Non-protein Nitrogen Supplementation Research Articles

Effect of dietary nitrogen content and ammonium phosphate inclusion on lysine requirement for nitrogen retention in growing pigs

Inclusion of a source of non-protein nitrogen (NPN) may improve essential amino acid (EAA) and nitrogen (N) utilization in N-limiting diets. Growing barrows (20.4 ± 0.5 kg) were randomly assigned to 1 of 10 dietary treatments ( n = 9 pigs/treatment) in nine blocks. Diets contained no ammonium phosphate (NAP) or 1.7% ammonium phosphate (AP) to have an EAA-N:total N ratio of 0.36 and 0.33, respectively, with graded levels of dietary lysine (Lys; 0.8%, 0.9%, 1.0%, 1.1%, and 1.2% standardized ileal digestible (SID)). Following a 7-day dietary adaptation, a 4-day N-balance collection period was conducted. Blood samples were obtained on day 2 of the collection period. Nitrogen retention (NR) increased and urinary N output decreased with inclusion of NPN and increasing Lys ( P < 0.01). Plasma urea N decreased with increasing Lys ( P < 0.05). Total plasma EAA content was reduced with NPN supplementation ( P < 0.05), while content of Arg, Asp, Gln, and Glu was increased ( P < 0.01). The linear breakpoint model indicated that NR was maximized at 1.00% SID Lys in NAP-fed pigs and at 1.09% SID Lys in AP-fed pigs. These results indicate that diets deficient in dietary N reduce NR and Lys requirement, which were in turn increased with NPN supplementation.

Impact of Supplementing a Backgrounding Diet with Nonprotein Nitrogen on In Vitro Methane Production, Nutrient Digestibility, and Steer Performance.

Two experiments were conducted to evaluate the effect of nonprotein nitrogen (NPN) supplementation on in vitro fermentation and animal performance using a backgrounding diet. In experiment 1, incubations were conducted on three separate days (replicates). Treatments were control (CTL, without NPN), urea (U), urea-biuret (UB), and urea-biuret-nitrate (UBN) mixtures. Except for control, treatments were isonitrogenous using 1% U inclusion as a reference. Ruminal fluid was collected from two Angus-crossbred steers fed a backgrounding diet plus 100g of a UBN mixture for at least 35 d. The concentration of volatile fatty acids (VFA) and ammonia nitrogen (NH3-N), in vitro organic matter digestibility (IVOMD), and total gas and methane (CH4) production were determined at 24h of incubation. In experiment 2, 72 Angus-crossbred yearling steers (303 ± 29kg of body weight [BW]) were stratified by BW and randomly allocated in nine pens (eight animals/pen and three pens/treatment). Steers consumed a backgrounding diet formulated to match the diet used in the in vitro fermentation experiment. Treatments were U, UB, and UBN and were isonitrogenous using 1% U inclusion as a reference. Steers were adapted to the NPN supplementation for 17 d. Then, digestibility evaluation was performed after 13 d of full NPN supplementation for 4 d using 36 steers (12 steers/treatment). After that, steer performance was evaluated for 56 d (24 steers/treatment). In experiment 1, NPN supplementation increased the concentration of NH3-N and VFA (P < 0.01) without affecting the IVOMD (P = 0.48), total gas (P = 0.51), and CH4 production (P = 0.57). Additionally, in vitro fermentation parameters did not differ (P > 0.05) among NPN sources. In experiment 2, NPN supplementation did not change dry matter and nutrient intake (P > 0.05). However, UB and UBN showed lower (P < 0.05) nutrient digestibility than U, except for starch (P = 0.20). Dry matter intake (P = 0.28), average daily gain (P = 0.88), and gain:feed (P = 0.63) did not differ among steers receiving NPN mixtures. In conclusion, tested NPN mixtures have the potential to be included in the backgrounding diets without any apparent negative effects on animal performance and warrant further studies to evaluate other variables to fully assess the response of feeding these novel NPN mixtures.

Non-protein nitrogen supplementation on in vitro fermentation profile, methane production, and microbial nitrogen synthesis in a corn silage-based substrate.

Non-protein nitrogen (NPN) supplements improve animal performance in backgrounding diets. However, there is scarce information regarding the effect of different NPN sources and combinations on ruminal fermentation profile. The current study aimed to evaluate the effect of different NPN sources and their combinations on in vitro fermentation, microbial N synthesis, and methane (CH4) production in a backgrounding diet. Incubations were conducted on three separate days for 24h using corn silage and cotton gin byproduct (70% and 30% of DM, respectively) as substrate. Treatments were control (without NPN), urea, and five different proportions of urea-biuret and nitrate (100:0, 75:25, 50:50, 25:75, and 0:100). Each treatment, except control, was formulated to be isonitrogenous and equivalent to 1% urea inclusion. Ruminal fluid was collected from two ruminally cannulated Angus crossbred steers fed ad libitum corn silage and cotton gin byproduct plus 100g of a urea-biuret-nitrate mixture. The concentration of volatile fatty acids (VFAs) and ammonia nitrogen (NH3-N) were determined at 12 and 24h of incubation. Final pH, in vitro dry and organic matter digestibility, total gas production, and concentration of CH4 were determined at 24h. The supplementation of NPN increased (P < 0.05) the concentration of NH3-N at 12 and 24h. Although NPN supplementation increased (P < 0.05) the concentration of total VFA and acetate at 12h, treatments did not differ (P > 0.05) at 24h. Supplementation of NPN increased (P < 0.05) the proportion of acetate at 12 and 24h but tended to reduce (P = 0.054) the proportion of propionate only at 12h. Digestibility and pH were not different (P > 0.05) among treatments. Increasing nitrates in the NPN supplement increased (P < 0.05) the proportion of acetate and reduced (P < 0.05) the proportion of butyrate at 12 and 24h. The supplementation of NPN increased (P < 0.05) microbial N synthesis. Furthermore, increasing nitrate proportion in the NPN supplement increased (P < 0.05) the microbial N synthesis and efficiency of N use. Supplementation of NPN did not modify (P > 0.05) total gas or CH4 production. However, increasing nitrate proportion in the NPN supplement linearly reduced (P < 0.05) CH4 production. Supplementation of NPN increased NH3-N concentration and microbial N while increasing the inclusion of nitrate decreased the production of CH4 and increased the microbial N synthesis in a corn silage-based substrate under in vitro conditions.

PSII-11 Supplementation of Non-Protein Nitrogen to a Nitrogen-Deficient Diet Increases Lysine Requirement for Nitrogen-Retention

Abstract Low protein (LP) diets have improved nutrient utilization while maintaining animal performance. Regardless, these diets may be limiting in nitrogen (N) content to meet non-essential amino acid (NEAA) requirements, potentially altering essential amino acid (EAA) utilization and requirements. Inclusion of a non-protein nitrogen (NPN) may be beneficial for improving utilization of EAA in LP diets. The objective of this study was to determine the impact of NPN in an N-deficient diet, as indicated by EAA-N:total N ratio (EAA-N:TN) on the Lys requirement for nitrogen retention (NR). A total of 90 growing barrows (initial BW of 20.4 ± 0.46 kg) were randomly assigned to 1 of 10 dietary treatments (n = 9 pigs/treatment) in 9 blocks in a 2 × 5 factorial design. Diets contained no ammonium phosphate (NAP; EAA-N:TN of 0.56) or were supplemented with 1.7% ammonium phosphate (AP; EAA-N:TN of 0.50) with graded levels of dietary lysine [Lys; 0.8%, 0.9%, 1.0%, 1.1% and 1.2% standardized ileal digestible (SID)]. Diets were corn and soybean meal-based and formulated to meet or exceed nutrient requirements according to NRC (2012). Diets were fed at 2.8 × maintenance metabolizable energy requirements in two equal meals per day. A 4-d nitrogen balance collection period was conducted following a 7-d dietary adaptation period. Urine was collected quantitatively, and fresh fecal samples were obtained daily. Nitrogen retention was determined as the difference between N intake and output (fecal and urinary). Linear breakpoint modeling with PROC NLIN was used to estimate Lys requirement. Nitrogen retention was optimized at 1.00% SID Lys (15.6 g/d NR; R2 = 0.68) in pigs fed NAP diets and 1.09% SID Lys (16.4 g/d NR; R2 = 0.61) in pigs fed AP diets. Overall, deficient dietary N reduced NR and Lys requirement, which were increased with NPN supplementation.

Effects of Sodium Nitrate and Coated Methionine on Lactation Performance, Rumen Fermentation Characteristics, Amino Acid Metabolism, and Microbial Communities in Lactating Buffaloes.

Sodium nitrate is used as a non-protein nitrogen supplement while methionine is considered as a common methionine additive for ruminants. This study investigated the effects of sodium nitrate and coated methionine supplementation on milk yield, milk composition, rumen fermentation parameters, amino acid composition, and rumen microbial communities in lactating buffaloes. Forty mid-lactation multiparous Murrah buffaloes within the initial days in milk (DIM) = 180.83 ± 56.78 d, milk yield = 7.63 ± 0.19 kg, body weight = 645 ± 25 kg were selected and randomly allocated into four groups (N = 10). All of animals received the same total mixed ratio (TMR) diet. Furthermore, the groups were divided into the control group (CON), 70 g/d sodium nitrate group (SN), 15 g/d palmitate coated L-methionine group (MET), and 70 g/d sodium nitrate +15 g/d palmitate coated L-methionine group (SN+MET). The experiment lasted for six weeks, including two weeks of adaption. The results showed that most rumen-free amino acids, total essential amino acids, and total amino acids in Group SN increased (p < 0.05), while the dry matter intake (DMI) and rumen acetate, propionate, valerate, and total volatile fatty acids (TVFA) in Group MET decreased (p < 0.05). However, there was no significant difference in milk yield, milk protein, milk fat, lactose, total solid content, and sodium nitrate residue in milk among groups (p > 0.05). Group SN+MET had a decreased rumen propionate and valerate (p < 0.05), while increasing the Ace, Chao, and Simpson indices of alpha diversity of rumen bacteria. Proteobacteria and Actinobacteriota were significantly increased (p < 0.05) in Group SN+MET, but Bacteroidota, and Spirochaetota were decreased (p < 0.05). In addition, Group SN+MET also increased the relative abundance of Acinetobacter, Lactococcus, Microbacterium, Chryseobacterium, and Klebsiella, which were positively correlated with cysteine and negatively correlated with rumen acetate, propionate, valerate, and TVFA. Rikenellaceae_RC9_gut_group was identified as a biomarker in Group SN. Norank_f__UCG-011 was identified as a biomarker in Group MET. Acinetobacter, Kurthia, Bacillus, and Corynebacterium were identified as biomarkers in Group SN+MET. In conclusion, sodium nitrate increased rumen free amino acids, while methionine decreased dry matter intake (DMI) and rumen volatile fatty acids. The combined use of sodium nitrate and methionine enriched the species abundance of microorganisms in the rumen and affected the composition of microorganisms in the rumen. However, sodium nitrate, methionine, and their combination had no significant effect on the milk yield and milk composition. It was suggested that the combined use of sodium nitrate and methionine in buffalo production was more beneficial.

Utilization of tannin from chestnut as a protective agent in slow release urea: An in vitro rumen fermentation study

Urea has been utilized as a non-protein nitrogen supplement for ruminants due to its affordable price, abundantly available, easy to use, and positively affect microbial protein synthesis in the rumen. However, urea have a weakness since it is rapidly converted into ammonia in the rumen and may lead to nitrogen loss and even ammonia toxicity. Development of a slow release urea (SRU) is therefore important in order to overcome such potential negative impacts. This experiment was conducted to evaluate the effects of SRU, made by complexing the urea with tannin from chestnut, on in vitro rumen fermentation parameters. The treatments were the addition of different forms and levels of urea into a basal diet, i.e., 1% conventional urea (T0), 1% SRU (T1), 2% SRU (T2), and 3% SRU (T3). Data were analyzed by using analysis of variance and continued with a post-hoc test namely the Tukey’s test. Results revealed that the SRU treatments (T1-T3) reduced (P<0.05) ruminal ammonia concentration at various time point intervals than that of the conventional urea (T0). However, the SRU did not alter microbial protein synthesis and nutrient digestibility. In conclusion, SRU made from tannin is an effective supplement for enhancing nitrogen utilization in the rumen.

O96 Non-protein nitrogen supplementation in corn silage-based diets for backgrounding beef cattle

O96 Non-protein nitrogen supplementation in corn silage-based diets for backgrounding beef cattle

Utilization of dragon fruit waste by-products and non-protein nitrogen source: Effects on in vitro rumen fermentation, nutrients degradability and methane production

ABSTRACT Tropical plant phytonutrients have impacts on rumen fermentation and methane production. Dragon fruit peel powder (DFPP) including condensed tannins (CT) and saponins (SP). The objective was to conduct the effects of phytonutrients and non-protein nitrogen (NPN) source on in vitro rumen fermentation, nutrients degradability and methane production. The treatments were randomly assigned in a 2 × 3 × 3 factorial arrangement in a Completely randomized design. The three factors contains the R:C ratio (60:40 and 40:60), the doses of NPN addition (0, 1 and 2% of the total substrate) and the doses of DFPP addition (0, 2 and 4% of total substrate). The results indicated that the gas production rate constant for the insoluble fraction (c) was highly significant as the results of the R:C ratio, DFPP and NPN supplementation, whilst there was no difference obtained among treatments for cumulative gas production. Ammonia nitrogen concentration was influenced by the R:C ratio, NPN and DFPP addition both 4 and 8 h after incubation. In part of microbial population, protozoa was significantly reduced with DFPP addition. Importantly, the production of methane was remarkably affected by the R:C ratios and it was decreased due to increasing level of DFPP. Furthermore, in vitro dry matter degradability (IVDMD) was significantly improved by combination between R:C ratio and supplementation of DFPP at 12 h. In conclusion, addition of DFPP and NPN source could improve rumen fermentation, nutrients degradability and DFPP would be a potential dietary rumen enhancer.

The effect of molasses nitrate lick blocks on supplement intake, bodyweight, condition score, blood methaemoglobin concentration and herd scale methane emissions in Bos indicus cows grazing poor quality forage

Context The Australian government has approved a greenhouse gas (GHG) offset method that requires cattle to consume nitrate in the form of a lick block. Field studies demonstrating the effectiveness of this methodology have not been previously reported. Aims This experiment was conducted to determine the effects on productivity and health when nitrate lick blocks were provided as a supplement to grazing beef cattle. We hypothesised that beef cattle given access to nitrate lick blocks would have similar productivity compared with cattle offered urea lick blocks. Methods Bos indicus breeding cows (n = 76) grazed a 467-ha paddock near Charters Towers, Queensland, between May and November 2014. A two-way remote automatic drafting system enabled allocation of cattle to different treatments while grazing in a common paddock. Treatments were 30% urea lick blocks (30U), or molasses nitrate lick blocks (MNB). At monthly intervals liveweight (LW), body condition score (BCS), and blood methaemoglobin concentration were recorded. Estimates of individual supplement intake were made on three separate occasions using a lithium marker technique. Results Mean daily supplement intake (±s.e.m.) of 30U (122 ± 13 g) was greater (P &amp;lt; 0.001) than MNB (67 ± 8 g). Lesser MNB intake was associated with greater variability for individual supplement intake, a greater proportion of non-consumers of supplement during July (P &amp;lt; 0.05) and reduced voluntary supplement intake until October (P &amp;lt; 0.001). Increasing MNB consumption during October and November was accompanied by elevated blood methaemoglobin concentration (P &amp;lt; 0.001). It was estimated that cattle offered MNB had insufficient supplementary nitrogen intake throughout the study to resolve rumen degradable nitrogen deficiency from grazed forage. Consequently, cattle provided access to MNB demonstrated conceptus free liveweight loss and lesser BCS compared with cattle treated with 30U (P &amp;lt; 0.001). Conclusion Nitrate lick blocks were ineffective as a dual-purpose non-protein nitrogen supplement and methane mitigant for beef cattle grazing poor quality forage. Further field experiments are required to determine if there may be situations where this GHG offset methodology is efficacious. Implications Caution is advised in implementing GHG mitigation methods that involve the use of nitrate lick blocks.

Nitrate is safe to feed ad libitum in molasses roller drums as a source of non-protein nitrogen

We investigated voluntary intake, growth and safety of cattle offered low-quality forage diets plus isonitrogenous molasses-based liquid supplements containing either urea (U) or a calcium nitrate-containing compound (NO3). We hypothesised that changing the nitrogen source from U to calcium nitrate would not jeopardise animal health or affect intake. Angus cattle (n = 24) were allocated to six pens, with three pens each receiving a molasses supplement containing U or a molasses supplement containing NO3 for 31 days. There was a trend (P = 0.06) for the NO3 treatment group to consume more of the (oaten chaff) basal diet than the U treatment group. The U group consumed more supplement than did the NO3 group (1.31 vs 0.40 kg DM/head.day s.e.m. = 0.094, P &amp;lt; 0.0001), but total DM intake was not different (6.45 vs 6.10 kg/head.day, P = 0.15). Mean final animal liveweight was not different between treatments. Methaemoglobin levels were higher in the NO3 group (2.1 vs 1.3%, P &amp;lt; 0.001). Low consumption of nitrate was also reflected in there being no effect of nitrate on the methane production rate when assessed in open-circuit calorimetry chambers (7.1 vs 7.0 g/head.2 h, P = 0.898). It is confirmed that nitrate may be safely provided to cattle when dissolved at 154 g/kg in a molasses-based liquid supplement available ad libitum, but may not be an effective methane mitigant due to low NO3 intake. It is speculated that nitrate may be a useful tool to limit voluntary intake of non-protein nitrogen supplements.

In vitro evaluation of Niacin Supplementation on Total Mixed Rations with Different NPN Sources

The present was aimed to study the effect of varying levels of niacin supplementation (0, 200, 400 and 600ppm, respectively) on medium urea based total mixed ration (TMR) replacing 20% of total crude protein (CP) of ration with different non protein nitrogen (NPN) sources by in vitro gas production technique. All the rations were iso-nitrogeneous in nature. On the basis of higher partition factor, TD%, OMD%, microbial mass production and efficiency of microbial mass production. Supplementation of niacin in low urea based TMR did not have any significant effect on microbial mass production and its efficiency. The in vitro pH and NH3 concentration was significantly reduced (p<0.05) at 600 ppm level of niacin supplementation. The TVFA concentration was significantly comparable in control and urea based TMR and lowest in uromol based TMR. Niacin supplementation produced significantly higher (p<0.05) TVFA at 400 ppm level and lowest at 600 ppm in TMR. It can be concluded that slow release urea seems to be better option than urea and uromol as NPN supplement in the diets of ruminants when medium (20% of total CP) urea based TMR is to be prepared.

Effect of Graded Levels of Niacin Supplementation on Total Mixed Ration Containing Different Non-Protein Nitrogen Sourcesin vitro

The present study was undertaken to study the effect of varying levels of niacin supplementation(0, 200, 400 and 600 ppm, respectively) on low urea based total mixed ration (TMR)replacing 10% of total crude protein (CP) of ration with different non protein nitrogen (NPN) sources by in vitro gas production technique. All the rations were iso-nitrogeneous in nature. On the basis of higher partition factor, neutral detergent fibre degradability (NDFD%), organic matter degradability (OMD%), microbial mass production and efficiency of microbial mass productionfrom different NPN sources. Supplementation of varying levels of niacin in low urea based TMR did not have any significant effect on microbial mass production and its efficiency. The in vitro pH and NH3 concentration was significantly (P<0.05) reduced at 600ppm level of niacin supplementation. The total volatile fatty acids (TVFA) concentration was significantly higher (P<0.05) in control TMR and lowest in uromol based TMR. Niacin supplementation produced significantly higher (P<0.05) TVFA at 200ppm level and lowest (P<0.05) at 600ppm in TMR. It can be concluded that slow release urea seems to be better option than urea and uromol as NPN supplement in the diets of ruminants when low (10% of total CP) urea based TMR is to be prepared.

Fructose 1,6-bisphosphatase and aldolase B location in organs of sheep supplemented with nonprotein nitrogen

In ruminants, ammonia interferes in gluconeogenesis, reducing conversion of propionate to glucose. The importance of renal and hepatic gluconeogenesis in ruminants is well established, but cellular localization of the key gluconeogenic enzymes liver fructose-1,6-bisphosphatase (FBPase, EC.3.1.3.11) and aldolase B (AldoB, EC.4.1.2.13) in these organs and the potential contribution of other tissues in this process have not been investigated. The objective of this study was to determine the effect of nonprotein nitrogen (NPN) diets on the cellular localization of FBPase and AldoB in sheep organs. Eighteen sheep, allotted to three groups, were supplemented with NPN in the diet every 8 h for 18 days: Control (no NPN, 16.8 % crude protein (CP)), moderate NPN = 182 mg N/kg0.75 (22.9 % CP), and high NPN = 425 mg N/kg0.75 (30.7 % CP). Animals were slaughtered and pieces of organs were collected. Immunostaining for FBPase and AldoB expressions were examined by light microscopy, and co-localizations of these enzymes were examined with a confocal microscope. FBPase and AldoB were expressed in the cytoplasm of periportal hepatocytes, proximal tubular cells of the kidney, columnar absorptive cells of the duodenum, submucosa of the rumen, and β cells of Langerhans’ islets in the pancreas. Moreover, AldoB revealed to be located in the nucleus of hepatocytes. The localizations of both enzymes were not modified by NPN supplementation. In conclusion, FBPase and AldoB were detected in sheep tissues other than the liver and kidney, suggesting their potential contribution to gluconeogenesis or other functions in these tissues and their expressions were not changed by the inclusion of NPN in the diet.

Non-protein nitrogen supplementation increases gluconeogenic capacity in sheep

The effect of non-protein nitrogen (NPN) supplementation on the gluconeogenic capacity of sheep was investigated. Three groups of six sheep each, control, moderate (MN=0.55gN/kg0.75/d) and high (HN=1.28gN/kg0.75/d) NPN were used. A propionate loading test (PLT) was performed in each animal after 7 or 15 days of NPN supplementation by infusing a bolus of sodium propionate, and plasma glucose, urea, lactate and insulin concentrations were measured up to 88min after infusion. Liver glycogen concentration and the activity of gluconeogenic enzymes and complementary ureagenic enzymes were determined at 9 or 17 days of the supplementation period. Glycemia and lactacidemia increased during the PLT in all groups, being highest in HN sheep. Liver activity of PEPCK was higher in HN than in the control sheep. NPN supplementation in sheep increased plasma urea and lactate concentrations and liver PEPCK activity associated to an increased gluconeogenic capacity from propionate or lower peripheral glucose utilization.

Consumo e digestibilidade de feno de baixa qualidade suplementado com nitrogênio não protéico em bovinos

O objetivo deste trabalho foi avaliar o efeito de níveis de inclusão de nitrogênio não protéico, em suplementos fornecidos a tourinhos Hereford, com 17 meses e peso médio de 220 kg, alimentados com feno de tifton (Cynodon dactylon) ad libitum. Os tratamentos avaliados foram: feno + suplemento sem uréia; feno + suplemento com 0,28 g de uréia kg-1 PV0,75; feno + suplemento com 0,55 g de uréia kg-1 PV0,75; feno + suplemento com 0,83 g de uréia kg-1 PV0,75 e feno + suplemento com 1,11 g de uréia kg-1 PV0,75. O feno apresentou, na média, 3,86% de proteína bruta e 84,66% de fibra em detergente neutro. Não se constatou efeito da suplementação sobre a digestibilidade da matéria orgânica, matéria orgânica do feno, fibra em detergente neutro, celulose e hemicelulose; o consumo total desses itens respondeu quadraticamente à suplementação com níveis crescentes de nitrogênio não protéico. A suplementação não afetou a excreção fecal metabólica de matéria orgânica, o que sugere aumento na taxa de passagem (variação no consumo) e na taxa de digestão (digestibilidade constante). O consumo de matéria orgânica digestível apresentou comportamento quadrático com aumento dos níveis de uréia na dieta. Quando o nível de proteína degradável no rúmen foi equivalente a 8,1% da matéria orgânica digestível, a relação de consumo entre esses componentes foi otimizada.

Impact of non-protein nitrogen supplements on nematode infected sheep

Inadequate nutrition and gastrointestinal nematode parasitism are major constraints to livestock production. In livestock rearing enterprises that rely on low quality roughage for the provision of digestible carbohydrate, the most critical nutritional deficiency is often nitrogen. The provision of non-protein nitrogen in the diet can compensate for this deficiency and enable increased productivity from the available feed resource. Numerous studies have shown that increasing the supply of protein for intestinal absorption can alleviate the detrimental effects of nematode parasites on production and can also result in improved protective immunological responses to infection. In many situations, the practical implementation of such a strategy for improved nematode parasite control is hampered by the high cost and/or unavailability of high quality protein sources for use as ruminant livestock feed. Evidence is presented from studies with young sheep to demonstrate that supplementation with urea can achieve similar qualitative benefits in reducing the effects and level of infection with parasitic nematodes to that achieved with protein supplements. Urea–molasses blocks are a popular low-cost means of delivering non-protein nitrogen and experimental evidence shows that the use of urea–molasses blocks can have a beneficial impact on enhancing the resilience and resistance of sheep to infection with nematode parasites. Consistent with other nutritional studies, urea appeared to confer increased benefits proportional to increasing supplement intake as shown by reduced pathological effects, parasite numbers and faecal egg output. It is suggested that application of these findings in Australian pasture systems may require revision of current systems for the delivery of non-protein nitrogen supplements to increase the level of urea consumed.

The potential of isobutyraldehyde monourea (propanal, 2-methyl-monourea) as a nonprotein nitrogen source for ruminant animals

Experiments were earned out with sheep and in vitro to evaluate isobutyraldehyde monourea (IBMU; propanal-2-methyl-monourea) as a slow-release nitrogen source for ruminant animals. Examination of the compound for carbon, hydrogen, and nitrogen composition and infrared, NMR and mass spectral analyses indicated that IBMU was present in significant amounts. Ten sheep were randomly assigned to diets containing bromegrass hay and corn grain and the following nitrogen supplementation treatments: (1) control, (2) urea, (3) soybean meal, (4) canola meal and (5) IBMU, with the protein supplements providing approximately 25% of the nitrogen intake. Similar treatments were also prepared and evaluated in vitro, with the exception that wheat straw rather than bromegrass hay was used in the incubation. The digestibility of nitrogen in the ration containing IBMU was higher (P &lt; 0.05) than its digestibility in the other rations when measurements were conducted with sheep over three 14-d periods. No differences in dry matter (DM) or energy digestibility were detected between the different treatments. The digestible energy content of IBMU was estimated to be greater than 21 MJ kg−1. The digestibilities of DM in vitro after 2, 4, 8, 12, 24, 48 and 72 h of incubation were not influenced by the presence of IBMU. No influence of nitrogen supplementation on nitrogen balance was observed, probably because of the high protein content of the control ration (10.6%). IBMU exhibited the characteristics of an ideal slow-release nonprotein nitrogen supplement, since concentrations of rumen ammonia nitrogen did not vary from 0 to 8 h after feeding and ammonia concentrations were higher (P &lt; 0.05) both before feeding and 8 h after feeding when IBMU was fed than when any of the other supplements were fed. The concentration of isobutyric acid averaged 2.6-fold higher when IBMU was fed than when canola meal or soybean meal was fed, confirming that most of the compound was degraded in the rumen. Sheep fed IBMU had lower concentrations of acetic, propionic and butyric acid in the rumen than those fed natural protein supplements. It was unclear whether the decrease in VFA concentration was positive or negative in terms of nutritional value. It was concluded that IBMU exhibited some ideal characteristics for a nonprotein nitrogen supplement for ruminant animals because it was degraded at an optimum rate in the rumen and provided rumen microflora with isobutyric acid. Further experimentation is warranted to determine its usefulness when nitrogen-deficient diets are fed to ruminant animals. Key words: Nonprotein nitrogen, isobutyric acid, isobutyraldehyde, slow-release, isobutyraldehyde monourea, propanal-2-methyl-monourea

Productivity of Russian wildrye as fall pasture with and without non-protein nitrogen supplementation

Russian wildrye (Psathyrostachys junceus) is recommended for fall pasture but little data are available from grazing trials to substantiate this advice. This study was initiated to evaluate forage yield and quality, and carrying capacity of Russian wildrye as fall pasture. The experiment was conducted at Swift Current, Saskatchewan from 1983 to 988 with Hereford cows and calves as the grazing units. Stockpiled yields of forage, available for grazing, averaged 650 kg ha−1 when determined in September. In vitro organic matter (OM) digestibility averaged 53% and nitrogen content of the forage averaged 1.3%. Yield of forage supported 34 animal-unit grazing days per hectare, when grazed with Hereford cows (540 ± 60 kg) and calves (190 ± 30 kg) for 4–7 wk in September and October. Cows weights were maintained, and calves gained, on average, 0.95 kg d−1. Supplementation with liquid urea-molasses, provided free choice in lick tanks, had no effect on stocking rate or average daily gain of cows or calves. Daily forage intake (OM basis), as measured by chromic oxide dilution, was 2.8% of cow body weight (BW). Daily forage intake by the calves was 1.6% of BW in 1987 and 2.2% of BW in 1988 when OM digestibility of the forage was 54 and 63%, respectively. Forage intake was not affected by supplementation. However, cows allowed access to the supplement grazed 1 h less each day than cows receiving no supplement (7.7 vs. 8.7 h). Russian wildrye provided excellent fall pasture for cows and calves but its production and, consequently carrying capacity, were below levels reported previously. Key words: Psathyrostachys junceus, forage intake, stocking rate

Evaluation of condensed molasses fermentation solubles as a nonprotein nitrogen source for ruminants.

Condensed molasses fermentation solubles (CMS), an effluent from the production of lysine, was evaluated as a nonprotein nitrogen supplement for ruminants by measuring the availability of its nitrogen to rumen microorganisms grown in batch cultures and by comparing CMS to urea as a source of supplemental nitrogen for growing cattle. In vitro dry matter digestion studies showed that, with 1 ml or less of rumen inoculum, microbial digestion was enhanced more (P less than .05) by the addition of CMS than by the addition of urea to 100 mg of cellulose. These stimulatory effects of CMS were absent when either the amount of inoculum (5.0 ml) or cellulose (250 mg) was increased and when wheat straw or alfalfa replaced cellulose as the substrate. Growth rate and feed intake for cattle fed a high-cob/cracked-corn diet containing 2.5 or 5.0% CMS were lower (P less than .05) than for cattle fed the control diet containing urea. Digestibility of dry matter, crude protein, neutral detergent fiber and acid detergent fiber were reduced (P less than .05) by the addition of CMS. Addition of CMS also decreased feed utilization, although the differences were not statistically significant. In conclusion, the nitrogen in CMS was available to rumen microorganisms growth in batch culture; however, CMS was not satisfactory as a substitute for all the urea in a diet for growing cattle containing over 45% of dietary N from the supplemental N source.

ISOALDEHYDEDIUREAS AS NONPROTEIN NITROGEN SOURCES FOR RUMINANT ANIMALS

In experiments designed to evaluate isovaleridenediurea (IVDU; butanal, 3-methyl-di-urea) as a nonprotein nitrogen supplement for ruminant animals IVDU and isobutylidenediurea (IBDU; propanal, 2-methyl-di-urea) were compared to urea. Ammonia concentrations were increased (P &lt; 0.05) by 2–5 mM when IBDU or IVDU were added to an in vitro incubation medium in comparison with up to 24 mM when equal amount of urea nitrogen was used. Isobutyric and isovaleric acid concentrations in the incubation medium were higher (P &lt; 0.05) when IBDU and IVDU, respectively, were present. In an in vivo experiment, ammonia concentrations were reduced (P &lt; 0.05) from 7.0 to 4.7 mM at 0.5 h after feeding when a mixture of 6 g IBDU and 6 g IVDU was substituted for 6.8 g urea in the diet of four sheep fed 1200 g hay and 100 g concentrate daily in a crossover experimental design. No differences (P &gt; 0.05) in isobutyric or isovaleric acid concentrations in the rumen fluid were observed between treatments. Apparent digestibilities were not influenced by diet. It was concluded that although IVDU and IBDU had potential as nonprotein nitrogen supplements, degradation rates of both compounds were low and excessive amounts of the compounds may escape from the rumen undegraded. Key words: Sheep, isobutylidenediurea, isovaleridenediurea, nonprotein nitrogen supplements, in vitro, in vivo