Partial Substitution of Cereal Grains With Sugar‐Rich Castella By‐Product on Nutrient Digestibility and Lactation Performance of Dairy Cows

This study investigated the effect of partially replacing corn with castella by-product, a sugar-rich feedstuff, on the lactation performance and nutrient digestibility of dairy cows. Eleven late-lactating Holstein cows were used in the experiment employing a crossover design with two periods of 21 days, including 18 days of adaptation and 3 days of data collection, under group-feeding. Castella by-product was incorporated into the diet at 7% on a dry matter (DM) basis, which replaced 30% DM of the starch-rich grains used in the diet. The results showed that the inclusion of the castella increased the digestibilities of DM, organic matter, and neutral detergent fiber (p < 0.05) despite its high sugar content, while decreasing starch digestibility (p < 0.05), without affecting fecal pH, fecal DM, or microbial protein synthesis in the rumen (p > 0.05). The castella diet did not differ significantly from the corn diet for milk yield, milk composition, milk fatty acid profile, or microbial protein synthesis in the rumen (p > 0.05). In summary, the partial replacement of corn with castella by-product in the diet yielded comparable lactation performance outcomes to those of the control diet in dairy cows.