Diet Supplementation With Sulfur Amino Acids Modulated Fermentation Metabolome and Gut Microbiome in Goats

Dietary amino acids shift hydrogen metabolism to an alternative hydrogen sink consisting of dissolved hydrogen sulfur (dH2S) rather than methanogenesis; and influences the fermentation metabolome and microbiome associated with particles and liquid fractions in gut regions (foregut, small intestine, and hindgut) of goats. A completely randomized block design with a total of 20 goats (5 goats per treatment) was used to conduct the trial. The goats were fed on a diet that consisted of a concentrated mixture with maize stover roughage (50:50, on a dry matter basis) and randomly assigned to one of the four treatments: without amino acid supplementation (a basal diet), a basal diet supplemented with methionine (Met), a basal diet supplemented with lysine (Lys), and a basal diet supplemented with methionine and lysine (ML). Goats fed Met alone or in combination had less acetate, acetate to propionate ratio, and greater propionate (p < 0.05) in the foregut and hindgut than those fed control or Lys. Nonetheless, the goats fed on the amino acid supplements had higher levels of branched-chain VFA (p < 0.05) in the foregut and hindgut than the control goats. Goats fed on ML had the highest ammonia (p < 0.01), followed by Met or Lys, both in the foregut and hindgut, compared with the control. Those fed on Met alone or in combination, had lower dH2, dCH4 (p < 0.01), and higher dH2S (p < 0.01) in the foregut and hindgut than the control or Lys. The goats that were fed on Met alone or in combination, had higher 16S rRNA gene copies of total bacteria, methanogens, and 18S rRNA gene copies of protozoa, fungi, and fiber-utilizing bacterial species (p < 0.01) associated with particles vs. liquid, both in the foregut and hindgut than the control goats. This study gives insights into the use of sulfur-containing amino acids, as an alternative dietary mitigation strategy of methanogenesis in ruminants and highlights the need for further research in this direction.

Effect of decreasing dietary crude protein in fattening calves on the emission of ammonia and greenhouse gases from manure stored under aerobic and anaerobic conditions

Dietary strategies can potentially help to reduce nitrogen (N) emissions and decrease the environmental impact of beef production. This study aimed to evaluate the effects of dietary crude protein (CP) concentration on animal performance, N excretion, and manure N volatilisation of finishing Holstein animals. In a first study, 105 Holstein bulls (BW 344 ± 2.6 kg; age 252 ± 0.9 days) were allocated to eight pens to evaluate the effect of two treatments (medium (M) and low (L), which contained CP 14.5% and 12% on a DM basis, respectively) on performance, and results confirmed that dietary CP decrease did not impair animal growth. In a second study, N excretion study, 24 Holstein heifers (BW 310 ± 5.3 kg; age 251 ± 1.4 days) were distributed randomly depending on the initial BW to three treatments (high (H), M, and L, which contained CP 17%, 14.5% and 12% on a DM basis, respectively). Based on N excretion, urinary N excretion was greater (P < 0.001) in H than in M and L diets, but no differences in faecal N excretion were observed among treatments. A third study with in vitro assays under aerobic and anaerobic conditions was designed to analyse gaseous emissions (volatilisation of N and carbon, C) during the storage stage of manure. Manure, faecal and urine samples, mixed at a ratio of 1:1 (wet weight), were collected during the N excretion study (manure-H, manure-M, manure-L). Under aerobic conditions, manure-M and manure-L showed a delay of 4-5 days in manure ammonia emission compared with manure-H (P < 0.01). Total N content was lower (P < 0.01) in manure-L compared with manure-M and manure-H, but N volatilisation (percentage relative to initial N) in manure-L and manure-M was greater (P < 0.01) than in manure-H. In contrast, the anaerobic N volatilisation was 20 times greater in manure-M and 10 times greater in manure-H compared with manure-L. Under aerobic and anaerobic conditions, the emission of C, as C-CO₂ and C-CH₄, was greater in manure-L than in manure-H and manure-M. Therefore, the decrease of dietary CP concentration from 17% to 14.5% and 12% is an efficient strategy to reduce urinary N excretion by 40%, without impairing performance, and also to reduce manure N losses through ammonia volatilisation under anaerobic conditions. However, a dietary CP content of 14.5% resulted in less environmental impact than a CP content of 12.8% when also considering manure emissions under aerobic or anaerobic conditions.

Dry Climate Aggravates Riverine Nitrogen Pollution in Australia by Water Volume Reduction

Freshwater is a scarce resource, and maintaining water quality is of great importance in dryland Australia. How water quality is affected by the dry climate and socio-economic influences in Australia remains widely unknown. Here, we find that agriculture activity dominates reactive nitrogen (N_r) emissions to water bodies. Such emissions not only contribute to deteriorating water quality in Southeastern Australia but also harm marine ecosystems, including the Great Barrier Reef, a World Natural Heritage site. A dry and warm climate reduces the share of N_r emitted directly to water bodies; however, it increases the N_r concentration in surface water due to reduced water volume, leading to a 3-fold higher water N_r concentration compared to major rivers globally, e.g., in the US or China. Business-as-usual socioeconomic development would increase the total N_r emitted to surface water by at least 43% by 2050, while effective mitigation measures could reduce N runoff by about 27%. Advanced agricultural management strategies should be considered to reduce future environmental pressures due to N runoff in Australia.

CH4 and N2O Emissions From Cattle Excreta: A Review of Main Drivers and Mitigation Strategies in Grazing Systems

Cattle production systems are an important source of greenhouse gases (GHG) emitted to the atmosphere. Animal manure and managed soils are the most important sources of emissions from livestock after enteric methane. It is estimated that the N2O and CH4 produced in grasslands and manure management systems can contribute up to 25% of the emissions generated at the farm level, and therefore it is important to identify strategies to reduce the fluxes of these gases, especially in grazing systems where mitigation strategies have received less attention. This review describes the main factors that affect the emission of GHG from manure in bovine systems and the main strategies for their mitigation with emphasis on grazing production systems. The emissions of N2O and CH4 are highly variable and depend on multiple factors, which makes it difficult to use strategies that mitigate both gases simultaneously. We found that strategies such as the optimization of the diet, the implementation of silvopastoral systems and other practices with the capacity to improve soil quality and cover, and the use of nitrogen fixing plants are among the practices with more potential to reduce emissions from manure and at the same time contribute to increase carbon capture and improve food production. These strategies can be implemented to reduce the emissions of both gases and, depending on the method used and the production system, the reductions can reach up to 50% of CH4 or N2O emissions from manure according to different studies. However, many research gaps should be addressed in order to obtain such reductions at a larger scale.

Equations to predict nitrogen outputs in manure, urine and faeces from beef cattle fed diets with contrasting crude protein concentration

Accurately predicting nitrogen (N) outputs in manure, urine and faeces from beef cattle is crucial for the realistic assessment of the environmental footprint of beef production and the development of sustainable N mitigation strategies. This study aimed to develop and validate equations for N outputs in manure, urine and faeces for animals under diets with contrasting crude protein (CP) concentrations. Measurements from individual animals (n = 570), including bodyweight, feed intake and chemical composition, and N outputs were (i) analysed as a merged database and also (ii) split into three sub-sets, according to diet CP concentration (low CP, 84-143 g/kg dry matter, n = 190; medium CP, 144-162 g/kg dry matter, n = 190; high CP, 163-217 g/kg dry matter, n = 190). Prediction equations were developed and validated using residual maximum likelihood analysis and mean prediction error (MPE), respectively. In low CP diets the lowest MPE for N outputs in manure, urine and faeces was 0.244, 0.594 and 0.263, respectively; diet CP-specific equations improved accuracy in certain occasions, by 4.9% and 18.3% for manure N output and faeces N output respectively, while a reduction by 5.7% in the prediction accuracy for urinary N output was noticed. In medium CP diets the lowest MPE for N outputs in manure, urine and faeces was 0.227, 0.391 and 0.394, respectively; diet CP-specific equations improved accuracy by 13.2%, 41.2% and 16.8% respectively. In high CP diets the lowest MPE for N outputs in manure, urine and faeces was 0.120, 0.154 and 0.144, respectively; diet CP-specific equations improved accuracy in certain occasions by 5.8%, 9.1% and 6.3% respectively. This study demonstrated that for improved prediction accuracy of N outputs in manure, urine and faeces from beef cattle, the use of dietary CP concentration is essential while dietary starch, fat, and metabolisable energy concentrations can be used to further improve accuracy. In beef cattle fed low CP concentration diets, using diet CP-specific equations improves prediction accuracy when feed intake or dietary CP concentration are not known. However, in beef cattle fed medium or high CP concentration diets, using equations that have been developed from animals fed similar CP concentration diets, substantially improves the prediction accuracy of N outputs in manure, urine and faeces in most cases.

Effects of replacing wet distillers grains with supplemental SoyPass in forage-based growing cattle diets

One hundred twenty individually fed steers (initial BW 283 kg ± 32) were utilized in an 84-d growing trial to evaluate the effects of increased metabolizable lysine from non-enzymatically browned soybean meal (SoyPass) in grass hay-based diets containing wet distillers grains plus solubles (WDGS). The treatments were arranged as a 2 × 3 factorial with two levels of protein supplement as 20% (low; DL20) or 35% (high; DL35) of dietary DM using WDGS as the basal protein source, and three increments of SoyPass (SP) replacing 0%, 30%, or 60% of the WDGS DM in the protein supplement yielding six dietary treatments. Average daily gain (ADG), dry matter intake (DMI), gain:feed (G:F), and plasma urea N (PUN) data were analyzed using the MIXED procedure of SAS as a 2 × 3 factorial. Animal was the experimental unit and fixed effects included body weight block, dietary inclusion of distillers grains (DL20, DL35), dietary inclusion of SoyPass (SP) (3 levels), and DL × SP inclusion interactions. Linear and quadratic interactions between DL and SP inclusion were analyzed using covariate regression. No interactions were detected for ADG between SP and DL (P = 0.76). Additionally, SP had no effect on ADG (P = 0.49). However, ADG was increased for steers consuming the DL35 diet compared to DL20 (1.13 vs. 0.86 kg/d, respectively; P < 0.01). A DL × SP interaction was detected for DMI (P = 0.01). As SP replaced WDGS in the DL35 diet, DMI increased linearly from 8.10 to 8.93 kg/d (P = 0.02). In the DL20 diet, DMI was not different as SP replaced WDGS (P ≥ 0.11). Therefore, G:F tended to decrease linearly (P = 0.06) as SP replaced WDGS in the DL35 diet, while no difference (P ≥ 0.11) was detected in the DL20 diet, suggesting SP contained less energy than WDGS but did improve dietary lysine balance. Furthermore, plasma urea nitrogen (PUN) increased linearly as SP replaced WDGS in the DL20 diet (P < 0.01) but was not affected by SP substitution in the DL35 diet (P ≥ 0.19). When WDGS is fed at a low (20% DM) or high (35% DM) inclusion rate in a forage-based diet, replacing the distillers with a source of protected amino acids supplied through heat-treated soybean meal, did not improve performance. A more concentrated or energy-dense form of amino acids may be beneficial in forage-based growing cattle diets containing 20% distillers grains but is not needed in diets with 35% distillers grains.

Effects of Dietary Tannins’ Supplementation on Growth Performance, Rumen Fermentation, and Enteric Methane Emissions in Beef Cattle: A Meta-Analysis

The environmental sustainability of beef production is a significant concern within the food production system. Tannins (TANs) can be used to minimize the environmental impact of ruminant production because they can improve ruminal fermentation and ruminants’ lifetime performances and mitigate methane (CH4) emissions. The objective of this study was to evaluate the effects of dietary supplementation with TANs as sustainable natural alternative to reduce the environmental impact on growth performance, rumen fermentation, enteric CH4 emissions, and nitrogen (N) use efficiency of beef cattle through a meta-analysis. A comprehensive search of studies published in scientific journals that investigated the effects of TANs’ supplementation on the variables of interest was performed using the Scopus, Web of Science, and PubMed databases. The data analyzed were extracted from 32 peer-reviewed publications. The effects of TANs were assessed using random-effects statistical models to examine the standardized mean difference (SMD) between TANs’ treatments and control (non-TANs). The heterogeneity was explored by meta-regression and subgroup analysis was performed for the covariates that were significant. TANs’ supplementation did not affect weight gain, feed consumption, feed efficiency, or N use efficiency (p > 0.05). However, it reduced the concentration of ammonia nitrogen in rumen (SMD = −0.508, p < 0.001), CH4 emissions per day (SMD = −0.474, p < 0.01) and per unit dry matter intake (SMD = −0.408, p < 0.01), urinary N excretion (SMD = −0.338, p < 0.05), and dry matter digestibility (SMD = −0.589, p < 0.001). Ruminal propionate (SMD = 0.250) and butyrate (SMD = 0.198) concentrations and fecal N excretion (SMD = 0.860) improved in response to TANs’ supplementation (p < 0.05). In conclusion, it is possible to use TANs as a CH4 mitigation strategy without affecting cattle growth rate. In addition, the shift from urinary to fecal N may be beneficial for environment preservation, as urinary N induces more harmful emissions than fecal N. Therefore, the addition of tannins in the diet of beef cattle could be used as a sustainable natural alternative to reduce the environmental impact of beef production.

Effect of Chitosan Inclusion and Dietary Crude Protein Level on Nutrient Intake and Digestibility, Ruminal Fermentation, and N Excretion in Beef Heifers Offered a Grass Silage Based Diet

Nitrogen (N) use efficiency in beef cattle is low (10-20%), resulting in large amounts of N excreted into the environment. The objective of this study was to evaluate the effects of chitosan inclusion and dietary crude protein (CP) level on nutrient intake and digestibility, ruminal fermentation, and N excretion in beef heifers. Eight Belgian Blue × Holstein Friesian cross beef heifers (752 ± 52 kg BW) were used in a 4 × 4 Latin square with a 2 × 2 factorial design. Factors were dietary CP concentration-high CP, 16% (HP) or low CP, 12% (LP)-and chitosan inclusion-0 or 10 g kg^-1 dry matter (DM) offered at 50:50 forage concentrate ratio on a dry matter (DM) basis. Apparent total tract digestibility of DM, organic matter (OM), and CP were reduced (p < 0.001) with chitosan inclusion, whereas offering the HP diets increased apparent total tract digestibility of CP (p < 0.001). Offering the HP diets increased urinary N excretion (p < 0.001), while chitosan inclusion increased N excretion in faeces (p < 0.05). Ruminal pH was increased with chitosan inclusion (p < 0.01). There was a CP × chitosan interaction for rumen ammonia (NH₃) concentrations (p < 0.05). Including chitosan in the HP diets increased ruminal NH₃ concentration while having no effect on the LP diets. Urinary N excretion was increased with increased levels of CP, but chitosan inclusion increased the quantity of N excreted in the faeces.

Effect of Two Nutritional Strategies to Balance Energy and Protein Supply in Fattening Heifers on Performance, Ruminal Metabolism, and Carcass Characteristics

Latin America is an important contributor to the worldwide beef business, but in general, there are limited studies considering strategies to reduce nitrogen contamination in their production systems. The study's goal was to assess the effect of two nutritional strategies to balance energy and protein supply in fattening heifers on performance, ruminal metabolism, and carcass characteristics. A total of 24 crossbred heifers (initial body weight 'BW 'of 372 ± 36 kg) were used to create two blocks (based on live weight) of two pens each, that were equipped with individual feeders. Within each block, half of the animals were assigned to a diet based on tabular Crude Protein (CP) requirements denominated Crude Protein Diet 'CPD' but without a ruminal degradable protein balance. The other half received a diet denominated Metabolizable Protein Diet 'MPD', formulated with the metabolizable protein system, balanced for the ruminal degradable protein. Both diets had the same ingredients and as well as similar synchrony indexes (0.80 and 0.83, respectively). For nitrogen concentration in feces and urine as well as microbial crude protein synthesis, a total of 12 heifers (three per pen) were randomly selected to collect samples. The dataset was analyzed as a randomized complete block design with a 5% significance. No diet × time interaction was observed for Average Daily Gain 'ADG' (p = 0.89), but there was an effect of the time on ADG (p ≤ 0.001). No differences were observed neither for final weight, dry matter intake 'DMI', and feed conversion rate (p > 0.05). Heifers fed with CPD showed greater cold carcass weight (p = 0.041), but without differences in ribeye area, backfat thickness, pH, dressing %, and marbling (p > 0.05). Differences between diets were observed for the in vitro parameters as well as for the Total Volatile Fatty Acids 'VFA' and NH3 (p < 0.05). Total N concentrations (urine + feces) of heifers fed with MDP was lower than in those fed with the CPD (p < 0.01), but no differences were observed in microbial protein, purine derivatives, and creatinine (p > 0.05). We conclude that the combination of synchrony and the metabolizable protein system achieve greater efficiency in the use of nitrogen, without negatively affecting animals' performance or the quality of the carcass.

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).

Critical analysis of excessive utilization of crude protein in ruminants ration: impact on environmental ecosystem and opportunities of supplementation of limiting amino acids-a review

Protein quality plays a key role than quantity in growth, production, and reproduction of ruminants. Application of high concentration of dietary crude protein (CP) did not balance the proportion of these limiting amino acids (AA) at duodenal digesta of high producing dairy cow. Thus, dietary supplementation of rumen-protected AA is recommended to sustain the physiological, productive, and reproductive performance of ruminants. Poor metabolism of high CP diets in rumen excretes excessive nitrogen (N) through urine and feces in the environment. This excretion is usually in the form of nitrous oxide, nitric oxide, nitrate, and ammonia. In addition to producing gases like methane, hydrogen carbon dioxide pollutes and has a potentially negative impact on air, soil, and water quality. Data specify that supplementation of top-limiting AA methionine and lysine (Met + Lys) in ruminants' ration is one of the best approaches to enhance the utilization of feed protein and alleviate negative biohazards of CP in ruminants' ration. In conclusion, many in vivo and in vitro studies were reviewed and reported that low dietary CP with supplemental rumen-protected AA (Met + Lys) showed a good ability to reduce N losses or NH₃. Also, it helps in declining gases emission and decreasing soil or water contamination without negative impacts on animal performance. Finally, further studies are needed on genetic and molecular basis to explain the impact of Met + Lys supplementation on co-occurrence patterns of microbiome of rumen which shine new light on bacteria, methanogen, and protozoal interaction in ruminants.

Effects of twenty percent alkaline-treated corn stover without or with yucca extract on performance and nutrient mass balance of finishing steers fed modified distillers grains-based diets

Two experiments were conducted with 192 steers each (during the winter [November to May] or summer [June to October]) to evaluate 3 diets with or without Yucca schidigera extract in a 3 × 2 factorial on steer growth performance and N mass balance. One factor was diet (DM basis): 1) 5% untreated corn stover, 51% corn, and 40% modified distillers grains plus solubles (MDGS; CON); 2) 20% calcium oxide-treated corn stover (CaO added at 5% of stover DM), 40% MDGS, and 36% corn (TRT); or 3) 20% untreated corn stover, 40% MDGS, and 36% corn (NONTRT). The other factor was dietary extract at 0 (NOYE) or 1.0 g/d per steer (YE). No interaction between diet and YE was detected (P > 0.51) for growth performance and carcass traits in winter and only for DMI in summer. Final BW, ADG, DMI, or G:F were not different (P ≥ 0.28) between cattle fed CON and TRT, whereas cattle fed NONTRT had lesser ADG, HCW, and G:F compared to CON and TRT in the winter experiment. During the summer, final BW and ADG tended to be greater (P ≥ 0.07) for CON compared to TRT. Cattle fed TRT had reduced (P < 0.01) G:F compared to CON. No difference was observed (P ≥ 0.36) between YE and NOYE in the winter experiment for performance or carcass traits. In the summer, cattle fed YE had greater (P < 0.02) HCW, ADG, and DMI compared to NOYE. In the summer experiment, cattle fed YE had greater (P < 0.01) N intake, N excretion, and amount of N lost (kg/steer) compared to NOYE, but no difference (P = 0.33) was observed for percentage of N volatilized (% of excretion). Diet had no effect (P > 0.18) on amount (kg/steer) or percentage of N volatized in the winter or summer. All diets had similar amounts (P > 0.13) of DM and OM removed from the pen surface in both summer and winter. Feeding CaO-treated corn stover as a partial grain replacement had no impact on performance in winter but decreased G:F in summer. Although high-fiber diets increased the amount of OM on pen surfaces, they did not impact N volatilized. Feeding a Y. schidigera extract did not affect N balance or manure characteristics.

Pre-breeding blood urea nitrogen concentration and reproductive performance of Bonsmara heifers within different management systems

This study investigated the association between pre-breeding blood urea nitrogen (BUN) concentration and reproductive performance of beef heifers within different management systems in South Africa. Bonsmara heifers (n = 369) from five herds with different estimated levels of nitrogen intake during the month prior to the commencement of the breeding season were sampled in November and December 2010 to determine BUN concentrations. Body mass, age, body condition score (BCS) and reproductive tract score (RTS) were recorded at study enrolment. Trans-rectal ultrasound and/or palpation was performed 4-8 weeks after a 3-month breeding season to estimate the stage of pregnancy. Days to pregnancy (DTP) was defined as the number of days from the start of the breeding season until the estimated conception date. Logistic regression and Cox proportional hazards survival analysis were performed to estimate the association of pre-breeding BUN concentration with subsequent pregnancy and DTP, respectively. After stratifying for herd and adjusting for age, heifers with relatively higher pre-breeding BUN concentration took longer to become pregnant when compared to those with relatively lower BUN concentration (P = 0.011). In the herd with the highest estimated nitrogen intake (n = 143), heifers with relatively higher BUN were less likely to become pregnant (P = 0.013) and if they did, it was only later during the breeding season (P = 0.017), after adjusting for body mass. These associations were not present in the herd (n = 106) with the lowest estimated nitrogen intake (P > 0.500). It is concluded that Bonsmara heifers with relatively higher pre-breeding BUN concentration, might be at a disadvantage because of this negative impact on reproductive performance, particularly when the production system includes high levels of nitrogen intake.

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

Crossbred beef steers (n = 312) were used in an experiment with a completely randomized design during the growing (235 ± 1.6 kg initial BW) and finishing (363 ± 2.7 kg) phase to determine the effects of dietary CP concentration and rumen degradability on NH3-N emissions, growth performance, and carcass traits. Diets were barley based and consisted of 55% silage and 45% concentrate in the backgrounding phase and 9% silage and 91% concentrate in the finishing phase. For each phase, there were 4 dietary treatments (6 pens of 13 cattle per diet): the basal diet with no protein supplementation (12% CP backgrounding and 12.6% CP finishing) or supplemented (14% CP) with urea (UREA), urea and canola meal (UREA+CM), or urea, corn gluten meal, and xylose-treated soybean meal (UREA+CGM+xSBM). Feed intake and BW of cattle were measured at 3-wk intervals. One pen of steers fed the 12 or 12.6% CP and 1 pen fed 1 of the 14% CP diets were housed in 2 isolated pens to quantify NH3-N emissions using the integrated horizontal flux technique with passive NH3 samplers. In the backgrounding phase final BW, ADG, and G:F were less (P < 0.05) in cattle fed the 12% CP and UREA compared with the UREA+CM and UREA+CGM+xSBM diets. Nitrogen-use efficiency of cattle fed UREA+CM and UREA+CGM+xSBM was equal to that of cattle fed 12% CP and averaged 19.8%. In the finishing phase, there was no effect (P > 0.10) of CP supplementation on BW, DMI, ADG, G:F, N-use efficiency, and carcass traits. The NH3-N emissions from December to February during the backgrounding phase ranged from 4.3 to 25.6 g N/(steer•d) and 3.8 to 16.3% of N intake and from April to July during the finishing phase ranged from 9.7 to 76.4 g N/(steer•d) and 4.4 to 26.7% of N intake. Differences in NH3-N emissions between the pens of cattle fed the backgrounding diets with 12 and 14% CP were not detected. For cattle fed the 12.6 and 14% CP finishing diets, NH3-N emissions tended (P ≤ 0.16) to be less for 2 of the 5 periods and averaged 14.4 and 28.1 g N/(steer•d) and 7.7 and 12.7% of N intake, respectively. The NH3-N emitted as a % of N intake averaged 42% less for cattle fed 12.6% compared with 14% CP. Feeding the barley-based concentrate diet to finishing cattle with 12.6% compared with 14% CP diets reduced NH3-N emissions with no effect on performance. Feeding the barley-based forage diet to backgrounding cattle with 12% CP, however, reduced performance compared with growing cattle fed supplementary degradable and undegradable true protein.

Ammonia emissions from livestock industries in Canada: feasibility of abatement strategies

An updated national ammonia (NH(3)) emissions inventory was employed to study the relationship between NH(3) emissions and livestock industries in Canada. Emissions from animal agriculture accounted for 322kilotonnes (kt) or 64% of Canadian NH(3) emissions in 2002. Cattle and swine accounted for the bulk of livestock emissions. The provinces of Alberta, Ontario, Quebec, and Saskatchewan accounted for 28.1%, 22.0%, 18.7%, and 13.1% of total livestock emissions, respectively. Emissions from Ontario and Quebec were attributed to the intensive production of dairy, hogs and poultry. Dairy cattle emissions per hectolitre of milk were higher in Ontario and Québec than in other provinces, while swine emissions per livestock unit were higher than either beef or dairy cattle. A review of the abatement literature indicated diet manipulation to improve N efficiency and land spreading methods are very effective techniques to lower NH(3) emissions. Future research is required to evaluate the feasibility of biofilters and feces/urine separation methods.