TRANSCRIPTOMIC CHANGES IN RUMINAL TISSUE INDUCED BY THE PERIPARTURIENT TRANSITION IN DAIRY COWS

To understand how the capacity for fat metabolism (uptake, synthesis, modification) changes in rumen epithelia immediately before and after onset of lactation in dairy cows, rumen fluid Short Chain Fatty Acid (SCFA) concentrations and mRNA expression profiles of rumen epithelia was determined in twelve Holstein dairy cows at three weeks prior to calving (wk -3, n = 12), one week post calving (week +1, n = 12) and six weeks (week +6, n = 12) after calving. The diet was modified from a dry cow formulation to a lactating cow formulation immediately following parturition and raised the non-fiber carbohydrate level from 34 to 43%. All data was analyzed using the mixed procedure of SAS, with cows blocked by anticipated calving date and week of sampling as the repeated measure. Propionate, butyrate, isovalerate and valerate levels rose significantly following the diet change (p≤0.001), although acetate and isobutyrate levels were unchanged (p>0.05). Mean rumen pH also changed during the transition period (6.38 Vs 5.81 and 5.85±0.08; -3 Vs +1 and +6; p