Reproduction Abstracts

Evidence suggests that excessive non-esterified fatty acid (NEFA) production during postpartum negative energy balance (NEB) increases the risk of uterine infection. The aims of our study were to investigate associations between circulating NEFAs and uterine gene expression in postpartum dairy cows with NEB using microarray and bioinformatics techniques. Mild NEB (n=6) and severe NEB (n=6) in 12 cows were produced using different milking and feeding protocols. The cows were slaughtered at 14±0.4 days postpartum. Circulating NEFA concentrations before slaughter were quantified. RNA extracted from uterine endometrium was analysed using Affymetrix 24K GeneChip Bovine Genome Arrays. Pearson correlation with Benjamini & Hochberg adjustment established the association between NEFA concentrations and normalized gene expression values. Ingenuity pathway analysis (IPA) was used to identify the biological processes, pathways, and networks. Circulating NEFA levels were significantly higher in SNEB than MNEB cows (1.4±0.1 mmol/l vs 0.3±0.1 mmol/l). Many uterine genes (1182) were significantly correlated with NEFA levels, of which about 80% were differentially expressed between SNEB and MNEB groups. The genes (806) with very large effect size (|r|>0.6) were selected for further analysis. Among them 253 were associated with inflammation, 178 with metabolism and 43 with reproduction. Most of the immune genes (196/253, 77%) were positively correlated with NEFAs, in which some genes involving in acute inflammation and infection, such as SAA3, CXCL6, CFB, and IL8, etc. had r values >0.8. IPA illustrated various aspects of immune/inflammatory processes, pathways and networks were on the top lists. Our results suggest that increased NEFA production in postpartum dairy cows interrupts uterine immune/inflammatory processes and predisposes the animals to uterine infection.