Fecal Microbiota and Performance of Dairy Cattle from a West Mexican Family Dairy Farm Supplemented with a Fiber-Degrading Enzymatic Complex

Non-starch polysaccharide-degrading enzymes are widely used as feed additives in monogastric and ruminant species, with positive effects reported. In this study, the commercial, fiber-degrading enzyme complex Hostazym^® X, derived from <i>Trichoderma citrinoviride</i> (DSM34663), was included in the total mixed rations of 17 mid-lactating (135 ± 61 days in milk) Holstein cows for 10 weeks. A control group (<i>n</i> = 17) was included. Dry matter intake (DMI), milk yield, 4% fat-corrected milk, solid yield, and milk fatty acid profile were assessed. The structure and composition of fecal bacterial communities, as well as PICRUSt2-based functional prediction of bacterial communities, were also evaluated. Higher DMI and milk yield scores were observed in the supplemented group (27.20 vs. 26.59 kgDM/cow/d; and 39.01 vs. 36.70 L/cow/d, respectively). No effects were observed in fat yield, contrary to lactose and protein, which were greater in the supplemented group compared to the control group (1.18 vs. 1.13 and 1.83 vs. 1.75 kg/cow/d, respectively; <i>p</i> < 0.05). Palmitic and oleic acids, in addition to monounsaturated fat in milk, were increased in the supplemented group (<i>p</i> > 0.05). Enzyme supplementation increased the Patescibacteria (<i>p</i> < 0.5) and Actinobacteriota (<i>p</i> > 0.05) in feces, but slightly reduced the Bacteroidota and Firmicutes. The <i>Turicibacter</i> genus remained at a lower relative abundance after supplementation but <i>Candidatus_Saccharimonas, Clostridioides, Prevotellaceae</i> UCG 003, <i>Corynebacterium, Akkermansia, Syntrophococcus, Erysipelotrichaceae</i> UCG 008, other <i>Lachnospiraceae</i>, other members of the <i>Eubacterium_coprostanoligenes_group, Bifidobacterium, Rumminococcus, Akkermansia</i>, and other <i>Spirochaetaceae</i> increased, modifying the functional predicted profile of bacterial communities. In conclusion, a positive effect on performance and milk composition were observed through modulation of microbiota induced by enzyme supplementation. The enzyme complex could be a viable supplement alternative in the feeding of dairy cows in semi-intensive productive systems, mainly when an ad libitum feeding scheme is used.