Rumen Degradable Nitrogen Research Articles

Effect of feeding Yucca schidigera extract and a live yeast on the rumen microbiome and performance of dairy cows fed a diet excess in rumen degradable nitrogen.

Nitrogen (N) loss from livestock agriculture via ammonia and nitrous oxide can reduce feed efficiency, production and negatively affect the environment. One option to reduce N loss is to add dietary supplements such as Yucca schidigera extract which has ammonia-binding properties and contains antimicrobial steroidal saponins, or Saccharomyces cerevisiae yeast, which can stabilise rumen pH and promote fibre degradation, increasing microbial growth and demand for degradable N. To determine the effect of Yucca schidigera extract when fed alone or in combination with a live yeast on the performance, rumen metabolism, microbiome and N balance, six rumen cannulated dairy cows were fed a mixed ration (C), mixed ration with Y. schidigera extract (De-Odorase®, Alltech®; 5g/cow/day; D), or mixed ration with Y. schidigera extract (5g/day) and Saccharomyces cerevisiae (Yea-Sacc®, Alltech®, 1g/cow per day; DY), in a 3×3 Latin rectangle design study with three periods of 49-day duration. Digesta samples were collected via the ruminal cannula during the final week of each period and separated into liquid (LPD) and solid (SPD) phases for microbiome analysis using 16S rRNA amplicon sequencing. DM intake was 0.8kg/d lower (P<0.05) in cows fed DY than C or D, with milk protein concentration 1.7g/kg higher in C than D or DY. There was a beta diversity (Bray Curtis) clustering of the LPD in cows fed D or DY compared to C (P<0.05), driven by an increase in Prevotella ruminicola-related operational taxonomic units (OTUs), and a decrease in P. brevis and P. bryantii OTUs. A methanogen OTU, Methanobrevibacter olleyae, was decreased in cows fed D or DY and an unclassified species of Gammaproteobacteria was increased in DY (LDA>2.0, P<0.05) compared to C. Rumen pH, ammonia and total VFA concentration were not affected by treatment (P>0.05) but the concentration of propionate and iso-butyrate were lower at 1700 and 2000h in cows fed DY compared to C (P <0.05). Measurements of N balance were unaffected by supplementation with D or DY, and there was no effect of treatment on slurry pH. In conclusion, supplementing with an extract of Yucca schidigera either alone or in combination with a live yeast had only a small effect on performance, with Yucca schidigera altering species associated with carbohydrate and protein metabolism, and reduced Methanobrevibacter olleyae which is involved in methanogenesis.

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.

Effects of nitrogen source on the performance and feeding behavior of lambs fed a high concentrate diet containing pomegranate peel

This experiment was conducted to investigate the effects of protein degradability on the performance, nutrient digestibility, rumen fermentation and behavior of lambs fed diets containing pomegranate peel (PP). Twenty-four male Iranian Arabic lambs (mean ± standard deviation; 16.3 ± 1.3 kg BW) were assigned randomly into four groups of six lambs each in a completely randomized design for 94 days. Treatments were: 1) control diet (CON); 2) diet containing PP with lower Rumen Degradable Nitrogen (RDN) (Soybean meal, PSOY); 3) diet containing PP with higher RDN (Urea, PUREA) and 4) free choice between diet 2 and 3 (PFREE). Forage to concentrate ratio of the diets was 20:80. The final body weight and dry matter intake were unaffected by treatments (P < 0.05), but there was a tendency to lower final body weight in PP groups compared to the CON (P = 0.09). A total replacement of soybean meal with urea negatively affected feed conversion ratio and OM digestibility. Daily weight gain was highest in lambs when offered CON (0.221 kg) and lowest in PUREA (0.182 kg), with lambs receiving PSOY (0.210 kg) and free choice (0.196 kg) having intermediate values. Apparent total tract digestibility of dry matter, organic matter, crude protein and ADF showed a decrease in PP containing diets (P < 0.05). Animals fed by urea containing diet showed higher mean rumen pH, rumen NH3-N concentration and blood urea nitrogen than CON and PSOY. Differences in volatile fatty acids concentrations were limited to valerate, which was lower for PP diets (P < 0.01). Providing lambs with PP diets increased time spent eating (190.7 vs. 166.5 min. d; P < 0.05) and intake per visit (70.5 vs. 50.1 g DM; P < 0.01), however, eating rate (7.56 g of DM/min) remained unchanged among treatments. Similarly, there was an increase (P < 0.01) in rumination and chewing activities with PP diets. In the free-choice treatment, lambs showed an increase in rumination and chewing time compared to the CON and PSOY groups. PP-fed lambs showed lower time spent self-grooming, social behavior, and lying, compared with the CON. The results suggest that in PP containing diets, the replacement of soybean meal with urea can be achieved with some adverse effects on performance, with the feed conversion being improved when free choice was given between protein sources. The inclusion level of 21.0% PP was probably too high for fattening lambs fed by high concentrate diets to ensure optimal growth performance and nutrient digestibility.

Feeding of groundnut haulms containing rumen degradable nitrogen on microbial protein supply and growth in lambs

Feeding of groundnut haulms containing rumen degradable nitrogen on microbial protein supply and growth in lambs

Responses to various protein and energy supplements by steers fed low-quality tropical hay. 1. Comparison of response surfaces for young steers

Response curves were established for different supplements, offered at intakes ranging from 0 to 20 g/kg liveweight (W).day to young Bos indicus crossbred steers fed low-quality Rhodes grass (Chloris gayana) hay ad libitum in two pen experiments. Supplements included protein meals of varying rumen-degradability (cottonseed meal (CSM) or fishmeal), as well as ‘energy sources’ comprising grains of high and low ruminal starch degradability (barley and sorghum) and a highly fermentable sugar source (molasses), with all diets adjusted for rumen-degradable nitrogen and mineral content. Unsupplemented steers gained 0.08 and 0.15 kg/day, in Experiments 1 and 2, respectively. Growth of steers increased linearly with intake of ‘energy source’ supplements in increasing order of molasses, sorghum and barley (all differences P &lt; 0.05). Steer growth rate also increased linearly with fishmeal, albeit over a narrow intake range (0–4.1 g/kg W.day), whereas the response with CSM was asymptotic, showing a steep response at low intake before levelling at ~1.2 kg/day. All supplement types were associated with a linear reduction in hay intake by the steers (energy substitution) where the reduction was greater (P &lt; 0.05) for barley and molasses (not different) than for sorghum (P &lt; 0.05), and for fishmeal compared with CSM (P &lt; 0.05). In concurrent metabolism studies with the same rations, organic matter digestibility of the total ration (561–578 g/kg DM, unsupplemented) was increased linearly by barley and molasses (both P &lt; 0.05) but was unaffected by CSM and sorghum supplements. The efficiency of microbial protein synthesis in steers increased linearly, from 91 g microbial crude protein/kg digestible organic matter (unsupplemented), in both molasses and CSM-supplemented steers, with the trend for a higher response to molasses (P = 0.05), and appeared most closely related to digestible organic matter intake. The response curves from these studies provide the practical framework upon which to formulate rations for cattle grazing low-quality forages.

Interaction effects of degradable nitrogen sources and straw treatment on rumen parameters and microbial protein synthesis in sheep

In this study, the effects of 2 rumen degradable nitrogen, N, source (urea vs. casein) were investigated on rumen degradability, ammonia concentration, dilution rate, microbial protein synthesis (MPS) and MPS efficiency (EMPS) in sheep fed diet based on untreated straw (US) or treated straw (TS). Four rumen fistulated sheep were assigned to 1 of the 4 treatments: (i) US with urea (USU); (ii) US with casein (USC); (iii) TS with urea (TSU); and (iv) TS with casein (TSC), according to a 4 × 4 Latin square design. Barley straw was treated with 4.1% sodium hydroxide (w/ w DM basis; pH 11.5) followed by 2% hydrogen peroxide. The treated straw was packed in 220 l drums and kept for 6 weeks. Compared to US diets, feeding the TS diets enhanced ruminal fiber degradability (62.3 vs 46.3%), total tract organic matter (OM) digestibility (59.4 vs 53.8%), OM intake (768 vs 546 g/d), dilution rate (0.082 vs 0.056/h), and MPS (45.7 vs 29.7 g/d), but it had no effect on EMPS. Rumen fiber degradability but not the DM one of only TS enhanced with casein supplementation as compared to urea supplementation. No interaction was found between supplemented nitrogen sources and straw type. It is concluded that substitution of US with TS increased intake, digestibility and MPS when supplemented with either urea or casein as nitrogen source. However, fiber degradability was improved with casein supplementation.

Effect of an energy restriction followed by a re-alimentation period on efficiency, blood metabolites and hormones in Belgian Blue double-muscled cows

The aim of the present study was to determine to what extent an energy restriction, followed by a re-alimentation, affects body weight (BW), feed efficiency and concentrations of blood metabolites and IGF-1 (insulin-like growth factor 1). Two experiments were conducted with 20 (initial BW 621±18(SE)kg) and 13 (initial BW 613±29kg) non-pregnant dry Belgian Blue double-muscled cows, respectively. A similar diet was fed in both experiments, consisting of maize silage, 0.5kg per day of a vitamin–mineral premix, and urea to prevent a negative rumen degradable nitrogen balance. In experiment 1, cows were divided into 2 groups and fed an energy level (EL) corresponding to their requirements (EL100; 224 days), or 0.7 of their requirements (EL70–130) during the first 112 days (Phase 1), and 1.3 times the requirements during the next 112 days (Phase 2). Cows were weighed, scored for body condition, and blood samples were collected at 8-week intervals. Glucose, non-esterified fatty acids (NEFA), creatinine, IGF-1, IGFBP (IGF Binding Protein)-2 and IGFBP-3 were analyzed. EL70 resulted in a larger BW change compared to EL100 (−10.2% of the initial BW; P<0.001) during phase 1, but BW loss was completely compensated during phase 2. Efficiency of nutrient use (gain/intake) for the restriction and the re-alimentation period as a whole was similar for both treatments (P>0.10). Blood concentrations of metabolites and IGF-1, IGFBP-2 and IGFBP-3 were not affected by energy restriction (P>0.10). Concentrations of glucose, NEFA, creatinine and IGFBP-3 were affected by sampling day, while a treatment×sampling day interaction was found for NEFA. In experiment 2, cows were fed at 0.8 or 1.0 of their energy requirements during 140 days, followed by a 70-day re-alimentation period, where all cows were fed ad libitum. EL80 resulted in a BW loss of 7.9% of the initial BW during phase 1. Average growth rate for the restriction period and the re-alimentation period together remained lower (P=0.014) in comparison with cows fed according to their requirements. Furthermore, efficiency of nutrient use for the whole period was adversely affected P<0.05). Therefore, feeding Belgian Blue double-muscled cows below their energy requirements should be discouraged.

Effect of different rumen degradable nitrogen levels on microbial protein synthesis and digestibility in sheep fed on finger millet straw (Eleucine coracana) based diet

Studies were conducted to determine adequate rumen degradable nitrogen (RDN) levels for optimum microbial protein synthesis and digestibility of nutrients in adult Bandur sheep fed on finger millet straw (FMS) based diet. Thirty Bandur sheep were divided into five groups of six animals each using a balanced completely randomized design. Animals in all groups were fed FMS as a basal roughage and solvent-extracted soybean meal (SBM) as a nitrogen source. The sheep in group 1 (G1) were offered FMS for ad libitum intake. Animals in group 2, 3, 4 and 5 (G2, G3, G4 and G5) were supplemented with SBM to provide RDN level of 16.2, 20.7, 24.7 and 26.6g/kg digestible organic matter intake (DOMI) or 24.9, 31.8, 38.1 and 41.0g/kg digestible organic matter apparently digested in the rumen (DOMR) respectively, along with FMS. The daily total dry matter (DM) and organic matter (OM) intakes showed a linear increase (P<0.05) with increasing levels of RDN supplementation. Digestibility coefficients of DM, OM (linear: P<0.01), crude protein (CP), ether extract (EE) (quadratic: P<0.001), neutral detergent fiber (NDF) and acid detergent fiber (ADF) (quadratic: P<0.05) increased as the level of RDN supplementation increased from G1 to G5. The values for total purine derivatives (TPD) excretion (mmol/day and mmol/kgW0.75) (quadratic: P<0.05), the levels of microbial purine absorption and microbial nitrogen supply (MNSg/day, g/kgDOMI and g/kgDOMR) (quadratic: P<0.01) increased, while microbial nitrogen to total urinary nitrogen ratio (MN:UN) decreased (linear: P<0.01) with the increased RDN level, indicating the efficient conversion of RDN into microbial protein synthesis for G2 animals among the RDN supplemented groups. This study indicated that 16gRDN/kgDOMI or 25gRDN/kgDOMR may be adequate for optimum microbial protein synthesis and digestibility of nutrients, thereby improving plane of nutrition in sheep fed on finger millet straw based diet. The additional RDN supplied beyond certain limit (above 16gRDN/kgDOMI or 25gRDN/kgDOMR) may not be beneficial for improving the digestibility of diet especially on straw based diets.

Microbial protein synthesis, nitrogen capture efficiency and nutrient utilisation in sheep fed on finger millet straw (Eleucine coracana)-based diet with different rumen-degradable nitrogen levels

Microbial protein synthesised in the rumen is a very important protein source for ruminants. It is essential to provide an adequate amount of rumen-degradable nitrogen (RDN) for optimum microbial protein synthesis in the rumen on straw-based diets. The objective of this study was to determine the RDN requirement for optimum microbial protein synthesis (MPS), nitrogen capture efficiency (NCE) and nutrient utilisation in Nellore rams fed on a finger millet straw (FMS)-based diet. Thirty-six Nellore sheep were randomly divided into four groups of nine animals each using a balanced, completely randomised design. The animals in group 1 (RDN0) were fed with ad libitum FMS. Those in groups 2, 3 and 4 (RDN1, RDN2 and RDN3) were supplemented with groundnut cake to provide RDN levels of 14, 18 and 23 g RDN kg⁻¹ digestible organic matter intake (DOMI) or 21, 27 and 35 g RDN kg⁻¹ digestible organic matter apparently digested in the rumen (DOMR) respectively along with FMS. The digestibility coefficients of all nutrients and MPS increased (P < 0.05) quadratically with increasing level of RDN supplementation. NCE decreased linearly (P < 0.05) as the level of RDN increased. The results suggest that 12 g RDN kg⁻¹ DOMI or 19 g RDN kg⁻¹ DOMR may be adequate for optimum MPS, NCE and digestibility of nutrients in sheep fed on an FMS-based diet.

Rumen degradable nitrogen requirements for optimum microbial protein synthesis and nutrient utilization in sheep fed on finger millet straw (Eleucine coracana) based diet

Studies were conducted to determine the rumen degradable nitrogen (RDN) requirement levels for optimum microbial protein synthesis and nutrient utilization in Nellore rams fed on finger millet straw (FMS) based diet. Thirty six Nellore sheep were randomly divided into four groups of nine animals each using the balanced completely randomized design. Animals in all the groups were fed finger millet straw as a basal roughage and groundnut cake (GNC) was offered daily in two equal halves in the morning (8.00AM) and evening (4.00PM) as RDN source. The animals in group I (GI) were fed with ad libitum FMS. Animals in group II, III and IV (GII, GIII, and IV) were offered GNC @ 12.4, 16.6, and 21.1g RDN/kg digestible organic matter (DOM) along with FMS. The daily total dry matter (DM) and organic matter (OM) intakes linearly increased (P<0.05) with increasing level of RDN supplementation while there was no difference in total DM and OM intake/kg W0.75 among different experimental groups. The digestibility coefficients of DM (P<0.001), OM (P<0.001), crude protein (CP) (P<0.001), ether extract (EE) (P<0.001), neutral detergent fibre (NDF) (P<0.01) and acid detergent fibre (ADF) (P<0.03) increased quadratically with increasing level of RDN supplementation from GI to GIV. The purine derivatives (PD) excretion, microbial purine absorption and microbial nitrogen supply (MNSg/day) linearly increased (P<0.001) as the level of RDN supplementation increased. There was no difference in nitrogen capture efficiency (NCE) and microbial nitrogen to total urinary nitrogen ratio (MN:UN) among the RDN supplemented groups. This study indicated that 12g RDN/kg digestible organic matter intake (RDNg/kg DOMI) or 18g RDN/kg OM apparently digested in the rumen (RDNg/kg DOMR) may be adequate for optimum microbial protein synthesis and digestibility of nutrients, there by improved plane of nutrition in sheep fed on finger millet straw based diet.

Estimation of true intestinal digestibility of dry matter, nitrogen and amino acids of cowpea and silverleaf desmodium forage legumes and Brachystegia spiciformis (musasa) browse legume

True intestinal digestibility of dry matter (DM), rumen-undegraded dietary protein (UDP) and amino acids of cowpea, silverleaf desmodium and Brachystegia spiciformis (musasa) were estimated. The true intestinal digestibility was calculated as the difference between the content of a bag that was preincubated in the rumen for 12, 24 and 48 h and was recovered in the faeces. Significantly higher DM and nitrogen disappearance rate in the rumen, postruminally and throughout the whole tract were found for cowpea than for silverleaf desmodium and musasa. Total amino acids or true nitrogen digestibility values of silverleaf desmodium and musasa tended to be higher than in cowpea. The true digestibilities for the individual amino acids in the different undegraded protein sources showed significant differences. The true intestinal digestibility of DM, nitrogen and amino acids in the mobile bags after 24 h and 48 h of preincubation in the rumen were higher for silverleaf desmodium and musasa, than in cowpea. Musasa and silverleaf desmodium provided little rumen-degradable nitrogen and supplied UDP to the intestines. The UDP supplied postruminally would be used for productive processes such as milk production and growth.

Effect of flow parameters of rumen digesta on effective degradability and microbial yield in sheep

The aim of this experiment was to examine the effect of rumen digesta flow parameters on effective degradability (EDG) and microbial nitrogen (MBN) yield in sheep fed diets of identical provision of both metabolizable energy and rumen degradable nitrogen (RDN). Ruminal degradation parameters of early-harvested perennial ryegrass hay (EH), late-harvested perennial ryegrasses hay (LH) and winter sown barley straw (BS) were determined by a nylon bag technique. Subsequently, three experimental diets (EHD, LHD and BSD) were formulated using the tested forages, sucrose and urea as supplements. An in vivo feeding study was conducted using four rumen cannulated sheep in a partial Latin square design. Digestibility, rate constants of rumen particle breakdown and passage, ruminal fermentation parameters and MBN supply to the small intestine were determined. Animals thoroughly consumed the forages fed at a restricted level. Digestion coefficients were greater for EHD than for LHD and were lowest for BSD (P < 0.05). The rate constant of large particle breakdown was 4.3, 5.9 and 6.7 %/h, respectively, and small particle passage was 5.3, 4.7 and 6.3 %/h for EHD, LHD and BSD, respectively. The estimates differed (P < 0.05) between the diets. The overall passage rate constant of total rumen particles was estimated to be higher for BSD than that for EHD or LHD (P < 0.05). Ruminal fermentation parameters were unaffected by dietary treatments (P > 0.05). Intake levels of rumen degradable organic matter (RDOM) and RDN were estimated to be greater for LHD than that for EHD or BSD (P < 0.05). Although dietary arrangements were made to give identical microbial efficiency, the estimated value was higher for EHD than that for LHD or BSD (P < 0.05); and the MBN yield for BSD was estimated to be lower than that for EHD or LHD (P < 0.05). Rumen kinetic parameters of degradation and particle flow of forage affected EDG values and MBN yield from forage-related RDN intake, although those had little effect on the efficiency of MBN yield from forage-related RDOM intake.

The Effects of Nitrogen and Forage Source on Feed Efficiency and Structural Growth of Prepubertal Holstein Heifers

Eighty Holstein heifers averaging 189.6 ± 6.8kg of BW were used to evaluate the effects of forage level and rumen degradable nitrogen source on feed efficiency and structural growth. A randomized complete block design was used with heifers blocked according to BW (≤ 136.0kg and > 136.0 kg) and assigned to 1 of 4 treatment diets in a 2 x 2 factorial design. Treatments were constructed with 2 levels of forage (65 or 75%) and 2 nitrogen sources. Forage sources were a mixture of corn silage and chopped timothy hay. Nitrogen sources were either soybean meal (SBM) or a slow-release, polymer-coated urea product (Optigen 1200, CPG Nutrients, Syracuse, NY), which was fed at 1.8% of diet DM on low-forage diets and at 1.3% of diet DM on high-forage diets. Average daily gain and feed efficiency did not differ between rations of different forage level or nitrogen source, averaging 0.87 ± 0.05kg and 7.4 ± 0.5, respectively, across treatments. Similarly, no differences were observed in change of withers height, hip height, hip width, or heart girth. No differences were observed in plasma urea nitrogen, which averaged 12.3 ± 0.4 mg/dL across treatments. Results of this experiment suggest that feeding moderately different levels of forage along with either SBM or a polymer-coated urea product does not result in any significant differences in feed efficiency or structural growth. Polymer-coated urea can be used in heifer diets to effectively replace SBM as a nitrogen source in either low- or high-forage nations.

Effect of timing of protein supplementation on the performance of lactating dairy cows

Two experiments were undertaken to determine the effect of timing of protein supplementation on performance of grazing, lactating Holstein–Friesian cows fed maize silage and grain-based concentrate. In experiment 1, 36 cows were fed 0.8 kg DM/day of solvent-extracted cottonseed meal (CSM) either as 1 meal at 1200 hours with maize silage (CSM 1200) or at 1530 hours with concentrate (CSM 1530), or in 2 meals at 0600 and 1530 hours with concentrate (CSM 600 + 1530). In experiment 2, 36 cows were either fed no CSM (control) or fed 1.0 kg DM/day as either CSM 1200 or CSM 600 + 1530. In experiment 1, daily yields of 4% fat-corrected milk (FCM) and milk fat for CSM 600 + 1530 were significantly higher than for CSM 1530 with respective means of 22.8 v. 20.7 L and 895 v. 804 g. Daily yields of FCM and milk fat for CSM 1200 were intermediate (21.7 L and 841 g/cow, respectively). A similar trend for daily protein yield per cow was noted (712, 695 and 666 g for CSM 600 + 1530, 1200 and 1530, respectively). In experiment 2, milk yield differed numerically between CSM 600 + 1530 and other treatments, with means (± s.e.d.) of 24.7 ± 0.78, 22.9 ± 0.78 and 22.9 ± 0.78 L/cow.day for CSM 600 + 1530, CSM 1200 and control, respectively. Mean (± s.e.d.) net energy requirements for milk production and liveweight change tended to be lower for the control (68 ± 3.6 MJ/cow.day) as opposed to CSM 600 + 1530 (79 ± 3.6 MJ/cow.day) and CSM 1200 (76 ± 3.6 MJ/cow.day). Cumulative time where rumen degradable nitrogen:rumen degradable dry matter was less than 22 g/kg were 2, 2 and 3 h for CSM 600 + 1530, CSM 1200 and CSM 1530, respectively, in experiment 1, and 6, 4 and 2 h for the control, 1200 and CSM 600 + 1530, respectively, in experiment 2. No differences in rumen ammonia-N concentrations were noted between treatments in experiment 1. In experiment 2, a significantly lower mean (± s.e.d.) rumen ammonia-N concentration was recorded for the control at 1530 hours (62 ± 14.1 mg/dL) in comparison to CSM 600 + 1530 (114 ± 14.1 mg/dL) and CSM 1200 (119 ± 14.1 mg/dL). These experiments show that for grazing dairy cows supplemented with maize silage and grain-based concentrate, feeding a daily aliquot of CSM as 2 meals at 0600 and 1530 hours rather than 1 meal at 1200 or 1530 hours improves milk production.

Purine excretion and estimated microbial protein yield in sheep fed diets differing in protein degradability

The greatest sources of uncertainty concerning the application of the metabolizable protein (MP) system for ruminant feeding concern assumptions as to the extent and efficiency of synthesis of microbial protein (MiN) both from quickly, slowly and undegraded forms of dietary nitrogen (QDN, SDN and DUN, respectively) and from recycled endogenous nitrogen. In order to test these assumptions 12 castrated male lambs were allocated to three experimental semi-synthetic diets, QNF1.3, SNF1.3 and UNF0.8, formulated to provide different ratios of total dietary N to fermentable energy (FME) and to vary the proportions of total N provided by QDN, SDN and DUN. Thus, QNF1.3 and SNF1.3 were formulated to provide the same nominal ratio of 1.3 g degradable N/MJ FME. UNF0.8 was formulated to provide a similar total N concentration to QNF1.3 but with the majority of N in the form of DUN thus providing only 0.8 g degradable N/MJ FME. The diets were fed at two levels (maintenance and twice maintenance) according to a balanced changeover design. The two principal sources of dietary N were dark corn grains-plus-solubles (high QDN) and corn gluten meal (high DUN). MiN yield was estimated from urinary excretion of total purines. The “net” efficiency of incorporation of dietary N into MiN was estimated from increments of purine excretion between the two diet levels. Mean values for purine excretion from sheep were similar when the three diets were fed at the low, maintenance level. The net efficiencies of utilization of increments of ‘effective rumen degradable nitrogen’ (ERDN=0.8QDN+SDN) between maintenance and twice maintenance were QNF1.3=0.50, SNF1.3=0.94 and UNF0.8=0.59. The value of 0.94 for diet SNF1.3 provides strong support for the assumption that the efficiency of capture of SDN can approach 1.0. The low (0.50) net efficiency of capture of increments of ERDN from diet QNF1.3 suggests the MP system is overoptimistic in assuming that QDN can be captured with an efficiency of 0.8. When diet UNF0.8 was fed at the high level, 6/8 sheep failed to sustain food intake presumably because they were unable to sustain the microbial population of the rumen. This suggests that the capacity of sheep to recycle endogenous N into MiN may not exceed the maximum amount permitted by the assumption of the MP system even when DUN is fed in excess of requirement for growth.

Effect of imbalance between energy and nitrogen supplies on microbial protein synthesis in growing double-muscled Belgian Blue bulls

Balancing the supply of nitrogen and energy-yielding substrates to rumen micro-organisms was proposed as a mechanism to maximise the capture of rumen degradable nitrogen (RDN) and to optimise microbial growth rate and efficiency. The objective of this study was to examine the effect of various time periods of imbalance between nitrogen and energy supplies for the rumen micro-organisms on the microbial protein synthesis (SPM) in growing double-muscled Belgian Blue bulls. This was realised by giving the same feedstuffs according to different meal patterns, which is one of the most robust test of the ‘synchrony’ hypothesis (Dewhurst et al., 2000).

The intake and digestibility in Raini male goats fed different ratios of effective rumen degradable nitrogen:sulphur

Nutrient deficiencies, such as sulfur (S), that reduce the activities of rumen microorganisms are liable to reduce food intake (McDonald et al., 1995). Hegarty et al (1994) found that a depression of appetite and digestibility in sheep deprived of sulfur. The amount of sulfur needed to optimize the rumen environment is dependent on several factors such as the level of dietary sulfur and the availability of the effective ruminal degradable nitrogen, ERDN (Underwood and Suttle, 1999). Therefore, this trial was conducted to assess the influence of different ERDN:S ratios on the dry matter intake (DMI) and nutrients digestibility in the male goat of Raini breed, an Iranian native cashmere goat.

Evaluation of Some Aquatic Plants from Bangladesh through Mineral Composition, In Vitro Gas Production and In Situ Degradation Measurements

A study was conducted to evaluate the nutritive potential value of different aquatic plants: duckweed (Lemna trisulaca), duckweed (Lemna perpusila), azolla (Azolla pinnata) and water-hyacinth (Eichhornia crassipes) from Bangladesh. A wide variability in protein, mineral composition, gas production, microbial protein synthesis, rumen degradable nitrogen and in situ dry matter and crude protein degradability were recorded among species. Crude protein content ranged from 139 to 330 g/kg dry matter (DM). All species were relatively high in Ca, P, Na, content and very rich in K, Fe, Mg, Mn, Cu and Zn concentration. The rate of gas production was highest in azolla and lowest in water-hyacinth. A similar trend was observed with in situ DM degradability. Crude protein degradability was highest in duckweed. Microbial protein formation at 24 h incubation ranged from 38.6-47.2 mg and in vitro rumen degradable nitrogen between 31.5 and 48.4%. Based on the present findings it is concluded that aquatic species have potential as supplementary diet to livestock.

Effect of level and origin of rumen degradable nitrogen on rumen microbial growth and nitrogen utilisation efficiency of animals fed maize silage at maintenance.

Isoenergetic maize silage diets, fed at maintenance to 24 suckling cows (Exp. 1) and to 3 (Exp. 2) or 4 (Exp. 3) rumen fistulated sheep, were compared with a urea and controlled release NPN diet (Exps. 1 and 2) and with a protein-N supplemented diet (Exp. 3). Supplementation increased blood urea concentrations (44.7 +/- 22.3 vs. 97.6 +/- 23.7 mg urea-N x L(-1)) (Exp. 1) and renal urea excretion (2.5 +/- 1.1 vs. 7.6 +/- 1.8 g urea-N x d(-1)) (Exps. 2 and 3), whereas blood allantoin concentrations (286.7 +/- 77.0 micromol x L(-1)) (Exp. 1) and renal excretion of purine derivatives (357.6 +/- 90.7 mg purine-N x d(-1)) (Exps. 2 and 3) were not affected, indicating additional N supplementation did not improve rumen microbial growth. However, some deficiency of rumen degradable N might occur in non supplemented diets as suggested by the reduced rumen NH3-N and RNA concentrations (868 +/- 270 vs. 1466 +/- 466 mg RNA x kg(-1) rumen contents).

Rumen degradable nitrogen inclusion in a native pasture diet for weaner goats

A complete block design was applied to employ 40 weaner goats, initial weighing average of 14.6 kg, which were grouped into 5 supplementary treatments, i.e. 125, 250, 300, 350 dan 400 g of skim milk/d. Each animal received.1.25 kg gliricidia leaves. Mixed pasture was consumed freely. The research was conducted in Tanjungrejo village, Tongas district, Probolinggo. A digestibility study was conducted for 7 days. Measurements included nutrient intakes and digestibilities, liveweight gain, and feed conversion ratio. Data were analyzed using the GLM procedure of SAS (SAS, 1986). The results showed that the medium skim milk level (300 g/d) gave the highest dry component digestibility. Cell wall digestibility from the group given 125-300 g skim milk/d was higher (P 0.05) difference in organic matter or protein digestibility was found among treatments. Supplementation with 350 g skim milk/d gave higher protein or digestible protein consumption (P<0.05), while supplementation with 125 g/d gave the best feed utilization efficiency. Levels at 125-250 g skim milk/d gave weight gain of about 65 g/d, while at more than 250 g gave 57 g/d or less. The best feed conversion ratio (7.8) was obtained in the group fed 125 g skim milk/d. In order to optimize microbial activity in the rumen, provision of slowly rumen degradable protein sources such as legumes, or rumen undegradable protein is of great importance. Key words: Rumen degradable N, weaner goats, digestibility, average daily gain