Fecal Nitrogen Excretion Research Articles

Trade-offs between selection of crude protein and tannins in growing lambs.

Tannins are phenolic compounds that provide benefits to ruminants due to their protein-binding affinities and antioxidant properties. However, tannins may also have negative orosensorial and postingestive effects that decrease feed intake. This study explored how lambs trade-off the ingestion of crude protein (CP) with the ingestion of potentially beneficial and toxic condensed and hydrolyzable tannins, and the ensuing impacts on diet digestibility, animal performance, and blood parameters. Thirty-two lambs were housed in individual pens for 8 weeks and had access to two isoenergetic diets that varied in the concentration of CP (High-HP or Low-LP) and the presence of a mix of condensed and hydrolyzable tannins (4% DM). Animals were assigned to 4 treatment groups (N=8 lambs/group) and received a simultaneous offer of: HP and LP (Control); HP and LP+tannins (HP-LP+); HP+tannins and LP (HP+LP-); and both HP and LP with tannins (HP+LP+). All lambs preferred HP over LP and they avoided tannins in the diets (P < 0.001). Dry matter and CP intake were the lowest in HP+LP- (P < 0.0001), and DMD did not differ between Control and the other groups (P > 0.05), but it was greater for HP-LP+ (P < 0.0001). Crude protein digestibility was greater for groups without tannins in HP (P < 0.0001), but ADG did not differ among treatments (P > 0.05). No differences between Control and HP+LP+ were found in plasma antioxidant activity, total phenolic concentration, or haptoglobin concentration (P > 0.05). Intake of tannins was HP+LP+ > HP+LP- > HP-LP+ (P < 0.0001), and fecal excretion of nitrogen (N) was HP+LP+ > HP-LP+ = HP+LP- > Control (P < 0.05). In addition, intake of tannins with both diets reduced blood urea nitrogen (BUN) concentration relative to Control (P < 0.05), thus suggesting a shift in the partitioning of N excretion from urine to feces. In summary, lambs prioritized selection of HP over LP, regardless of the presence of a tannin extract in either or both diets. Nevertheless, lambs modulated their tannin consumption as a function of the specific diet where the tannin extract was added, with increasing levels of intake as tannins were present in just LP, then in just HP, and finally in both diets. Dietary tannins did not constrain ADG and resulted in a shift in the partitioning of N excretion from urine to feces. Such shifts have been found to result in reduced production of environmental pollutants such as ammonia, nitrous oxide, and nitrates.

PSXII-18 Nitrogen balance and ruminal bacterial diversity indexes of Nellore cattle fed with amylolytic and fibrolytic enzymes in feedlot

Abstract This study was carried out to evaluate the use of dietary exogenous enzyme (ENZ) products with amylolytic and fibrolytic activity on nitrogen balance and ruminal alpha and beta diversity of Nellore cattle in feedlot. Rumen cannulated Nellore steers [n = 10; body weigh (BW) = 543 kg ± 28.6 kg] were distributed in a replicate 5 × 5 Latin-square design using individual pens. The treatments consisted of a negative control (CON; without ENZ); Amylase [AML, Amaize, Alltech; 0.5 g/kg of diet dry matter (DM); Xylanase (FBL, Fibrozyme, Alltech; 0.9 g/kg of diet DM]; Half dose (HD; AML 0.25 g/kg of diet DM and FBL 0.45 g/kg of diet DM); and Full dose (FD; AML 0.5 g/kg of diet DM and FBL 0.90 g/kg of diet DM; Table 1). The experimental period lasted 19 d (14 d of adaptation and 5 d of collection). Between d 15 and 18, total urine collection was performed to calculate the nitrogen balance. On d 19 a mixed ruminal sample (6 mL of solid and liquid content) was taken 4 h after feeding and stored at -80 ºC until DNA extraction. Total genomic DNA was extracted using the ZymoBIOMICS DNA Miniprep Kit. The library was prepared using primers for the region V3V4 of the16S rRNA gene; 341F (5’-CCTAYGGGRBGCASCAG-3’) x 806R (5’- GGACTACNNGGGTATCTAAT-3’). The amplicons (~ 470 bp) were sequenced with the Illumina NovaSeq 6000 PE 250 platform. The sequences were analyzed using qiime2 with the SILVA database for the taxonomic assignment. Alpha and beta diversities were calculated in Rstudio using phyloseq. All data were analyzed as orthogonal contrasts assuming treatment as a fixed effect: 1) CON vs. ENZ, 2) AML vs. FBL, 3) HD vs. FD, and 4) AML + FBL vs. HD + FD. Animals that received ENZ had reduced fecal nitrogen excretion (FNE, P = 0.014) and greater efficiency of nitrogen utilization (ENU, P = 0.031) than animals in the CON group. The FBL treatment resulted in greater CP/DOM ratio (P = 0.049), nitrogen balance (P = 0.089), and ENU (P = 0.015) compared with AML treatment. No differences were observed between HD and FD for any nitrogen balance variable (P &amp;gt; 0.10). Animals supplemented with both enzymes (HD + FD) had greater values of N intake (P = 0.018), greater CP/DOM ratio (P = 0.006), and greater FNE (P = 0.002) than animals fed either enzyme alone (AML + FBL). The ENZ supplementation did not impact alpha diversity index or beta diversity (P &amp;gt; 0.10). In conclusion, the addition of exogenous enzymes affected nitrogen balance but not ruminal alpha and beta diversity of Nellore cattle in feedlot.

225 Kidney function and nitrogen excretion in Brown Swiss and Holstein dairy cows

Abstract The agricultural sector contributes to nitrogen (N) emissions since farm animals excrete considerable N amounts via feces and urine. To reduce N emissions by dairy cattle, methods predicting accurately individual N emissions are of great interest. Recent data showed that Brown Swiss (BS) cows have greater urea concentrations in milk and blood than Holstein (HO) cows. However, it is still unknown if greater BUN concentrations in a particular breed are congruently reflected by concomitantly increased contents of nitrogenous compounds in other media (e.g., urine and saliva). Thus, the present study simultaneously assessed biomarkers for kidney function like urea, and creatinine and symmetric dimethylarginine (SDMA) concentrations in several body fluids (i.e., blood, urine, milk, and saliva) as well as nitrogen excretion in feces in BS and HO cows under identical feeding conditions. Blood, saliva, urine, and feces were sampled in 31 multiparous BS and 46 HO cows kept under identical feeding and management conditions. Samples were collected at different lactational stages after the monthly DHIA control test-day. Concentrations of urea and creatinine were measured in serum, urine, and saliva. Symmetric dimethylarginine was determined in serum, which is an established indicator for glomerular filtration rate (GFR). Feces were analyzed for dry matter content and nitrogen concentrations. Data on milk urea and protein concentrations, and daily milk yield were obtained from the monthly DHIA test-day records. The effects of breed, time, and parity number on blood, saliva, urine, feces, and milk parameters were evaluated with the GLM procedure with breed, time, and parity number as fixed effects. Differences between BS and HO were assessed by the Tukey-corrected t-test at P &amp;lt; 0.05. Dry matter intake and body weight were similar in BS and HO cows (P &amp;gt; 0.05). No differences between BS and HO were observed for milk yield, fecal DM and nitrogen content. BS cows showed greater urea concentration (25.8 ± 0.7 vs 21.8 ± 0.7 mg/dL), and protein content in milk (3.70 ± 0.08 vs 3.45 ± 0.07%) than HO cows (P &amp;lt; 0.01). Concentrations of urea, creatinine, and SDMA in serum, were greater in BS than in HO cows (P &amp;lt; 0.01) with 5.46 ± 0.19 vs 4.72 ± 0.13 mmol/L for urea, 105.96 ± 2.23 vs 93.07 ± 1.50 mmol/l creatinine, and 16.78 ± 0.69 vs 13.39 ± 0.44 µg/dL SDMA, respectively. Urea and creatinine concentrations in urine and saliva did not differ among breeds. Despite greater urea and creatinine concentrations in blood, and milk urea content in BS compared with HO, excretion of these parameters did not differ between breeds in urine. Our results suggest a reduced renal glomerular filtration rate in BS compared with HO. The underlying mechanisms require further investigations.

Effect of feeding time and time of harvest of fresh pasture on urinary and faecal nitrogen excretion patterns in sheep

ABSTRACT Under New Zealand grazing systems, a high proportion of the nitrogen consumed by ruminants is excreted. This experiment examined the effect of feeding morning and afternoon harvested annual ryegrass, fed shortly after harvest, on the timing of nitrogen excretion in one-year-old sheep during winter. Dry matter and water-soluble carbohydrate (WSC) content increased in the afternoon-harvested ryegrass. This resulted in increased protein and WSC intakes and a decrease in nitrogen loss in the sheep fed in the afternoon with afternoon-harvested grass. The pattern of urinary nitrogen excretion was related to feeding time with peak urinary urea excretion in the period 4–8 hours after feeding, with over 60% of the daily urinary urea excreted in the 12 hours after the feed was offered. This study suggests that shifting stock onto new pasture breaks in the afternoon could reduce nitrous oxide production by increasing the efficiency of nitrogen utilisation in animals and reducing the total amount of nitrogen excreted. It may be possible to utilise the potential diurnal differences in pasture composition to reduce nitrogen losses. This practise could also improve animal performance as well as change the timing of nitrogen excretion.

Taurine drives body protein renewal and accretion in beef steers

The aims of the present study were to investigate the effects of dietary supplementation with rumen-protected taurine (RPT) on whole-body protein turnover, plasma metabolomics, and whole blood cell transcriptomics in steers. Eight steers, averaging 220 ± 3.26 (mean ± SD) kg of liveweight, were allocated in a replicate 4 × 4 Latin square design. The experimental treatments consisted of four levels of RPT supplementation: 0, 25, 50, and 75 g RPT per day, added to a basal diet. The results showed that supplementation with RPT linearly decreased the fecal nitrogen (N) excretion (P = 0.001) and the 15N fractional recovery rate (P = 0.047), while it linearly increased the urinary excretion of taurine (P = 0.045) as well as the average daily weight gain (P = 0.003), protein synthesis (P < 0.001), protein degradation (P < 0.001) and the whole-body protein turnover (P < 0.001). Supplementation with RPT linearly increased the plasma concentrations of growth hormone (P = 0.005) and quadratically affected the plasma concentration of insulin-like growth factor-1 (P = 0.013), and it linearly decreased the plasma concentration of albumin (P = 0.022). Supplementation with RPT altered the whole blood cell mRNA expression and upregulated the expressions of the marker genes, including RPS6KB1, PRSS42, COL1A2, ENSBTAG00000013055 and ENSBTAG00000038159 which are related to protein metabolism. The plasma metabolome profiling indicated that supplementation with RPT upregulated the plasma concentrations of taurine, lysine and methionine. The experiment revealed the impact and the mechanisms of taurine on driving whole-body protein turnover and protein accretion in steers. Two novel marker genes which could be related to body protein degradation in steers were identified.

Using faecal nitrogen as a marker to estimate intake and digestibility in sheep fed multi-species native forage

Livestock production in southern South America heavily relies on extensive native grasslands, characterized by high plant species diversity, which makes estimating forage digestibility and intake by ruminants in this pastoral ecosystem challenging. Therefore, the aim of this study was to develop regression models to establish the relationship between total faecal nitrogen excretion (FNe) and organic matter (OM) intake, and faecal nitrogen content (FNc) and OM digestibility in sheep fed multi-species native forage. In a completely randomized design, 16 Corriedale sheep averaging 44 kg of body weight (BW) were housed in metabolism cages and received forage in amounts of 15, 20, 25 g of dry matter per kg of BW or ad libitum. During the spring of 2019 and the summer of 2020, four measurement periods were carried out. The sheep had 5 days of adaptation to the metabolism cage, 10 days to adapt to the treatments of amounts of forage offered, and 5 days for intake and digestibility measurements. The forage was harvested once a day, and then the fresh forage was offered at two different times, 8 and 17 h. A linear regression model was developed to estimate OM intake in sheep fed multi-species native forage based on the FNe [Intake (g OM/sheep/day) = 107.7 + 101.5 × FNe]. An exponential regression model was developed to estimate forage OM digestibility in sheep based on the FNc (Digestibility = 0.31411e0.02995 × FNc). In conclusion, our findings highlight that the OM intake can be precisely estimated using FNe and a reasonably precise estimation of the forage OM digestibility can be reached by assessing FNc in sheep fed a multi-species native forage from the Rio de la Plata region in South America.

Evaluation of different ratios of neutral detergent-soluble carbohydrate fractions on performance, ingestive behavior, and nitrogen balance in dairy goats.

Cell components soluble in neutral detergent are a diverse group, both compositionally and nutritionally. The present study aimed to evaluate production responses, behavior (eating, ruminating, and idling), and nitrogen balance of dairy goats fed different ratios of neutral detergent-soluble carbohydrate fractions. Five multiparous Alpine does with mean ± SD initial body mass of 49.5 ± 7.9kg and 60days of lactation were randomly assigned in a 5 × 5 Latin square design. The treatments were the ratios of starch (starch associated with soluble sugar [StSS]) to neutral detergent-soluble fiber (NDSF) (StSS:NDSF): 0.89, 1.05, 1.24, 1.73, and 2.92. No effect was observed (P > 0.05) of StSS:NDSF on the intakes of neutral detergent fiber (NDF) and NDSC. However, DM intake showed a quadratic behavior (P = 0.049). The ingestive behavior was affected by StSS:NDSF linearly increased (P = 0.002) the feeding efficiency. The increase in StSS:NDSF caused a linear increase in fecal (P = 0.011), urinary (P < 0.001), and milk nitrogen excretion (P = 0.024). The increase in StSS:NDSF affected (P = 0.048) milk yield and net energy lactation (P = 0.036). In conclusion, dairy goats experience reduced dry matter intake and milk yield when subjected to high-NDSC diets, specifically those above 1.24 StSS:NDSF ratio. Elevated NDSC levels in the diets lead to decreased feeding time, whereas rumination remains unaffected. Nitrogen losses in goats increase linearly with high-NDSC diets, and a significant impact on nitrogen balance.

Performance and nutrient digestibility of growing pigs fed highly or low fermentable coarse or finely ground fibre-rich feedstuffs

ABSTRACT Dietary fibre is mainly classified according to its chemical characteristics but structure and particle size of fibre-rich feedstuff can also be decisive for digestion and performance. So far, only few studies investigated this in pigs. This experiment aimed to compare coarse and finely ground dried hemp plants and apple pomace regarding performance and ileal and total tract nutrient digestibility of growing pigs. Coarse or finely ground apple pomace or dried hemp plants were added to the diet of 56 nine weeks old growing pigs (DanBred x Duroc), housed in flat decks with each 2 animals. The growing pigs received the experimental diets for three weeks while performance was recorded. Eight pigs per group were sacrificed and digesta and organ tissue sampled. The stomach health was evaluated by visually scoring of the mucosa integrity. Apparent ileal (AID) and total tract digestibility (ATTD) were calculated using titanium dioxide as marker. Statistical analyses were performed using two-way ANOVA (p < 0.05). The highest feed intake (fibre particle size, p = 0.018) and bodyweight gain (fibre particle size, p = 0.018; fibre source x particle size interaction, p = 0.040), was observed in animals fed finely ground apple pomace, while the feed conversion ratio was 8–12% lower in pigs fed finely ground fibre sources (p = 0.012). No differences in stomach mucosa integrity were detected between the groups. The relative pancreas (p = 0.045), stomach (p < 0.001), and jejunum (p = 0.010) weights were higher in animals fed diets containing apple pomace. In contrast, the relative liver, caecum and colon weights were not affected by fibre source or particle size. The AID of protein and amino acids was not affected, while ATTD was increased by fibre source (hemp vs. apple pomace) reducing faecal nitrogen excretion. The AID of calcium was increased when diets contained apple pomace (p < 0.001), while zinc AID and ATTD were enhanced when diets contained dried hemp (p = 0.016; p = 0.016, respectively). Our results suggest that the structure as well as the chemical characteristics should be considered in a future fibre evaluation system in pigs.

145 The effect of a plant secondary metabolite blend on energy metabolism and nutrient balance of beef cattle consuming low-quality warm season grass hay

Abstract Plant secondary metabolites (PSM) such as condensed tannins, hydrolysable tannins, saponins and essential oils purportedly impact rumen fermentation at low inclusion rates in beef cattle diets. Twelve steers (347 ± 23 kg BW) of British and continental influence were allocated to 1 of 4 replicated 3 x 3 Latin squares. Latin squares each had 14 d periods (10 d adaptation and 4 d for sample collection). All cattle were fed ground warm-season hay (89.5% DM, 92.8% OM, 65.9% NDF, 43.6% ADF, 6.70% CP) at 1.5% of BW (DM-basis) and supplemented with soybean meal at 0.18% of BW (DM-basis) once daily. Treatments consisted of a blend of tannins, saponins and essential oils provided at 0% (Control), 0.1% (Low) and 0.3% (High) of hay offering. Treatments were mixed with daily soybean meal allotment and provided before feeding of hay. Urine and feces were completely collected from d 11 through 14 at 0730 h and daily amounts of urine and feces produced were measured gravimetrically. Measures of gaseous exchange were determined via indirect calorimetry on d 13 and 14. Open-circuit respiration calorimeters (91.4 × 91.4 × 191.2 cm) were used to collect respired gas and ruminal methane production. Total oxygen consumption and production of carbon dioxide and methane were calculated from the difference in concentration of oxygen, carbon dioxide, and methane from air exhausted from each calorimeter and concentration of oxygen, carbon dioxide, and methane in ambient air and multiplied by amounts of air flowing from each calorimeter standardized for temperature, pressure, and humidity. Data were analyzed for a Latin square using the MIXED procedure of SAS with fixed effect of treatment, period and square and random effect of steer. Linear and quadratic contrast coefficients were assigned using PROC IML for uneven spacing of treatments. Significance was declared when P ≤ 0.05. Per experimental design, forage N and OM intake did not differ (P ≥ 0.77). Apparent total tract digestion of OM, NDF and ADF did not differ (P ≥ 0.66) among treatments. Fecal nitrogen excretion, and the percentage of N excreted in feces increased linearly (P = 0.01). N balance tended (P = 0.08) to decrease linearly with increasing PSM supplemented. Methane (L/kg DMI) was not affected (P = 0.28) by treatments. Methane, GE, DE, and ME (mcal/kg DMI) was unaffected (P = 0.19) by treatment. Under the conditions of this experiment, a blend of PSM had little effect on rumen fermentation or energy metabolism in beef steers.

Condensed tannins fed to dairy goats: Effects on digestibility, milk production, blood parameters, methane emission, and energy and nitrogen balances

Condensed tannins (CT) are plant polyphenols that can affect feed digestibility and are potentially able to reduce enteric CH4 emissions in ruminants. In this in vivo trial with 8 lactating goats, we investigated the effects of 4 levels of inclusion of a commercial CT extract from quebracho (0%, 2%, 4%, and 6% on dry matter basis; CON, Q2, Q4, and Q6, respectively). The experimental design was a repeated 4 × 4 Latin square with 28-d periods (24 d of diet adaptation and 4 d of sample collection) using metabolic cages and 4 open-circuit respiration chambers. The inclusion of CT in the diets did not affect the dry matter intake (DMI) but caused a linear decrease in diet digestibility, with reductions up to -11% for dry matter, -21% for crude protein (CP), -23% for α-amylase- and sodium sulfite-treated neutral detergent fiber corrected for insoluble ash (aNDFom), and -13% for gross energy, when comparing the Q6 and CON diets. However, ruminal total volatile fatty acids (VFA) concentration was not affected by CT, although there were changes in VFA proportions. Milk yield was highest for Q4 (3,371 g/d) and lowest for Q6 (3,066 g/d). In terms of milk composition, CT induced a linear reduction of fat and CP concentrations. The reduction in CP digestibility resulted in a linear reduction in the milk urea level, up to -37% with Q6. Positively, CT linearly reduced the somatic cells count expressed as linear score. The feed efficiency was linearly decreased by CT inclusion. Furthermore, a shift from urinary to fecal nitrogen excretion was observed with CT. The retained nitrogen was always negative (on average -1.93 g/d). The CH4 yield (on average 19.2 g of CH4/kg DMI) was linearly reduced by CT inclusion, up to -18% with Q6. Regarding the CH4 intensity, CT induced a linear reduction when expressed per kilogram of milk, but not per kilogram of fat and protein-corrected milk. Moreover, the CH4 production per kilogram of digestible aNDFom was linearly increased by CT. The metabolizable energy intake (MEI) was not affected by the treatments, but the metabolizability (q = MEI/gross energy intake) was reduced as CT inclusion increased. From the results of the present study, it turned out that CT have a negative impact on feed digestibility and feed use efficiency. Condensed tannins can lower CH4 emissions from ruminants; however, the main mechanism of action is likely the decrease in feed digestibility. Furthermore, CT did not improve the N use efficiency. According to these findings, the positive environmental impacts of CT are only related to the shift from urinary to fecal N excretion.

УРОВНИ ПРОТЕИНА, АМИНОКИСЛОТ И ИХ СООТНОШЕНИЯ ДЛЯ ПОВЫШЕНИЯ ПРОДУКТИВНОСТИ СВИНЕЙ МЯСНОГО ТИПА

The article presents the results of research when using complete compound feeds with different levels of protein, amino acids and their ratio in the diet of meat-type pigs, which allow to obtain average daily gains during the growing period 442–450 g with feed consumption per unit of increase 3.14–3.19 kg, crude protein – 531–560 g and metabolic energy – 42.7–43.6 MJ accordingly. Compound feeds with low protein levels with the addition of amino acids can reduce the excretion of nitrogen in feces and urine.

Models to predict nitrogen excretion from beef cattle fed a wide range of diets compiled from South America.

The objective of this meta-analysis was to develop and evaluate models for predicting nitrogen (N) excretion in feces, urine, and manure in beef cattle in South America. The study incorporated a total of 1,116 individual observations of N excretion in feces and 939 individual observations of N excretion in feces and in urine (g/d), representing a diverse range of diets, animal genotypes, and management conditions in South America. The datasetalso included data on dry matter intake (DMI; kg/d) and nitrogen intake (NI; g/d), concentrations of dietary components, as well as average daily gain (ADG; g/d) and average body weight (BW; kg). Models were derived using linear mixed-effects regression with a random intercept for the study. Fecal N excretion was positively associated with DMI, NI, nonfibrous carbohydrates, average BW, and ADG and negatively associated with EE and CP concentration in the diet. The univariate model predicting fecal N excretion based on DMI (model 1) performed slightly better than the univariate model, which used NI as a predictor variable (model 2) with a root mean square error (RMSE) of 38.0 vs. 39.2%, the RMSE-observations SD ratio (RSR) of 0.81 vs. 0.84, and concordance correlation coefficient (CCC) of 0.53 vs. 0.50, respectively. Models predicting urinary N excretion were less accurate than those derived to predict fecal N excretion, with an average RMSE of 43.7% vs. 37.0%, respectively. Urinary and manure N excretion were positively associated with DMI, NI, CP, average BW, and ADG and negatively associated with neutral detergent fiber concentration in the diet. As opposed to fecal N excretion, the univariate model predicting urinary N excretion using NI (model 10) performed slightly better than the univariate model using DMI (model 9) as predictor variable with an RMSE of 36.0% vs. 39.7%, RSR 0.85 vs. 0.93, and CCC of 0.43 vs. 0.29, respectively. The models developed in this study are applicable for predicting N excretion in beef cattle across a broad spectrum of dietary compositions and animal genotypes in South America. The univariate model using DMI as a predictor is recommended for fecal N prediction, while the univariate model using NI is recommended for predicting urinary and manure N excretion because the use of more complex models resulted in little to no benefits. However, it may be more useful to consider more complex models that incorporate nutrient intakes and diet composition for decision-making when N excretion is a factor to be considered. Three extant equations evaluated in this study have the potential to be used in tropical conditions typical of South America to predict fecal N excretion with good precision and accuracy. However, none of the extant equations are recommended for predicting urine or manure N excretion because of their high RMSE, and low precision and accuracy.

Predicting nitrogen excretion of cattle kept under tropical and subtropical conditions using semimechanistic models.

The present study aims at evaluating whether current semimechanistic models developed for temperate cattle systems can be adopted for cattle under (sub-) tropical husbandry systems to adequately (accurately and precisely) predict total nitrogen (TN), urine nitrogen (UN), faecal nitrogen (FN) excretion and its partition into different FN fractions. Selected models were built based on the feeding recommendations for ruminants of the British (Model A), German (Model G) and French (INRA; Model I) system. Model evaluation was conducted using eight nitrogen balance studies performed in El Salvador, Kenya and Peru (n = 392 individual observations including lactating cows, heifers and steers). Concordance correlation coefficient, root mean square errors (RMSE), and mean biases were estimated to evaluate the models' adequacy in predicting nitrogen excretion. Input variables causing greatest variation in nitrogen excretion prediction were identified by a sensitivity analysis and adjusted. Model G was able to adequately (i.e., RMSE of <25% of observed mean, systematic error of <5% of the mean square error) predict TN excretion through a compensation between overestimation of UN excretion and underestimation of FN excretion. None of the models were able to adequately predict UN, FN, and different FN fractions. Model I adequately predicted FN (RMSE = 18%) when duodenal microbial crude protein flow was increased, and the intercept used to predict FN excretion was reduced from 4.30 to 3.82 g of nitrogen per kilogram of dry matter intake. These adjustments, however, were not sufficient to predict adequately UN excretion (RMSE = 38%), individual FN fractions (RMSE > 56%), and TN (RMSE = 22%) excretion, by Model I.

PSXI-18 Prediction of Fecal and Urinary Nitrogen Excretion in Growing Pigs Based on the Ingredient Composition

Abstract The objective was to develop prediction models for estimating fecal and urinary nitrogen (N) excretion from growing pigs based on ingredient composition. Ninety-three observations were collected from 23 studies that determined fecal N excretion (ranging from 3.6 to 11.6 g/d) and urinary N excretion (2.5 to 54.7 g/d) from pigs with a mean body weight (BW) ranging from 20 to 105 kg. Average daily feed intake (ADFI; 0.7 to 3.2 kg/d) and ingredient composition data were also collected. Fecal N excretion can be estimated based on the apparent total tract digestibility (ATTD) of N in the ingredients used for a diet. As the NRC (2012) provides only apparent ileal digestibility (AID) of N, the ratio of ATTD of N to AID of N (NATTD:NAID) is essential to accurately estimate fecal N excretion unless ATTD values of N are available. Based on the NATTD values for 93 diets obtained from the 23 studies in the literature, and the NAID values for the same diets calculated using the NAID for each ingredient in the NRC, NATTD:NAID linearly increased with increasing ADFI: NATTD:NAID = 0.088 × ADFI + 0.917 with r² = 0.42 and P &amp;lt; 0.001. To predict urinary N excretion, it is necessary to determine the limiting standardized ileal digestible (SID) indispensable amino acid (IDAA) order and convert the dietary concentrations of the first-limiting SID IDAA expressed as a percentage of the pig's requirement (IDAA1st, %). The SID IDAA requirements in the 23 studies were calculated using the NRC models. The NRC feed ingredient tables were used to calculate total N, SID IDAA, and SID dispensable AA (DAA) in the diet for these studies. Utilized all SID AA can be estimated using the SID AA intake and urinary N excretion. Assuming that all SID IDAA are utilized up to 100% of their requirements when IDAA1st exceeds 100% of the requirement and that all SID IDAA are utilized up to IDAA1st of their requirements when IDAA1st is lower than 100%, the urinary N excretion can be predicted by estimating the ratio of utilized SID IDAA to utilized all SID AA (SID IDAA:SID all AA, %). Based on the urinary N excretion, IDAA1st (12.5 to 170%) and SID IDAA:SID all AA (31.6 to 84.6%) in the 93 diets, a prediction equation for SID IDAA:SID all AA was developed: SID IDAA:SID all AA = 52.0 + 0.510 × (54.7 – IDAA1st) where IDAA1st is less than 54.7%, with R2 = 0.85. Overall, NATTD:NAID increases linearly with an increase in ADFI. When the IDAA1st exceeds 54.7%, the SID IDAA:SID all AA reaches a plateau of 52.0%, corresponding to a SID IDAA:SID DAA of 52:48.

360 Effect of Dietary Protein Levels and Growth Promotants in Dairy-Beef Cross Steers on Nitrogen Utilization Efficiency

Abstract Reducing nitrogen excretion of finishing beef cattle is needed to protect the environment but methods used to decrease nitrogen excretion need to have economic benefits as well. The objective of this experiment was to determine the potential of implant strategy and phase-feeding crude protein (CP) to reduce urinary nitrogen (UN) and fecal nitrogen excretion. Holstein × Angus steers (n = 72) were blocked by body weight (BW) and treatments were randomly assigned to pens (n = 4 per treatment). This experiment was a 2 × 2 factorial design, where cattle were fed a constant CP (control), or the CP content of the diet was reduced every 49 days (phase-fed) and cattle received either an aggressive or moderate implant strategy. All cattle were implanted on d-0 and d-98. Body weight was measured, and blood, urine, and fecal samples were collected on days 0, 49, 98, 147, and at shipping. Phase-feeding CP and implant strategy had no effect (P ≥ 0.47) on dry matter intake or average daily gain. There was a tendency (P = 0.10) for a diet × implant-strategy interaction for feed efficiency, indicating that phase-fed cattle were more efficient with the moderate implant strategy than the aggressive implant strategy. UN excretions decreased (P &amp;lt; 0.01), on day-147 among both implant treatments, indicating that re-implanting on d-98 may have reduced nitrogen excretion. There was a sampling-day × implant interaction (P ≤ 0.03) and a sampling-day × diet interaction (P &amp;lt; 0.01) for blood urea nitrogen concentrations (BUN) and total UN excretion, where BUN and total UN excretion were decreased among the moderate implant and the phase-fed groups on day-147 compared with the aggressive implant and control-fed groups, respectively. Overall, fecal nitrogen concentrations were less for the phase-fed treatment group compared with the control (P ≤ 0.05). These results suggest that phase-feeding CP can be an effective strategy to reduce nitrogen excretion from cattle in the feedlot without negatively affecting performance.

Effects of monensin supplementation on rumen fermentation, methane emissions, nitrogen balance, and metabolic responses of dairy cows: A systematic review and dose-response meta-analysis

To investigate the effects of supplemental monensin administration on the metabolic responses of dairy cows, a systematic review and dose-response meta-analysis were conducted. Initially, 604 studies were identified through comprehensive database searches, including Google Scholar, Scopus, Science Direct, and PubMed, using key words related to dairy cows, monensin, and metabolic outcomes. After a 2-stage screening process, 51 articles with a total of 60 experiments were selected for meta-analysis based on criteria such as study implementation date between 2001 and 2022, presence of a control group that did not receive monensin supplementation, reporting of at least 1 outcome variable, and presentation of means and corresponding errors. The meta-analysis used the 1-stage random-effects method, and sensitivity analyses were performed to assess the robustness of the results. The results showed that the administration of monensin at a dosage of 19 to 26 mg/kg was inversely related to methane emissions and that the administration of monensin at a dosage of 18 to 50 mg/kg resulted in a significant decrease in dry matter intake. Administration of monensin at doses of 13 to 28 and 15 to 24 mg/kg also resulted in a significant decrease in ruminal acetate proportion and an increase in propionate proportion, respectively, with no effects on ruminal butyrate, NH3, or pH levels. We found no effects on blood parameters or nitrogen retention, but a significant negative correlation was observed between monensin supplementation and fecal nitrogen excretion. Based on the analysis of all variables evaluated, the optimal dose range of monensin was estimated to be 19 to 24 mg/kg.

Fecal nitrogen excretion in dairy cows supplemented with feed additive containing active dry yeast

The aim of the study was to determine the fecal excretion of N (TN and NH4 +-N) in dairy cows receiving the feed supplement Biolife® (Eurovix S.p.A., Italy) containing active dry yeast Saccharomyces cerevisiae. Two groups of 14 Holstein cows (B – experimental; C – control) at tie-stalled breeding participated in the experiment. Group B received the feed supplement through the total mixed ration (TMR). Fresh feces samples from both groups were collected on d 7, 14, 21, 28, 35 from the start of supplementation. Mean values of fecal pH and excreted DM did not differ between groups. The concentration of NH4 +-N in the fecal samples of group B was reduced by 28.05%, average for the entire studied period (P&lt;0.05). In the period d 21-35, this reduction was 35% (P=0.095). Excreted TN, averaged over the entire period, was reduced by 16.18% in group B, but the difference was not statistically significant. The reduction of TN content in feces from group B was more pronounced in the period d 21-35, when the reduction was 31.99% compared to group C (P=0.084). A period of at least 14 days is required for adaptation to the supplement and for an occur effect on N excretion.

Lactational performance, rumen fermentation, nutrient use efficiency, enteric methane emissions, and manure greenhouse gas-emitting potential in dairy cows fed a blend of essential oils

The objective of this experiment was to investigate the effects of an essential oil (EO) blend on lactational performance, rumen fermentation, nutrient utilization, blood variables, enteric methane emissions and manure greenhouse gas-emitting potential in dairy cows. A randomized complete block design experiment was conducted with 26 primiparous and 22 multiparous Holstein cows. A 2-wk covariate and a 2-wk adaptation periods preceded a 10-wk experimental period used for data and sample collection. Treatments were: (1) basal diet supplemented with placebo (CON); and (2) basal diet supplemented with a blend of EO containing eugenol and geranyl acetate as main compounds. Supplementation with EO did not affect dry matter intake, milk and energy-corrected milk yields, and feed efficiency of cows, compared with CON. Milk fat and lactose concentrations were increased, and milk total solids (TS) concentration and milk fat yield tended to be increased by EO. Multiparous cows supplemented with EO tended to have slightly decreased dry matter and crude protein digestibility compared with CON multiparous cows. There was a tendency for increased ruminal pH by EO, whereas other rumen fermentation variables did not differ between treatments. Daily methane emission was not affected by EO supplementation, but methane emission intensity per kg of milk fat was decreased by 8.5% by EO. Methane emission intensity per kg of milk lactose and milk TS were decreased and methane emission intensity per kg of milk yield tended to be decreased by up to 10% in EO multiparous cows, but not in primiparous cows. The greenhouse gas-emitting potential of manure was not affected by EO supplementation. Compared with CON, fecal nitrogen excretion was increased by EO supplementation in multiparous, but not in primiparous cows, and milk nitrogen secretion (as a % of nitrogen intake) tended to be increased in EO supplemented cows. Blood variables were not affected by EO supplementation in the current study. Overall, dietary supplementation of EO did not affect lactational performance of the cows, although milk fat and lactose concentrations were increased. Most enteric methane emission metrics were not affected, but EO decreased methane intensity per kg of milk fat by 8.5%, compared with the control.

Effects of dietary niacinamide and CP concentrations on the nitrogen excretion, growth performance, and meat quality of pigs.

Reducing the dietary CP concentration in the formulation of low-protein diets without adverse effects on animal growth performance and meat quality remains challenging. In this study, we investigated the effects of nicotinamide (NAM) on the nitrogen excretion, growth performance, and meat quality of growing-finishing pigs fed low-protein diets. To measure the nitrogen balance, we conducted two trials: in nitrogen balance trial 1, four crossbred (Duroc×Landrace×Large White) barrows (40±0.5kg BW) were used in a 4×4 Latin square design with four diets and periods. The diets consisted of a basal diet+30mg/kg NAM (a control dose), basal diet+90mg/kg NAM, basal diet+210mg/kg NAM, and basal diet+360mg/kg NAM. In nitrogen balance trial 2, another four barrows (40±0.5kg BW) were used in a 4×4 Latin square design. The diets consisted of a basal diet+including 30mg/kg NAM (control), basal diet+360mg/kg NAM, low-protein diet+30mg/kg NAM, and low-protein diet+360mg/kg NAM. To measure growth performance, two trials were conducted. In growth performance trial 1, 40 barrows (37.0±1.0kg) were randomly allocated to one of four dietary treatments (n=10 per group), whereas in growth performance trial 2, 300 barrows (41.4±2.0kg) were randomly allocated to one of four dietary treatments, with each dietary treatment conducted in five repetitions with 15 pigs each. The four diets in the two growth performance trials were similar to those in nitrogen balance trial 2. Supplementing the diet with 210 or 360mg/kg NAM reduced urinary nitrogen excretion and total nitrogen excretion and increased nitrogen retention comparted with the control diet (P<0.05). Compared with the control diet, the low-protein diet with 360mg/kg NAM reduced faecal, urinary, and total nitrogen excretion (P<0.05) without affecting nitrogen retention and average daily gain (P>0.05). Pigs fed the low-protein diet with 360mg/kg NAM showed a decreased intramuscular fat content in the longissimus thoracis muscle when compared with pigs fed the control diet (P>0.05). Our results suggest NAM as a suitable dietary additive to reduce dietary CP concentration, maximise nitrogen retention and growth performance, and decrease fat deposition in pigs.

Effects of taurine on rumen fermentation, nutrient digestion, rumen bacterial community and metabolomics and nitrogen metabolism in beef steers.

The objectives of this study were to investigate the effects of taurine on rumen fermentation, rumen bacterial community and metabolomics, nitrogen metabolism and plasma biochemical parameters in beef steers. Six castrated Simmental steers (liveweight 402 ± 34 kg) and three levels of taurine (0, 20, 40 g d-1 ) were assigned in a replicated 3 × 3 Latin square design. Each experimental period included 15 days for adaptation and 5 days for sampling. Supplementing taurine did not affect the ruminal pH or concentrations of ammonia nitrogen and volatile fatty acids (P > 0.10), but linearly increased the ruminal concentrations of taurine (P < 0.001) and microbial crude protein (P=0.041). Supplementing taurine linearly increased the neutral detergent fiber digestibility (P=0.018), and tended to linearly increase dry matter digestibility (P=0.095), tended to increase the fecal nitrogen excretion (P=0.065) and increased the urinary taurine excretion (P < 0.001). Supplementing taurine quadratically increased the plasma concentration of triglycerides (P=0.017), tended to linearly decrease growth hormone (P=0.074), but did not affect other plasma parameters (P > 0.10). Supplementing taurine modified the rumen bacterial community and increased the ruminal concentration of taurine metabolite 2-hydroxyethoxysulfonic acid (P < 0.001). It was concluded that taurine improved ruminal microbial crude protein synthesis and increased fiber digestibility through modifying rumen bacterial community. It is necessary to clarify the ruminal hydrolysis of taurine in steers. © 2023 Society of Chemical Industry.