Effect of duration on a high-starch diet on fecal pH and particle size in Simmental Cows

This study aims to evaluate the changes in fecal pH, fecal particle size, and rumen pH during high starch feeding. These factors give insight into the fermentation dynamics and health of dairy cows. 39 lactating Simmental cows were transitioned to 50 % concentrate feed and used over two 28-day experimental periods. Measurements of fecal pH, ruminal pH and fecal particle size distribution were conducted on days 14 and 28. Data were analyzed using SAS, with experimental day as fixed effect and cows as random effect. Results show a significant rise in fecal pH and a change in fecal particle size distribution but no statistically significant change in rumen pH. Specifically, fecal pH rose by 0.24 (P < 0.05) with a minimum of 6.34 on day 14, and 6.98 on day 28. Particle size distribution shifted to significantly higher soluble fraction (P < 0.05) on day 28. There was significant correlation between fecal particle size and fecal pH but no significant correlation with ruminal pH. Specifically, there was a negative correlation between fecal pH and the largest particles (> 4 mm; > 2 mm) (P < 0.05), and a positive correlation with the soluble fraction (< 0.15 mm) (P < 0.05). The study concludes that fecal pH and the larger fecal particle size fractions shifts towards ranges similar to those seen with forage feeding. However, not all of the evaluated parameters showed the same trend during extended high starch feeding.