear-factor-erythroid-2-related factor 2 (Nrf2) is an important protective regulatory factor in numerous inflammatory responses. However, the mechanism by which Nrf2 modulates inflammation by participating in ERS remains unclear. The objective of the present study was to explore the role of Nrf2 in lipopolysaccharide (LPS)-induced injury to BEECs and to decipher the underlying molecular mechanisms of this injury. The expression of Nrf2- and ERS-related genes increased significantly in bovine uteri with endometritis. Isolated BEECs were treated with LPS to stimulate the inflammatory response. The expression of Nrf2 was significantly higher in cells exposed to LPS, which also induced ERS in BEECs. Activation of Nrf2 led to enhanced expression of the genes for the inflammation markers TNF-α, p65, IL-6, and IL-8 in BEECs. Moreover, stimulation of Nrf2 was accompanied by activation of ERS. In contrast, Nrf2 knockdown reduced the expression of TNF-α, p65, IL-6, and IL-8. Additionally, Nrf2 knockdown decreased expression of ERS-related genes for the GRP78, PERK, eIF2α, ATF4, and CHOP proteins. Collectively, our findings demonstrate that Nrf2 and ERS are activated during inflammation in BEECs. Furthermore, Nrf2 promotes the inflammatory response by activating the PERK pathway in ERS and inducing apoptosis in BEECs. [ABSTRACT FROM AUTHOR]

Milk fat is a main nutritional component of milk, and it has become one of the important traits of dairy cow breeding. Recently, there is increasing evidence that microRNAs (miRNA) play significant roles in the process of milk fat synthesis in the mammary gland. Primary bovine mammary epithelial cells (BMEC) were harvested from midlactation cows and cultured in DMEM/F-12 medium with 10% fetal bovine serum, 100 units/mL penicillin, 100 µg/mL streptomycin, 5 µg/mL bovine insulin, 1 µg/mL hydrocortisone, and 2 µg/mL bovine prolactin. We found that miR-34b mimic transfection in BMEC reduced the content of intracellular triacylglycerol (TAG) and lipid droplet accumulation via triacylglycerol assay and Oil Red O staining; meanwhile, overexpression of miR-34b inhibited mRNA expression of lipid metabolism-related genes such as peroxisome proliferator-activated receptor gamma (PPARγ), fatty acid synthase (FASN), fatty acid binding protein 4 (FABP4), and CCAAT enhancer binding protein alpha (C/EBPα). Whereas miR-34b inhibitor resulted in completely opposite results. Furthermore, q-PCR and western blot analysis revealed the mRNA and protein expression levels of DCP1A were downregulated in miR-34b mimic transfection group and upregulated in miR-34b inhibitor group. Moreover, luciferase reporter assays verified that DCP1A was the direct target of miR-34b and DCP1A gene silencing in BMEC-inhibited TAG accumulation and suppressed lipid droplet formation. In conclusion, these findings revealed a novel miR-34b–DCP1A axis that has a significant role in regulating milk fat synthesis and suggested that miR-34b may be used to improve the beneficial ingredients in milk. [ABSTRACT FROM AUTHOR]

Milk fat is a main nutritional component of milk, and it has become one of the important traits of dairy cow breeding. Recently, there is increasing evidence that microRNAs (miRNA) play significant roles in the process of milk fat synthesis in the mammary gland. Primary bovine mammary epithelial cells (BMEC) were harvested from midlactation cows and cultured in DMEM/F-12 medium with 10% fetal bovine serum, 100 units/mL penicillin, 100 µg/mL streptomycin, 5 µg/mL bovine insulin, 1 µg/mL hydrocortisone, and 2 µg/mL bovine prolactin. We found that miR-34b mimic transfection in BMEC reduced the content of intracellular triacylglycerol (TAG) and lipid droplet accumulation via triacylglycerol assay and Oil Red O staining; meanwhile, overexpression of miR-34b inhibited mRNA expression of lipid metabolism-related genes such as peroxisome proliferator-activated receptor gamma (PPARγ), fatty acid synthase (FASN), fatty acid binding protein 4 (FABP4), and CCAAT enhancer binding protein alpha (C/EBPα). Whereas miR-34b inhibitor resulted in completely opposite results. Furthermore, q-PCR and western blot analysis revealed the mRNA and protein expression levels of DCP1A were downregulated in miR-34b mimic transfection group and upregulated in miR-34b inhibitor group. Moreover, luciferase reporter assays verified that DCP1A was the direct target of miR-34b and DCP1A gene silencing in BMEC-inhibited TAG accumulation and suppressed lipid droplet formation. In conclusion, these findings revealed a novel miR-34b–DCP1A axis that has a significant role in regulating milk fat synthesis and suggested that miR-34b may be used to improve the beneficial ingredients in milk. [ABSTRACT FROM AUTHOR]

Trueperella pyogenes is an important bacterial pathogen of a wide range of domestic and wild animals. Autophagy plays a key role in eliminating T. pyogenes in a process that is dependent on mechanistic target of rapamycin (mTOR). The endoplasmic reticulum (ER) stress response also is critical for autophagy regulation. However, the relationship between ER stress and T. pyogenes is uncharacterized and the intracellular survival mechanisms of T. pyogenes have not been investigated adequately. In this study, we show that T. pyogenes invades goat endometrial epithelial cells (gEECs). Meanwhile, we observed that GRP78 was upregulated significantly, and that unfolded protein response (UPR) also were activated after infection. Additionally, treatment with activators and inhibitors of ER stress downregulated and upregulated, respectively, intracellular survival of T. pyogenes . Blocking the three arms of the UPR pathway separately enhanced T. pyogenes survival and inflammatory reaction to different levels. We also show that LC3-labeled autophagosomes formed around the invading T. pyogenes and that autolysosome-like vesicles were visible in gEECs using transmission electron microscopy. Moreover, tunicamycin did not inhibit the intracellular survival of T. pyogenes under conditions in which autophagy was blocked. Finally, severe challenge with T. pyogenes induced host cell apoptosis which also may indicate a role for ER stress in the infection response. In summary, we demonstrate here that ER stress and UPR are novel modulators of autophagy that inhibit T. pyogenes intracellular survival in gEECs, which has the potential to be developed as an effective therapeutic target in T. pyogenes infectious disease.