Effect of Gestational Direct-Fed Microbials Supplementation on the Metabolic Profile in Periparturient Dairy Cows

This study was conducted at a commercial dairy farm in Queensland, Australia to evaluate the effects of feeding a lactic acid bacteria-based direct-fed microbial (DFM) during gestation on the metabolic profile of periparturient dairy cows and its effects on milk production and body weight. A total of 150 multiparous Holstein cows were randomly selected based on parity (2.3) and days in milk (130 DIM) and divided into two groups of 75 cows each (control and DFM). The control cows were assigned to a basal diet consisting of a silage-based partial mixed ration (PMR), concentrate fed in the dairy twice a day, and <i>ad libitum</i> pasture. The DFM group received the same basal diet supplemented with three strains of <i>Lactobacillus</i> top-dressed in the feed. The DFM supplementation continued during both the dry period and the subsequent lactation. A subset of 82 cows (40 control and 42 DFM) were monitored during the calving season (March to July 2022) to assess the metabolic profile and postpartum performance. Blood samples were collected during the periparturient period (-4 to -2 w prepartum, around calving, and at weeks 1, 3, and 6 postpartum) to measure the levels of metabolites, enzymes, and minerals. Overall, the serum glucose, NEFA, and chloride levels were higher, while protein and urea were lower in cows supplemented with the DFM (<i>p</i> < 0.005). The pre-calving levels of glucose were higher and the total bilirubin, urea, and BHB were lower in cows supplemented with DFM than in the control (<i>p</i> < 0.05). The post-calving levels of glucose and Mg were also higher in the DFM cows than in the control cows (<i>p</i> < 0.05). Average milk production at 110 DIM was significantly higher in the DFM cows compared to control cows (<i>p</i> = 0.03). Although the total milk production over 305 days was numerically greater in the DFM cows, the difference was not statistically significant (<i>p</i> = 0.3), whereas the milk protein percentage was higher in the control cows (<i>p</i> = 0.03). The body weight of the DFM cows was greater during the periparturient period (<i>p</i> = 0.001) than that of the control cows. In the DFM cows, glucose levels had a positive correlation (r = 0.16) with milk yield, at 110 DIM, while serum total protein had a positive correlation with body weight (r = 0.32) (<i>p</i> < 0.05). In conclusion, feeding <i>Lactobacillus</i>-based DFM during gestation can positively influence the metabolic profile of periparturient cows, which, in turn, may affect the milk production and body weight of postpartum dairy cows.