Increased serum nonesterified fatty acid and low ionised calcium concentrations are associated with post partum colic in mares.

REASONS FOR PERFORMING STUDY: Increased serum nonesterified fatty acids (NEFA) and decreased serum electrolytes are linked to abdomasal displacements in post partum dairy cattle. Post partum colic in mares may be associated with metabolic changes specific to pregnancy and the periparturient period. OBJECTIVES: To determine if fluctuations in serum NEFA, ionised calcium (iCa) and magnesium (iMg) occurred in periparturient mares and if these alterations were associated with post partum colic. STUDY DESIGN: Longitudinal observational study. METHODS: Mares from 3 farms in central Kentucky were enrolled. Blood samples were collected 14 days prior to the estimated foaling date, within 4 days post parturition, and 14 and 28 days after foaling for batch analysis of serum NEFA, iCa and iMg. Health information was provided by farm managers and veterinarians. Data were analysed using Kruskal-Wallis χ(2) statistic for nonparametric data and a matched case/control approach. Repeated measures logistic regression models were developed. RESULTS: Serum NEFAs were higher at 14-1 day before foaling (mean ± s.d., mmol/l), 0.28 ± 0.12, P = 0.04 and from foaling to 4 days after foaling, 0.29 ± 0.20 (P = 0.05) in mares that developed colic compared with those that did not colic, 0.19 ± 0.05 and 0.21 ± 0.14, respectively. Ionised calcium was lower at 15-28 days post foaling in mares that showed colic, 1.50 ± 0.17 compared to mares that did not colic, 1.60 ± 0.12, P = 0.02. Risk of colic in post partum mares increased 38% for each 0.1 mmol/l increase in serum NEFA (odds ratio = 1.38, 95% confidence interval 1.06-1.81, P = 0.02). CONCLUSIONS: Mares with post partum colic had significantly higher serum NEFA and lower iCa prior to the colic episode compared with mares that did not develop colic. Monitoring these metabolic alterations may lead to predictive and preventive colic strategies for post partum mares.

Changes in the faecal microbiota of mares precede the development of post partum colic.

REASONS FOR PERFORMING STUDY: Disruptions in the gastrointestinal microbiota may trigger development of post partum colic. OBJECTIVES: To determine the effects of the periparturient period on the faecal microbiome and identify associations between the faecal microbiota and post partum colic. STUDY DESIGN: Longitudinal case-control study. METHODS: Pre- and post partum faecal samples were collected from mares on 3 farms in central Kentucky. Next generation sequencing of the V4 region of the 16S rRNA gene was performed on samples from 13 mares that developed colic, 13 mares that did not display colic and 5 nonpregnant controls. RESULTS: There were 4,523,727 sequences from 85 samples evaluated (mean ± s.d. 53,220 ± 29,160, range 8442-122,535). Twenty-five phyla were identified, although only Firmicutes, Verrucomicrobia, Actinobacteria and Proteobacteria were present at a relative abundance of 1% or greater. The faecal microbiota of late-term mares differed from nonpregnant mares, with differences in microbial community membership and structure but not the relative abundance of major phyla. There was limited impact of foaling and the post partum period on the faecal microbiome. Faecal samples obtained from mares prior to episodes of colic had significantly higher relative abundance of Proteobacteria (8.2%, P = 0.0006) compared with samples from mares that did not display colic (3.7%). All samples with a relative abundance of Firmicutes of ≤50% preceded colic, as did 6/7 (86%) samples with >4% Proteobacteria. Differences in microbiota membership and structure were also present between mares that developed large colon volvulus and matched controls that did not have colic. Sixty-one indicator operational taxon units were identified for the control (vs. volvulus) samples, and these were dominated by Lachnospiraceae (n = 38) and Ruminococcaceae (n = 8). CONCLUSIONS: Foaling had minimal effects on the mares' faecal microbiota. Numerous differences in the faecal microbiota preceded colic. Associations between Firmicutes (particularly Lachnospiraceae and Ruminococcaceae) and Proteobacteria and development of colic could lead to measures to predict and prevent colic. The Summary is available in Chinese - see Supporting information.