Effects of Ruminal Crabtree-negative Yeast Ensiled Rice Straw on Feed Intake, Rumen Fermentation, and Performance in Tropical Crossbred Lactating Holstein Cows

This research aimed to determine the effects of ruminal Crabtree-negative yeast ensiled rice straw (RS) on feed intake, ruminal fermentation, milk production, and milk composition in tropical crossbred lactating Holstein cows. This study used 6 multiparous crossbreds between Holstein Frisian × Zebu dairy cows in their mid-lactation period (165.5 ± 44.0 of day-in-milk) with an initial body weight of 363.9 ± 55.80 kg (average milk yield 8.58 kg/d). Dairy cows were randomly allocated to three ensiled RS with various yeast species including S. cerevisiae , P. kudriavzevii KKU20, and C. tropicalis KKU20 according to a 3 × 3 replicated Latin square design. The ruminal yeasts were obtained by isolating, screening, and identifying the rumen of crossbred Thai-Holstein Friesian dairy cattle. The yeast species did not change the RS intake, concentrate diet, and total intake (P > 0.05). Crabtree-negative yeast ( P. kudriavzevii and C. tropicalis ) increased the apparent digestibility of dry matter by about 6.9% when compare with Crabtree-positive yeast ( S. cerevisiae ). Rumen pH and ammonia-nitrogen concentration were not changed among yeast species (P > 0.05). The bacterial populations at both 0 hours and 4 hours after feeding and the mean value were highest (P < 0.05) with ensiled RS with C. tropicalis KKU20. Ensiled RS with P. kudriavzevii KKU20 and C. tropicalis KKU20 were significantly increased with a total volatile fatty acids (VFAs) at 0 and 4 hours after feeding (P 0.05). The yeast strains’ effects were not observed (P > 0.05) on actual milk yields. The treatments did not alter the milk composition (P > 0.05); except for when the protein in the milk was highest in the C. tropicalis KKU20 fed group. In conclusion, C. tropicalis KKU20 could enhance the RS’s nutrition value through increasing digestibility, the ruminal bacterial population, and total VFAs as well as could increase the milk protein.