Corrigendum: Effect of five hours of mixed exercise on urinary nitrogen excretion in healthy moderate-to-well-trained young adults.

[This corrects the article DOI: 10.3389/fnut.2024.1345922.].

Growth performance and nitrogen excretion of broiler chickens fed low protein diets supplemented with crystalline amino acids.

This study was conducted to determine the effects of amino acid (AA) supplementation in low-protein (LP) diets on growth performance and nitrogen (N) excretion. A total of 175 7-day-old Ross 308 male broilers, with a mean body weight (BW) of 165 g (standard deviation = 11.2 g), were grouped into five blocks by BW and allocated to seven treatments according to a randomized complete block design with five replicate cages at five birds per cage. Dietary treatments comprised a control diet containing 20.0% crude protein (CP) and six LP diets containing either 18.5% or 17.0% CP. These LP diets were supplemented with either no AA supplementation, indispensable AA, or both indispensable and dispensable AA (glutamic acid and glycine). Birds were fed experimental grower diets from day 7 to 21 and then commercial finisher diets until day 28. During the grower period (day 7 to 21), birds fed LP diets supplemented with indispensable AA exhibited greater (p < 0.05) BW, body weight gain (BWG), feed intake (FI), and gain-to-feed ratio (G:F) than birds fed LP diets without crystalline AA and were comparable to birds fed the control diet. During the finisher period (day 21 to 28), birds fed LP diets supplemented with indispensable AA showed greater (p < 0.05) BW than birds fed LP diets without crystalline AA, and their growth performance was comparable to birds fed the control diet. Throughout the overall period, supplementing indispensable AA in LP diets resulted in elevated (p < 0.05) BWG, FI, and G:F more than those of LP diets without crystalline AA and were comparable to those of the control diet. Supplementing indispensable AA in LP diets decreased amount and coefficient of N excretion as much as the control diet. Dispensable AA supplementation in LP diets did not influence growth performance and N excretion. In conclusion, supplementing indispensable AA in LP diets maintains growth performance and N excretion until the dietary CP lowers from 20.0% to 17.0% during the grower period. As long as dietary CP is above 17.0%, dispensable AA may not be deficient in LP diets during the grower period.

Effect of five hours of mixed exercise on urinary nitrogen excretion in healthy moderate-to-well-trained young adults.

Introduction: Carbohydrates and fats are the primary energy substrates during exercise, but proteins can also contribute. When proteins are degraded in the body, the amino groups are mainly converted to urea and excreted. Therefore, nitrogen excretion has been used as a marker of protein degradation, but a clear conclusion has yet to be reached on the effect of exercise on nitrogen excretion. Thus, we tested whether exercise increases nitrogen excretion. Methods: Fifteen young, healthy, moderate-to-well-trained participants (4 females, 11 males, VO2max 54.4 ± 1.7 mL·kg-1·min-1; mean ± SEM) participated in a randomized, balanced cross-over design investigation consisting of 1 day with 5 h of exercise (exercise day, EX) and 1 day with no exercise (control day, CON). The participants recorded their dietary intake the day before from 16:00 and throughout the intervention day. They then repeated these dietary intakes on the second trial day. A standardized lunch was provided on both days. In addition, participants were allowed to consume almost protein-free snacks in EX to ensure the same energy balance during both trial days. Urine was collected throughout the whole testing period, and urinary 3-methylhistidine (3-MH) excretion was measured to examine muscular catabolism. The sweat rate was calculated during the exercise period. Results and discussion: The urinary nitrogen and 3-MH excretions did not differ significantly between EX and CON (p = 0.764 and p = 0.953). The sweat rate was 2.55 ± 0.25 L in EX and 0.14 ± 0.15 L in CON (p < 0.001), and by estimating sweat nitrogen excretion, total nitrogen excretion was shown to differ with exercise. Our results showed that 5 hours of mixed exercise did not significantly impact urinary nitrogen and 3-MH excretions in healthy moderate-to-well-trained young adults.

Gastrointestinal Parasite Infections and Environmental Sustainability of the Ovine Sector: Eimeria spp. Infections and Nitrogen and Phosphorus Excretions in Dairy Sheep in Italy.

In sheep farming, gastrointestinal parasites can be responsible for significant reductions in animal health and production. Nitrogen (N) and phosphorus (P) fecal excretions are the main determining factors for N2O emissions from manure management and may pose other environmental problems, such as the acidification and eutrophication of natural habitats. By using the Mini-FLOTAC technique on fecal samples from sheep of different ages and physiological status from 19 dairy sheep farms in Tuscany (central Italy), gastrointestinal parasite infections were evaluated. The animal N and P fecal contents were also assessed, with the aim of evaluating possible relationships between the identified parasites and the environmental sustainability of the examined farms. The obtained results showed that Eimeria spp. (86.36%) and gastrointestinal strongyle (54.55%) infections are prevalent in the examined farms. Moreover, significantly higher (p ≤ 0.05) P and Eimeria oocyst/gram-of-feces (OPG) values were found in fecal samples from animals < 1 year of age, and a significant (p ≤ 0.05) positive correlation resulted between N content and Eimeria OPG in fecal samples from animals in the first month of lactation. The findings from this study suggest for the first time that Eimeria spp. infections may have an impact on the environmental sustainability of sheep farming.

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 ± 13.0 g/kg DM). This resulted in very low dietary CP concentration, which decreased from 108 to 86 g/kg DM when maize silage in the diet increased from 0 to 51% DM, respectively. DM intake and milk yield both decreased linearly by 3.3 kg/day from 0 to 51% DM of maize silage in the diet. Thus, N intake decreased linearly by 100 g/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 23 g/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 (8 mg/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.

Early onset of urea synthesis and ammonia detoxification pathways in three terrestrially developing frogs.

Frogs evolved terrestrial development multiple times, necessitating mechanisms to avoid ammonia toxicity at early stages. Urea synthesis from ammonia is a key adaptation that reduces water dependence after metamorphosis. We tested for early expression and plasticity of enzymatic mechanisms of ammonia detoxification in three terrestrial-breeding frogs: foam-nest-dwelling larvae of Leptodactylus fragilis (Lf) and arboreal embryos of Hyalinobatrachium fleischmanni (Hf) and Agalychnis callidryas (Ac). Activity of two ornithine-urea cycle (OUC) enzymes, arginase and CPSase, and levels of their products urea and CP in tissues were high in Lf regardless of nest hydration, but reduced in experimental low- vs. high-ammonia environments. High OUC activity in wet and dry nests, comparable to that under experimental high ammonia, suggests terrestrial Lf larvae maintain high capacity for urea excretion regardless of their immediate risk of ammonia toxicity. This may aid survival through unpredictably long waiting periods before rain enables their transition to water. Moderate levels of urea and CP were present in Hf and Ac tissues and enzymatic activities were lower than in Lf. In both species, embryos in drying clutches can hatch and enter the water early, behaviorally avoiding ammonia toxicity. Moreover, glutamine synthetase was active in early stages of all three species, condensing ammonia and glutamate to glutamine as another mechanism of detoxification. Enzyme activity appeared highest in Lf, although substrate and product levels were higher in Ac and Lf. Our results reveal that multiple biochemical mechanisms of ammonia detoxification occur in early life stages of anuran lineages that evolved terrestrial development.

Effect of enzymolytic soybean meal supplementation on performance, nitrogen excretion, serum biochemical parameters and intestinal morphology in broilers fed low-protein diets.

OBJECTIVE: The objective of this study was to investigate the effect of supplementation with enzymolytic soybean meal (ESBM) on broilers fed low crude protein (CP) diets. METHODS: A total of 360 one-day-old broilers were randomly assigned to six treatments with 6 replicates per treatment and 10 chicks per replicate for a period of 42 days. Chicks were fed a basal standard high-CP diet as a positive control (PC), a low-CP diet (reducing 10 g/kg CP from the PC) as a negative control (NC), or an NC + 0.5%, 1.0%, 1.5%, or 2.0% ESBM diet. RESULTS: Compared to chicks fed the PC, chicks fed the NC had a decreased body weight gain (BWG, p<0.05) from 1 to 42 days, but supplementation with 2.0% ESBM restored BWG (p<0.05) and even linearly improved the feed conversion rate (FCR, p<0.05). Digestibility of CP and ether extract was increased (p<0.05) in chicks fed a 1.0% ESBM diet compared to the PC. With increasing levels of ESBM, nitrogen (N) excretion decreased (p<0.05). The addition of ESBM to the diet did not affect (p>0.05) serum concentrations of total protein, albumin and total cholesterol but led to a descending trend in triglycerides and an ascending trend in calcium and urea N at 42 days (p<0.10). There were no differences (p>0.05) in villus height (VH), crypt depth (CD), and VH/CD (V/C) of the duodenum and jejunum between the PC and NC at both 21 days and 42 days, while increasing dietary ESBM levels linearly (p<0.05) decreased CD and increased V/C of the duodenum and jejunum at both 21 days and 42 days. CONCLUSION: The findings indicated that ESBM could be used in broiler low-CP diets to improve production performance, decrease N excretion, and enhance intestinal health.

Effects of dietary protein levels on performance, nitrogen excretion, and odor emission of growing pullets and laying hens.

The objective of this study was to determine the effects of dietary crude protein (CP) levels on production performance, nitrogen balance, and odor emission of excreta in growing pullets and laying hens from 13 to 32 wk of age. Two hundred and forty pullets (Hy-Line Brown) were randomly assigned to 1 of 4 dietary groups with 10 replicates per group, and 6 birds per replicate. Experimental diets were formulated to contain 4 graded CP levels in the diets of pullets ranging from 180, 160, 140, and 120 g/kg of diet during 13 to 18 wk (phase 1) and in the diets of laying hens from 190, 170, 150, and 130 g/kg of diet during 19 to 32 wk (phase 2). The limiting amino acids including lysine, methionine, and threonine were supplemented to maintain constant equal amino acid concentrations in all experiment diets. In phase 1, decreasing dietary CP levels did not affect growth performance but increased (linear and quadratic effect, P < 0.05) the relative abdominal fat contents and triglyceride concentration in serum samples. High-density lipoprotein cholesterol in serum samples decreased as the CP levels decreased in the diets of pullets. Dietary CP levels quadratically increased (P < 0.05) the villus height and the villus height to crypt depth ratio but did not affect tibia traits and relative organ weights in pullets at 18 wk. Apparent digestibility of dry matter and ether extract increased with decreasing dietary CP levels in pullets. Graded CP levels linearly increased the digestibility of dry matter, CP, and ether extracts but lowered that of crude ash in laying hens. Nitrogen excretion was linearly decreased (P < 0.05) as the dietary CP levels decreased in both pullets and laying hens. Dietary CP levels only affected carbon dioxide emission in pullets. In phase 2, dietary CP levels did not affect growth performance and the ages at first egg laying and to reach 50% egg production in laying hens. However, egg weights were decreased (linear and quadratic effect, P < 0.05) as the dietary CP level decreased in laying hens. Increasing dietary CP levels increased Haugh unit at 26 wk but lowered corticosterone concentrations in yolk samples at 22 wk. Collectively, this study shows that dietary CP levels could be decreased to reduce nitrogen excretion without adverse effects on performance and egg quality of growing pullets and laying hens.

Effects of Feeding Low Protein Diets with Different Energy-to-Protein Ratios on Performance, Carcass Characteristics, and Nitrogen Excretion of Broilers.

This study shows the effects of feeding low protein (LP) diets with different energy-to-protein ratios were evaluated on the production parameters, carcass composition, meat quality, nitrogen retention, and excreta composition of broilers. A total of 576-day-old Ross 308 broilers were fed a control diet (C) and three LP diets containing 1.5% less crude protein than diet C for 41 days. The LP1 treatment was isocaloric with diet C, while the dietary apparent metabolizable energy corrected by nitrogen (AMEn) levels in the case of the LP2 and LP3 treatments were reduced by 1.5% and 3%, respectively. The LP diets were supplemented with six crystalline essential amino acids (AA) to meet the standardized ileal digestible AA requirements of broilers. The LP1 treatment did not affect the performance parameters of broilers and increased the breast meat yield, the nitrogen retention and decreased drip loss of breast meat and the total-N and uric acid-N nitrogen excretion of birds in comparison with the C group. Although the energy-reduced LP2 and LP3 diets resulted in lower final body weight, they did not affect the carcass composition, breast meat quality, nitrogen retention, and excreta composition of birds compared with the control treatment.

Meta-Regression to Develop Predictive Equations for Urinary Nitrogen Excretion of Lactating Dairy Cows.

Dairy cows' urinary nitrogen (N) excretion (UN; g/d) represents a significant environmental concern due to their contribution to nitrate leaching, nitrous oxide (a potent greenhouse gas), and ammonia emissions (contributor to N deposition). The first objective of the current study was to determine the adequacy of existing models to predict UN from total mixed ration (TMR)-fed and fresh forage (FF)-fed cows. Next, we aimed to develop equations to predict UN based on animal factors [milk urea nitrogen (MUN; mg/dL) and body weight (BW, kg)] and to explore how these equations are improved when dietary factors, such as diet type, dry matter intake (DMI), or dietary characteristics [neutral detergent fiber (NDF) and crude protein (CP) content], are considered. A dataset was obtained from 51 published experiments composed of 174 treatment means. The whole dataset was used to evaluate the mean and linear biases of three existing equations including diet type as an interaction term; all models had significant linear and mean biases and two of the three models had poor predictive capabilities as indicated by their large relative prediction error (RPE; root mean square error of prediction as a percent of the observed mean). Next, the complete data set was split into training and test sets, which were used to develop and to evaluate new models, respectively. The first model included MUN and BW, and there was a significant interaction between diet type and the coefficients. This model had the worst 1:1 agreement [Lin's concordance correlation coefficient (CCC) = 0.50] and largest RPE (24.7%). Models that included both animal and dietary factors performed the best, and when included in the model, the effect of diet type was no longer significant (p > 0.10). These models all had very good agreement (CCC ≥ 0.86) and relatively low RPE (≤13.1%). This meta-analysis developed precise and accurate equations to predict UN from dairy cows in both confined and pasture-based systems.

Dairy Cows Grazing Plantain-Based Pastures Have Increased Urine Patches and Reduced Urine N Concentration That Potentially Decreases N Leaching from a Pastoral System.

The objective of this study was to determine the effect of grazing plantain-based pastures on urine volume, urination frequency, and urinary nitrogen (UN) concentration of dairy cows under a typical pastoral dairy practice offering approximately 25% supplemented feeds. The experiment was a completely randomised design with three pasture treatments (perennial ryegrass-white clover (RGWC); RGWC + low plantain rate (PLL); and RGWC + high plantain rate (PLH)), five replicate plots, and repeated in two sequential grazing periods. Forty-five lactating Friesian × Jersey cows were randomly assigned into three groups of 15 animals each to graze over six days in adaptation paddocks and three days in experimental plots. Urine flow sensors were used to measure urine volume and urinary frequency, while spot urine sampling was conducted to determine nitrogen (N) concentration in cow urine. The results showed that including 25% plantain in the diet (PLH) increased daily urine volume by 44% and the daily number of urinations by 28%, compared to grazing the RGWC pasture. In addition, N concentration in cow urine was decreased by 18 and 29% when the diet contained 18% and 25% plantain, respectively. In conclusion, under a typical dairy farm practice, incorporating plantain into the RGWC pasture with the proportion of 25% plantain in the diet can increase the number of urine patches and reduce the concentration of N in the urine, thereby providing the opportunity to decrease N leaching from pastoral systems.

Impact of ileal indigestible protein on fecal nitrogen excretion and fecal microbiota may be greater compared with total protein concentration of diets in growing pigs.

In the current study, we hypothesized that an increase in dietary ileal indigestible protein concentration induces an increase in hindgut nitrogen utilization and nitrogen excretion and a shift in fecal microbiota in growing pigs, when compared to pigs given a high total protein diet. Three diets were prepared: 1) standard protein diet based on corn and soybean meal, 2) high-indigestible protein diet in which autoclaved, low-digestible soybean meal replaced soybean meal in the first diet, and 3) high protein diet where the inclusion rate of soybean meal was greater than that of the other diets. The 3 diets were fed to 18 barrows that were fitted with T-cannula at the ileo-cecal junction (initial body weight = 63.4 ±â€…8.0 kg) in a randomized complete block design with body weight as a blocking factor. Pigs were individually housed in pens and the experiment lasted for 23 d. On days 7 and 21, fecal samples were collected by rectal massage for microbiota analysis. Grab samples of feces were collected on days 20 and 21, and ileal digesta were collected on days 22 and 23 for the determination of energy and nitrogen utilization. Lower apparent ileal digestibility of nitrogen in the high-indigestible protein diet containing autoclaved soybean meal resulted in greater ileal indigestible nitrogen concentration (P < 0.05). Apparent total tract digestibility of nitrogen was lower (P < 0.05), and correspondingly nitrogen concentration and daily fecal nitrogen output were greater (P < 0.05) in the high-indigestible protein diet compared with the other diets. Apparent post-ileal digestibility and hindgut disappearance of nitrogen and gross energy were the greatest (P < 0.05) in the high protein diet, whereas a statistical difference was not observed in those variables between the standard protein diet and the high-indigestible protein diet. Beta diversity metrics of feces in the high-indigestible protein diet on day 21 were different (q < 0.05) from those in the other two diets, which indicates a shift in microbial communities. According to the results of the DESeq2, the direction of microbiota shift induced by the high-indigestible protein diet may have reduced fiber utilization in the hindgut. In conclusion, an increase in dietary ileal indigestible protein concentration increased fecal nitrogen excretion and shifted fecal microbial communities but did not increase nitrogen utilization in the hindgut.

Dietary protein concentration has been gradually reduced because reductions in protein concentration in swine diets are known to be beneficial in terms of feed costs, nitrogen excretion, and intestinal microbiota. However, ileal indigestible protein concentration may be more influential in those variables of pigs compared with total protein concentration in diets because ileal indigestible protein considers both protein concentration and digestibility of diets. In the current study, three diets were prepared: 1) corn-soybean meal diet, 2) high-indigestible protein diet replacing soybean meal in the first diet with autoclaved soybean meal, and 3) high protein diet where the inclusion rate of soybean meal was greater than that of the other diets. The experimental diets were fed to cannulated pigs and ileal digesta and fecal samples were collected. Fecal nitrogen output was greater in pigs fed the high-indigestible protein diet. Fecal microbiota was shifted by the high-indigestible protein diet, and this shift may not be beneficial. In conclusion, the impact of changes in ileal indigestible protein on fecal nitrogen excretion and fecal microbiota may be greater compared to changes in total protein concentration of diets in growing pigs.

Amino Acids Supplementation Affects Sustainability of Productive and Meat Quality, Survivability and Nitrogen Pollution of Broiler Chickens during the Early Life.

The response to amino acid (AAs) supplementation on broiler production, carcass and meat traits and nitrogen in the excreta during the early growth period was evaluated. Two experiments were performed during 1-28 d (245 birds, experiment 1) and 1-21 d of age (455 birds, experiment 2). In both experiments, the positive control (PC) diet had 22.5% crude protein (CP) and the negative control group (NC) diet had around 18% CP with the same methionine (Met) plus lysine (Lys) concentration as the PC diet. In experiment 1, the NC diet was fed to the other five groups supplemented with synthetic amino acids, such as L-arginine (Arg), L-threonine (Thr), L-valine (Val), L-isoleucine (Ile) or all these AAs, respectively. In experiment 2, the NC diet was formulated to contain 18% CP with either corn-soybean meal and animal protein or with only vegetable protein. Both NC diets were offered to the other ten groups with synthetic amino acids such as L-Arg, L-Thr, L-Val, L-tryptophan (Trp) or a combination of all these AAs plus L-isoleucine (Ile), respectively. In conclusion, broilers fed 18% CP supplemented with DL-Met plus L-Lys showed lower performance and a European production efficiency value (EPEV); Arg, Thr and Val addition improved growth, the feed conversion ratio and EPEV of the diets containing animal protein only, but broiler performance and EPEV was lower than with PC, indicating that DL-Met, L-Lys, L-Arg, L-Thr and L-Val supplementation may be limited in low-protein diets. Furthermore, a low-protein diet supplemented with amino acids did not affect the survivability of broilers up to 28 days of age.

Interactive effects of high temperature and crude protein levels on growth performance, nitrogen excretion, and fecal characteristics of broilers.

In the present study, we aimed to explore the interactive effects of high temperature (HT) and dietary crude protein (CP) levels on nitrogen (N) excretion, fecal characteristics, and growth performance of broilers. A total of 288 broilers (Arbor Acres) were divided into six groups with eight replicates (six broilers per replicate). Two temperatures (ambient temperature: AT, 23 °C; HT: 28 ~ 32 ~ 28 °C) and three diets (CP: 14.90%, 18.18%, or 21.19%, with equal amounts of essential amino acids) were examined in a 2 × 3 factorial design. The experiment arrangement was from 4 to 6 weeks of age. The results showed that HT led to a significant decrease in the N excretion (P < 0.0001), average daily feed intake (P < 0.0001), and weight gain of broilers (P < 0.0001), while it markedly increased the fecal pH (P = 0.015), fecal moisture (P = 0.0014), uric acid (UA) contents (P = 0.0018), and feed/gain ratio (P < 0.0001). A low CP diet significantly decreased the N excretion (P < 0.001), fecal pH (P = 0.016), fecal moisture (P < 0.0001), and UA contents (P < 0.0001), while it markedly increased the feed/gain ratio (P < 0.001). In conclusion, HT had a negative impact on the fecal characteristics and growth performance of broilers but showed positive effects on N excretion. Moreover, decreased CP levels had a positive effect on the N excretion and fecal characteristics in broilers.

Prediction of nitrogen excretion from data on dairy cows fed a wide range of diets compiled in an intercontinental database: A meta-analysis.

Manure nitrogen (N) from cattle contributes to nitrous oxide and ammonia emissions and nitrate leaching. Measurement of manure N outputs on dairy farms is laborious, expensive, and impractical at large scales; therefore, models are needed to predict N excreted in urine and feces. Building robust prediction models requires extensive data from animals under different management systems worldwide. Thus, the study objectives were (1) to collate an international database of N excretion in feces and urine based on individual lactating dairy cow data from different continents; (2) to determine the suitability of key variables for predicting fecal, urinary, and total manure N excretion; and (3) to develop robust and reliable N excretion prediction models based on individual data from lactating dairy cows consuming various diets. A raw data set was created based on 5,483 individual cow observations, with 5,420 fecal N excretion and 3,621 urine N excretion measurements collected from 162 in vivo experiments conducted by 22 research institutes mostly located in Europe (n = 14) and North America (n = 5). A sequential approach was taken in developing models with increasing complexity by incrementally adding variables that had a significant individual effect on fecal, urinary, or total manure N excretion. Nitrogen excretion was predicted by fitting linear mixed models including experiment as a random effect. Simple models requiring dry matter intake (DMI) or N intake performed better for predicting fecal N excretion than simple models using diet nutrient composition or milk performance parameters. Simple models based on N intake performed better for urinary and total manure N excretion than those based on DMI, but simple models using milk urea N (MUN) and N intake performed even better for urinary N excretion. The full model predicting fecal N excretion had similar performance to simple models based on DMI but included several independent variables (DMI, diet crude protein content, diet neutral detergent fiber content, milk protein), depending on the location, and had root mean square prediction errors as a fraction of the observed mean values of 19.1% for intercontinental, 19.8% for European, and 17.7% for North American data sets. Complex total manure N excretion models based on N intake and MUN led to prediction errors of about 13.0% to 14.0%, which were comparable to models based on N intake alone. Intercepts and slopes of variables in optimal prediction equations developed on intercontinental, European, and North American bases differed from each other, and therefore region-specific models are preferred to predict N excretion. In conclusion, region-specific models that include information on DMI or N intake and MUN are required for good prediction of fecal, urinary, and total manure N excretion. In absence of intake data, region-specific complex equations using easily and routinely measured variables to predict fecal, urinary, or total manure N excretion may be used, but these equations have lower performance than equations based on intake.

Nitrogen excretion from beef cattle fed a wide range of diets compiled in an intercontinental dataset: a meta-analysis.

Manure N from cattle contributes to nitrate leaching, nitrous oxide, and ammonia emissions. Measurement of manure N outputs on commercial beef cattle operations is laborious, expensive, and impractical; therefore, models are needed to predict N excreted in urine and feces. Building robust prediction models requires extensive data from animals under different management systems worldwide. Thus, the study objectives were to 1) collate an international dataset of N excretion in feces and urine based on individual observations from beef cattle; 2) determine the suitability of key variables for predicting fecal, urinary, and total manure N excretion; and 3) develop robust and reliable N excretion prediction models based on individual observation from beef cattle consuming various diets. A meta-analysis based on individual beef data from different experiments was carried out from a raw dataset including 1,004 observations from 33 experiments collected from 5 research institutes in Europe (n = 3), North America (n = 1), and South America (n = 1). A sequential approach was taken in developing models of increasing complexity by incrementally adding significant variables that affected fecal, urinary, or total manure N excretion. Nitrogen excretion was predicted by fitting linear mixed models with experiment as a random effect. Simple models including dry matter intake (DMI) were better at predicting fecal N excretion than those using only dietary nutrient composition or body weight (BW). Simple models based on N intake performed better for urinary and total manure N excretion than those based on DMI. A model including DMI and dietary component concentrations led to the most robust prediction of fecal and urinary N excretion, generating root mean square prediction errors as a percentage of the observed mean values of 25.0% for feces and 25.6% for urine. Complex total manure N excretion models based on BW and dietary component concentrations led to the lowest prediction errors of about 14.6%. In conclusion, several models to predict N excretion already exist, but the ones developed in this study are based on individual observations encompassing larger variability than the previous developed models. In addition, models that include information on DMI or N intake are required for accurate prediction of fecal, urinary, and total manure N excretion. In the absence of intake data, equations have poor performance as compared with equations based on intake and dietary component concentrations.

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.

Nitrogen Excretion by Dairy Cows Grazing Plantain (Plantago lanceolata) Based Pastures during the Lactating Season.

The use of plantain pasture in dairy systems can potentially reduce nitrogen (N) leaching losses via the lower N concentration in the urine (UNc) of cows. Reducing the urinary N load while cows graze pastures can reduce the risk of N leaching losses from urine patches. Research needs to demonstrate that these environmental benefits are not at the expense of milk production and farm profit. Three groups of 20 cows grazed in the following three pasture treatments: (i) plantain, (ii) plantain-clover mix (plantain, red [Trifolium pratense] and white clover), or (iii) ryegrass-white clover (wc) pastures, from spring to autumn for two years. Each year, pasture intake, diet quality, milk production and animal N (milk and urine) excretion were evaluated in spring, summer, and autumn. The cows grazing the plantain and plantain-clover mix pastures produced similar milk solids as cows grazing ryegrass-wc pasture but reduced their UNc during summer and autumn, when compared to those grazing the plantain-clover mix and ryegrass-wc pastures. Plantain reduced urinary N loads onto pastures by a greater number of urine patches with lower urinary N loading rates. The results demonstrate that plantain pastures do not diminish milk solids production from cows, and the lower UNc from summer to autumn could reduce N being lost to the environment.

Effect of supplement crude protein concentration on milk production over the main grazing season and on nitrogen excretion in late-lactation grazing dairy cows.

The objectives of this study are to evaluate the effects of (1) a potential interaction between supplement crude protein (CP) concentration and differing cow genotypes on milk production, (2) differing cow genotypes on milk production, and (3) decreasing the supplement CP concentration on milk production and N excretion during the main grazing season within a spring-calving herd. A 2 × 2 factorial arrangement experiment, with 2 feeding strategies [14%; n = 30 (lower CP; LCP) and 18%; n = 28 (higher CP; HCP) CP concentrate supplements] offered at varying levels according to pasture availability and days in milk (DIM) was conducted over the main grazing season from April 3 to September 3, 2019, at University College Dublin Lyons Farm. Cows were also grouped into 2 genotype groups: lower milk genotype; n = 30 [LM; milk kg predicted transmitting ability (PTA): 45 ± 68.6 (mean ± SD); fat kg PTA: 10 ± 4.9; and protein kg PTA: 7 ± 2.3] and higher milk genotype; n = 28 [HM; milk kg PTA: 203 ± 55.0; fat kg PTA: 13 ± 3.8; and protein kg PTA: 10 ± 2.4]. A total of 46 multiparous and 12 primiparous (total; 58) Holstein Friesian dairy cows were blocked on parity and balanced on DIM, body condition score, and Economic Breeding Index. Cows were offered a basal diet of grazed perennial ryegrass pasture. The N partitioning study took place from August 25 to 30, 2019 (187 ± 15.2 DIM). No interactions were observed for any milk production or milk composition parameter. No effect of supplement CP concentration was observed for any total accumulated milk production, daily milk production, or milk composition parameter measured. The HM cows had increased daily milk yield (+1.9 kg), fat and protein (+0.15 kg), and energy-corrected milk (+1.7 kg), compared with the LM cows. Furthermore, HM cows had decreased milk protein concentration (-0.1%) compared with LM cows. For the N partitioning study, cows offered LCP had increased pasture dry matter intake (PDMI; +0.9 kg/d), dietary N intake (+0.022 kg/d), feces N excretion (+0.016 kg/d), and decreased N partitioning to milk (-2%), and N utilization efficiency (-2.3%). In conclusion, offering cows LCP had no negative influence on milk production or milk composition over the main grazing season where high pasture quality was maintained. However, any potential negative effects of offering LCP on milk production may have been offset by the increased PDMI. Furthermore, offering cows LCP decreased N utilization efficiency due to the higher PDMI and feed N intake associated with cows on this treatment in our study.

Digestibility and nitrogen and water balance in horses fed rhizoma peanut hay.

Rhizoma peanut (RP, Arachis glabrata) hay has the potential to meet horses' crude protein (CP) requirements with less nitrogen excretion than other legumes. This study aimed to evaluate nutrient intake, apparent digestibility, and nitrogen balance of RP "Florigraze" hay compared with alfalfa (ALF, Medicago sativa L. "Legendary XHD") and bermudagrass (BG, Cynodon dactylon L. "Coastal") hays when fed to maintenance horses at 2% body weight/d on a dry matter (DM) basis. We hypothesized that nutrient intake would be comparable between the legume hays and lesser for BG and that RP would result in reduced nitrogen excretion compared with ALF. Six mature Quarter Horse geldings (593 ± 40 kg; mean ± SD) were randomly assigned to one of the hays in a replicated 3 × 3 Latin square with 21-d periods. A 14-d adaptation phase was followed by a 3-d total fecal and urine collection. Days 18 to 21 were used for a companion study. Intake of nutrients is reported on a DM basis. Digestible energy (DE) intakes from ALF (29.91 Mcal/d) and RP (29.37 Mcal/d) were greater (P < 0.0001) than BG (20.78 Mcal/d). CP intake was greater (P < 0.0001) for ALF (2.5 kg/d), followed by RP (1.9 kg/d) and BG (1.5 kg/d). All hays exceeded maintenance requirements for DE, CP, Ca, and P. Apparent digestibility of DM and CP was greatest (P < 0.0001) for ALF (69% and 84%), intermediate for RP (61% and 72%), and least for BG (46% and 64%). Apparent digestibility of neutral detergent fiber did not differ (P = 0.2228) among hays, while digestibility of acid detergent fiber (P = 0.0054) was least for RP but similar for ALF and BG. Water intake (kg/d) for ALF (57) was greater (P = 0.0068) than RP (45) and BG (41). Greater (P = 0.0271) water retention (kg/d) was observed for ALF (13.5), followed by RP (10.8) and BG (7.5). There was a difference in nitrogen excretion, with greatest urinary nitrogen excretion for ALF (P < 0.0001) and greatest fecal nitrogen excretion for BG (P = 0.0001). Total nitrogen excretion was greater (P < 0.0001) for ALF (278 g/d), followed by RP (211 g/d) and BG (179 g/d). Nitrogen retention was greater (P = 0.0005) for ALF when represented as g/d (ALF: 129, RP: 86, and BG: 57 g/d) but similar (P = 0.0377) to RP when presented as percent of nitrogen intake (ALF: 32%, RP: 29%, and BG: 24%). Results indicate that RP hay is a suitable legume for horses by meeting DE and CP requirements and having a significant reduction in nitrogen compared with ALF.