Animal Science, Department of


Document Type


Date of this Version



Applied Animal Science 39:44–55.


Open access.


Objective: The objective of this research was to evaluate site of infusion of a commercially available direct-fed microbial (DFM) containing 109 cfu/g of Lactobacillus acidophilus and 109 cfu/g Propionibacterium freudenreichii on DMI, rumen kinetics, ruminal VFA, digestibility, milk production, milk components, and blood metabolites in lactating dairy cows.

Materials and Methods: Four Holstein cows equipped with ruminal cannulas were used in a Latin square design experiment with 4 periods. Each 37-d period consisted of 14 d of no treatment to prevent crossover contamination, 14 d of adaptation to treatments, 8 d of sampling, and 1 d for ruminal evacuations. Within each period, cows were assigned to 1 of 4 treatments: (1) cows were fed a TMR formulated to meet or exceed nutrient requirements plus 5 g of lactose twice daily without the addition of DFM (control); (2) cows were fed the TMR with a daily dose of DFM top dressed on the feed twice daily (TD); (3) cows were fed the TMR with ruminal infusion of the DFM administered twice daily (RuI); or (4) cows were fed the TMR plus abomasal infusion of the DFM twice daily (AbI). During the sampling period within each period, DMI and milk production were measured daily with set days for blood and rumen fluid collection. Data were analyzed using the MIXED procedure of SAS with animal within period as a random effect. Dry matter intake was not different among treatments.

Results and Discussion: No differences were detected in rumen kinetics, pH, individual VFA or VFA ratios, ammonia, or digestibility. There were no differences in kilograms of milk production (P > 0.87); SCC (P > 0.54); or percentage of butter fat (P > 0.21), milk protein (P > 0.83), lactose (P > 0.91), SNF (P > 0.88), and MUN (P> 0.49). No difference existed in most of the milk fatty acids except for 8:0, which had a greater concentration (P > 0.01) in AbI versus control, TD, and RuI.

Implications and Applications: Route of administering DFM overall had no effects on DMI, rumen kinetics, ruminal VFA, digestibility, milk production, or milk components in the present experiment.