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Four ruminally cannulated and four ruminally and duodenally cannulated beef heifers (476 ± 25 kg, initial BW) were used in a replicated 4 × 4 Latin square to determine the effects of feeding condensed and hydrolysable tannin extracts with a high protein diet containing wheat distillers grains on ruminal fermentation, digestibility, and route of nitrogen (N) excretion. Periods were 4 wk and included a 1-wk washout, 2 wk for adaptation to the tannin extracts, and 1 wk for measurements. Dietary treatments were control (CON, basal diet), 2.5% Acacia mearnsii (ACA), 2.5% quebracho (QUE), and 2.5% chestnut (CHE; DM basis). The basal diet was composed of 71% barley grain concentrate, 20% wheat distillers grains and solubles, and 9% barley silage and contained 16.8% CP (DM basis). Diets were fed as total mixed rations once per day for ad libitum intake. Feed offered and refused were measured daily. Total collection of urine and feces were made for 6 d. Plasma was collected at 3 h and rumen fluid was collected at 0, 3, 6, 9, 12, 15, and 18 h after feeding at the end of the collection period. Data were analyzed using a mixed linear model with square, period, and treatment as fixed effects and animal within square as a random effect. Dry matter intake tended (P = 0.10) to be lower when heifers were fed the CHE compared to the CON and QUE, and was intermediate for the ACA. Total tract digestibility of DM was similar among heifers fed the tannin extracts (78.1, 77.4, and 77.6% for ACA, QUE, and CHE, respectively), however, all tannin extracts reduced DM digestibility compared to the CON (80.8%, SEM 0.98%; P < 0.05). Plasma urea-N and ruminal NH3-N were also similar among heifers fed the tannin extracts and were reduced (P < 0.05) compared to the CON. There was no effect of the dietary treatments on total N output (P > 0.05), but fecal N output was increased (P < 0.05) and conversely urinary N output was decreased (P < 0.05) for heifers fed ACA and QUE compared to the CON. Fecal and urinary N outputs were intermediate for the CHE. Feeding tannins to beef cattle fed high protein diets containing wheat distillers grains reduced ruminal NH3-N and plasma urea-N and shifted the route of N excretion from labile forms in urine to feces although there was a 4% decrease in DM digestibility. [ABSTRACT FROM AUTHOR]

In situ and in vitro experiments were conducted to determine the nitrate (NO3 -) release rate from encapsulated NO3 - (EN; 71% NO3 -) in the rumen and to examine metabolism of ENNO 3 - in conjunction with methane (CH4), hydrogen (H2), and nitrous oxide (N2O) production. Three ruminally-cannulated beef heifers were used to incubate the following substrates in the rumen for 72 h: soybean meal, EN, and unencapsulated NO3 - (UEN). Because of immediate solubilization, the soluble nitrogen (N) fraction of UEN was assumed to be 100%. A non-linear regression model fitted to N disappearance of EN (r2 = 0.93, P < 0.01) indicated 35.4% and 54.7% of soluble and slowly degradable N fraction, respectively. Two in vitro experiments were conducted where UEN and EN were incubated for 24 h in buffer alone or with buffered-rumen fluid with substrates containing urea, UEN, or EN as sole N sources. When UEN was incubated with buffer, 99.9% of UEN-NO3 --N was recovered as NO3 --N in the buffer over 24 h. However, recovery of EN-NO3 - as NO3 --N gradually increased over 24 h up to 58%. When urea, EN or UEN were incubated with buffered-rumen fluid, total gas production decreased (P = 0.022) for UEN compared with urea and EN. Methane production decreased (10.7 and 13.3 vs 19.6 mL; P < 0.01) for UEN and EN, respectively, compared with urea. Hydrogen production increased (0.2 vs 0.07 and 0.08 mL; P < 0.01) for UEN compared with urea and EN, respectively. Nitrous oxide production was greater for UEN (20.8, 7.5 and 0.02 μL, respectively; P < 0.05) followed by EN and urea. During the incubation with buffered-rumen fluid, 100% of UEN-NO3 - was recovered as NO3 --N in the medium until 6 h and then the recovery gradually decreased to 18% at 24 h while recovery as nitrite (NO2 -)-N increased up to 22% at 24 h. However, recovery of EN-NO3 --N as NO3 --N in the medium increased by 20% at 12 h and then gradually decreased to 5% at 24 h without accumulation of NO2 --N in the medium. In conclusion, EN released NO3 - comparatively slowly in the rumen and decreased CH4 production without negatively affecting microbial fermentation. Increases in H2 and N2O production and accumulation of NO3 - and NO2 - in the medium were not observed for EN compared with UEN, indicating that EN could be a promising NO3 - source to lower CH4 production with less risk of NO3 -/NO2 - toxicity. [ABSTRACT FROM AUTHOR]

A finishing feedlot study was conducted with beef steers to determine effects of encapsulated nitrate (EN) on growth performance, carcass characteristics, methane production, and nitrate (NO3-) residues in tissues. The 132 crossbred steers were backgrounded in a feedlot and transitioned to the high concentrate diets evaluated in the present study. The steers were initially assigned to 22 pens (6 animals per pen) in a randomized complete block design with BW (18 pens) and animals designated for methane measurement (4 pens) as blocking factors. Five animals in each pen designated for methane measurement were monitored for methane emissions in respiratory chambers twice during the finishing period. Pens received 3 dietary treatments (7 pens each): Control, a finishing diet supplemented with urea (0.03% NO3- and 0.9% urea in dietary DM); 1.25% EN, the control diet supplemented with 1.25% EN (1.1% NO3-) which partially replaced urea; 2.5% EN, the control diet supplemented with 2.5% EN (2.0% NO3-) fully replacing urea. The final pen designated only for methane measurement received a fourth dietary treatment, 2.3% UEN; control diet supplemented with unencapsulated NO3- (UEN; 2.0% NO3- in dietary DM) fully replacing urea. The cattle weighed 449 ± 32 kg at the start of the finishing period. The 2.5% EN diet decreased DMI (9.9 vs 10.7 and 10.7 kg/d; P < 0.01) compared with Control and 1.25% EN. Feeding EN tended to increase ADG (1.41 vs 1.36 kg/d; P = 0.09) and increased gain:feed (0.137 vs 0.127 kg/kg; P < 0.01) for EN compared with Control. No differences in methane production and yield were observed among treatments. Inclusion of EN in the diets increased (P  0.03) sorting in favor of large and medium particles and against small and fine particles. Plasma NO3- and NO2 - concentrations were elevated (0.06 to 3.68 mg/L of NO3- and 1.47 to 9.23 g/L of NO2 -; P < 0.01) with EN in a dose response manner, but blood methemoglobin levels for all treatments were below 1%. Feeding EN increased (P < 0.01) NO3- concentrations in muscle, fat, liver, and kidney and NO3- concentrations of those were similar between 1.25% EN and 2.3% UEN. In conclusion, including up to 2.5% of EN on a DM basis in a finishing diet did not cause NO3- toxicity or health problems in a long term study. In comparison with supplemental urea, feeding EN improved feed efficiency despite increases in sorting against dietary EN. [ABSTRACT FROM AUTHOR]

A backgrounding feedlot study was conducted to examine the effects of feeding encapsulated calcium ammonium nitrate (EN) on growth, enteric methane production, and nitrate (NO3 -) toxicity in beef cattle. A total of 108 crossbred steers (292 ± 18 kg) were blocked by BW and randomly assigned to 18 pens. The pens (experimental unit; 6 animals per pen) received 3 dietary treatments: Control, a backgrounding diet supplemented with urea (0.2% NO3 - and 0.9% urea in dietary DM); 1.25% EN, control diet supplemented with 1.25% EN (1.2% NO3 -) in dietary DM, which partially replaced urea; or 2.5% EN, control diet supplemented with 2.5% EN (2.3% NO3 -) in dietary DM, fully replacing urea. Twenty four steers were allocated to additional 4 pens and randomly assigned to 1 of the above 3 dietary treatments plus a fourth treatment: 2.3% UEN, control diet supplemented with 2.3% unencapsulated NO3 - (UEN; 2.4% NO3 -) fully replacing urea. Animals in the additional 4 pens were used for methane measurement in respiratory chambers and the pens (except UEN) were also part of the performance study (i.e., n = 7 pens/treatment). The experiment was conducted for 91 d in a randomized complete block design. During the experiment, DMI was not affected by inclusion of EN in the diet. Changes in BW, ADG, and gain:feed were not observed (P ≥ 0.57) by feeding EN. Methane production (g/d) tended to decrease (P = 0.099) by NO3 -(188, 174, 156, and 152 g/d for Control, 1.25%, 2.5% EN, and UEN, respectively), but yield (g/kg DMI) did not differ (P=0.56) among treatments. Inclusion of EN in the diet increased (P ≤ 0.02) sorting of the diets in favor of large and medium particles and against small and fine particles resulting in considerable increases in NO3 - concentrations of orts without affecting DMI. Plasma NO3 - and NO2 - concentrations increased (P ≤ 0.05) for EN compared with Control in a dose response manner, but blood methemoglobin levels were below the detection limit. Nitrate concentration in fecal samples slightly increased (from 0.01% to 0.14%; P < 0.01) with increasing levels of EN in the diet. In conclusion, EN can be used as a feed additive replacing urea in beef cattle diets during the backgrounding phase without NO3 - intoxication or any negative effects on growth performance. In addition, the study confirmed that feeding EN tended to decrease enteric methane production in the long term. [ABSTRACT FROM AUTHOR]

Selenium is an essential trace mineral for dairy cattle and can be provided in the diet in various forms that may differ in bioavailability. The objective of this study was to determine how source of Se affects animal performance, Se status, retention, and apparent and true absorption. Multiparous Holstein cows (n = 24; 597 ± 49 kg of BW) were blocked by DIM (161 ± 18) and randomly assigned to receive 0.3 mg Se/kg of DM (100% of National Academies of Sciences, Engineering, and Medicine requirements) of either organic Se (ORG; selenized yeast) or inorganic Se (INO; sodium selenite). The Se premix was top dressed on a common TMR fed daily and mixed into the top 15 cm directly before feeding. Following an 11-wk adaptation period, cows received simultaneous infusions of an intraruminal isotope dose of 77 Se in the same chemical form as the premix, and an intravenous dose of 82 Se in an inorganic form. Infusions were followed by a 4-d period of blood and rumen fluid sampling, and total collection of feces, urine, and milk. Daily DMI (23 ± 0.6 kg), milk yield (35 ± 1.2 kg), and serum Se (0.11 ± 0.003 µg/g) were not different between treatments during the adaptation period, but milk Se concentrations were greater for ORG compared with INO. Serum 77 Se maximum concentration and area under the curve (AUC) were not different between treatments for 72 h following infusion, but rumen fluid 77 Se AUC was higher for ORG than INO. Apparent absorption (64% ± 1.4%), and retention (44% ± 1.5%) of the 77 Se dose did not differ between treatments. True absorption was calculated using 82 Se enrichment in serum and feces and was determined to be 69% ± 1.3% and did not differ between treatments. Fecal excretion of the 77 Se dose was not different between treatments (36% ± 1.4%), but ORG had lower urinary excretion and higher milk excretion compared with INO. These results indicate that organic Se resulted in greater Se concentration of milk and lower urinary Se excretion into the environment, but absorption, Se status, and performance of the cow were not affected by Se source at this supplementation level., (© 2024, The Authors. Published by Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).)