Role of Dietary Inclusion of Phytobiotics and Mineral Adsorbent Combination on Dairy Cows′ Milk Production, Nutrient Digestibility, Nitrogen Utilization, and Biochemical Parameters

**Background:** The development of dairy cattle breeding increasingly relies on improving feeding technologies, including the use of biologically active feed additives. Local cattle breeds, such as the Suksun breed in Russia, possess valuable genetic variability but often exhibit lower productivity compared to international cross-breeds, leading to their displacement. Natural feed additives, including phytobiotics (e.g., algae) and mineral adsorbents (e.g., shungite), offer a potential strategy to enhance productivity and health without synthetic chemicals. While the individual effects of Fucus vesiculosus and shungite have been studied, their combined effect on dairy cows had not been investigated. This study aimed to evaluate the impact of a combination of dry Fucus vesiculosus grits (FG) and a heat-treated mineral shungite (TMS) adsorbent on milk production, nutrient digestibility, nitrogen utilization, and blood biochemistry in Suksun dairy cows.

**Methods:** The study was conducted from June to December 2022 at LLC Suksunskoe in Perm Krai, Russia. Eighty dry-hardy Suksun cows were divided into four groups (n=20 each), balanced by breed, age, body weight (512.0 ± 1.28 kg), BCS (3.0–3.5), and previous lactation milk yield (6250 kg). Cows were enrolled 21 days before expected calving and received supplements from day 1 to day 90 of lactation. The control group (CON) received a basic ration (TMR). The TMS group received the basic ration plus 50 g/day of heat-treated shungite. The FG group received the basic ration plus 100 g/day of dry Fucus vesiculosus grits. The TMS+FG group received the basic ration plus both 50 g shungite and 100 g Fucus vesiculosus. Milk yield was measured weekly, and milk composition (fat, protein) was analyzed using a CombiFoss FT+ analyzer. A balance experiment was conducted on day 90 of lactation with 5 cows per group to determine nutrient digestibility and nitrogen balance. Rumen fluid was collected via probe to measure pH, ammonia (Conway microdiffusion), and short-chain fatty acids (SCFAs, steam distillation). Blood samples were taken at 30 and 90 days in milk (DIM) for biochemical and morphological analysis. Data were analyzed using one-way ANOVA with Tukey's post-hoc test.

**Key Results:** Milk yield (total and average daily) did not differ significantly between groups (p > 0.05). However, milk fat content was significantly higher in all supplemented groups (TMS: 4.37%, FG: 4.35%, TMS+FG: 4.36%) compared to the control (3.95%, p = 0.018). Milk total protein content was significantly higher in the FG group (3.08%) and TMS+FG group (3.06%) compared to the control (3.03%, p = 0.012). The digestibility of ether extract (EE) was significantly higher in the TMS+FG group (54.74%) compared to CON (51.71%) and FG (50.75%) (p = 0.012). Crude fiber (CF) digestibility was also significantly higher in the TMS+FG group (60.68%) compared to CON (55.15%) and FG (55.62%) (p = 0.027). Nitrogen intake was significantly higher in the FG (360.88 g) and TMS+FG (363.02 g) groups compared to CON (349.58 g, p = 0.003). Rumen ammonia concentration was significantly lower in the TMS (8.01 mg%) and TMS+FG (8.09 mg%) groups compared to CON (10.21 mg%, p = 0.004). At 90 DIM, blood glucose was significantly higher in the FG (3.13 mmol/L) and TMS+FG (3.27 mmol/L) groups compared to CON (2.37 mmol/L, p = 0.002). Globulin levels were significantly lower in the TMS group (34.03 g/L) compared to CON (45.63 g/L, p = 0.043), and the albumin/globulin ratio was significantly higher in the TMS group (1.04) compared to CON (0.72, p = 0.025). Triglycerides were significantly lower in the FG (0.15 mmol/L) and TMS+FG (0.17 mmol/L) groups compared to CON and TMS (both 0.22 mmol/L, p = 0.019). No significant differences were observed in other blood parameters, and all values remained within reference ranges.

**Clinical Implications:** The inclusion of a combination of heat-treated shungite (50 g/day) and dried Fucus vesiculosus grits (100 g/day) in the diet of Suksun dairy cows during early lactation improved milk composition (increased fat and protein content), enhanced the digestibility of ether extract and crude fiber, and improved nitrogen utilization without negatively impacting animal health. The reduction in rumen ammonia suggests improved nitrogen efficiency, likely due to the sorption properties of shungite. The increased blood glucose and decreased triglycerides in supplemented groups indicate favorable metabolic effects. These findings support the use of this natural feed additive combination as a safe and effective strategy to enhance the productivity and feed efficiency of local dairy breeds, potentially contributing to their conservation and competitiveness.