Nitrogen in browse species: ruminal degradability and post-ruminal digestibility measured by mobile nylon bag and in vitro techniques

This study determined nitrogen degradability and digestibility of rumen undegradable nitrogen using mobile nylon bag (MNB) and pepsin/pancreatin in vitro technique (IV) of 40 browse species. Thirty Ethiopian highland sheep fitted with rumen cannulae were used in nitrogen (N) degradability studies. Six steers fitted with rumen cannulae were used in preparation of 16-h and 24-h ruminal undegraded residues and four steers fitted with distal abomasal cannulae were used in MNB technique. The browses varied widely in nitrogen solubility (15–468 g kg⁻¹), potential degradability (223–976 g kg⁻¹), rate of degradation (0·13–24% h⁻¹) and effective degradability (135–821 g kg⁻¹). The apparent N digestibility (ND) of the rumen undegraded residues differed significantly (P<0·05) among browse species. No significant difference (P>0·05) was observed in ND of 16-h and 24-h residues. The ND of the 16-h residue varied from -218 to 759 g kg⁻¹ and 169 to 851 g kg⁻¹ for MNB and IV methods, respectively. Browse species with high tannin contents such as Acacia hockii, A horrida, A melanoxylon, A persiciflora, A salicina, A saligna and Flemingia macrophylla had high rumen by-pass and a low ND, while Sesbania spp and A nilotica with low tannin contents underwent rapid and extensive dry matter and nitrogen degradation in the rumen. Acacia sieberiana, Chamaecytisus palmensis, Erythrina spp, Gliricidia sepium, Samanea saman and Enterolobium cyclocarpum had high proportions of protein escaping rumen degradation (BP ) and with a high proportion of the by-pass protein digested in the intestine, therefore these browses had a high potential as protein supplements. The ND measured with the MNB were significantly lower (P<0·001) than by the IV method. The correlation between MNB and IV was high and significant (R²=0·89, P<0·0001) as also indicated by the regression equation (SE in parentheses): MNB=-22·8 (4·55)+1·0 (0·08)IV (RSD=10·56, R²=0·79, n=40, P<0·001). The intercept of the linear relationship obtained was different from zero while the slope was not different from unity. Multiple regression analysis suggested that some of the unexplained variation could be accounted for by either nitrogen, acid detergent fibre, total phenolics or neutral detergent fibre bound tannin levels in browses. The IV method is accurate for estimating digestibility of ruminally undegradable N, and hence its use would considerably reduce the need for delicate surgery and the elaborate procedures involving the MNB technique. © 1998 SCI.     

Short communication: Short-term intravenous amino acid infusions as a method to detect limiting amino acids in dairy cattle diets

We hypothesized that the addition of limiting AA increases dry matter intake (DMI) by reducing anaplerosis and hepatic oxidation. Accordingly, the objective of this work was to examine the effects of short-term intravenous infusions of Met, Lys, and His (which are considered the most limiting AA) on DMI as a method to detect whether specific AA are limiting in dairy cow diets. We conducted 4 experiments using Holstein cows in the immediate postpartum period to address this objective. The first experiment used 4 cows 6 to 10 d postpartum (PP) in a 4 × 4 Latin square design with 1-d periods including 12 h for infusions and 12 h for recovery. Treatments were continuous infusions of 5 (low), 10 (medium), or 15% (high) of the calculated requirement of metabolizable Met, Lys, and His or 0.9% saline (control, CONT). In the second and third experiments, 8 cows (4–12 d PP) were divided into 2 groups of 4 cows, and each group received a different diet formulated to either be low in Lys (experiment 2) or Met (experiment 3). Each experiment was a crossover design with two 1-d periods with 12-h infusions (continuous) and 12 h for recovery. Treatments were 15% of the calculated requirement of metabolizable Met, Lys, and His (high), or 0.9% saline (CONT). In the fourth experiment, 5 cows (4–14 d PP) were used in a 5 × 5 Latin square design. Periods were 2 d in which treatments were continuously infused for the first 46 h. Treatments were 0.9% saline (CONT), all (Lys, Met, and His), LM (Lys and Met), LH (Lys and His), and MH (Met and His); dosages were equal to the estimated shortage in each specific AA. In each experiment, feed intake was recorded by a computerized data acquisition system, milk yield was recorded, and milk composition was analyzed for fat, protein, lactose, and milk urea nitrogen (MUN) concentrations. Treatments did not affect DMI or yield of milk or milk components in the first experiment. In the second experiment, AA treatment increased protein percentage and reduced lactose percentage but had no effect on protein and lactose yields or DMI. In the third experiment, the AA treatment tended to increase yields of milk, lactose, and protein as well as MUN concentration but did not affect DMI. In the fourth experiment, no effects were detected for DMI and milk yield, whereas the all, LH, and LM treatments reduced milk lactose concentration compared with CONT, and MH increased MUN concentration compared with CONT and other treatments. These results failed to provide support for our hypothesis that short-term addition of these potentially limiting AA will increase DMI. This may be due to our hypothesis being inaccurate or to other factors; other limiting AA could have prevented the effects of Lys, Met, and His infusions or the infusion periods could have been too short to induce a response in DMI. Accordingly, short-term infusion of AA is probably not a sensitive method to detect limiting AA in dairy cow diets.     

Estimation of the proportion of feed protein digested in the small intestine of cattle consuming wet corn gluten feed

The objectives of this study were to expand the database and determine the intestinal digestibility of rumen undegradable protein (dRUP) of common dairy feeds and to determine the effects of feeding 37.9% wet corn gluten feed on these estimates. Two ruminally and duodenally fistulated steers were assigned randomly to a crossover design with 4-wk periods. The mobile bag technique was used to determine rumen undegradable protein (RUP), dRUP, total tract digestible protein, and total tract digestible dry matter of alfalfa hay, brome hay, alfalfa haylage, corn silage, whole cottonseed, soybean meal, soyhulls, ground corn, nonenzymatically browned soybean meal, and dried distillers grains. There was no consistent effect of diet on RUP, dRUP, total tract digestible protein, and total tract digestible dry matter. The RUP (% of crude protein) ranged from 5.97% for alfalfa haylage to 75.6% for nonenzymatically browned soybean meal. The dRUP ranged from 15.3% for alfalfa haylage to 96.5% for nonenzymatically browned soybean meal. The dRUP for alfalfa hay (33.9%), brome hay (39.1%), alfalfa haylage (15.5%), and corn silage (19.9%) were lower than National Research Council reported values. The higher dRUP of the nonenzymatically browned soybean meal is reflective of more total protein reaching the small intestine. The large range in dRUP was not reflected in total tract digestible protein (% of crude protein), with corn silage being the lowest at 85.2% and nonenzymatically browned soybean meal the highest at 97.9%. In this study, diet had little effect on intestinal digestibility of protein or dry matter.     

Effect of slowly and rapidly degraded protein sources on the concentrations of amino acids and peptides in the rumen of steers

Four steers were given diets of straw and tapioca supplemented with urea, casein, formaldehyde treated casein (FTC), decorticated groundnut meal (DCGM), soya bean meal (SBM), maize gluten meal (MGM) or fish meal (FM) to determine the effect of degradability on rumen amino acid and peptide concentrations. Maximum concentrations of amino acid and peptide-N in rumen ultrafiltrates occurred 1 h after feeding. Total amino acid-N concentrations (mg litre^?1) at this time were low, ranging from 1.2 SE 0.8 (urea) to 15.6 SE 6.0 (casein) with little variation in individual amino acids. The peptide-N concentrations (mg litre^?1) were higher, ranging from 2.4 SE 0.5 (urea) to 160.0 SE 21.0 (casein), but were poorly correlated with degradability and solubility. Apart from casein, the highest concentrations of peptide-N were for those protein supplements, MGM (136.0 SE 25.0), FM (90.0 SE 15.0), and FTC (87.0 SE 14.0), with the lowest degradability suggesting that other factors, such as hydrophobicity, are also involved in the control of rumen peptide concentrations. Pooled samples taken 1 h after the morning feed were separated into three molecular weight (MW) fractions, 5000–50 000 da, 250–5000 da and < 250 da by gel filtration chromatography. From amino acid analysis it was found that the highest proportion of peptide-N was in the 250–5000 da fraction, and although some high MW (5000–50 000) constituents were present, only the FTC and MGM diets gave rise to significant amounts.     

Digestibility of amino acids in maize,wheat and barley meal,measured in pigs with ileo-rectal anastomosis and isolation of the large intestine

Maize, soft wheat and barley diets were compiled to have similar crude fibre (CF) concentration by addition of purified cellulose. Protein-free diets, with purified cellulose included at 60 g kg^?1 dry matter (DM) (PF1) and 90 g kg^?1 DM (PF2), were formulated. Each of four littermate, male pigs (22 kg liveweight) was surgically modified to create an ileo-rectal anastomosis with complete isolation of the large intestine. Diets were fed, and the ileal digesta, excreted via the anus, were collected. Endogenous amino acid output was higher after feeding PF2 than PF1. The choice of factor for correction of apparent digestibility (AD) to true digestibility (TD) was based upon CF intake of cereal diet. AD of most essential amino acids was greater in wheat than in maize or barley, although AD of lysine in barley (67.1%) was higher than in maize (56.8%) or wheat (63.4%). TD of most essential amino acids was higher for wheat and maize than for barley, although TD of lysine was similar for all cereals. Lysine and threonine were the most poorly digested essential amino acids in all cereals.     

Ruminal degradation and intestinal digestibility of protein and amino acids in high-protein feedstuffs commonly used in dairy diets

A study was conducted to determine the rumen degradation and intestinal digestibility of crude protein (CP) and AA, and AA composition of the rumen-undegradable protein (RUP) from 3 sources of blood meal (BM1, BM2, and BM3), canola meal (CM), low-fat distillers dried grains with solubles (LFDG), soybean meal (SBM), and expeller soybean meal (ESBM). Two Holstein cows fitted with ruminal and proximal duodenal cannulas were used for in situ incubation of 16 h and for the mobile bag technique. To correct for bacterial contamination of the RUP, 2 methods were used: purines and DNA as bacterial markers. Ruminal degradations of CP were 85.3, 29.8, 40.7, 75.7, 76.9, 68.8, and 37.0 ± 3.93% for BM1, BM2, BM3, CM, LFDG, SBM, and ESBM, respectively. Ruminal degradation of both total essential AA and nonessential AA followed a similar pattern to that of CP across feedstuffs. Based on the ratio of AA concentration in the RUP to AA concentration in the original feedstuff, ruminal incubation decreased (ratio <1) the concentrations of His, Lys, and Trp, and increased (ratio >1) the concentrations of Ile and Met across feedstuffs. Compared with purines, the use of DNA as bacterial marker resulted in a higher estimate of bacterial CP contamination for CM and lower estimates for LFDG and ESBM. Intestinal digestibility of RUP could not be estimated for BM1, BM3, and SBM due to insufficient recovery of residue. For the remaining feedstuffs, intestinal digestibility of RUP was highest for ESBM, followed by BM2 and LFDG, and lowest for CM: 98.8, 87.9, 89.7, and 72.4 ± 1.40%, respectively. Intestinal absorbable dietary protein was higher for BM2 compared with CM and LFDG, at 61.7, 17.9, and 20.7 ± 2.73% CP, respectively. As prices fluctuate, intestinal absorbable protein or AA may be used as a tool to aid in the selection among feedstuffs with different protein quality.     

青刺尖中水解氨基酸含量测定分析

目的:分析研究新鲜及腌制青刺尖氨基酸组成。方法:采用日立L-8800型氨基酸自动分析仪,色谱条件:标准分析柱4.6mm×60.0mm,反应柱温度:57.0℃,反应器温度:136.0℃,测定了新鲜和腌制青刺尖水解氨基酸。分析结果表明:新鲜和腌制样品均测定出17种氨基酸,其中必需和半必需氨基酸有12种。新鲜青刺尖的水解氨基酸总量为5.35%,腌制品为3.81%。结论:青刺尖氨基酸种类齐全,含量丰富,是一种天然绿色、营养健康的食品。     

Determining the contents of protein and amino acids in peanuts using near‐infrared reflectance spectroscopy

BACKGROUND: The protein and amino acid contents of peanuts play a key role in determining their quality and value. Therefore, accurate, nondestructive, quick, and automated measurement of these components would be valuable in a commercial environment. This study explored the feasibility of determining the contents of protein and amino acids in peanuts using near infrared–reflectance spectroscopy (NIRS). RESULTS: 141 peanut samples were collected from 12 provinces in China. The spectra were scanned and obtained with an NIRS system. The determination coefficient and the ratio of the standard deviation in the validation set to the standard error of validation corresponded to 0.99 and 6.53 for protein, 0.88 and 2.52 for Asp, 0.83 and 3.00 for Thr, 0.86 and 2.40 for Ser, 0.87 and 2.57 for Glu, 0.88 and 2.36 for Gly, 0.88 and 3.00 for Leu, 0.89 and 2.88 for Arg, and 0.96 and 7.50 for Cys. CONCLUSIONS: NIRS combined with multivariate calibration has significant potential in determining the protein and amino acid contents of peanuts. This method is suitable for use in an industrial setting owing to its ease of use as well as the relatively low cost of obtaining and running the necessary equipment. Copyright © 2012 Society of Chemical Industry     

Effect of supplemental L-lysine-HCL and corn source on rumen fermentation and amino acid flow to the small intestine

Four lactating Jersey cows fitted with ruminal and duodenal cannulae were used in a 4 x 4 Latin square design trial to determine the effect of supplemental lysine in diets containing dry ground (GC) or steam-flaked (SFC, 360 g/L) corn on ruminal fermentation and amino acid (AA) flow to the duodenum. Supplemental L-lysine-HCL provided 10 g/d of additional Lys to the total mixed rations. There were no interactions between supplemental Lys and corn source. Supplemental Lys increased Lys intake, but did not alter nutrient intake and digestibility or N flow to the duodenum. Intake of dry matter (DM), organic matter (OM), and neutral detergent fiber (NDF) and ruminal digestibility of starch tended to be higher, whereas ruminal digestibility of DM, OM, acid detergent fiber, and NDF was lower for diets supplemented with SFC compared with GC. Whole-tract digestibility was similar for both corn supplements. Ruminal pH and molar proportions of volatile fatty acids were not affected by supplemental Lys or corn source; however, ruminal NH(3) concentrations were lowest when SFC was fed. Intake of N tended to be higher and the flow of total N and individual AA to the duodenum was higher for diets supplemented with SFC. There was a trend for increased flow of microbial N for diets supplemented with SFC. Supplemental L-lysine-HCL did not alter ruminal fermentation, flow of amino acid to the small intestine, or nutrient digestibility, but feeding SFC reduced ruminal fiber digestion and increased microbial protein synthesis and flow of amino acid to the duodenum.     

Apparent ileal digestibility of amino acids in feed ingredients determined with broilers and layers

The apparent ileal digestibility of amino acids in eight feed ingredients were determined using broilers and layers. The ingredients included three cereals (wheat, sorghum and maize), one cereal by‐product (wheat middlings), three oilseed meals (canola, cottonseed and soybean meals) and one animal protein meal (meat and bone meal). Dietary protein in the assay diets was supplied solely by the test ingredient. All diets contained 20 g kg^?1 acid‐insoluble ash as an indigestible marker, and each diet was offered ad libitum in mash form to five replicate pens of 42‐day‐old broilers and 60‐week‐old layers. The digestibility coefficients of most amino acids for wheat and sorghum were similar (P > 0.05) in broilers and layers. The digestibility of most amino acids for maize was higher (P < 0.05) in broilers compared to those in layers. The digestibility of individual amino acid for wheat middlings was higher (P < 0.05) in layers than in broilers. In general, the digestibility of amino acids for cottonseed meal, soybean meal, and meat and bone meal were similar (P > 0.05) between broilers and layers. The influence of class of bird on digestibility in canola meal was variable. The digestibility of threonine, valine, isoleucine, leucine, phenylalanine, glutamic acid and alanine were higher (P < 0.05), and those of methionine, histidine and lysine were lower (P < 0.05) in broilers compared to layers. These results suggest that the practice of using amino acid digestibility values generated with broilers for layers may not be appropriate for all feed ingredients. Copyright © 2006 Society of Chemical Industry     

Effect of varying levels of fatty acids from palm oil on feed intake and milk production in Holstein cows

To determine the optimum feeding level of fatty acids of palm oil (PALM; Energizer RP10; 86.6% palmitic acid) on milk production, lactating cows (n = 18) were randomly assigned to a treatment sequence in replicated 4 × 4 Latin squares. Animals were assigned to squares by parity (3 multiparous and 1 primiparous squares with primiparous in the incomplete square). The 4 diets were designed to provide 0, 500, 1,000, and 1,500 g of PALM per day. Cows were fed individually with feed intake measured daily. Each period lasted 16 d with milk production and composition determined the final 2 d. Milk production, milk composition and feed intake data were analyzed using the MIXED procedure of SAS. Milk yields were 30.9, 34.0, 34.2, and 34.2 kg/ d (SEM = 1.9) for the 0, 500, 1,000, and 1,500 g levels, respectively. Milk yield was increased by the addition of PALM; however, there were no differences among the levels of PALM. Milk fat percentage was also increased from 3.44% for 0 g to 3.95% (SEM = 0.17) across all levels of PALM but there were no differences among the PALM treatments. Dry matter intakes were 23.3, 26.4, 24.7, and 23.8 kg/d (SEM = 1.4) for the 0, 500, 1,000 and 1,500 g levels, respectively. The addition of PALM increased milk yield and milk fat percentage, and no adverse effects on dry matter intake were observed.     

Cow and environmental factors associated with protein fractions and free amino acids predicted using mid-infrared spectroscopy in bovine milk

The objective of the present study was to identify the factors associated with both the protein composition and free amino acid (FAA) composition of bovine milk predicted using mid-infrared spectroscopy. Milk samples were available from 7 research herds and 69 commercial herds. The spectral data from the research herds comprised 94,286 separate morning and evening milk samples; the spectral data from the commercial herds comprised 40,260 milk samples representing a composite sample of both the morning and evening milkings. Mid-infrared spectroscopy prediction models developed in a previous study were applied to all spectra. Factors associated with the predicted protein and FAA composition were quantified using linear mixed models. Factors considered in the model included the fixed effects of calendar month of the test, milking time (i.e., morning, evening, or both combined), parity (1, 2, 3, 4, 5, and ≥6), stage of lactation, the interaction between parity and stage of lactation, breed proportion of the cow (Friesian, Jersey, Norwegian Red, Montbéliarde, and other), and both the general heterosis and recombination coefficients of the cow. Contemporary group as well as both within- and across-lactation permanent environmental effects were included in all models as random effects. Total proteins (i.e., total casein, CN; total whey; and total β-lactoglobulin) and protein fractions (with the exception of α-lactalbumin) decreased postcalving until 36 to 65 days in milk and increased thereafter. After adjusting the statistical model for differences in crude protein content and milk yield separately, irrespective of stage of lactation, younger animals produced more total proteins (i.e., total CN, total whey, and total β-lactoglobulin) as well as more total FAA, Glu, and Asp than their older contemporaries. The concentration of all protein fractions (except β-CN) in milk was greatest in the evening milk, even after adjusting for differences in the crude protein content of the milk. Relative to a purebred Holstein cow, Jersey cows, on average, produced a greater concentration of all CN fractions but less total FAA, Glu, Gly, Asp, and Val in milk. Relative to their respective purebred parental average, first-cross cows produced more total CN and more β-CN. Results from the present study indicate that many cow-level factors, as well as other factors, are associated with protein composition and FAA composition of bovine milk.     

Ruminal fermentation and amino acid flow in Holstein steers fed whole cottonseed with elevated concentrations of free fatty acids in the oil

The influence of feeding whole cottonseed (WCS) containing elevated concentrations of free fatty acids (FFA) in the oil on ruminal fermentation and amino acid (AA) flow to the abomasum was evaluated in a 4 x 4 Latin square trial. Four ruminally and abomasally cannulated Holstein steers were fed diets containing 12.5% of dry matter as WCS with concentrations of 8.0, 11.3, 14.7, or 18.0% FFA in the oil. Intake, ruminal digestibility, and flow to the abomasum of dry matter, organic matter, and acid detergent fiber were not affected by FFA level of WCS. Intake of neutral detergent fiber and total kilograms of neutral detergent fiber digested in the rumen were similar for all treatments. Ruminal neutral detergent fiber digestibility was lower for 8 and 14.7% FFA, resulting in a cubic effect on flow to the abomasum. Ruminal pH, molar proportions of isobutyrate, and total branched-chain volatile fatty acids (VFA) decreased linearly, whereas molar proportions of acetate and acetate:propionate ratio increased linearly as FFA in WCS increased. Total VFA were lower, and molar proportions of propionate were higher, for 8 and 14.7% FFA, resulting in a cubic effect. Intake of N, total N flow, and nonmicrobial N flow to the abomasum were similar among treatments. Flow of microbial N was lower for the 11.3% FFA treatment, resulting in a quadratic response. Only nonsignificant differences were observed in AA flow to the abomasum. Results of this trial indicate that WCS with FFA up to 18% may result in small changes in rumen fermentation.     

6种葡萄籽中水解氨基酸和游离氨基酸含量测定及比较

以异硫氰酸苯酯为柱前衍生试剂,采用Thermo Acclaim~(TM) 120 C_(18)色谱柱(250mm×4.6mm,5μm),流动相A为pH 6.5的乙酸钠缓冲溶液,流动相B为甲醇—乙腈—水(体积比20:60:20),在流速1.0mL/min,梯度洗脱,柱温30℃,检测波长254nm的条件下,建立了高效液相色谱法测定葡萄籽中水解氨基酸和游离氨基酸的含量。结果表明,在试验浓度范围内,17种氨基酸的R~2均0.999 0;水解氨基酸的加样回收率为92.0%～104.6%,RSD为0.83%～4.07%;游离氨基酸的加样回收率为95.2%～102.4%,RSD为1.06%～3.98%。同时,6种葡萄籽中水解氨基酸的含量为130.46～163.24 mg/g,游离氨基酸的含量为2.04～5.13mg/g;用于酿造白葡萄酒的雷司令、赛美容和贵人香3种葡萄籽中游离氨基酸含量较高,用于酿造红葡萄酒的黑皮诺、蛇龙珠和赤霞珠3种葡萄籽中水解氨基酸含量较高。该方法稳定可靠,可用于葡萄籽中水解氨基酸和游离氨基酸的含量测定。     

Assessing availability of amino acids from various feedstuffs in dairy cattle using a stable isotope-based approach

Nitrogen efficiency in dairy cows can be improved by more precisely supplying essential amino acids (EAA) relative to animal needs, which requires accurate estimates of the availability of individual EAA from feedstuffs. The objective of this study was to determine EAA availability for 7 feed ingredients. Seven heifers (258 ± 28 kg BW) were randomly chosen and assigned to 8 treatment sequences in a 7 × 8 incomplete Latin square design. Treatments were a basal diet (BD), and 10% (on a dry matter basis) of BD replaced by corn silage (CS), grass hay (GH), alfalfa hay (AH), dried distillers grain (DDGS), soybean hulls (SH), wet brewers grain (BG), or corn grain (CG). Total plasma AA entry rates were estimated for each EAA within each diet by fitting a 4-pool dynamic model to observed plasma, ¹³C AA enrichment resulting from a 2-h constant infusion of a ¹³C algal AA mixture. Individual EAA availability from each test ingredient was determined by regression of entry rates for that AA on crude protein intake for each ingredient. The derived plasma total EAA entry rates for corn silage, grass hay, alfalfa hay, dried distillers grain, soyhulls, brewers grain, and corn grain were 30.6 ± 3.4, 27.4 ± 3.2, 31.3 ± 3.4, 37.2 ± 3.2, 26.4 ± 3.2, 37.8 ± 3.2, and 33.5 ± 3.2% (±standard error) of EAA from each ingredient, respectively. Using the previous estimate of 8.27% EAA utilization by splanchnic tissues during first pass, total rumen-undegradable protein EAA absorbed from the gut lumen was 33.4, 29.9, 34.1, 40.6, 28.8, 41.2, and 36.5% of the EAA in each ingredient respectively.     

Postharvest changes in ammonium,amino acids and enzymes of amino acid metabolism in asparagus spear tips

Harvested asparagus (Asparagus officinalis L) spears accumulate ammonium and amino acids in their tips during storage at ambient temperatures. To further investigate these phenomena the authors held spears at 20°C in the dark after harvest and examined several parameters of amino acid metabolism in the tips. Soluble protein content declined faster than total protein over the 5-day storage period. Protein loss was accompanied by an increase in total free amino acids with asparagine showing the most dramatic increase. A pronounced accumulation of ammonium occurred, starting after 3 days. The activities of glutamine synthetase (EC 6.3.1.2) and aspartate and alanine aminotransferases (EC 2.6.1.1 and EC 2.6.1.2, respectively) declined slightly whereas glutamate dehydrogenase (EC 1.4.1.2) activity almost doubled over 5 days. Phenylalanine ammonia lyase (EC 4.3.1.5) activity declined rapidly during the first 2 days and then partially recovered. Asparagine synthetase (EC 6.3.1.1), asparagine aminotransferase (EC 2.6.1.14), asparaginase (EC 3.5.1.1) and glutaminase (EC 3.5.1.2) activities were not detectable at any time during the storage period. Ammonium accumulation could be caused by increased glutamate dehydrogenase activity coupled with a shortage of aspartate.     

大麦苗粉中氨基酸组成及含量

对大麦苗粉中的氨基酸进行了定性、定量分析研究。结果表明:大麦苗粉中共分析检测出26种氨基酸,其中,水解氨基酸17种,游离氨基酸26种。大麦苗粉中17种水解氨基酸总含量为9 163.422mg/100g,其中人体必需氨基酸含量占总含量的40%以上,大麦苗粉中含有9种药用氨基酸,其中Glu含量最高,达1 390.873mg/100g;大麦苗粉中26种游离氨基酸总含量为983.852 mg/100g;其中Asp、Glu、Arg、Pro、His、Val 6种游离氨基酸,是形成大麦苗粉风味的主要氨基酸。     

Digestibility of amino acids in soya-bean,sunflower and groundnut meal,measured in pigs with ileo-rectal anastomosis and isolation of the large intestine

Each of four littermate male pigs of 25 kg liveweight was surgically adapted to create a bypass of the large intestine by ileo-rectal anastomosis. The large intestine was sealed at both ends and a cannula was exteriorised from the lumen to allow any products of residual fermentation to escape. Ileal digesta were excreted via the anus. Three isonitrogenous diets were formulated containing soya-bean or groundnut (dehulled) or sunflower (not dehulled) meals as the sole protein sources. Each diet was fed, in turn, for 7 consecutive days to all pigs, and Heal digesta from feeds on days 5 and 6 (indicated by chromic oxide addition to feeds) were collected. This procedure was conducted twice for each diet. Apparent digestibility coefficients (AD) of nitrogen (N) and amino acids were calculated (as percentages of the respective intake). AD of N and the majority of amino acids of soya-bean and groundnut meals were greater (P<0.05) than those of sunflower meal. In the order soya-bean, groundnut and sunflower meal, coefficients were: for lysine, 87.7, 83.5, 71.0% (standard error of the differences between means (SED) 1.06); for threonine, 81.0, 80.5, 74.4% (SED 1.03); for methionine, 89.1, 84.9, 88.5% (SED 0.49); and for the sum of the amino acids, 85.4, 88.1, 78.8% (SED 0.75).     

Effects of reduced dietary protein and supplemental rumen-protected essential amino acids on the nitrogen efficiency of dairy cows

When fed to meet the metabolizable protein requirements of the National Research Council, dairy cows consume an excess of N, resulting in approximately 75% of dietary N being lost to the environment as urine and feces. Reductions in environmental N release could be attained through an improvement in N efficiency. The objective of this study was to determine if the predicted reduction in milk yield associated with feeding a low-protein diet to lactating dairy cows could be avoided by dietary supplementation with 1 or more ruminally protected (RP) AA. Fourteen multiparous and 10 primiparous Holstein cows, and 24 multiparous Holstein × Jersey crossbred cows were used in a Youden square design consisting of 8 treatments and 3 periods. The 8 dietary treatments were (1) a standard diet containing 17% crude protein [CP; positive control (PC)], (2) a 15% CP diet [negative control (NC)], (3) NC plus RP Met (+M), (4) NC plus RP Lys (+K), (5) NC plus RP Leu (+L), (6) NC plus RP Met and Lys (+MK), (7) NC plus RP Met and Leu (+ML), and (8) NC plus RP Met, Lys, and Leu (+MKL). Dry matter intake was not affected by treatment. Crude protein intake was lower for NC and RP AA treatments compared with the PC treatment. No detrimental effect was detected of the low-CP diet alone or in combination with AA supplementation on milk and fat yield. However, milk protein yield decreased for NC and +MKL diets, and lactose yield decreased for the +MKL compared with the PC diet. Milk urea N concentrations were lower for all diets, suggesting that greater N efficiency was achieved by feeding the low-protein diet. Minimal effects of treatments on arterial plasma essential AA concentrations were detected, with only Ile and Val being significantly lower in the NC than in the PC diet. Phosphorylation ratios of signaling proteins known to regulate mRNA translation were not affected by treatments. This study highlights the limitations of requirement models aggregated at the protein level and the use of fixed postabsorptive efficiency to calculate milk protein requirements. Milk protein synthesis regulation by signaling pathways in vivo is still poorly understood.