Ammonia emissions and performance of backgrounding and finishing beef feedlot cattle fed barley-based diets varying in dietary crude protein concentration and rumen degradability

Intake, Growth and Carcass Traits of Steers Offered Grass Silage and Concentrates Based on Contrasting Cereal Grain Types Supplemented with Field Beans, Peas or Maize By-Products

The study objective was to determine intake and performance of beef cattle individually offered perennial ryegrass-dominant grass silage ad libitum supplemented with 4 kg dry matter daily of, rolled barley or maize meal-based concentrate rations containing supplements of flaked field beans, flaked peas, maize dried distillers grains (MDD) or maize gluten feed (MGF) for 110 days (Experiment 1), rolled barley or rolled oats with or without supplements of flaked field beans or flaked peas for 146 days (Experiment 2), and to quantify the nitrogen balance of diets similar to those offered in Experiment 2 (Experiment 3). The protein supplements were formulated to have similar crude protein concentrations. Cereal type or protein source did not affect intake, growth, feed efficiency and carcass traits in Experiment 1 or 2. Inclusion of a legume protein supplement with barley or oats had no effect on intake or growth performance (Experiment 2), whereas their exclusion decreased nitrogen intake, plasma urea concentrations and urinary and total nitrogen excretion (Experiment 3). The feeding value of barley was similar to oats and maize meal, and flaked beans and peas were similar to MGF and MDD, as supplements to grass silage. Excluding protein ingredients from a cereal-based concentrate did not affect animal performance and reduced nitrogen excretion.

Effects of rumen undegradable protein sources on nitrous oxide, methane and ammonia emission from the manure of feedlot-finished cattle

The effects of sources of rumen undegradable protein (RUP) in diets on methane (CH₄), nitrous oxide (N₂O) and ammonia (NH₃) emissions from the manure of feedlot-finished cattle were evaluated. We hypothesized that the use of different RUP sources in diets would reduce N loss via urine and contribute to reduced N₂O, CH₄ and NH₃ emissions to the environment. Nellore cattle received different diets (18 animals/treatment), including soybean meal (SM, RDP source), by-pass soybean meal (BSM, RUP source) and corn gluten meal (CGM, RUP source). The protein source did not affect the N and C concentration in urine, C concentration in feces, and N balance (P > 0.05). The RUP sources resulted in a higher N₂O emission than the RDP source (P = 0.030), while BSM resulted in a higher N₂O emission than CGM (P = 0.038) (SM = 633, BSM = 2521, and CGM = 1153 g ha⁻² N–N₂O); however, there were no differences in CH₄ and NH₃ emission (P > 0.05). In conclusion, the use of RUP in diets did not affect N excretion of beef cattle or CH₄ and NH₃ emission from manure, but increased N₂O emission from the manure.

The Effects of Dietary Crude Protein Level on Ammonia Emissions from Slurry from Lactating Holstein-Friesian Cows as Measured in Open-Circuit Respiration Chambers

Simple Summary

Farmed livestock, particularly dairy cows, are the largest source of ammonia (NH₃) emissions to the atmosphere in Europe and other parts of the developed world. Generally, more than 80% of the total agricultural NH₃ emissions in Europe come from manure slurries (mixtures of urine and faeces) with hydrolysis of urea nitrogen (N) in urine, and ammonification of the organic N fraction in faeces as the two main sources of the NH₃. It is also worth noting that the concentration of these two main sources of NH₃ emissions from manure slurries (particularly urea N in urine) is positively associated with dietary protein content.

Abstract

The effect of dietary crude protein (CP) level on ammonia (NH₃) emissions from slurry from lactating Holstein-Friesian cows was studied. Twenty-four-hour total collections of faeces and urine were made from 24 lactating Holstein-Friesian cows fed four total mixed rations containing 141, 151, 177, and 201 g CP/kg DM (6 cows/diet). The collected urine and faeces from each cow were combined to form 2 kg duplicate slurry samples (weight/weight; fresh basis) according to the proportions in which they were excreted. NH₃ emissions from the slurry samples were measured, during 0–24 and 24–48 h intervals in six open-circuit respiration chambers maintained at two temperatures (8 or 18 °C). NH₃ emissions for the 0–24 and 0–48 h intervals, as well as the average daily emissions, increased linearly with increasing dietary CP level. Increasing the temperature from 8 to 18 °C positively affected NH₃ emissions, but only for the 0–24 h interval. In situations where direct measurements are impossible, NH₃ emissions from slurry can be predicted accurately using equations based on dietary CP level supported by either urinary nitrogen, faeces nitrogen, or both. In summary, increasing dietary CP level linearly increased average daily NH₃ emissions from slurry, with a 5.4 g increase for each 10 g increase in dietary CP.

Effects of feeding lubabegron on gas emissions, growth performance, and carcass characteristics of beef cattle housed in small-pen environmentally monitored enclosures during the last 3 mo of the finishing period

The development of technologies that promote environmental stewardship while maintaining or improving the efficiency of food animal production is essential to the sustainability of producing a food supply to meet the demands of a growing population. As such, Elanco (Greenfield, IN) pursued an environmental indication for a selective β-modulator (lubabegron; LUB). LUB was recently approved by the United States Food and Drug Administration (FDA) to be fed to feedlot cattle during the last 14 to 91 d of the feeding period for reductions in gas emissions/kg of unshrunk final BW and HCW. A 4 × 2 factorial arrangement of treatments was used with the factors of dose (0.0, 1.38, 5.5, or 22.0 mg·kg⁻¹ DM basis) and sex (steers or heifers). Three 91-d cycles were conducted (112 cattle/cycle) with each dose × sex combination being represented by a single cattle pen enclosure (CPE; 14 cattle/CPE) resulting in a total of 168 steers and 168 heifers (n = 6 replicates/dose). There were no interactions observed between dose and sex for any variable measured in the study (P ≥ 0.063). Five gases were evaluated for all pens based on CPE concentrations relative to ambient air: NH₃, CH₄, N₂O, H₂S, and CO₂. Cumulative NH₃ gas emissions were reduced by feeding cattle 5.5 and 22.0 mg·kg⁻¹ LUB (P ≤ 0.023) and tended (P = 0.076) to be lower for the cattle fed 1.38 mg·kg⁻¹ LUB compared with the negative controls (CON). The cumulative NH₃ gas emission reductions of 960 to 1032 g, coupled with HCW increases (P ≤ 0.019) of 15 to 16 kg for all LUB doses vs. CON, led to reductions in NH₃ gas emissions/kg HCW for all three LUB treatments (P ≤ 0.004). Similar to HCW, reductions in NH₃ gas emissions/kg of unshrunk final BW were observed for all LUB doses (P ≤ 0.009) and were attributable to both decreases in NH₃ gas emissions and numerical increases in BW. Dose had no effect on cumulative emissions or emissions standardized by BW or HCW for the other four gases (P ≥ 0.268). LUB is a novel tool to reduce emissions of NH₃ gas per kilogram of unshrunk live BW and hot carcass weight.

Increasing dietary proportion of wheat grain in finishing diets containing distillers' grains: impact on nitrogen utilization, ruminal pH, and digestive function

Because of its high crude protein (CP) content, dietary inclusion of corn dried distillers' grains with solubles (DDGS) in finishing cattle diets can increase the ruminal loss of ammonia-nitrogen (NH3-N), which ends up excreted as urine urea-N (UUN). Increasing dietary fermentable energy supply can enhance ruminal use of N; however, it could also lead to acidotic conditions that compromise digestive function and animal performance. We evaluated the effects of partially replacing dietary corn grain with 20% or 40% (dry matter [DM] basis) wheat grain in finishing diets containing 15% corn DDGS on N utilization, ruminal pH, and digestive function. Nutrient intake and digestion, ruminal fermentation characteristics, microbial protein synthesis, route of N excretion, and blood metabolites were measured. Six ruminally fistulated crossbred beef heifers (initial body weight ± SD; 797 ± 58.8 kg) were used in a replicated 3 × 3 Latin square design with 28-d periods. Dietary treatments were either corn (73% of diet DM; CON), 53:20 corn:wheat blend (20W), or 33:40 corn:wheat blend (40W) as the major fermentable energy source. Dry matter intake (DMI) tended to be lower for heifers fed the 40W than CON and 20W diets. Feeding diets containing wheat grain led to an increase (P = 0.04) in neutral detergent fiber (NDF) intake. However, there was no diet effect (P ≥ 0.60) on apparent total tract DM and NDF digestibility. Feeding wheat grain led to a decrease (P ≤ 0.03) in mean and minimum pH, an increase (P = 0.04) in pH < 5.8 duration, and a tendency for an increase in the area and acidosis index for pH < 5.8 and 5.5. Nitrogen intake, which was lower (P = 0.04) for 40W than 20W heifers did not differ between CON and 20W heifers. There was no diet effect (P = 0.80) on ruminal NH3-N concentration and estimated microbial N flow. However, feeding diets containing wheat grain led to a decrease (P = 0.045) in UUN excretion (% total urine N). Fecal and total N excretion (% of N intake) increased (P < 0.01) following the addition of wheat grain to the diet. Apparent N retention was lower (P = 0.03) for 40W than CON and 20W heifers. In summary, although it led to a desirable decrease in UUN excretion, feeding wheat grain in corn DDGS-containing diets increased acidotic conditions in the rumen, which possibly led to the tendency for a decrease in DMI. The negative apparent N retention at the 40% wheat grain inclusion also suggests a decrease in nutrient supply, which could compromise feedlot performance.

In Vitro Assessment of Enteric Methane Emission Potential of Whole-Plant Barley, Oat, Triticale and Wheat

The study determined in vitro enteric methane (CH₄) emission potential of whole-plant cereal (WPC) forages in relationship to nutrient composition, degradability, and rumen fermentation. Two varieties of each WPC (barley, oat, triticale, and wheat) were harvested from two field replications in each of two locations in central Alberta, Canada, and an in vitro batch culture technique was used to characterize gas production (GP), fermentation, and degradability. Starch concentration (g/kg dry matter (DM)) was least (p < 0.001) for oat (147), greatest for wheat (274) and barley (229), and intermediate for triticale (194). The aNDF concentration was greater for oat versus the other cereals (531 vs. 421 g/kg DM, p < 0.01). The 48 h DM and aNDF degradabilities (DMD and aNDFD) differed (p < 0.001) among the WPCs. The DMD was greatest for barley, intermediate for wheat and triticale, and least for oat (719, 677, 663, and 566 g/kg DM, respectively). Cumulative CH₄ production (MP; mL) from 12 h to 48 h of incubation was less (p < 0.001) for oat than the other cereals, reflecting its lower DMD. However, CH₄ yield (MY; mg of CH₄/g DM degraded) of barley and oat grown at one location was less than that of wheat and triticale (28 vs. 31 mg CH₄/g DM degraded). Chemical composition failed to explain variation in MY (p = 0.35), but it explained 45% of the variation in MP (p = 0.02). Variation in the CH₄ emission potential of WPC was attributed to differences in DMD, aNDFD, and fermentation end-products (R² ≥ 0.88; p < 001). The results indicate that feeding whole-plant oat forage to ruminants may decrease CH₄ emissions, but animal performance may also be negatively affected due to lower degradability, whereas barley forage may ameliorate emissions without negative effects on animal performance.

Optimum roughage proportion in barley-based feedlot cattle diets: growth performance, feeding behavior, and carcass traits

High grain diets are fed to finishing beef cattle to maximize animal performance in a cost-effective manner. However, a small amount of roughage is incorporated in finishing diets to help prevent ruminal acidosis, although few studies have examined optimum roughage inclusion level in barley-based diets. The objective of the study was to evaluate the effects of roughage proportion in barley-based finishing diets on growth performance, feeding behavior, and carcass traits of feedlot cattle. Crossbred beef steers (n = 160; mean body weight ± SD, 349.7 ± 21.4 kg) were allocated to 20 pens that were assigned randomly to four dietary treatments (five pens of eight steers per treatment). The treatment diets contained barley silage at 0%, 4%, 8%, and 12% of dietary dry matter (DM). The remainder of the diets (DM basis) consisted of 80%, 76%, 72%, and 68% barley grain, respectively, 15% corn dried distiller's grains, 5% mineral and vitamin supplement, and 32 mg monensin/kg diet DM. The diets were fed as total mixed rations for ad libitum intake (minimum of 5% refusal) once per day. Cattle were weighed on 2 consecutive days at the start and end of the experiment and on 1 d every 3 wk throughout the experiment (124 d). Two pens for each treatment group were equipped with an electronic feeding system (GrowSafe Systems Ltd., Calgary, Alberta) to monitor feed intake and feeding behavior of individual cattle. The data for dry matter intake (DMI), average daily gain (ADG), gain:feed (G:F) ratio, and carcass traits were analyzed as a completely randomized design with fixed effect of barley silage proportion and pen replicate as experimental unit. Feeding behavior data were analyzed similarly, but with animal as experimental unit. Averaged over the study, DMI increased linearly (11.1, 11.3, 11.7, 11.8 kg/d; P = 0.001) as barley silage proportion increased from 0%, 4%, 8%, and 12% of DM, but ADG was not affected (carcass-adjusted,1.90, 1.85, 1.87, 1.89 kg/d; P ≥ 0.30). Consequently, G:F ratio decreased linearly (carcass-adjusted, 168.9, 163.8, 158.5, 160.6 g/kg DMI; P = 0.023). When averaged over the study, proportion of barley silage in the diet had no linear or quadratic effects (P > 0.10) on meal frequency, duration of meals, intermeal duration, or meal size, but eating rate decreased linearly with increasing silage proportion (P = 0.008). There was no diet effect on liver abscesses (P ≥ 0.92), and effects on carcass characteristics were minor or nonexistent. We conclude that increasing the proportion of barley silage in a feedlot finishing diet at the expense of barley grain to minimize the incidence of ruminal acidosis may decrease feed conversion efficiency.

Effect of crude protein content and undegraded intake protein level on productivity, blood metabolites, carcass characteristics, and production economics of Hanwoo steers

Objective

This study was designed to determine how feeding diets differing in crude protein (CP) and undegraded intake protein (UIP) levels affected productivity, blood metabolites, carcass characteristics, and the production economics of Hanwoo steers.

Methods

Thirty-six Hanwoo steers (age = 8.2±0.5 mo; body weight = 254±16.1 kg) were assigned at random to one of three treatments (4 steers/pen; 3 pens/treatment): i) a low-CP diet (LP; control) containing 12.1% CP with 35.1% UIP, 12.0% CP with 36.8% UIP, and 12.9% CP with 48.8% UIP, in the growing, fattening, and finishing periods, respectively; ii) a high-CP, low-UIP diet (HPLU) containing 15.0% CP with 33.7% UIP, 14.0% CP with 35.7% UIP, and 13.1% CP with 46.7% UIP, respectively; and iii) a high-CP, high-UIP diet (HPHU) containing 15.0% CP with 45.8% UIP, 14.0% CP with 44.6% UIP, and 13.0% CP with 51.1% UIP, respectively.

Results

The treatments did not affect feed intake and growth performance, except for average daily gain during the fattening period that tended to be the lowest (p = 0.08) in the HPLU-fed steers. The feed CP conversion ratio over the entire feeding period was higher with high-CP diets. The treatments did not affect most blood metabolites; however, blood cholesterol and low-density lipoprotein concentrations during the fattening and finishing periods were the lowest in steers fed a HPLU diet. The treatments had negligible effects on cold carcass weight, yield traits including longissimus muscle area, backfat thickness, yield index, and yield grade, plus quality traits including meat color, fat color, texture, and maturity. However, marbling score and frequency of carcass quality grade 1⁺⁺ were greater in HPHU-fed steers.

Conclusion

Feeding diets with higher CP and UIP levels did not affect growth performance but tended to improve the carcass quality of Hanwoo steers, resulting in greater economic return.

Use of gallic acid and hydrolyzable tannins to reduce methane emission and nitrogen excretion in beef cattle fed a diet containing alfalfa silage1,2

The objective of this study was to determine the effects of different forms of hydrolyzable tannin [HT; source (chestnut, CN; tannic acid, TA); subunit (gallic acid, GA)] on apparent total-tract digestibility, methane (CH4) production, and nitrogen (N) utilization in beef cattle fed an alfalfa silage-based diet. Eight ruminally cannulated heifers with an initial BW of 480 ± 29.2 kg (mean ± SD) were used in a double 4 × 4 Latin square experiment. The experiment consisted of four 28-d periods (14-d adaptation, 14-d measurements) and a 7-d washout between periods. The animals received a basal diet with 19.8% CP (DM basis) content containing 75% alfalfa silage, 20% barley silage, and 5% supplement (DM basis) with or without different forms of HT. The dietary treatments were as follows: control (no HT), GA (1.5% of diet DM), TA (1.5% of diet DM), and CN (2% of diet DM). Animals were fed 95% of their ad libitum intake during the measurement phase. Total fecal excretion was collected for 4 d, CH4 was measured for 72 h using respiration chambers, and ruminal fermentation variables and plasma urea N (PUN) concentration were measured on 2 nonconsecutive days before and after feeding. The restricted DM (DMI; 10.79 ± 1.076 kg/d) and nutrient intakes did not differ (P ≥ 0.22) among treatments. Furthermore, apparent DM digestibility (60.3 ± 0.86%) was not affected (P = 0.20) by treatment, but CP digestibility decreased for TA and CN compared with control and GA treatments (63.1 vs. 69.0%; P < 0.001). Total VFA concentration tended (P = 0.089) to increase for GA compared with control and TA (134 vs. 125 and 126 mM) and intermediate for CN (129 mM). The PUN concentration was lower for all HT treatments compared with control (196 vs. 213 mg/L; P = 0.02). Both TA and CN increased the proportion of N excreted in feces and decreased the proportion in urine compared with control and GA (43.9% vs. 37.8% and 56.1% vs. 62.2%; respectively; P < 0.001). However, the proportion of urea N in urinary N decreased for all HT treatments compared with control (47.2% vs. 51.2%; P = 0.02). Also, GA tended to decrease CH4/DMI (20.4 vs. 22.3 g/kg DMI; P = 0.07) and decreased the proportion of GE intake emitted as CH4 (5.16 vs. 5.71%; P = 0.04) compared with control. Thus, among the different forms of HT applied to a high-protein alfalfa silage-based diet, both TA and CN had no effect on CH4 production, but decreased CP digestibility and shifted N excretion from urine to feces, whereas GA (i.e., HT subunit) decreased CH4 production and decreased the proportion of urea N in urinary N in beef cattle without affecting CP digestibility. Thus, feeding the HT subunit, GA, has the potential to decrease environment impact of ruminants (lower CH4 and ammonia emissions), without decreasing animal performance.

Effect of inclusion rate of Fermenten on performance, carcass traits, and apparent total tract digestibility of growing Angus crossbred steers

In Phase 1 (days 0 to 56) of a two-phase experiment, 81 steers (initial BW = 189 ± 22 kg) were arranged in a generalized randomized block design, allocated to nine pens (nine steers per pen) and assigned to one of three dietary treatments. Treatments consisted of different inclusion rates of Fermenten (FER) in a backgrounding diet fed ad libitum, and were as follows: 0% (CON), 2%, or s FER in the diet DM. Steer was considered the experimental unit, and individual DMI was measured using the GrowSafe system. In Phase 2 (days 57 to 112), treatments were discontinued and steers were relocated to a paddock with free access to a common basal diet, to assess potential residual effects of FER. Effect of treatment was measured on performance, concentration of serum urea nitrogen (SUN), NEFA and glucose, and apparent total tract digestibility of nutrients. On day 56, steers fed 4% FER had lesser (P = 0.01) BW than 2% FER steers. Steers fed CON also tended (P = 0.08) to have greater BW than 4% FER steers. ADG was not different (P = 0.96) between CON and 2% FER steers, whereas steers in the 4% FER treatment had lesser (P ≤ 0.01) ADG than CON and 2% FER. Steers in the 4% FER treatment had lesser (P = 0.04) DMI than CON, and were less feed efficient (P ≤ 0.04) than 2% FER and CON steers. However, DMI as a percentage of the BW did not differ (P = 0.07) across treatments. A treatment effect was observed for final BW on day 112 (P = 0.05), where 4% FER tended (P = 0.07) to have lesser BW than CON. In Phase 2, ADG was not different (P = 0.18) among treatments. However, overall ADG (days 0 to 112) was lesser (P = 0.02) for steers fed 4% FER when compared with CON. There was no difference (P ≥ 0.12) in longissimus muscle area gain or 12th rib fat depth gain. There was a treatment × day interaction for serum concentrations of glucose (P < 0.001), NEFA (P < 0.001), and SUN (P < 0.001). Steers fed 4% FER had greater (P < 0.001) DM, OM, NDF, ADF, and CP apparent total tract digestibility than CON. Similarly, 4% FER steers had greater (P ≤ 0.02) DM, OM, NDF, and ADF digestibility than 2% FER. Results show that although inclusion of FER increased apparent total tract digestibility of nutrients, DMI and overall performance of growing beef cattle were negatively affected, mainly when FER was included at 4% of the diet DM.

Effects of hydrolyzable tannin with or without condensed tannin on methane emissions, nitrogen use, and performance of beef cattle fed a high-forage diet

Sustainability of animal agriculture requires efficient use of energy and nitrogen (N) by ruminants fed high-forage diets. Thus, there is a need to decrease methane (CH4) emissions and prevent excessive N release into the environment. Therefore, this experiment examined the long-term effects of feeding hydrolyzable tannin (HT) with or without condensed tannin (CT) on animal performance, rumen fermentation, N use, and CH4 production in beef cattle fed a high-forage diet. A total of 75 weaned crossbred steers (292 ± 4.1 kg) were grouped by body weight (BW), housed in individual pens, and randomly assigned to 1 of 5 dietary treatments (15 animals/treatment) in a completely random design. The animals were fed a basal diet of alfalfa:barley silages (50:50; dry matter [DM] basis) with a crude protein content of 17.1% and supplemented with HT extract (chestnut, CN) or a combination (50:50) of HT and CT extracts (quebracho, Q) in a powdered form at different levels of dietary DM. The treatments for determining animal performance and N use were control (no tannin), 0.25% CN, 1.5% CN, combination of CN and Q at 0.125% each (0.25% CNQ), and CN and Q at 0.75% each (1.5% CNQ) of dietary DM. The treatments for the CH4 measurement were control, 1.5% CN, and 1.5% CNQ of dietary DM. The first 84 d of the study were used to measure animal performance, rumen fermentation, and N use, and the next 30 d were used to measure CH4 emissions with the tracer gas technique. There were no effects of treatment on DM intake (DMI), BW, average daily gain, and gain: feed (P ≥ 0.10). The plasma urea N concentration was greater (P < 0.05) for 1.5% CN and 1.5% CNQ than those fed 0.25% CNQ (120.9 and 120.4 vs. 111.7 mg/L, respectively), but not different (P > 0.05) from animals fed control or 0.25% CN (117.2 and 117.5 mg/L, respectively). Tannin inclusion did not affect rumen pH, total volatile fatty acid concentration, proportions of acetate and propionate, and total protozoa populations (P ≥ 0.16). Tannin, irrespective of type or dose, decreased (P < 0.01) ruminal ammonia concentration. Tannin type and dose did not affect (P = 0.54) daily CH4 production (154 ± 5.9 g/d) but 1.5% CNQ tended to decrease CH4 yield compared with control (20.6 vs. 22.0 g/kg DMI; P = 0.094). HT from CN alone or in combination with CT from Q can be added at a low (0.25% DM) or high (1.5% DM) level to a forage-based diet to decrease ruminal ammonia concentration in growing beef cattle fed a high-protein diet without adverse effects on animal performance. A combination of HT and CT at a concentration of 1.5% dietary DM also tended to decrease CH4 emissions without negatively affecting performance.

Feeding condensed tannins to mitigate ammonia emissions from beef feedlot cattle fed high-protein finishing diets containing distillers grains

Two experiments were conducted to determine the effects of feeding a condensed tannin extract (CT) on dry matter intake (DMI), growth performance, carcass traits, and NH3-N emissions of beef feedlot cattle fed high-protein barley-based finishing diets. In Exp. 1, 36 crossbred steers (346 ± 4.2 kg) were individually fed 4 diets with 20% corn dried distillers grains (DG) and increasing concentrations of a CT extract from Acacia mearnsii (black wattle) at 0%, 1.2%, 2.4%, and 3.5% of DM (9 steers per diet) for 52 d. The DMI was not affected at 1.2% and 2.4% but tended (P = 0.08, quadratic effect) to decrease at 3.5% CT extract. There was no effect (P ≥ 0.12) of increasing CT extract on ADG, but G:F tended (P = 0.09) to decrease linearly. In Exp. 2, 148 crossbred steers (457 ± 3.8 kg) were allocated to 16 pens with 4 pens per treatment in a completely randomized design and fed for 83 d. The 4 dietary treatments included 0% corn DG (0DG), 20% DG (20DG), 40% DG (40DG), and 40% DG with 2.5% CT extract (40DGCT) and contained 13.3, 15.9, 20.4, and 19.4% CP, respectively. All cattle were weighed, and blood was collected from 5 steers per pen every 3 wk. Ammonia emissions were measured in four 3-wk periods using the integrated horizontal flux technique with passive NH3 samplers from 2 pens of cattle fed 0DG and 20DG (Period 1), 40DG and 40DGCT (Period 2), 0DG and 40DG (Period 3), and 0DG and 40DGCT (Period 4). There was no effect (P ≥ 0.15) of diet on final body weight (621 ± 7.1 kg), DMI (11.9 ± 0.25 kg/d), ADG (1.98 ± 0.07 kg/d), G:F (166 ± 5.4 g/kg), and carcass traits. Plasma urea N (PUN) increased (P < 0.001) from 0DG to 40DG (113 to 170 ± 6.0 mg N/L) and was reduced (P < 0.001) by 40DGCT (146 mg N/L) compared with 40DG and tended (P = 0.09) to be reduced compared with steers fed 20DG (153 mg N/L). Ammonia-N emissions were greater from cattle fed 40DG [113.7 vs. 70.8 ± 4.57 g N/(steer·d), P = 0.003] and tended to be greater from cattle fed 20DG [51.3 vs. 26.3 ± 11.2 g N/(steer·d), P = 0.11] compared with 0DG. Cattle fed 40DGCT tended to have lower NH3-N emissions compared with cattle fed 40DG [72.7 vs. 95.1 ± 9.3 g N/(steer·d), P = 0.09 and 20.5 vs. 26.5 ± 2.64% N intake, P = 0.11]. Feeding 2.5% CT to beef feedlot cattle fed a high-protein diet had no detrimental effect on performance, reduced PUN indicating lower urinary urea N excretion, and lowered NH3-N emissions by 23%.

Effect of feeding condensed tannins in high protein finishing diets containing corn distillers grains on ruminal fermentation, nutrient digestibility, and route of nitrogen excretion in beef cattle

Eight ruminally cannulated crossbred beef heifers (427 ± 41.2 kg, body weight) were used in a replicated 4 × 4 Latin square to determine the effects of feeding a condensed tannin (CT) extract with high protein diets containing corn dried distillers grains and solubles (DG) on ruminal fermentation, nutrient digestibility, and route of nitrogen (N) excretion. Dietary treatments included [dry matter (DM) basis]: 0 (0DG), 20 (20DG), and 40% DG (40DG), and 40% DG with 2.5% CT extract (1.33% CT) from Acacia mearnsii (40DGCT). The DG and CT extract were substituted for grain in a barley-based diet that contained 91% concentrate and 9% silage (DM basis) and was fed as a total mixed ration once daily. The crude protein concentrations of the diets were 12.9, 16.8, 20.4, and 20.5% for 0DG, 20DG, 40DG, and 40DGCT, respectively. Periods were 5 wk with 2 wk for transition to the DG level of the diets, 1 wk for adaptation to CT, and 2 wk for measurements. Feed offered and refused were measured daily. Total urine and fecal output were collected daily for 4 d consecutively. Data were analyzed using a mixed linear model with diet and period as fixed effects and square and animal within square as random effects. There was no effect (P ≥ 0.22) of CT on DM intake, but 40% DG in the diet (40DG and 40DGCT) decreased (P ≤ 0.015) DM intake compared with 20DG. As a result, nitrogen (N) intake was not different (P > 0.15) among heifers fed 20DG, 40DG, and 40DGCT (313 g N/d) and was less (P ≤ 0.001) for heifers fed 0DG (220 ± 18 g N/d). Apparent total tract N digestibility was less (P ≤ 0.001) in heifers fed 40DGCT (70.6 ± 1.07%) compared with to 0DG, 20DG, and 40DG (78.4%). There was no effect (P = 0.84) of CT (40DGCT vs. 40DG) on the total N output, however, feeding 40DGCT decreased (P ≤ 0.001) the excretion of total urinary N and urea N in urine by 17 and 21%, respectively, compared with heifers fed 40DG and was equivalent (P ≥ 0.12) to the amount excreted by heifers fed 20DG. The reduction of N digestibility reflected the protein binding effects of CT within the gastrointestinal tract and the shift in excess N excretion from labile urea N in urine to bound NDIN and ADIN in feces (P ≤ 0.001) in heifers fed 40DGCT compared with 40DG. Supplementation of CT in high protein diets fed to feedlot cattle reduced urinary N and increased the capture of N in manure to potentially lesson the loss of N as ammonia and provide opportunities for improved nutrient management of beef production.

Recent advances to improve nitrogen efficiency of grain-finishing cattle in North American and Australian feedlots

Formulating diets conservatively for minimum crude-protein (CP) requirements and overfeeding nitrogen (N) is commonplace in grain finishing rations in USA, Canada and Australia. Overfeeding N is considered to be a low-cost and low-risk (to cattle production and health) strategy and is becoming more commonplace in the US with the use of high-N ethanol by-products in finishing diets. However, loss of N from feedlot manure in the form of volatilised ammonia and nitrous oxide, and nitrate contamination of water are of significant environmental concern. Thus, there is a need to improve N-use efficiency of beef cattle production and reduce losses of N to the environment. The most effective approach is to lower N intake of animals through precision feeding, and the application of the metabolisable protein system, including its recent updates to estimation of N supply and recycling. Precision feeding of protein needs to account for variations in the production system, e.g. grain type, liveweight, maturity, use of hormonal growth promotants and β agonists. Opportunities to reduce total N fed to finishing cattle include oscillating supply of dietary CP and reducing supply of CP to better meet cattle requirements (phase feeding).

Simultaneous measurements of ammonia volatilisation and deposition at a beef feedlot

The nitrogen (N) excreted at intensive livestock operations is vulnerable to volatilisation, and, subsequently, may form a source of indirect nitrous oxide (N2O) emissions. The present study simultaneously investigated volatilisation and deposition of N at a beef feedlot, semi-continuously over a 129-day period. These data were examined relative to pen manure parameters, management statistics and emission-inventory calculation protocols. Volatilisation measurements were conducted using a single, heated air-sampling inlet, centrally located in a feedlot pen area, with real time concentration analysis via cavity ring-down spectroscopy and backward Lagrangian stochastic (bLS) modelling. Net deposited mineral-N was determined via two transects of soil-deposition traps, with samples collected and re-deployed every 2 weeks. Total volatilised ammonia amounted to 210 tonnes of NH3-N (127 g/animal.day), suggesting that the inventory volatilisation factor probably underestimated volatilisation in this case (inventory, 30% of excreted N; 65 g N volatilised/animal.day; a value of ~60% of excreted N is indicated). Temperature contrast between the manure and air was observed to play a significant role in the rate of emission (R2 = 0.38; 0.46 Kendall’s tau; P &lt; 0.05). Net deposition within 600 m of the pen boundary represented only 1.7% to 3% of volatilised NH4+-N, between 3.6 and 6.7 tonnes N. Beyond this distance, deposition approached background rates (~0.4 kg N/ha.year).

Corn Forage Yield and Quality for Silage in Short Growing Season Areas of the Canadian Prairies

The development of short-season hybrids has made corn (Zea mays L.) silage (CS) production possible in cooler areas. This work aimed at determining biomass yield and nutritive quality of short-season corn CS hybrids. Six corn hybrids were grown in three years at four locations within the Canadian prairies with four field replications. Hybrids were harvested before occurrence of frost at a target dry matter (DM) content of 300 to 400 g kg−1. Corn heat units (CHU) from seeding to harvesting (CHUseed-harv) and water supply were recorded. Samples were analysed for nutrient content; i.e., DM, neutral detergent fiber (NDF), crude protein (CP), starch, and in vitro DM and NDF digestibilities (48 h incubation). Then, CHUseed-harv, water supply, whole plant DM, CHU rating of the hybrid, and cob percentage were assessed as predictors of nutrient content. Location, hybrid, and year affected nutrient composition and yield. Overall, CP and NDF were positively correlated (r = 0.48, p < 0.01), but both were negatively correlated with DM yield (r = −0.63, −0.28, p < 0.01) and starch (both r = 0.71, p < 0.01). Within and among locations, CHUseed-harv differently affected nutrient composition and DM yield. However, DM yield was the most predictable factor (R2 = 0.86) with CHUseed-harv being the strongest contributor (48%) to the overall variability, followed by water supply (23%). Whole plant DM and CHUseed-harv were also good predictors of starch (R2 = 0.54). This work showed the high variability of biomass yield and nutritive quality of short-season CS hybrids grown in Northern areas.

Effects of encapsulated nitrate on growth performance, carcass characteristics, nitrate residues in tissues, and enteric methane emissions in beef steers: Finishing phase

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 (NO) residues in tissues. The 132 crossbred steers were backgrounded in a feedlot for 91 d and transitioned for 28 days to the high-concentrate diets evaluated in the present study, maintaining the treatment and pen assignments designated at the start of the backgrounding period. 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 (total of 20 animals) were monitored for methane emissions in respiratory chambers twice during the experiment. Pens received 3 dietary treatments (7 pens each): Control, a finishing diet supplemented with urea; 1.25% EN, control diet supplemented with 1.25% encapsulated NO in dietary DM that partially replaced urea; and 2.5% EN, control diet supplemented with 2.5% EN (DM basis) fully replacing urea. The final pen designated only for methane measurement received a fourth dietary treatment, 2.3% UEN, the control diet supplemented with unencapsulated NO (UEN) fully replacing urea. The cattle weighed 449 ± SD 32 kg at the start of the 150-d finishing period. The 2.5% EN diet decreased ( < 0.01) DMI compared with Control and 1.25% EN diets. Feeding EN tended to increase ( = 0.092) ADG compared with Control, and G:F was improved ( < 0.01) for EN compared with Control. No differences in methane production (g/d) and yield (g/kg DMI) were observed among treatments. Inclusion of EN in the diets increased ( ≤ 0.03) sorting in favor of large and medium particles and against small and fine particles. Plasma NO and NO concentrations were elevated ( < 0.01) with EN in a dose-response manner, but total blood methemoglobin levels for all treatments were low, below the detection limit. Feeding EN increased ( < 0.01) NO concentrations of samples from muscle, fat, liver, and kidney; NO concentrations of these tissues were similar between 1.25% EN and 2.3% UEN. In conclusion, inclusion of 2.5% EN in a finishing diet (DM basis; about 2% NO) did not cause NO toxicity or any health problems in the long term. In comparison with supplemental urea, feeding EN improved feed efficiency despite increases in sorting against dietary EN.

Effects of encapsulated nitrate on growth performance, nitrate toxicity, and enteric methane emissions in beef steers: Backgrounding phase

A long-term experiment was conducted to examine the effects of feeding encapsulated nitrate (EN) on growth, enteric methane production, and nitrate (NO) toxicity in beef cattle fed a backgrounding diet. 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; 1.25% EN, control diet supplemented with 1.25% encapsulated calcium ammonium NO (i.e., EN) in dietary DM, which partially replaced urea; or 2.5% EN, control diet supplemented with 2.5% EN (DM basis) fully replacing urea. Additionally, 24 steers were located in 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 calcium ammonium NO (UEN) 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., = 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. Feeding EN had no effect on BW, ADG, and G:F ( ≥ 0.57). Methane production (g/d) tended to decrease ( = 0.099) with EN and UEN, but yield (g/kg DMI) did not differ ( = 0.56) among treatments. Inclusion of EN in the diet increased ( ≤ 0.02) sorting of the diets in favor of large and medium particles and against small and fine particles, resulting in considerable increases in NO concentrations of orts without affecting DMI. Plasma NO-N and NO-N concentrations increased ( ≤ 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% DM; < 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 during a backgrounding phase in the long term without NO 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.

Effect of urea-supplemented diets on the ruminal bacterial and archaeal community composition of finishing bulls

In this study, we evaluated the effects of urea-supplemented diets on the ruminal bacterial and archaeal communities of finishing bulls using sequencing technology. Eighteen bulls were fed a total mixed ration based on maize silage and concentrate (40:60) and randomly allocated to one of three experimental diets: a basal diet with no urea (UC, 0%), a basal diet supplemented with low urea levels (UL, 0.8% dry matter (DM) basis), and a basal diet supplemented with high urea levels (UH, 2% DM basis). All treatments were iso-nitrogenous (14% crude protein, DM basis) and iso-metabolic energetic (ME = 11.3 MJ/kg, DM basis). After a 12-week feeding trial, DNA was isolated from ruminal samples and used for 16S rRNA gene amplicon sequencing. For bacteria, the most abundant phyla were Firmicutes (44.47%) and Bacteroidetes (41.83%), and the dominant genera were Prevotella (13.17%), Succiniclasticum (4.24%), Butyrivibrio (2.36%), and Ruminococcus (1.93%). Urea supplementation had no effect on most phyla (P > 0.05), while there was a decreasing tendency in phylum TM7 with increasing urea levels (P = 0.0914). Compared to UC, UH had lower abundance of genera Butyrivibrio and Coprococcus (P = 0.0092 and P = 0.0222, respectively). For archaea, the most abundant phylum was Euryarchaeota (99.81% of the sequence reads), and the most abundant genus was Methanobrevibacter (90.87% of the sequence reads). UH increased the abundance of genus Methanobrevibacter and Methanobacterium (P = 0.0299 and P = 0.0007, respectively) and decreased the abundance of vadinCA11 (P = 0.0151). These findings suggest that urea-supplemented diets were associated with a shift in archaeal biodiversity and changes in the bacterial community in the rumen.

Effects of Feeding Encapsulated Nitrate to Beef Cattle on Ammonia and Greenhouse Gas Emissions from Their Manure in a Short-Term Manure Storage System

A study was conducted to investigate effects of feeding encapsulated nitrate (EN) to beef cattle on ammonia (NH) and greenhouse gas emissions from their manure. Eight beef heifers were randomly assigned to diets containing 0 (control), 1, 2, or 3% EN (55% forage dry matter; EN replaced encapsulated urea in the control diet and therefore all diets were iso-nitrogenous) in a replicated 4 × 4 Latin square design. Urine and feces collected from individual animals were reconstituted into manure and incubated over 156 h using a steady-state flux chamber system to monitor NH, methane (CH), carbon dioxide (CO), and nitrous oxide (NO) emissions. Urinary, fecal, and manure nitrate (NO)-N concentration linearly increased ( < 0.001) with feeding EN, and urinary urea concentration tended to be lower ( = 0.078) for EN versus Control. The hourly emissions of NH, CO, and NO (mg head h) were not affected, although NH emission rates tended to be lower ( = 0.070) for EN compared with Control at 0 to 12 h. Cumulative NH, CO, and NO emissions over 156 h were not affected, but CH emissions were less (4.5 vs. 7.4 g head; = 0.027) for EN compared with Control. In conclusion, although NH emissions were initially lower for EN manures, total NH emitted over 156 h was not affected. Dietary EN lowered CH emissions from manure, and, despite greater NO concentrations in EN manure, NO emissions were not affected in this short-term incubation.

Mitigation of ammonia, nitrous oxide and methane emissions from manure management chains: a meta-analysis and integrated assessment

Livestock manure contributes considerably to global emissions of ammonia (NH3 ) and greenhouse gases (GHG), especially methane (CH4 ) and nitrous oxide (N2 O). Various measures have been developed to mitigate these emissions, but most of these focus on one specific gas and/or emission source. Here, we present a meta-analysis and integrated assessment of the effects of mitigation measures on NH3 , CH4 and (direct and indirect) N2 O emissions from the whole manure management chain. We analysed the effects of mitigation technologies on NH3 , CH4 and N2 O emissions from individual sources statistically using results of 126 published studies. Whole-chain effects on NH3 and GHG emissions were assessed through scenario analysis. Significant NH3 reduction efficiencies were observed for (i) housing via lowering the dietary crude protein (CP) content (24-65%, compared to the reference situation), for (ii) external slurry storages via acidification (83%) and covers of straw (78%) or artificial films (98%), for (iii) solid manure storages via compaction and covering (61%, compared to composting), and for (iv) manure application through band spreading (55%, compared to surface application), incorporation (70%) and injection (80%). Acidification decreased CH4 emissions from stored slurry by 87%. Significant increases in N2 O emissions were found for straw-covered slurry storages (by two orders of magnitude) and manure injection (by 26-199%). These side-effects of straw covers and slurry injection on N2 O emission were relatively small when considering the total GHG emissions from the manure chain. Lowering the CP content of feed and acidifying slurry are strategies that consistently reduce NH3 and GHG emissions in the whole chain. Other strategies may reduce emissions of a specific gas or emissions source, by which there is a risk of unwanted trade-offs in the manure management chain. Proper farm-scale combinations of mitigation measures are important to minimize impacts of livestock production on global emissions of NH3 and GHG.