Every feed change is an adjustment for billions of microbes. Give them time with the 2 to 3 week method: days 1-5 a quarter new, days 6-10 half, days 11-15 three quarters, days 16-21 fully over. Your green light between each step is stable, normal droppings. This applies to everything — new hay, new concentrate, new supplements. Ten to twenty-one days feels slow to us; for the microflora it is just right.
