The main objective of our current study was evaluating the effects of NFC supplementation and forage type on rumen microbiota and metabolism, by comparing microbial structures and composition among samples collected from cows fed AH (alfalfa-based diet), H-NFC (CS-based diet with high NFC) and L-NFC (CS-based diet with low NFC) diets. Our results show that microbial communities were structurally different but functionally similar among groups. When compared with L-HFC, NFC increased the population of Treponema, Ruminobacter, Selenomonas and Succinimonas that were negatively correlated with ruminal NH3-N, and urea nitrogen in blood, milk and urine, as well as significantly increasing the number of genes involved in amino acid biosynthesis. However, when compared to the AH group, H-NFC showed a higher abundance of bacteria relating to starch degradation and lactate production, but a lower abundance of bacteria utilizing pectin and other soluble fibers. This may lead to a slower proliferation of lignocellulose bacteria, such as Ruminococcus, Marvinbryantia and Syntrophococcus. Lower fibrolytic capacity in the rumen may reduce rumen rotation rate and may limit dry matter intake and milk yield in cows fed H-NFC. The enzyme activity assays further confirmed that cellulase and xylanase activity in AH were significantly higher than H-NFC. In addition, the lower cobalt content in Gramineae plants compared to legumes, might have led to the significantly down-regulated microbial genes involved in vitamin B12 biosynthesis in H-NFC compared to AH. A lower dietary supply with vitamin B12 may restrict the synthesis of milk lactose, one of the key factors influencing milk yield. In conclusion, supplementation of a CS-based diet with additional NFC was beneficial for nitrogen conversion by increasing the activity of amino acid biosynthesis in rumen microbiota in dairy cattle. However, lower levels of fibrolytic capacity may limit dry matter intake of cows fed H-NFC and may prevent increased milk yield.

The objective of this study was to evaluate the effects of rumen-protected betaine supplementation on performance of postpartum dairy cows and immunity of newborn calves. Twenty-four multiparous Holstein dairy cows were randomly divided into the control (CON, n = 12) and rumen-protected betaine (BET, n = 12) groups after blocking by parity and milk yield during the previous lactation cycle. The cows were fed a basal total mixed ration diet without BET (CON) or with BET at 20 g/d per cow (BET) from four weeks before expected calving to six weeks postpartum. The results showed that betaine supplementation had no effect on dry matter intake and milk yield of the cows. The BET cows tended to increase feed efficiency (energy-corrected milk/dry matter intake) and body weight loss postpartum compared to the CON cows. The plasma β-hydroxybutyrate concentrations of the BET cows were greater at d seven after calving than those of the CON cows. Moreover, compared to the CON calves, the BET calves had greater plasma total protein and globulin concentrations. The plasma glucose concentrations of the BET calves tended to decrease relative to CON cows. In conclusion, rumen-protected betaine supplementation from four weeks before expected calving tended to increase fat mobilization of postpartum dairy cows, and might improve the immunity of newborn calves.

Objective: The objective of current study was to investigate the lactation performance and rumen fermentation characteristics of dairy cows fed a diet with alfalfa hay replaced by corn stover but supplemented with molasses. Methods: Sixteen Holstein cows in mid-lactation were randomly assigned to 1 of 2 dietary treatments: i) alfalfa based diet (AH), and ii) corn stover based diet supplemented with molasses (CSM). The experiment was conducted according to a 2x2 crossover design with 22-d each period, consisting of 17 d for adaptation and 5 d for data and samples collection. Results: Dry matter intake and milk yield were higher for cows fed AH than CSM (p< 0.01). Milk protein content and nitrogen conversion were higher (p< 0.05), while milk urea nitrogen was lower (p< 0.01) for cows fed AH than CSM-fed cows. Contents of milk total solids, fat and lactose were not different between two groups (p> 0.10). Total rumen volatile fatty acid concentration tended to be higher (p = 0.06) for cows fed AH than CSM-fed cows. Molar proportion of acetate was lower (p = 0.04), but valerate was higher (p = 0.02) in cows fed AH than CSM-fed cows. Rumen concentration of propionate, and isobutyrate, and ratio of acetate to propionate tended to be different (p< 0.10) between two groups. The feed cost per kilogram of milk was lower in CSM than AH (p< 0.01). No differences were found in feed efficiency and most plasma parameters tested (p> 0.10). Conclusion: In comparison with AH diet, CSM diet could be fed to dairy cows without negative effect on feed efficiency, ruminal fermentation, but economically beneficial, indicating that CSM could be an alternative choice for dairy farms instead of AH to feed midlactation dairy cows.

One hundred and thirteen mid-lactation cows fed same diets and supplemented with 20 g/d rumen-protected methionine (RPM) for 8 weeks were used to investigate the individual responses of dairy cows to RPM in terms of lactation performance, amino acids (AA) metabolism, and milk metabolites. Among the cows, 10 cows exhibited positive responses (PR) and 10 cows showed limited responses (LR) in energy-corrected milk yield to RPM were used for further analysis. The lactation performance changed from gradual decline to steady increase in PR cows, while kept downward trend in LR cows following RPM supplementation. In PR cows, the AA metabolism was notably enhanced after RPM supplementation, evidenced by increased mammary blood flow (69.4%, P = 0.05), mammary uptake and clearance rate and uptake-to-output ratio (U:O) of essential AA. The improved AA metabolism could be attributed to the enrichment of pyrimidine (P = 0.06) and pyruvate (P = 0.07) metabolism pathways, which may have stimulated mammary cell proliferation and enhanced AA uptake. Additionally, the upregulation of milk biotin (fold change > 2, variable importance projection > 1), known to support milk yield, likely contributed to the PR observed in PR cows. Conversely, in LR cows, RPM supplementation did not improve AA metabolism, decrease was observed in mammary uptake, mammary clearance rate, and U:O of cysteine, potentially due to cysteine being irreversibly converted from methionine. Moreover, the enrichment of central carbon metabolism in cancer pathway (P = 0.06), which also utilize methionine, along with the lysine degradation pathway (P = 0.04), suggests that methionine in the mammary glands may have been diverted toward non-lactational metabolic processes, resulting in absence of PR in LR cows. Our results indicate that the responses to RPM in dairy cows are individualized, with variation in lactation performance likely driven by differential AA metabolism.

To determine the effects of lower dietary protein (CP) on lactation and metabolism in lactating cows, 274 primiparous (37.8 ± 3.98 kg/d milk, 141 ± 24.1 DIM) and 260 multiparous cows (44.6 ± 7.13 kg/d milk, 134 ± 21.0 DIM, 3.21±1.26 of parity) were randomly assigned to one of 2 diets: 170 g CP/kg DM (CON) or 162 g CP/kg DM (LCP) for 10 weeks. In primiparous cows, LCP has no effect on milk yield and most other parameters (P > 0.10) except for tendency of decreasing milk urea nitrogen (MUN) (P = 0.08). In multiparous cows, LCP show no effect on milk yield and other parameters (P > 0.10) for cows with milk yield < 50 kg/d, while high-yield cows (50-60 kg/d) exhibited 1.37 kg/d milk yield reduction (P < 0.01), along with higher content of fat (P < 0.05) and total solids (P < 0.01) and lower MUN (P < 0.01). LCP decreased blood urea nitrogen (P < 0.01), albumin (P < 0.05) and NEFA (P < 0.05), tended to increase rumen total volatile fatty acids (VFA) concentration (P = 0.09), decreased molar proportion of isobutyrate (P < 0.05) and total branched-chain VFA (P < 0.05). In conclusions, 162 g CP/kg DM of diet has no impact on lactation performance in primiparous cows or multiparous cows producing < 50 kg/d, but induced milk depression (-1.37 kg/d) in high-yielding multiparous cows (50-60 kg/d) coupled with enhanced milk fat and total solids content, suggesting yield-dependent trade-offs between diet protein supply and dairy cows requirement.

Objective: This study aimed to investigate whether transition dairy cows experience a negative oxygen balance due to increased metabolic demands postpartum and to assess how this imbalance affects their health and production performance. The goal was to elucidate the longitudinal changes in blood gas parameters and establish links between hypoxic stress and physiological, inflammatory, and productive indicators.Methods: Ninety Holstein cows were monitored from 21 days before to 49 days after calving, with blood gas parameters, plasma biochemical indices, dry matter intake, and milk production being recorded at multiple time points. To assess the impact of hypoxia, cows were further grouped by postpartum hypoxia-inducible factor 1α (HIF-1α) levels into high and low hypoxic stress groups for comparative analysis.Results: During the transition period, dairy cows exhibited a significant postpartum reduction in arterial and venous hemoglobin (Hb), hematocrit (HCT), and oxygen concentration, reaching the lowest levels at 21 days after calving, while CO2-related parameters like TCO2, HCO3–, and BEecf increased. Cows with higher HIF-1α levels (HHS group) showed decreased dry matter intake and milk fat concentration, along with higher plasma β-hydroxybutyrate, malondialdehyde, and haptoglobin levels. Furthermore, significant correlations were observed between blood gas indicators and health parameters, including a negative correlation of SAA with Hb and HCT, highlighting the link between impaired oxygen transport and systemic stress responses.Conclusion: Postpartum dairy cows characterized by decreased oxygen delivery (lower Hb and HCT) and increased oxygen consumption (elevated CO2-related parameters), leading to relative metabolic systemic hypoxic stress. This imbalance is associated with liver stress, inflammation, oxidative damage, and reduced feed intake and milk production. These findings underscore the critical need for nutritional and management strategies targeting oxygen availability to support health and productivity during the transition period.