Ruminal NH3-N Concentration Research Articles

Feeding milk thistle (Silybum mariamum) seed powder to fattening lambs: Effects on growth performance, digestibility and rumen metabolism

This experiment was conducted to evaluate the effect of milk thistle (Silybum marianum) seed powder supplementation in the diet on weight gain, feed conversion efficiency, and physiological parameters in fattening lambs. In this experiment, thirty crossbred Shawl × Romanov male lambs were divided into three groups based on a completely randomized design. The experimental treatments included a control group receiving a diet without milk thistle seed powder (MSP), a group receiving a diet containing 1 % MSP, and a group receiving a diet containing 2 % MSP. Animals fed the diet containing 2 % MSP exhibited higher nutrient intake, average daily gain, and final body weight compared to the other treatment groups (P < 0.05). Lambs receiving the 2 % MSP diet had the most favorable feed conversion ratio (P < 0.05). The apparent digestibility of dry matter, organic matter, and crude protein was highest in lambs fed the diet containing MSP compared to the control group (P < 0.05). Ruminal NH3-N concentration and populations of total protozoa and Entodinium genus were lowest in lambs fed the MSP-containing diets (P < 0.05). The molar concentrations of acetate and valerate in the rumen fluid of lambs receiving the diet containing 2 % MSP were lower compared to the control group, while propionate concentration was higher (P < 0.05). Feeding the diet containing 2 % MSP reduced serum cholesterol, triglycerides, LDL, and liver enzyme activities compared to the control group (P < 0.05). Based on these results, supplementing lamb diets with 2 % MSP increased growth performance measures, nutrient digestibility coefficients, and reduced blood cholesterol and LDL concentrations.

Partially substituting alfalfa hay with hemp forage in the diet of goats improved feed efficiency, ruminal fermentation pattern and microbial profiles

The use of hemp as a forage source in livestock diets has been less studied because bioactive residues in animal tissues may pose a risk to consumers. This study investigated the effects of partial substitution of alfalfa hay (AH) with hemp forage (HF) in growing goat diets on growth performance, carcass traits, ruminal fermentation characteristics, rumen microbial communities, blood biochemistry, and antioxidant indices. Forty Xiangdong black goats with body weight (BW) 7.82 ± 0.57 kg (mean ± SD) were grouped by BW and randomly assigned into one of the four treatment diets (n = 10/treatment) in a completely randomized design. The goats were fed ad libitum total mixed rations containing 60% forage and 40% concentrate (DM basis). The diets included control (CON; 60% AH and 40% concentrate), 55% AH and 5% HF (HF5), 50% AH and 10% HF (HF10), and 40% AH and 20% HF (HF20). Increasing the substitution of HF for AH linearly decreased (P = 0.004) DM intake and improved feed conversion efficiency. However, final BW, average daily gain, carcass traits, meat quality, and most blood biochemistry indices did not differ among treatments. The ruminal NH3-N concentration (P = 0.003) and blood urine nitrogen (P = 0.050) linearly increased (P < 0.01) with increasing substitution rate of HF, whereas the total volatile fatty acids concentration quadratically changed (P = 0.007). Substitution of AH with HF had no effect on the diversity and richness of ruminal microbes, though it linearly decreased (P = 0.040) Prevotella_1 and linearly increased (P = 0.017) Rikenellaceae_RC9_gut_group. The cannabinoids and/or their metabolites were detected in both ruminal filtrates (8) and plasma (4), however, no detectable cannabinoid-related residues were observed in meat. These results indicate that the HF could be used to partially substitute AH in goat diets, whereas the effects vary between substitution rates of HF for AH. Although no cannabinoid-related residues were detected in meat, the presence of cannabinoids residues in blood warrants further study of HF feeding to confirm the cannabinoids residues are not present in the animal products.

Dietary selenium levels affect mineral absorbability, rumen fermentation, microbial composition and metabolites of the grazing sheep

Selenium (Se) is an essential trace element for the growth of all livestock. However, little is known about the effects of dietary selenium levels on production metrics, nutrient digestion and absorption, ruminal microbiota, and metabolites in grazing sheep. Therefore, in this research, 28 individually-housed grazing sheep were randomly divided into a low-Se feeding group (LSe) and a control group for the low-Se feeding phase (LCG), supplemented with multi-nutrient salts containing 0 mg Se and 0.63 mg Se, respectively, for 53 days. After 53 days of feeding, a 7-day digestion test was conducted, then seven sheep in each group were randomly slaughtered. Then, the remaining sheep in LSe and LCG were transferred to a high-Se supplementation group (SSe) and a control group for the high-Se feeding phase (SCG), supplemented with multi-nutrient salts containing 1.90 mg and 0.63 mg Se, respectively. This phase consisted of a 34-day diet adaptation period, a 7-day digestive test, and eventual slaughter. LSe reduced and elevated ruminal Se and copper (Cu) content, respectively, and decreased Se apparent absorbability compared to LCG (P < 0.05). Conversely, SSe reduced and increased ruminal Cu and Se content, respectively, and increased Se apparent absorption in comparison to SCG (P < 0.05). It also increased the ruminal NH3-N concentration (P < 0.05). Amplicon sequencing analysis revealed a decrease in Lentimicrobium and Treponema abundance and an increase in Lawsonibacter and Sporobacter abundance (P < 0.05) in LSe group. Metabolomic analysis confirmed an elevated level of ruminal citrulline, ornithine and glutathione affecting amino acid and glutathione metabolic pathways (P < 0.05) in LSe group. In SSe group, Alistipes were significantly reduced (P < 0.05) with metabolomics showing elevated levels of L-carnitine and arginine, affecting ruminal antioxidant capacity and arginine biosynthesis pathways (P < 0.05). Notably, both treatments had no significant effect on production metrics and apparent digestibility of organic nutrients (P > 0.05). In conclusion, Se deficiency affects Se absorption and amino acid metabolism in grazing sheep, while supplementing Se in diet effectively ameliorates these deficiencies and improves ruminal antioxidant capacity.

Effects of bacterial direct-fed microbial mixtures offered to beef cattle consuming finishing diets on intake, nutrient digestibility, feeding behavior, and ruminal kinetics/fermentation profile.

Effects of bacterial direct-fed microbial (DFM) mixtures on intake, nutrient digestibility, feeding behavior, ruminal fermentation profile, and ruminal degradation kinetics of beef steers were evaluated. Crossbred Angus ruminally cannulated steers (n = 6; body weight [BW] = 520 ± 30kg) were used in a duplicated 3 × 3 Latin square design and offered a steam-flaked corn-based finisher diet to ad libitum intake for 3, 28-d periods. Treatments were 1) Control (no DFM, lactose carrier only); 2) Treat-A (Lactobacillus animalis, Propionibacterium freudenreichii, Bacillus subtilis, and Bacillus licheniformis), at 1:1:1:3 ratio, respectively; totaling 6 × 109 CFU (50mg)/animal-daily minimum; and 3) Treat-B, the same DFM combination, but doses at 1:1:3:1 ratio. Bacterial counts were ~30% greater than the minimum expected. Data were analyzed using the GLIMMIX procedure of SAS with the model including the fixed effect of treatment and the random effects of square, period, and animal (square). For repeated measure variables, the fixed effects of treatment, time, and their interaction, and the random effects of square, period, animal (square), and animal (treatment) were used. Preplanned contrasts comparing Control × Treat-A or Treat-B were performed. Intake and major feeding behavior variables were not affected (P ≥ 0.17) by treatments. Steers offered Treat-A had an increased (P = 0.04) ADF digestibility compared with Control. Steers offered Treat-A experienced daily 300min less (P = 0.04) time under ruminal pH 5.6, a greater (P = 0.04) ruminal pH average and NH3-N concentration (P = 0.05) and tended (P = 0.06) to have a lower ruminal temperature compared to Control. Ruminal VFA was not affected (P ≥ 0.38) by treatments. Steers offered Treat-A increased (P = 0.02) and tended (P = 0.08) to increase the ruminal effective degradable NDF and ADF fractions of the diet-substrate, respectively. When the forage-substrate (low quality) was incubated, steers offered Treat-A tended (P = 0.09) to increase the effective degradable hemicellulose fraction compared to Control. In this experiment, the bacterial combinations did not affect intake and feeding behavior, while the combination with a greater proportion of B. licheniformis (Treat-A) elicited an improved core-fiber digestibility and a healthier ruminal pH pattern, in which the ruminal environment showed to be more prone to induce the effective degradability of fiber fractions, while also releasing more NH3-N.

The influence of virginiamycin on digestion and ruminal parameters under feedlot conditions.

This experiment aimed to assess the impact of virginiamycin on in vitro gas production dynamics, rumen kinetics, and nutrient digestibility in beef steers fed a grain-based diet. Nine ruminally cannulated British-crossbred steers (596 ± 49kg) were assigned to this experiment. Animals were housed in three pens (n = 3/pen) equipped with a Calan gate feed system and water troughs. Pens were enrolled in a 3 × 3 Latin square design containing three periods of 16 d, and a 5-d washout interval between periods. Dietary treatments consisted of virginiamycin (VM) administration at 0 (VM0), 180 (VM180), or 240mg/d (VM240). During days 15 and 16 of each period, about 600mL of rumen fluid and urine samples were collected before (0h), and at 4, 8, 12, and 16h after the morning feed (0730 hours), rumen inoculum was used to take pH and redox potential measurements immediately after collection using a portable pH and redox meter, and subsamples were taken for volatile fatty acids (VFA) and NH3-N analyses, and urine samples were composited daily and analyzed for creatinine and purine derivatives (PD) content to estimate microbial crude protein flow. During the 4-h post-morning feed rumen collection, rumen inoculum was utilized to perform in vitro gas production measurements. Fecal samples were collected on day 16 of each period to estimate nutrient digestibility using acid detergent insoluble ash as an internal marker. Animals were considered the experimental unit for the statistical analyses, and periods and squares were included as random variables. The total and rate of gas production were similar among treatments (P ≥ 0.17). The second-pool (i.e., fiber) gas production increased linearly as VM inclusion increased (P = 0.01), with VM240 being greater compared to VM180 and VM0 (7.84, 6.94, and 6.89mL, respectively). Ruminal pH linearly increased as VM increased, with VM240 being greater than VM0 and VM180 intermediate (5.90, 5.82, and 5.86, respectively; P = 0.03). The VFA concentrations did not differ (P ≥ 0.13), but the acetate-to-propionate ratio was the highest in VM240 (P = 0.005). Branched-chain VFA increased (P ≤ 0.03) while lactate concentrations decreased (P = 0.005) linearly with VM. The ruminal NH3-N concentration was the lowest in the VM0 (P = 0.006). The estimated absorbed PD, purine derivative to creatinine index, and microbial N flow increased linearly with VM (P ≤ 0.07). The provision of VM influenced rumen dynamics in a dose-dependent manner.

PSXII-30 Changes in Ruminal Digesta and Ruminal Ammonia-N Concentration with Differing Durations Feed Restriction for Sheep

Abstract During transient periods of feed restriction (FR), ruminal ammonia-N (NH3-N) concentrations and fluid volume may parallel the reduction in feed and water intake. However, changes in ruminal digesta characteristics and NH3-N during FR have not been characterized. Thus, the objective was to determine how FR duration impacts ruminal digesta weight and the liquid and solid fractions, and ruminal NH3-N concentration. Lambs (n = 9 wethers and 12 rams, stratified by BW and castration status) were fed ad libitum (AL, n = 7) or subjected to 5-d (FR5, n = 7) or 10-d of FR (FR10, n = 7) at 30% of AL intake. Lambs were killed 4 h post-feeding to excise the gastrointestinal tract and ruminal digesta was weighed. Sub-samples of digesta were collected for separation into solid and liquid fractions using a winepress, used for DM determination, and another was strained and preserved with sulfuric acid to analyze ruminal NH3-N concentration. Data were analyzed with PROC GLIMMIX (SAS 9.4) with the fixed effect of treatment and random effects of lamb specified to the R-sided matrix. Linear regression (PROC REG) was used to evaluate the relationship between ruminal NH3-N concentration and quantity relative to ruminal fluid weight and PROC CORR was used to generate Pearson correlation coefficients. The ruminal digesta weight did not differ (P = 0.97) among treatments but AL ruminal digesta was drier (P &amp;lt; 0.01) than FR5 and FR10 digesta (40.2% decrease in DM% relative to AL). As such, FR5 and FR10 had 0.7 ± 0.16 kg less (P = 0.01) ruminal solids than AL while they tended to have more (P = 0.09) ruminal fluid. Ruminal NH3-N concentration was greater (P &amp;lt; 0.01) for FR5 and FR10 compared with AL (2.4 and 2.0 vs. 0.4 ± 0.52 mg/dL, respectively). The quantity of ruminal NH3-N (mg) followed the same pattern with FR5 and FR10 having, on average, 51.5 ± 18.39 mg NH3-N more (P &amp;lt; 0.01) in their ruminal fluid than AL. The quantity of ruminal NH3-N was strongly correlated (ρ = 0.87, P &amp;lt; 0.01) to the total ruminal fluid such that 75% of the variance was explained by the relationship. The strength of the correlation (ρ = 0.81, R2 = 0.66, P &amp;lt; 0.01) between ruminal NH3-N concentration and total ruminal fluid was slightly lesser, but the two parameters were still strongly associated. From these data, we surmise that FR is associated with a reduction in ruminal DM content and may increase ruminal liquid that corresponds to increased ruminal NH3-N, independent of the duration of exposure.

PSVIII-A-6 Effects of Feeding Ground Whole Flaxseed, Defatted Flaxseed Meal and Organic Flaxseed Meal on Production Performance, Rumen Fermentation, and Total-Tract Nutrient Digestibility in Dairy Cows

Abstract This study aimed to determine the effects of feeding ground whole flaxseed and two types of mechanically extracted flaxseed meals on dry matter intake (DMI), milk production and composition, ruminal fermentation characteristics, and total-tract nutrient digestibility in dairy cows. Twelve multiparous Holstein cows [122 ± 20 days in milk (DIM) at the start of the study] were used in a replicated 4 × 4 Latin square design with 4 dietary treatments. One square had 4 ruminally cannulated cows that were used to determine dietary effects on ruminal fermentation characteristics and total tract nutrient digestibility. The 4 dietary treatments tested were a barley silage-based diet with canola meal (CM; 21.1% of diet DM) as the main protein source (designated CON), and diets containing ground whole flaxseed (designated GWF; 4.92% of diet DM), defatted flaxseed meal (designated DFM; 19.7% of diet DM), or organic flaxseed meal (designated OFM; 20.2% of diet DM) as partial replacements for CM. The crude fat contents of CM, GWF, DFM, and OFM were 3.20, 37.7, 9.9, and 12.9% (DM basis), respectively, and experimental diets were balanced for crude fat content (4.51%; DM basis). Experimental periods consisted of 18 d of dietary adaptation and 10 d of data and sample collection. Orthogonal contrasts were used to test for the following treatment differences: CON vs. GWF; CON vs. [DFM + OFM]; and GWF vs. [DFM + OFM]. Dry matter intake was lower (P &amp;lt; 0.01) for cows fed CON compared with those fed GWF and [DFM + OFM]. Milk yield tended to be greater (P = 0.06) for cows fed CON compared with those fed GWF (P = 0.06) and [DFM + OFM] (P = 0.06). Milk fat content and yield were unaffected by diet; however, milk protein content was reduced for cows fed CON compared with those fed GWF (P = 0.001) and [DFM + OFM] (P &amp;lt; 0.001). Milk urea-N (MUN) concentration was greater (P ≤ 0.001) in cows fed CON compared with those GWF and [DFM + OFM]. Also, MUN concentration was decreased for cows fed GWF compared with those fed [DFM + OFM]. Ruminal NH3-N concentration was less (P ≤ 0.04) in cows fed CON than those fed GWF and [DFM + OFM], but ruminal pH and short-chain fatty acid concentrations were unaffected by diet. Fecal N excretion (g/d) was greater (P &amp;lt; 0.01) for cows fed CON compared with those fed GWF and [DFM + OFM] and, therefore, total-tract CP digestibility was reduced (P &amp;lt; 0.001) in cows fed CON compared with those fed GWF and [DFM + OFM]. In conclusion, partial replacement of CM with GWF or [DFM + OFM] increased DMI; however, it tended to reduce milk yield.

PSI-6 Effects of a Postbiotic Program Consisting of Liquid and Solid Saccharomyces Cerevisiae Fermentation Products on Digestibility, Ruminal Fermentation, and Plasma Metabolome of Finishing Beef Steers

Abstract The objective of this study was to determine the effects of a postbiotic feeding program consisting of liquid and solid Saccharomyces cerevisiae fermentation products (SCFP) on digestibility, ruminal fermentation, and plasma metabolome of finishing beef steers. Eight Holstein steers (BW 467 ± 13.9 kg) equipped with rumen cannulas were used in a crossover design study, with 21-d per period and 7-d washout period in between periods. Steers were blocked based on initial BW to one of two treatments: 1) Control, basal diet only (CON), or 2) SCFP, one day feeding of LiquiCare RTU (Diamond V, dosed via rumen cannula at 11 mL/100 kg BW) followed by daily feeding of 12 g NaturSafe (Diamond V, top-dressed). Feed and fecal samples were collected during d 17 to 20 for determination of digestibility and fecal excretion of N, P, Cu and Zn using acid-insoluble ash as an internal marker. Blood samples were collected on d 21 before morning feeding. Rumen fluid samples were collected on d 0, 1, 2, 3, 5 and 21 at 0, 4, 8, or 12 h post morning feeding via rumen cannula. Results were analyzed with the GLIMMIX procedure of SAS 9.4 (SAS, 2022). BW, DMI and digestibility were not affected by treatment. There was a tendency of treatment by period interaction (P = 0.09) on feed efficiency, which was improved by feeding SCFP only in period 1. Feeding SCFP did not affect (P &amp;gt; 0.10) ruminal pH. Feeding SCFP tended to reduce ruminal lactate concentration on d 21 (0.09 vs. 0.02 mM, P = 0.10). Supplementing SCFP reduced ruminal NH3-N concentration on d 2 (4.24 vs. 7.31 mg/dL, P = 0.03) and d 21 (4.86 vs. 6.83 mg/dL, P = 0.04). By feeding SCFP, ruminal total VFA concentration was increased 4-h post-feeding on d 5 (139.7 vs. 126.7 mM, P = 0.01) and numerically increased 4-h post-feeding on d 21 (151.2 vs. 133.3 mM, P = 0.12). For VFA composition, no treatment differences were observed on day 21. However, feeding SCFP reduced (P = 0.01) propionate proportion and increased (P = 0.05) butyrate proportion on day 3. The enriched plasma metabolic pathways (P ≤ 0.05) by feeding SCFP are citric acid cycle, pyrimidine metabolism, glycolysis/gluconeogenesis, retinol metabolism, and inositol phosphate metabolism pathways. Overall, our results indicated potential benefits of the SCFP feeding program on improving ruminal fermentation, preventing acidosis and improving N utilization in the rumen. Furthermore, feeding SCFP enriched several important pathways in lipid, protein, and glucose metabolism, which may improve feed efficiency of energy and protein in finishing beef cattle.

Nitrogen balance in dairy cows fed low-nitrogen diets based on various proportions of fresh grass and maize silage.

To ensure sustainable and efficient production, dairy farms must reduce their environmental impacts and nitrogen losses, which are sources of pollution, while increasing their feed self-sufficiency. Grass-based dairy systems, frequently combine fresh grass with maize silage when grass is scarce or during dietary transitions. However, the effects of combining fresh grass and maize silage on cow performance and N excretion are poorly known. This study aimed to quantify the effects of increasing the proportion of maize silage in a fresh grass diet on cow N flows and metabolism, in the context of grass-based dairy systems. Four proportions of maize silage in a fresh grass diet (objectives of 0, 17, 34 and 51% DM of maize silage) were investigated. The experiment was performed in a 4×3 Latin square design using eight lactating cows during three 3-week periods. DM intake (DMI), milk yield, faeces and urine outputs, and their N concentrations were measured for each cow. The fresh grass CP concentration was lower than planned (106±13.0g/kg DM). This resulted in very low dietary CP concentration, which decreased from 108 to 86g/kg DM when maize silage in the diet increased from 0 to 51% DM, respectively. DM intake and milk yield both decreased linearly by 3.3kg/day from 0 to 51% DM of maize silage in the diet. Thus, N intake decreased linearly by 100g/day from 0 to 51% DM of maize silage in the diet. The N concentration of milk was highest for the diet with 0% DM of maize silage. Nitrogen excreted in faeces and urine decreased linearly by 29 and 23g/day, respectively, from 0 to 51% DM of maize silage in the diet. The low dietary N concentration resulted in low ruminal NH3-N concentrations (8mg/L, on average) and urinary urea excretion (down to 8% urea N in urinary N). Increasing the proportion of maize silage in an unusually low-N grass diet, without protein-rich concentrates, induced highly N-deficient diets with minimal N losses in faeces and urine but large and unsustainable decreases in DMI and milk yield.

Dose response to postruminal urea in lactating dairy cattle

Inclusion of urea in dairy cattle diets is often limited by negative effects of high levels of feed urea on dry matter intake (DMI) and efficiency of rumen N utilization. We hypothesized that supplying urea postruminally would mitigate these limitations and allow greater inclusion of urea in dairy cattle diets. Four rumen-fistulated Holstein-Friesian dairy cows (7 ± 2.1 lactations, 110 ± 30.8 d in milk; mean ± standard deviation) were randomly assigned to a 4 × 4 Latin square design to examine DMI, milk production and composition, digestibility, rumen fermentation, N balance, and plasma constituents in response to 4 levels of urea continuously infused into the abomasum (0, 163, 325, and 488 g/d). Urea doses were targeted to linearly increase the crude protein (CP) content of total DMI (diet plus infusion) by 0%, 2%, 4%, and 6% and equated to 0%, 0.7%, 1.4%, and 2.1% of expected DMI, respectively. Each 28-d infusion period consisted of a 7-d dose step-up period, 14 d of adaptation, and a 7-d measurement period. The diet was fed ad libitum as a total mixed ration [10.9% CP, 42.5% corn silage, 3.5% grass hay, 3.5% wheat straw, and 50.5% concentrate (dry matter basis)] and was formulated to meet 100%, 82%, and 53% of net energy, metabolizable protein, and rumen-degradable protein requirements, respectively. Linear, quadratic, and cubic effects of urea dose were assessed using polynomial regression assuming the fixed effect of treatment and random effects of period and cow. Dry matter intake and energy-corrected milk yield responded quadratically to urea dose, and milk urea content increased linearly with increasing urea dose. Apparent total-tract digestibility of CP increased linearly with increasing urea dose and ruminal NH3-N concentration responded quadratically to urea dose. Mean total VFA concentration was not affected by urea dose. The proportion of N intake excreted in feces decreased linearly and that excreted in urine increased linearly in response to increasing urea dose. The proportion of N intake excreted in milk increased linearly with increasing urea dose. Urinary urea excretion increased linearly with increasing urea dose. Microbial N flow responded cubically to urea dose, but the efficiency of microbial protein synthesis was not affected. Plasma urea concentration increased linearly with increasing urea dose. Regression analysis estimated that when supplemented on top of a low-CP diet, 179 g/d of postruminal urea would maximize DMI at 23.4 kg/d, corresponding to a dietary urea inclusion level of 0.8% of DMI, which is in line with the current recommendations for urea inclusion in dairy cattle diets. Overall, these results indicate that postruminal delivery of urea does not mitigate DMI depression as urea dose increases.

Feeding Damascus goats humic or fulvic acid alone or in combination: in vitro and in vivo investigations on impacts on feed intake, ruminal fermentation parameters, and apparent nutrients digestibility.

In vitro and in vivo experiments were carried out to investigate the effects of the supplementation of different levels of humic and fulvic acids alone or their combination (2:1 ratio) on ruminal fermentation constituents, and nutrients digestibility in goats. The treatments in Exp. 1 were the following: (1) basal substrate (50% concentrate: 50% forage) was incubated humic at 0, 2, 4, and 6g/kg DM; (2) fulvic at 0, 1, 2, and 3g/kg DM; and (3) a combination of humic and fulvic (in a 2:1 ratio) at 0, 3, 6, and 9g/kg DM" of treatments. The results of Exp. 1 revealed that methane (CH4) production was linearly decreased (P < 0.001) upon increasing humic doses. Whereas, the combination of fulvic acid with humic acid resulted in a quadratic decrease (P < 0.001) in net CH4 production. Supplementing humic and fulvic acids, either separately or in combination, resulted in reduced (P < 0.05) ammonia nitrogen (NH3-N) and total volatile fatty acid (VFA) concentrations. In Exp. 2 to further examine the findings obtained in Exp. 1, forty Damascus non-lactating goats (2-3years of age and body weight 29 ± 1.5kg) were fed the same basal diet as in Exp. 1, plus one of four treatments. Treatments were the following: (1) control (no supplement); (2) basal diet plus 5g humic alone; (3) basal diet plus 2.5g fulvic alone, and (4) basal diet plus 7.5g their combination. Goats fed diets supplemented with humic acid, fulvic acid, either alone or in combination, increased concentrations of butyrate (P = 0.003), total VFA (P < 0.001), and improved (P < 0.001) digestibility of nutrients, but reduced (P < 0.001) ruminal NH3-N concentrations. In conclusion, applying humic and fulvic acids alone or in combination attenuated in vitro CH4 production, while improved intake and diet digestibility without adverse effect on rumen fermentation profiles in Damascus goats.

Effect of coated urea and monensin on rumen metabolism of Nellore cows fed low-quality forage-based diet

ABSTRACT This study investigated the effect of coated urea supplementation associated with monensin on rumen metabolism and fermentation, in cattle consuming a low-quality forage-based diet. Eight ruminally cannulated Nellore cows consuming Brachiaria brizantha cv. Marandu hay were randomly assessed to two 4 × 4 Latin square design, in a 2 × 4 factorial arrangement, with a factorial treatment arrangement with the factors: (i) urea source: (CON) no urea, (URE) common urea, (PCU) polymer-coated urea and (LCU) lipid-coated urea; (ii) monensin: (MON) addition of monensin in the diet; and (NM) no addition of monensin in the diet. Ruminal NH3-N concentration was affected by urea source and there was an interaction between time and the urea source. Rumen acetate molar concentration was lower, while rumen propionate was greater for URE compared to coated urea. The total tract apparent digestibility of crude protein (CP) and non-protein nitrogen (NPN) were greater for URE compared to coated urea treatments and for LCU compared to PCU. Animals fed URE had greater urea excretion compared to coated urea. In conclusion, coated urea generates a lower ammonia peak; however, both coated urea did not promote total nitrogen release. No synergy was observed with the combination of urea and monensin.

Effects of dietary N-carbamylglutamate on rumen fermentation parameters, and bacterial community diversity of Holstein dairy cows in Tibet.

The Tibetan Plateau is characterized by low temperature and hypoxia. N-carbamylglutamic acid (NCG) can increase blood oxygen saturation, and have the potential to be used to prevent the high-altitude hypoxia stress state of cows. However, its beneficial effect on the rumen microbiota of Holstein dairy cows remains unclear. Hence, the experiments 12 multiparous (parity ranged from 2 to 7) Holstein dairy cows (413.0 ± 42 kg) were randomly assigned to 2 treatments with 6 replicates in each treatment: basal diet (CON, control group) and basal diet plus 20 g/d/cow of NCG (NCG, experiment group), respectively. To study the effects of dietary NCG supplementation on rumen microbiota of Holstein dairy cows in Tibet. The experiment lasted for 45 days, with 15 days of pre-feeding and 30 days of formal trail period. The results showed that ruminal NH3-N concentration in NCG group was lower (p < 0.05) than that in the CON group, while molar proportion of acetic acid and total volatile fatty acid (VFA) concentration were increased (p < 0.05) with the addition of NCG. Microbial diversity increased (p < 0.05) in NCG group, with Bacteroidetes, Firmicutes, and Patescibacteria as the most abundant phyla. The KEGG pathway analysis showed that the potential function of ruminal bacteria was mainly enriched in metabolism (carbohydrates, amino acids, lipids, energy, and nucleotides) and genetic information processing (replication, repair, and translation). In conclusion, NCG can improve rumen nitrogen utilization, total VFA and acetic acid production, and increase rumen microbial diversity, all of which could make the introduced Holstein dairy cows to better adapt to the harsh environment in Tibet and improve their production performance.

Ruminal fermentation pattern of acidosis-induced cows fed either monensin or polyclonal antibodies preparation against several ruminal bacteria.

This study was designed to evaluate a spray-dried multivalent polyclonal antibody preparation (PAP) against lactate-producing bacteria as an alternative to monensin (MON) to control ruminal acidification. Holstein cows (677 ± 98 kg) fitted with ruminal cannulas were allocated in an incomplete Latin square design with two 20 days period. Cows were randomly assigned to control (CTL), PAP, or MON treatments. For each period, cows were fed a forage diet in the first 5 days (d-5 to d-1), composed of sugarcane, urea and a mineral supplement, followed by a 74% concentrate diet for 15 days (d 0 to d 14). There were no treatment main effects (P > 0.05) on dry matter intake (DMI) and microbial protein synthesis. However, there was a large peak (P < 0.01) of intake on d 0 (18.29 kg), followed by a large decline on d 1 (3.67 kg). From d2, DMI showed an increasing pattern (8.34 kg) and stabilized around d 8 (12.96 kg). Higher mean pH was measured (P < 0.01) in cattle-fed MON (6.06 vs. PAP = 5.89 and CTL = 5.91). The ruminal NH3-N concentration of CTL-fed cows was lower (P < 0.01) compared to those fed MON or PAP. The molar concentration of acetate and lactate was not affected (P > 0.23) by treatments, but feeding MON increased (P = 0.01) propionate during the first 4 days after the challenge. Feeding MON and PAP reduced (P = 0.01) the molar proportion of butyrate. MON was effective in controlling pH and improved ruminal fermentation of acidosis-induced cows. However, PAP was not effective in controlling acidosis. The acidosis induced by the challenge was caused by the accumulation of SCFAs. Therefore, the real conditions for evaluation of this feed additive were not reached in this experiment, since this PAP was proposed to work against lactate-producing bacteria.

Feeding amylolytic and proteolytic exogenous enzymes: Effects on nutrient digestibility, ruminal fermentation, and performance in dairy cows

Exogenous enzymes are added to diets to improve nutrient utilization and feed efficiency. A study was conducted to evaluate the effects of dietary exogenous enzyme products with amylolytic (Amaize, Alltech) and proteolytic (Vegpro, Alltech) activity on performance, excretion of purine derivatives, and ruminal fermentation of dairy cows. A total of 24 Holstein cows, 4 of which were ruminally cannulated (161 ± 88 d in milk, 681 ± 96 body weight, and 35.2 ± 5.2 kg/d of milk yield), were blocked by milk yield, days in milk, and body weight, and then distributed in a replicated 4 × 4 Latin square design. Experimental periods lasted 21 d, of which the first 14 d were allowed for treatment adaptation and the last 7 d were used for data collection. Treatments were as follows: (1) control (CON) with no feed additives, (2) amylolytic enzyme product added at 0.5 g/kg diet dry matter (DM; AML), (3) amylolytic enzyme product at 0.5 g/kg of diet DM and proteolytic enzyme product at 0.2 g/kg of diet DM (low level; APL), and (4) amylolytic enzyme products added at 0.5 g/kg diet DM and proteolytic enzyme product at 0.4 g/kg of diet DM (high level; APH). Data were analyzed using the mixed procedure of SAS (version 9.4; SAS Institute Inc.). Differences between treatments were analyzed by orthogonal contrasts: CON versus all enzyme groups (ENZ); AML versus APL+APH; and APL versus APH. Dry matter intake was not affected by treatments. Sorting index for feed particles with size <4 mm was lower for ENZ group than for CON. Total-tract apparent digestibility of DM and nutrients (organic matter, starch, neutral detergent fiber, crude protein, and ether extract) were similar between CON and ENZ. Starch digestibility was greater in cows fed APL and APH treatments (86.3%) compared with those in the AML group (83.6%). Neutral detergent fiber digestibility was greater in APH cows compared with those in the APL group (58.1 and 55.2%, respectively). Ruminal pH and NH3-N concentration were not affected by treatments. Molar percentage of propionate tended to be greater in cows fed ENZ treatments than in those fed CON. Molar percentage of propionate was greater in cows fed AML than those fed the blends of amylase and protease (19.2 and 18.5%, respectively). Purine derivative excretions in urine and milk were similar in cows fed ENZ and CON. Uric acid excretion tended to be greater in cows consuming APL and APH than in those in the AML group. Serum urea N concentration tended to be greater in cows fed ENZ than in those fed CON. Milk yield was greater in cows fed ENZ treatments compared with CON (32.0, 33.1, 33.1, and 33.3 kg/d for CON, AML, APL, and APH, respectively). Fat-corrected milk and lactose yields were higher when feeding ENZ. Feed efficiency tended to be greater in cows fed ENZ than in those fed CON. Feeding ENZ benefited cows' performance, whereas the effects on nutrient digestibility were more pronounced when the combination of amylase and protease was fed at the highest dose.

Supplementation of high-quality fresh forage to lambs fed a total mixed ration increased in vitro ruminal fermentation and digestibility

The supplementation of fresh alfalfa into the diet of growing lambs fed with decreasing levels of a total mixed ration (TMR) was studied for its effect on in vitro ruminal fermentation activity. Twenty-four catheterized lambs [25.2 ± 3.67 kg body weight (BW)] were assigned to one of the following treatments: “TMR100”—TMR ad libitum; “TMR75’” and “TMR50”—TMR at 0.75 and 0.50 of potential intake, respectively, supplemented with alfalfa; and ‘TMR0’—only alfalfa ad libitum. In vitro gas production kinetics and true digestibility (IVTD) were evaluated using the rumen liquid as inocula. Ruminal pH values and NH3-N and volatile fatty acid concentrations were studied at the same time as inocula extraction. As the amount of alfalfa in the diet increased—by decreasing the level of TMR—in vitro gas production, ruminal pH values, NH3-N concentrations, and acetic acid proportions linearly increased (p = 0.005, 0.008, 0.004, and 0.018, respectively). IVTD tended to linearly rise (p = 0.083) and the fermentation rate (p = 0.004) and propionic acid proportion (p&amp;lt; 0.001) linearly decreased. We conclude that the increase in the level of fresh alfalfa resulting from the decrease in TMR levels in lambs’ diet positively impacted rumen fermentation activity and in vitro digestibility through the promotion of a suitable environment for ruminal microbiota.

Effect of coated cysteamine hydrochloride and probiotics supplemented alone or in combination on feed intake, nutrients digestibility, ruminal fermentation, and blood metabolites of Kamphaeng Saen beef heifers.

This study aimed to determine the effects of coated cysteamine hydrochloride (CSH) and probiotics (PB) supplemented alone or in combination on feed intake, digestibility, ruminal fermentation, and blood metabolites of heifer beef cattle. Sixteen heifers (body weight = 210 ± 41 kg; age = 9 ± 2 months) were assigned according to a randomized complete block design in a 2 × 2 factorial arrangement. All animals were fed the basal diet, which contained an 82:17 concentrate-to-forage ratio, and the forage source was rice straw. The treatments were as follows: (1) 0% PB + 0 g/d CSH, (2) 0.1% PB + 0 g/d CSH, (3) 0% PB + 20 g/d CSH, and (4) 0.1% PB + 20 g/d CSH. The main effect of CSH supplementation has been found to improve feed intake (P < 0.05). There were no treatment interactions with nutrient digestibility or rumen fermentation parameters. Supplementation of CSH did not affect any of the variables evaluated, while probiotics supplementation increased DM digestibility due to the increases in CP and fiber fraction digestibility. Compared to controls and CSH, at 16 h post-feeding, heifers receiving probiotics tended (P = 0.07) to show 17% greater ruminal NH3-N concentration, but this effect was not evident at 2 h post-feeding. However, the main effects of probiotic supplementation showed a tendency to increase the number of total bacteria and fungal zoospores in the rumen at 2 h post-feeding. The blood triglyceride (BTG) concentration of heifers fed a diet supplemented with 20 g/d CSH and 0.1% probiotics was found to be greater than those fed CSH alone (P < 0.1) at 16 h post-feeding, and then, there were greater BTG concentrations than other treatments (P < 0.05) at 2 h post-feeding. In conclusion, the combination of CSH and PB did not potentiate the effects of probiotics on digestibility and rumen fermentation and had minimal effects on blood parameters.

Effect of Post-Ruminal Urea Supply on Growth Performance of Grazing Nellore Young Bulls at Dry Season.

The objective of this study was to evaluate the effect of the use of post-ruminal urea on performance, nitrogen metabolism and the ruminal environment of Nellore cattle reared on pasture during the dry season. In experiment 1 (Exp. 1), nine ruminal-cannulated Nellore steers, 30 ± 2 months old (651 ± 45 kg body weight (BW)), were allotted to a 3 × 3 Latin triple square. In experiment 2 (Exp. 2), 84 Nellore bulls, 18 ± 3 months old (315 ± 84 kg BW), were distributed in complete randomized blocks, by initial BW. Protein supplements were supplied daily, in the amount of 2 g/kg BW, and consisted of either CONT: protein + conventional urea (50% CP), PRU: protein + post ruminal urea (50% CP) and U + PRU: protein + urea conventional + post-ruminal urea (70% CP). The paddocks were composed of Urochloa brizantha cv. Marandu grass. In Exp. 1, there was no treatment effect for DM, OM, NDF, forage intake, and CP, but there was a higher intake for PRU (p &lt; 0.005) and a higher digestibility for U+ PRU (p = 0.001). There was no effect on ruminal pH or NH3-N concentration (p ≥ 0.232), but there was an interaction between treatment and time for them (p &lt; 0.039). Furthermore, there was a treatment effect on the total SCFA concentration, with CONT being higher than the others. A difference in the acetate:propionate ratio was found (p &lt; 0.027), with a greater relationship for PRU and U + PRU. A treatment effect (p = 0.049) was found for the propionate proportion, with a higher proportion in the CONT. Nitrogen intake was consequently lower for the CONT and higher urinary excretion for the U + PRU (p = 0.002). Animals supplemented with CONT showed a tendency to have more Bacteria and fewer Archaea (p = 0.086). In Exp. 2, there was a treatment effect for the disappearance rate of the supplement (p &lt; 0.001). Intake was faster for PRU and CONT, but performance was not affected by PRU (p = 0.311). The use of post-ruminal urea alters the microbial population, but does not affect performance. Therefore, supplementation with post-ruminal urea presented similar results compared to conventional urea. Ruminal and blood parameters and animal performance were not influenced by treatments.

Effects of starch sources varying in particle sizes on ruminal fermentation, nutrient flow, starch digestibility, and lactation performance of dairy cows.

Cereal grains are the predominant starch source (SS) for dairy cows; however, starch digestibility varies greatly depending on source, grain processing, and potentially interactions between these factors. The objective was to study the effects of the interactions between SS, and particle sizes (PS) on ruminal fermentation, nutrient flow, starch digestibility, and lactation performance of dairy cows. Four ruminally cannulated multiparous Holstein cows were used in a 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments. Two SS (corn or sorghum) used in this study were either finely or coarsely ground (using a 1- or 4-mm screen sieve). Digesta flow was quantified using the reticular sampling technique, applying the triple-marker method. Data were analyzed using the GLIMMIX procedure of SAS version 9.3 (SAS Institute Inc., Cary, NC, USA). For ruminal pH, data were analysed with time as repeated measure. There were no interactions between SS and PS on production or intake, flow, and digestibility of nutrients. Dry matter intake was greater for the corn diet compared to the sorghum diet (25.15 vs. 21.98 kg/d), which consequently affected nutrient intake, however, PS did not affect intake. Milk yield was not affected by SS; however, it was greater for cows fed fine grains than cows fed coarser grains (25.32 vs. 23.16 kg/d). Milk fat and milk protein were not affected by SS or PS. Interactions (SS × PS) were observed for ruminal pH, reticular pH, and volatile fatty acids (VFA) concentrations but not for ruminal NH3-N concentration. Ruminal and reticular pH were greater for sorghum when coarsely ground and the total VFA concentration was decreased, compared to coarse corn and fine sorghum; however, coarsely grinding corn did not affect ruminal or reticular pH nor VFA concentration. Acetate concentration was lower for corn when finely ground; however, finely grinding sorghum did not affect acetate. Decreasing PS increased ruminal digestibility of starch (87.18% vs. 83.43%), reduced the flow of starch to the reticulum (0.79 vs. 0.96 kg/d) but decreased neutral detergent fiber digestibility in the rumen (30.23% vs. 34.88%). Although SS were differently affected by processing, the effects of PS on production, intake, flow, and digestibility of nutrients were observed regardless of the SS. Furthermore, the effects of decreasing PS on pH and VFA concentrations were more pronounced in sorghum compared to corn.

Influence of encapsulated pepper on ruminal fermentation, nutrient digestibility, and performance in dairy cows

The aim of this study was to evaluate the effects of a feed additive containing encapsulated pepper on total-tract apparent nutrient digestibility, sorting index, ruminal fermentation, milk yield and composition, serum concentrations of urea-N and glucose, purine derivative excretion, and N utilization efficiency in dairy cows. Twenty-two Holstein cows (182 ± 86.3 days in milk, 35.4 ± 4.85 kg/d milk yield), of which 4 were rumen cannulated, were used in a crossover design experiment with 21-d periods (14 days allowed to treatment adaptation and 7 days for sampling). Cows were blocked according to parity, days in milk, and milk yield and randomly assigned to the following treatments: Control (CON), or 1.5 g/d (CAP) of a feed additive containing encapsulated pepper (Capcin; NutriQuest, Campinas, Brazil) added to the concentrate along with minerals. Data were analyzed using the mixed procedure of SAS modeling the fixed effects of treatment, period, and the random effect of animal. Ruminal fermentation data were analyzed as repeated measurements adding the fixed effect of time and its interaction with treatments to the previous model. No differences in intake of dry matter or nutrients were detected. Sorting for feed particles between 19 and 8 mm size was greater in cows fed CAP compared to CON (1.000 and 0.992 kg/kg, respectively). Feeding CAP had no effects on digestibility of dry matter, crude protein, ether extract, or neutral detergent fiber. Nor treatment or interaction effect between treatment and time were observed for ruminal pH, NH3N concentration, or short-chain fatty acids concentration. Yields of milk (35.3 vs 34.3 kg/d) and fat-corrected milk (37.4 vs 36.0 kg/d) were greater for cows under CAP treatment compared to CON. Yield of milk solids (fat, protein, and lactose) was increased when feeding CAP. Milk fat concentration tended to be greater in cows fed CAP than those in CON group (39.5 vs 38.3 g/kg, respectively). Feed efficiency (fat-corrected milk ÷ dry matter intake) tended to be greater in cows fed CAP than CON-cows (1.45 vs 1.40, respectively). Serum concentrations of urea-N and glucose were similar between treatment groups. Feeding CAP did not alter purine derivative excretion (allantoin in urine and milk, and uric acid in urine), as well as the nitrogen excreted (g/g N intake) through feces, milk, or urine. In conclusion, feeding CAP at 1.5 g/d improved performance without altering nutrient digestibility, ruminal fermentation, excretion of purine derivatives, or efficiency of nitrogen utilization in dairy cows.