PSIII-9 The supplementation of rumen-inert unsaturated fatty acids and rumen-protected choline modulates the uterine luminal fluid metabolome of pregnant beef cows during the peri-elongation period.

Abstract Early embryonic mortality is a major concern to the beef industry, as nearly 32.3% of multiparous cows will not maintain pregnancy past the first sixteen days of gestation. During this period, the uterine luminal fluid provides nutrients to support embryonic growth and development. Therefore, our objective was to modulate the uterine luminal fluid at the onset of the embryonic elongation period in pregnant cows receiving a targeted dietary supplementation to support early embryonic development. One hundred multiparous Bos taurus cows were weighed, body condition recorded, and stratified to be allocated in pens. Cows were acclimated to the individual feeding system for 15 days. On d -30, cows within pens were randomly assigned to receive either TARG) 100 g of a rumen-inert mono- and polyunsaturated fatty acid source plus 60 g of a rumen-protected choline source or CON) 114 g of a saturated fatty acid source. Treatments were top-dressed daily into a similar total mixed ration. Starting on d -10, all cows were synchronized using the 7-day CO-synch + CIDR protocol. On d 0, ovarian ultrasonography was conducted, and cows were bred by TAI by the same technician using semen from two bulls balanced by treatment. On d 14, blood collection was performed to analyze the concentration of progesterone (P4), and ovarian ultrasonography was performed to measure the corpus luteum area. In addition, cows were subjected to a cytobrush collection in the uterine body for metabolomics analysis (TARG = 42 and CON = 49). However, only samples from cows confirmed to be pregnant, on d 16 or d 30, were analyzed (TARG = 16 and CON = 18). The fixed effects of treatment, group, and their interactions on P4 and CL area were analyzed by ANOVA. There were no differences in P4 and CL area at d 14 (P ≥ 0.19). The concentration of metabolites was analyzed in Rstudio with data filtering including metabolites measured in at least 75% of the samples or in at least 60% of one sample group. Depending on normality, data were analyzed either by ANOVA or Wilcoxon-Mann-Whitney test. Significance was stated as P ≤ 0.05 and tendency as 0.05 < P ≤ 0.1. The concentration of 12 metabolites were significant and 11 tended to be significant in the uterine luminal fluid between TARG and CON. Among these metabolites, the concentration of unsaturated fatty acids, amino acids, and phospholipid classes such as phosphatidylcholine, phosphatidylinositol, phosphatidylserine, and phosphatidylethanolamine were greater in TARG. In addition, choline and betaine were also greater in TARG. In conclusion, the dietary supplementation provided herein modulated the uterine luminal metabolome during the period of embryonic elongation increasing the concentration of important metabolites that are integral components of membranes and fertility outcomes deserve further investigation.