100 Effects of days in milk and body condition score loss after parturition on oocyte triacylglycerol content in Holstein cows
E. Furukawa A , Z. Chen B , T. Kubo C , M. Chelenga A , Y. Wu B , H. Chiba D , Y. Yanagawa A , S. Katagiri A , S. Hui B and M. Nagano EA Laboratory of Theriogenology, School of Veterinary Medicine, Hokkaido University, Sapporo, Hokkaido, Japan
B Department of Health Sciences and Technology, Faculty of Health Sciences, Hokkaido University, Sapporo, Hokkaido, Japan
C Dairy Cattle Group, Dairy Research Center, Hokkaido Research Organization, Nakashibetsu, Hokkaido, Japan
D Department of Nutrition, Sapporo University of Health Sciences, Sapporo, Hokkaido, Japan
E Laboratory of Animal Reproduction, School of Veterinary Medicine, Kitasato University, Towada, Aomori, Japan
Reproduction, Fertility and Development 34(2) 287-287 https://doi.org/10.1071/RDv34n2Ab100
Published: 7 December 2021
© 2022 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of the IETS
It has been thought that the elevated circulating free fatty acids (FFA) in postpartum dairy cows induce lipotoxicity in oocytes. Our preliminary study found that early postpartum cows showed higher oocyte triacylglycerol (TAG) content and higher circulating FFA concentration than heifers. To obtain further information on oocyte lipid contents, plasma FFA concentrations and oocyte FFA and TAG contents in lactating cows were determined in relation to days in milk (DIM) and body condition score (BCS). Twenty lactating Holstein cows (21–155 DIM, median 55 DIM) were used from a single farm with average milk production of 8900 kg/305 days. Oocytes were collected using ovum pick-up method at the same time of blood sampling. FFA and TAG molecular species of plasma and oocytes were analysed quantitively and qualitatively by liquid chromatography mass spectrometry. Lipids were annotated as “carbon numbers: double bond numbers” (e.g. 16:0). The relationship between two parameters was analysed using Pearson correlation coefficient, and P-values were calculated by a regression analysis. Oocyte FFA contents showed positive correlations with plasma FFA concentrations and oocyte TAG contents (r = 0.63 and 0.46, P < 0.05), while plasma FFA concentrations and oocyte TAG contents did not show a correlation (r = 0.27, P > 0.05). Plasma FFA concentrations and oocyte FFA and TAG contents were high in 21–30 DIM (107.0–274.5 μmol L−1, 290.0–368.7 pmol/oocyte, and 31.6–70.9 pmol/oocyte, respectively), decreased by 50 DIM (before reaching BCS nadir), and maintained a low level after 50 DIM (56.2–170.4 μmol L−1, 200.2–274.5 pmol/oocyte, and 23.9–44.7 pmol/oocyte, respectively). However, regarding cows at ∼140 DIM, two cows with larger BCS loss (1.5 and 1.75) showed 2- to 3-fold higher oocyte TAG contents than the remaining three cows with smaller BCS loss (0.25–0.5), although oocyte FFA contents were similar between them. The ratios of oocyte FFA 16:1/16:0 and 18:1/18:0 showed positive correlations with oocyte FFA contents (r = 0.79 and 0.56, respectively, P < 0.05) and oocyte TAG contents (r = 0.67 and 0.81, respectively, P < 0.05). Except for two cows with BCS loss ≥1.5, oocyte FFA 16:1/16:0 and 18:1/18:0 ratios were high at 21–30 DIM, decreased by 50 DIM, and maintained a low level after 50 DIM. An increase in oocyte TAG content together with oocyte FFA 16:1/16:0 and 18:1/18:0 ratios (a marker of TAG biosynthesis from FFA) in the early postpartum cows may reflect a protective mechanism of converting FFA (a cytotoxic agent) to TAG, as a non-cytotoxic form. Although it is necessary to confirm the significance of this observation in a larger study, the present study found high oocyte TAG contents in a few cows that had experienced a large BCS loss. Our study provides preliminary evidence that may help in understanding the relationships between energy metabolic disorders and oocyte quality of cows, by indicating detailed changes of oocyte energy-related lipid profiles in relation to DIM and BCS changes.
