Effects of rumen-native microbial feed supplementation on milk yield, composition, and feed efficiency in lactating dairy cows.

The link between the rumen, the rumen microbial population, and production efficiency is well established. Recent developments sug­gest that the species composition of the rumen is predictive of dairy cow productivity and the interactions among micro-or­ganisms may play a more significant role than previously considered. Therefore, the ability to alter the rumen microbial population in a precise manner and skew the community towards a state that enables higher feed digestibility and improved animal production is a desir­able strategy to improve productivity in dairy farming. One promis­ing strategy to achieve this is to influence the host’s micro­bial population by feeding live micro-organisms which are more associated with production efficiency. Thus, in the study of the authors cited a number of micro-organisms in this association was isolated from the rumen of a cow and fed to cows as a microbial feed supplement (MFS) to study its effect on milk production, milk com­position, and feed efficiency.    

A total of 90 multi-lactation cows between 40 and 60 days in milk were enrolled in a randomized block design study. Within each block (baseline milk yield), cows were randomly assigned to: control (no microbial feed supplementation), MFS1 (0.33 g per kg total mixed ration [TMR] of an MFS containing a minimum of Clostridium beijerinckii at 2 × 10⁶ colony forming units (CFU) per g and Pichia kudriavzevii at 2 × 10⁷CFU per g), or MFS2 (0.33 g per kg TMR of a MFS containing a minimum of C. beijerinckii at 2 × 10⁶CFU per g, P. kudriavzevii at 2 × 10⁷CFU per g, Ruminococcus bovis at 2 × 10⁷CFU per g, and Butyrivibrio fibrisolvens at 2 × 10⁷CFU per g). Cows were housed in a single group and fed the study diets ad libitum for 270 days. Individual milk yield was recorded using electronic milk meters, and milk fat and protein were measured using optical in-line analyzers at each of two daily milkings.

Treatment effects were observed for milk and energy-corrected milk (ECM) yields, milk fat and protein yields and concentrations, dry matter intake (DMI), and feed efficiency; the effects being dependent on time for milk yield, DMI, and feed efficiency. Overall, milk, ECM, fat, and protein yields were higher for MFS2 compared with control cows (+3.0, 3.7, 0.12, and 0.12 kg per day, respectively). Compared with MFS1, milk yield was higher and protein yield tended to be higher for MFS2 cows (+2.9 and 0.09 kg per day, respectively). In contrast, MFS1 cows produced 0.17 and 0.08 units of percentage per day more fat and protein than MFS2 cows, and 0.07 units of percentage per day more protein than control cows. Dry matter intake and feed efficiency were higher for MFS2 cows compared with MFS1 cows (+1.3 kg per day and 0.06 kg per kg, respectively), and feed efficiency was higher for MFS2 cows compared with control cows (+0.04kg per kg). Where observed, treatment by time effects suggest that the effects of MFS2 were more evident as time progressed after supplementation was initiated. No effects of microbial supplementation were observed on body weight, body condition score, somatic cell count, or clinical mastitis case incidence.

In conclusion, the supplementation of MFS2 effectively improved the economically important parameters milk yield, milk solids, and feed efficiency and thus, the supplementation of native rumen microbes in TMR is a promising strategy to improve dairy production efficiency.