Neutral Detergent Insoluble N Research Articles

Brachiaria Hybrid and Pennisetum purpureum Supplemented with Pueraria phaseoloides Increased the Concentration of Rumen-Undegradable Protein in Forages for Ruminants

Supplementing tropical grasses with leguminous forages is known to improve the nutritive value of forage-based diets. However, it is not clear how basal grass forages supplemented with Kudzu (Pueraria phaseoloides) affect the nitrogen (N) and crude protein (CP) fractions of grass/legume forages. The aim of this study was to determine the N and CP fractions and in vitro ruminal CP degradability of Brachiaria hybrid (B. ruziziensis × B. decumbens × B. brizantha) and elephant grass (Pennisetum purpureum) supplemented with Kudzu at a target CP content of 133 ± 0.6 g/kg of dry matter (DM). The grass/legume forages were evaluated for total N, buffer-soluble N (BSN), buffer-insoluble N (BISN), non-protein nitrogen (NPN), neutral detergent-insoluble N (NDIN), acid detergent-insoluble N (ADIN), CP fractions A, B1, B2, B3, C, rumen-degradable protein (RDP), rumen-undegraded protein (RUP), and in vitro ruminal CP degradability. The CP concentration of Kudzu was 217 g/kg DM, while grass forages ranged between 79.9 and 112 g/kg DM. The BISN, CP degradability parameters b, and potential degradability were approximately 56, 41, and 74%, respectively, higher in grass forages supplemented with Kudzu. The concentrations of RUP in the grass forages (23.9–32.5 g/kg DM) were significantly improved when they were supplemented with Kudzu (72.0–79.9 g/kg DM). Therefore, we concluded that basal grass forages supplemented with Kudzu to a target CP content can improve the amount of RUP supplied by the forage portion of the diet. This can have a positive effect on forage utilization and animal performance while reducing the cost to feed for ruminants.

Nitrogen balance and blood urea nitrogen by gestating sheep offered alfalfa silage wrapped with or without an enhanced oxygen barrier plastic after time delays up to three days

Exposing ensiling forage to oxygen can result in dry matter deterioration and reduce silage intake by animals. This study was conducted to investigate the effects of two different wrapping sources and time intervals between baling and wrapping on N utilization in gestating sheep offered alfalfa silage. Alfalfa silage was baled in large round bales (moisture concentration = 591 ± 43.0 g/kg), then wrapped with plastic using either an enhanced oxygen-limiting barrier (EOB) or no additional barrier (conventional wrap; CW) on the day of baling or 1, 2 or 3 d after baling. After 5 months of storage, silages were chopped, then offered randomly for ad libitum consumption to 16 gestating ewes [63.5 ± 1.71 kg body weight] to provide 2 observations per treatment for each of 3 experimental total collection periods. Each study period consisted of a 10-d dietary adaptation period followed by 7 d of total fecal and urine collection. Blood was collected immediately prior to feeding and four hours after feeding on the last day of each period. Data were analyzed using PROC MIXED of SAS for a 2 × 4 factorial treatment arrangement, while blood data were treated as repeated measures. When expressed as a portion of total N, neutral detergent insoluble N (NDIN) content of silage increased (P ≤ 0.02) linearly and quadratically, and acid detergent insoluble N (ADIN) concentrations increased (P < 0.01) linearly with longer wrapping delays. Nitrogen apparent absorption (g/d and g/kg N intake) and urinary N (g/d) decreased (P ≤ 0.04) linearly with extended time delays between baling and wrapping. Retained N (g/kg of N intake and of absorbed N) was greater (P = 0.04) from silage wrapped with EOB. Blood urea N concentrations (mg/dL) decreased (P = 0.02) quadratically with extended delay between baling and wrapping. Digestion of NDIN (g/kg NDIN intake) increased (P = 0.03) linearly with extending time delay when silage was wrapped with EOB and linearly and quadratically (P < 0.01) when wrapped with CW. Digestion of ADIN increased (P = 0.02) quadratically with increasing delay between baling and wrapping averaged across wrap types. Therefore, management practices to limit oxygen exposure during packaging and ensiling can prevent a decline in N utilization by ruminants.

55 Rumen undegradable protein content of native range and sub irrigated meadow forages

Abstract The in situ mobile bag procedure was used to compare rumen undegradable protein (RUP) content and RUP digestibility of Nebraska Sandhills range and meadow diet samples. Meadow samples (n = 12) were from June, July and August of 2 years while range samples (n = 19) were from June, July, September and December of 6 years. Samples were collected using esophageally fistulated cows (samples from 2 cows composited per time point), freeze-dried, and ground through a 2 mm screen. For each sample, 1.25 g was weighed into 8 replicate 8×10 cm Dacron bags with 50-µm pore size. Rumen incubation time was based on estimated digestibility and passage rate. Following rumen incubation, analysis of neutral detergent insoluble N (NDIN) on one-half of the bags was used to calculate RUP content. Remaining bags were treated with pepsin/HCl solution (37 °C) and stirred for three hours before duodenal incubation. Analysis of NDIN after recovery from feces determined RUP digestibility. Data were analyzed using month as a fixed effect and year and experiment as random effects. In meadow samples, CP (15.0% of DM) was consistent across June, July, and August (P = 0.72). Range samples tended to differ in CP content (P = 0.11), with June, July and September being similar (8.15% of DM) while December was 6.01%. In meadow samples, RUP averaged 21.9% of CP while range samples averaged 26.7% of CP, with no differences due to month (P ≥ 0.32). Because CP content was changing in range samples, RUP as a % of DM tended (P = 0.14) to decrease in December (1.66) compared to June, July, and Sept (2.25). In meadow samples, RUP digestibility (%) declined from 74.7% in June to 61.4% in July and Aug (P = 0.07). RUP digestibility (%) averaged 43.9% for all range samples (P = 0.66).

In vitro investigation of the ruminal digestion kinetics of different nitrogen fractions of 15N-labelled timothy forage.

An in vitro method based on 15N-labelled forage nitrogen (N) was developed to study ruminal N metabolism of soluble N (SN), insoluble N (ISN) and neutral detergent insoluble N (NDIN) fractions of timothy forage. Timothy grass was grown on replicated experimental plots with one plot receiving 15N-labelled and the other unlabelled N fertilizer. Harvested grass was preserved as dried grass or as formic acid treated or untreated silage. The intact forages and their corresponding N fractions were incubated in buffered rumen fluid in vitro to determine degradation parameters based on the 15N fluxes between labelled feed N and ammonia N pools. A high percentage (25–38%) of 15N-labelled ammonia disappeared from ammonia N pool during the first 15 min of incubation. Microbial uptake of dried grass SN fraction was higher than of silage SN fractions. Fractional degradation rates of SN from formic acid treated silage, untreated silage and dried grass during the first 6 hours of incubation were 0.145, 0.125 and 0.115 /h, respectively. By the end of the incubation period (28 h), 69, 66 and 43%, of the SN fraction of formic acid treated silage, untreated silage and dried grass, respectively were recovered as ammonia. The percentage of ISN fractions degraded to ammonia N were 9, 34 and 27%, respectively. Based on the changes in 15N-labelled ammonia N pool in blank incubation and appearance of 15N to ammonia N pool from 15N-labelled NDIN fractions, it was estimated that a significant portion of microbial lysis occurred when incubations were carried out for longer than 20 hours. With dried grass the contribution of ammonia N for microbial N synthesis was greater than with silages. Use of 15N-labelled forages together with this in vitro method is a promising technique for determining soluble N degradation parameters, but it requires further development to be used for determining degradation parameters of insoluble N fractions and work with whole feeds.

The acid detergent insoluble nitrogen (ADIN) analysis overestimates the amount of N associated to acid detergent fibre

The acid detergent insoluble nitrogen (ADIN) fraction of feeds is usually assumed to be indigestible, and some feeding systems for ruminants use the ADIN analysis as a measure of nitrogen (N) availability. In a preliminary study conducted with 3 different feeds, we observed lower 15N abundance in ADIN compared with that in both total N and neutral detergent insoluble N (NDIN). Based on these results, we hypothesized that ADIN analysis overestimates the amount of N associated to acid detergent fibre (ADFom) due to N-contamination from cetyltrimethylammonium bromide (CTAB), a reagent used in the ADFom analysis. The objective of this work was to verify lower 15N abundances of ADIN than of total N and NDIN in different feeds, and to assess the magnitude of ADIN contamination. Samples from one corn crop (aerial biomass, grain and root) and two sunflower crops (SF; aerial biomass and seeds) were analysed for 15N abundance and content of total N, NDIN and ADIN. Samples had been 15N-labelled by fertilizing with either 15NH4NO3 or NH415NO3, and there were three replicates per type of sample. The 15N-abundance of total N and NDIN was similar (P > 0.05) for all samples, whereas that of ADIN was lower (P < 0.001 to 0.037) than values for total N and NDIN for all samples, excepting for SF seeds from one crop. Estimates of N-contamination of ADIN from CTAB were not affected by the fertilizer used to label N (P ≥ 0.207), and values (g/g) ranged from 0.129 for corn grains to 0.447 for corn aerial biomass. N-contamination of ADIN was positively correlated with neutral detergent fibre (aNDFom), ADFom, hemicelluloses and cellulose content (P < 0.001; r = 0.770 to 0.905; n = 18 and 22 for corn and SF, respectively), and negatively (P < 0.001 to 0.048) with ADIN content (expressed as proportion of ADFom). The negative correlations (P < 0.001) between N-contamination of ADIN and lignin (Lignin (sa))/ADFom ratio observed for all samples would indicate that N-contamination of ADIN was reduced by cell wall lignification. In conclusion, the results showed that the use of CTAB in the ADFom analysis resulted in increased ADIN values, and therefore overestimated the amount of N associated to ADFom, questioning the use of ADIN as a parameter indicative of N availability. The possibility of replacing CTAB by a N-free reagent in the ADFom analysis should be explored.

Drying procedures affect non-structural carbohydrates and other nutritive value attributes in forage samples

Forage non-structural carbohydrates (NSC) are an important source of energy readily available to rumen microbes. Sampling procedures that quickly reduce plant metabolic activity after cutting and preserve macromolecular structures are required for accurate estimation of forage NSC concentration and other nutritive value attributes. Although several drying procedures exist, their efficiency to reflect composition of fresh samples is unclear. We compared five drying procedures on fresh samples of timothy ( Phleum pratense L.) and alfalfa ( Medicago sativa L.): (1) oven-drying at 55 °C for 48 h; (2) high-temperature pretreatment at 100 °C for 1 h followed by oven-drying at 55 °C for 48 h; (3) freezing pretreatment at −20 °C for 1 mo followed by oven-drying at 55 °C for 48 h; (4) microwave pretreatment for 1 min followed by oven-drying at 55 °C for 48 h; and (5) freezing at −20 °C for 1 mo followed by freeze-drying. Starch, sucrose, glucose, fructose, fructans (timothy) or pinitol (alfalfa), N, neutral detergent fibre assayed with a heat-stable amylase (aNDF), acid detergent fibre (ADF), neutral detergent insoluble N (NDIN), and acid detergent insoluble N (ADIN) concentrations, and in vitro true digestibility of DM (IVTD) and digestibility of neutral detergent fibre (dNDF) were determined in the spring growth and summer regrowth of two production years. Soluble carbohydrate (SC) concentration was estimated using the sum of sucrose, glucose, fructose, and fructans or pinitol. The NSC concentration was obtained by adding SC and starch. Averaged across forage species and growth periods, NSC concentrations were similar and generally highest ( P<0.001) in freeze-dried samples (89.8 mg/g DM), the reference procedure, and the microwave-pretreated samples (86.7 mg/g DM); oven-drying at 55 °C resulted in the lowest NSC concentration (57.6 mg/g DM). Values of other nutritive value attributes with the microwave pretreatment were comparable to those of the other drying procedures, except that it tended to increase forage NDIN. The NDIN concentration was lowest ( P<0.001) in freeze-dried samples (2.1 mg/g DM) and generally highest in microwave-pretreated samples (7.5 mg/g DM). The effect of drying procedure on aNDF, ADF, IVTD, dNDF, and ADIN concentrations varied slightly with forage species and growth period. Principal component analysis (PCA) highlighted the closeness between freeze-drying and microwave pretreatment for the global assessment of the nutritive value of forages, including NSC concentration. Microwave pretreatment should be given greater consideration as an effective and easy-to-use sample preparation procedure for the characterization of the nutritive value of fresh forages.

CASE STUDY: In Situ Ruminal Nitrogen and Neutral-Detergent Insoluble Nitrogen Disappearance from Bermudagrass Fertilized with Different Nitrogen Rates and Harvested on Two Dates

Fertilizing bermudagrass (Cynodon dactylon L. Pers.) with N can produce large quantities of forage and increase plant N concentrations. Bermudagrass growing on a caged-layer manure-amended site was fertilized with ammonium nitrate at 4 rates (0, 56, 112, and 168kg N/ha) approximately 1 mo before first and third harvests on May 30 and August 18, 2000, to determine in situ disappearance kinetics of N and neutral detergent insoluble N (NDIN). Five crossbred ruminally cannulated steers (BW = 422 ± 21.0 kg) were used to evaluate in situ disappearance kinetics in a randomized complete block design with a 2 × 4 factorial arrangement. Immediately soluble N (fraction A) and rate of N disappearance increased linearly (P < 0.05) with fertilization rate for both harvests, but N disappearing at a measurable rate (fraction B) decreased linearly (P < 0.01) with fertilization rate for both harvests. A linear N fertilization rate × harvest date interaction (P < 0.05) was detected for the unavailable N fraction (fraction C) and for potential extent of ruminal N disappearance. Effective ruminal N disappearance (% of N) increased quadratically (P < 0.01) with N fertilization rate. The intercept of the regression of effective N disappearance on N fertilization rate was greater (P < 0.05) for bermudagrass harvested in May compared with that harvested in August. For NDIN, quadratic N fertilization rate × harvest date interactions (P < 0.05) were detected for fractions A and C and the potential extent of NDIN disappearance; rate of NDIN disappearance did not differ (P = 0.17) across harvest dates or fertilization rates. Effective NDIN disappearance (% of NDIN) increased linearly (P < 0.01) with N fertilization rate. The pool of total N (% of DM) effectively disappearing was composed largely of neutral-detergent soluble N (NDSN; 75.1 and 66.6%, respectively from May and August harvests). Effective NDSN and NDIN disappearance (% of DM) increased quadratically and linearly (P < 0.01), respectively, with N fertilization rate, and these NDSN and NDIN pools were larger (P < 0.01) from bermudagrass harvested in May. Nitrogen fertilization may enhance the ruminal disappearance of both total N and NDIN from bermudagrass. On a percentage of DM basis, later harvests may have less extensive ruminal disappearance from both NDIN and NDSN pools.

Ruminal in situ disappearance kinetics of nitrogen and neutral detergent insoluble nitrogen from common crabgrass forages sampled on seven dates in northern Arkansas1

Southern crabgrass (Digitaria ciliaris [Retz.] Koel.) is often an undesirable species in field and forage crops, but visual observations suggest that livestock prefer it to many other summer forages. The objectives of this study were to assess the nutritive value of crabgrass sampled weekly between July 11 and August 22, 2001 and then to determine ruminal in situ disappearance kinetics of N and neutral detergent insoluble N (NDIN) for these forages. A secondary objective was to compare these kinetic estimates for crabgrass with those of alfalfa (Medicago sativa L.), bermudagrass (Cynodon dactylon [L.] Pers.), and or-chardgrass (Dactylis glomerata L.) as control hays. All kinetic evaluations were conducted with 5 ruminally cannulated Gelbvieh x Angus x Brangus steers (383 +/- 22.7 kg). Concentrations of N for crabgrass decreased linearly (P < or = 0.002) across sampling dates for leaf, stem, and whole-plant tissues. Conversely, percentages of the total N pool within NDIN and ADIN fractions generally increased over sampling dates in mostly linear patterns. For crabgrass, the immediately soluble portion of the total N pool (fraction A; overall mean = 54.6% of N) was greater (P < 0.001) than for all control hays. Crabgrass exhibited a more rapid N disappearance rate (overall mean = 0.093/h; expressed as a proportion disappearing/h) than that of bermudagrass (0.046/h; P < 0.001), but the disappearance rate for alfalfa N (0.223/h) was considerably faster (P < 0.001) than for crabgrass. The effective ruminal disappearance of N was greater (P < 0.001) for crabgrass (overall mean = 85.4%) than for the alfalfa (83.3%), bermudagrass (72.3%), or orchardgrass (76.0%) control hays. For alfalfa, the ruminal disappearance rate of NDIN (0.150/h) was more rapid (P < 0.001) than for crabgrass (overall mean = 0.110/h); however, the disappearance rate for crabgrass was faster than that for bermudagrass (0.072/h; P < 0.001) or for orchardgrass (0.098/h; P = 0.010). Effective ruminal disappearance of NDIN was greater (P < 0.001) for crabgrass (overall mean = 72.0%) than for the bermudagrass (69.0%) or alfalfa hays (50.5%), but there was no difference (P = 0.865) between crabgrass and orchardgrass (72.1%). Although crabgrass forages exhibited concentrations of total N that were comparable with those of alfalfa and rates of ruminal N disappearance that were < 50% of those for the alfalfa hay control, improvements in N use efficiency relative to alfalfa are questionable because of the excessively large Fraction A for crabgrass.

Chemical composition and feeding value of urea-treated corncobs ensiled with additives for sheep

This study examined the effects of various additives on ammonia nitrogen (N) capture in urea-treated corncobs (UTC), and measured the effect of UTC ensiled with or without enzose on nutrient intake, digestibility, N balance, and growth performance in sheep. In Expt 1, 5% UTC were ensiled in laboratory silos using enzose, cane molasses, acidified cane molasses, and acidified water (having a pH of 4.4, similar to enzose), each at 0, 4, 5, and 6% of corncobs dry matter (DM). Total N, ammonia N, and neutral detergent insoluble N (NDIN) contents in UTC ensiled with additives were significantly higher than in those ensiled without additives. Total N and NDIN contents of UTC were affected both by additive type and level. Total N and NDIN contents of UTC ensiled with enzose were significantly higher than of those ensiled with other additives. Neutral detergent fibre (NDF) and hemicellulose contents of UTC ensiled with additives were significantly higher than of those ensiled without additives. The NDF and hemicellulose were higher in UTC ensiled with enzose compared with all other additives. In Expt 2, 32 Lohi breed sheep, 4 months of age and of similar weights, were randomly assigned to 4 dietary groups. The control ration contained 30% DM from UTC ensiled without enzose, and the other 3 rations contained 30, 35, and 40% DM from UTC ensiled with enzose. Dry matter, OM, and NDF intakes were significantly increased in sheep fed increasing levels of UTC ensiled with enzose. Dry matter and NDF digestibilities were significantly higher in sheep fed UTC ensiled with enzose than in those fed UTC ensiled without enzose. The DM and NDF digestibilities were similar in sheep fed diets containing varying levels of UTC ensiled with enzose. Nitrogen balance was positive and was significantly higher in sheep fed rations containing UTC ensiled with enzose than in those fed UTC ensiled without enzose. Daily weight gain was higher in sheep fed rations containing UTC ensiled with enzose than in those fed UTC ensiled without enzose. These results indicated that ensiling UTC with enzose improved ammonia N capture. Inclusion of 5% UTC ensiled with 5% enzose up to 40% DM resulted in better nutrient intake, digestibility, N balance, and growth in Lohi sheep.

Nitrogen Retention and Chemical Composition of Urea Treated Wheat Straw Ensiled with Organic Acids or Fermentable Carbohydrates

The influence of varying levels of urea and additives on nitrogen (N) retention and chemical composition of wheat straw was studied. The wheat straw was treated with 4, 6 and 8% urea and ensiled with 1.5, 2 and 2.5% of acetic or formic acid and 2, 4 and 6% of corn steep liquor (CSL) or acidified molasses for 15 days. The N content of wheat straw was significantly different across all treatments. The N content of urea treated wheat straw was increased with the increasing level of urea. The N content was higher in urea treated wheat straw ensiled with acetic or formic acid as compared to urea treated wheat straw ensiled without these organic acids. The N content of urea treated wheat straw was further enhanced when it was ensiled with CSL or acidified molasses. This effect was significant across all levels of urea used to treat the wheat straw. Nitrogen retention in urea treated wheat straw was decreased linearly as the urea level was increased to treat the wheat straw. The N content was increased linearly when higher levels of CSL or acidified molasses were used to ensile the urea treated wheat straw. Most of the N in urea treated wheat straw was held as neutral detergent insoluble N (NDIN). The NDIN content was increased linearly with the increasing levels of urea and additives. The neutral detergent fiber (NDF) contents were higher in urea treated wheat straw ensiled with acetic or formic acid as compared to urea treated wheat straw ensiled without additive. The NDF content further increased in urea treated wheat straw ensiled with CSL and acidified molasses. The entire increase in NDF content was because of fiber bound N. The hemicellulose content of urea treated wheat straw ensiled with CSL or acidified molasses was higher as compared to urea treated wheat straw ensiled with acetic or formic acid. The acid detergent fiber content of urea treated wheat straw ensiled with or without additives remained statistically non-significant. The cellulose contents of wheat straw was linearly reduced when urea level was increased from 4 to 6 and 8% to treat the wheat straw. This effect was further enhanced when urea treated wheat straw was ensiled with different additives. The results of the present study indicated that fermentable carbohydrates might improve the Nitrogen retention and bring the favorable changes in physiochemical nature of wheat straw. However, biological evaluation of urea treated wheat straw ensiled with fermentable carbohydrates is required.

Nutrient intake and utilisation by goats fed dried leaves of the shrub legumes Acacia angustissima, Calliandra calothyrsus and Leucaena leucocephala as supplements to native pasture hay

Thirty-six indigenous goats were used to determine the potential of sun-dried leaves of the shrub legumes Acacia angustissima, Calliandra calothyrsus and Leucaena leucocephala as supplements to native pasture hay (NPH). The dried leaves were included at the rates of 80, 160 and 320 g/head/day. Cottonseed meal fed at the same levels, and NPH fed alone were included as controls. Among the browses, C. calothyrsus had the lowest N content of 19.0 g/kg dry matter (DM) and A. angustissima the highest of 35.0 g/kg DM. The leaves from the legumes had significantly less N and higher cell wall, neutral detergent insoluble N (NDIN) and acid detergent insoluble N (ADIN) contents than cottonseed meal. The values of NDIN as a fraction of total N were 19, 456, 526 and 816 g/kg for cottonseed meal, L. leucocephala, A. angustissima and C. calothyrsus, respectively. Proanthocyanidin contents were 33, 196 and 134 g/kg DM for A. angustissima, C. calothyrsus and L. leucocephala, respectively. Type of supplement did not affect ( P>0.05) NPH, total and digestible DM intakes although NPH intake was depressed ( P<0.05) at the highest level of supplementation compared to the first two levels. Animals fed legumes excreted significantly more ( P<0.001) faecal N (g/kg N intake) than animals consuming cottonseed meal. The reverse was observed for urine N. Among the legumes, C. calothyrsus had significantly higher ( P<0.001) N in faeces (958 g/kg N intake) than A. angustissima (630) and L. leucocephala (615). Significant ( P<0.05) correlation coefficients were obtained between proanthocyanidins (PAs) intake and faecal N, NDIN and ADIN (0.535, 0.501 and 0.786, respectively). Regressing digestible N on N intake indicated that A. angustissima and C. calothyrsus tannins had significant effects on the digestion of dietary N. The animal responses were discussed in relation to PAs content. It was concluded that both the type and level of PAs were important determinants of the animal responses.

In situ neutral detergent insoluble nitrogen as a method for measuring forage protein degradability.

A method of estimating the undegraded intake protein (UIP) concentration of forages was developed and validated with a series of in situ experiments. The hypothesis was that UIP calculated from in situ neutral detergent insoluble N (NDIN) is equal to total in situ N minus the microbial N that is estimated from purines (MN). The in situ disappearance rates of total in situ N (TN), MN, and NDIN were measured for six hay samples and two range masticate samples. Hypothetical rates of passage (2 or 5%/h) were used to calculate UIP (% of DM) for each N pool. Estimates of UIP from TN were higher (P = .0001) than those from either MN or NDIN, and MN estimates of UIP were similar (P = .48) to NDIN estimates. A low-N fiber source (solka floc) was incubated in situ for 8 h. Analysis of the residue detected purines before, but not after, neutral detergent extraction. Several in situ incubation (i.e., Dacron bag size and number of Dacron bags in a mesh bag) and neutral detergent extraction conditions were tested. None of the factors tested affected in situ NDIN disappearance (P > .05). The hypothesis that NDIN is completely digestible in the rumen was tested. Estimates of the extent of NDIN digestion were made using 96-h in situ incubations, and UIP was recalculated for the test samples. Mean in situ UIP concentration decreased upon recalculation (P = .05). In situ NDIN provides estimates of forage UIP that are equal to estimates from MN. Forage UIP estimates are less when extent of N degradation is estimated and included in the calculation.

In sacco degradation characteristics of organic matter, neutral detergent fibre and crude protein of fresh grass fertilized with different amounts of nitrogen

Thirty composite grass samples, containing mainly Lolium perenne, were taken at three measuring periods in the spring and summer of 1991 and 1992 and two in the autumn of 1992 and 1993 from plots fertilized with 150, 300 and 450 kg N ha −1 year −1. In each period × N plot combination, grass samples were taken at a dry matter (DM)-yield of 1500 to 2000 kg ha −1 over four consecutive days and subsequently combined to one composite sample. These samples were incubated in rumen and intestinal cannulated lactating cows using the nylon-bag and mobile-nylon bag techniques to study the effects of N fertilizer on rumen degradation of organic matter (OM), crude protein (CP) and neutral detergent fibre (NDF) and on the intestinal digestibility of ruminal escaped CP (DRE CP). Nitrogen fertilizer increased CP content and decreased the content of DM and sugar whereas NDF content and in vitro digestibility (d OM) were not markedly influenced. The NDF content and d OM were more related to differences in age of the grass than to differences in the amounts of N applied. The content of neutral detergent insoluble N (NDIN) was increased significantly at higher rates of N fertilization. However, this effect on NDIN was difficult to interpret because of the fact that NDIN was highly influenced by the method of sample preparation. The N fertilizer had no effect on the content of acid detergent insoluble N (ADIN) which was negligible compared to the level of NDIN. The washable OM fraction was not influenced by N fertilizer whereas the washable CP fraction increased significantly. The results showed a decrease of the undegradable OM, CP and NDF fractions by using more N fertilizer. The rate of degradation of potentially degradable, but insoluble OM, CP and NDF fractions increased significantly at higher levels of N fertilization. As a consequence, more N fertilizer decreased the fraction of ruminal escaped CP (RE CP) significantly. However, during the whole season the total amount of RE CP entering the small intestine was increased although the increase was more pronounced in spring and early summer than in late summer and autumn. Only in autumn small intestine digestibility of RE CP tended to be higher at higher rates of N fertilization.

Characteristics of Nitrogen Fractions and Amino Acids of Feedstuffs Common to the Pacific Northwest

Thirty-nine forage samples and 47 grain and by-product feed samples were collected from various sites in Washington. Total crude protein (total N), soluble protein (soluble N), soluble nonprotein N (soluble NPN), soluble true PN, neutral detergent insoluble N (NDIN), and acid detergent insoluble N (ADIN) were determined. The soluble N in forages contributed 30 to 70% of total N, in which 60 to 80% was soluble NPN. Grains and by-product feeds had a lower percentage of soluble Nand NPN. Nitrogen degradability of feeds was estimated by Streptomyces grise us fermentation and in situ disappearance in the rumen. Effective N degradability of feeds was calculated. The rate and extent of N degradability offeeds, estimated by in situ technique, were generally greater than by S. griseus. In situ N degradability of most feeds could be accurately predicted by its DM degradability or by S. griseus N degradability. The proportion of microbial N in the incubated feeds was calculated from concentrations of purines or diaminopimelic acid. Eighty to 90% of total N for most feeds was degraded in the rumen after 24h of incubation.

Proanthocyanidins (condensed tannins) and the use of leaves from Sesbania sesban and Sesbania goetzei as protein supplements

Three accessions of Sesbania sesban (10865, 15019 and 15036) and one accession of Sesbania goetzei (15007) were used as protein supplements for rams fed maize ( Zea mays) stover in a growth trial and a digestion trial which investigated the effects of proanthocyanidins (PAs) on protein digestion. Levels of soluble and insoluble PAs were highest in accessions 15036 and 15007, intermediate in 15019 and lowest in 10865. In a 70 days growth trial, 60 rams were fed these accessions of sesbania which provided three levels of crude protein (25, 50, and 75 g day −1). Intakes of maize stover by rams fed accessions 10865 and 15019 were significantly higher ( P < 0.05) than rams fed 15036 and 15007. Rate of gain for rams fed accessions 10865 and 15019 were significantly higher ( P < 0.01) than for rams fed accessions 15036 and 15007. In the digestion trial, 12 rams were fed the four sesbania accessions and three levels of sesbania in a replicated 3 × 3 Latin square design. Intake of maize stover decreased as the level of sesbania increased for rams fed accessions 15036 and 15007. High levels of PAs depressed the digestibility of neutral-detergent fiber (NDF) which decreased the intake of maize stover. The digestion coefficients for acid-detergent lignin (ADL) were negative for accessions 15019, 15036, and 15007. The digestion coefficients for neutral-detergent insoluble N (NDIN) were negative for rams fed accessions 15036 and 15007. Negative digestion coefficients resulted from more fecal excretion of these fractions than were consumed. PAs may form detergent insoluble complexes in the digestive tract. Rams fed accessions 15036 and 15007 had the highest excretion of total fecal N and fecal NDIN and the lowest urinary N. Rams fed accession 10865 had the highest urinary N excretion and the lowest excretion of total fecal N and fecal NDIN. Rams fed accession 15019 had the highest N retention. The intermediate level of PAs in accession 15019 may have beneficial effects on protein digestion. High levels of PAs in accessions 15036 and 15007 may have detrimental effects. Forage N had nutritionally non-uniform digestion in accessions 15019, 15036, and 15007. Fecal excretion of NDIN was significantly correlated to intake of soluble PAs ( r = 0.941) and insoluble PAs ( r = 0.789). The formation of detergent insoluble complexes in the digestive tract violate principles of detergent analysis but this deviation from ideal behavior can be used to determine the effects of PAs on protein digestion.