Using direct fed microbials and exogenous fibrolytic enzymes to enhance fiber digestibility of dairy cow diets

Exogenous fibrolytic enzyme and DFMs additives are emerging technologies that show promise in terms of increasing diet formulation flexibility. They may improve fiber digestibility making possible greater inclusions of forages in the ration without negatively impacting animal performance. The objectives of this dissertation were to investigate the effect of Bacillus pumilus 8G-134 (BP) supplementation on total tract nutrient digestibility and milk yield of postpartum dairy cows fed low (20%, LS) or high (27%, HS) starch diets. Moreover, to examine the effect of adding a fibrolytic enzyme preparation through a molasses-based liquid feed (MLF) to diets on digestibility, ruminal patterns and production performance of primiparous cows. We hypothesized that BP, a spore forming Gram-positive bacteria, would increase production of ruminal xylanase and increase fiber digestion, dry matter intake (DMI), and performance of cows fed LS and HS diets postpartum. In addition, fibrolytic enzymes would increase fiber digestibility, efficiency of nutrient use of pre- and postpartum diets and assure greater performance compared to control diets. Results indicated that BP supplementation during early lactation decreased body lipid mobilization; therefore further research is needed to investigate the use of BP as a feeding strategy during the early postpartum period. During the 112 d of BP supplementation, DMI and milk fat yield increased, and milk protein yield tended to increase for both LS and HS diets fed to primiparous dairy cows. Moreover, BP tended to improve 3.5% FCM yield by 4.3% and 8.9% for LS and HS, respectively. Results also indicated that BP supplementation to primiparous cows can increase fiber digestibility and milk yield resulting in potential increases in profitability. Biological cows' response when fed enzyme supplementation was small, although positive. Future research is required to elucidate how different doses and length of feeding enzymes may affect growth and performance of animals in first lactation.