Proteolysis and in situ ruminal degradation of lucerne ensiled with Cistus ladanifer tannins

The effects of ensiling lucerne with graded inclusion of Cistus ladanifer condensed tannins (CT) on in silo fermentative parameters, in vitro organic matter digestibility (IVOMD) and on in situ rumen degradability of dry matter (DM) and crude protein (CP) were studied. Lucerne forage ( Medicago sativa subsp. sativa ) was sprayed with different solutions of C. ladanifer CT extract in 60 ml of water in order for dose 0 (control), 40 (L40), 80 (L80) and 120 (L120) g of CT per kg of lucerne DM and was ensiled in lab‐scale silos. After 35 days, the silages were analysed for chemical composition, and the in situ ruminal degradability was determined in rams. The inclusion of CT in the silages caused an important dose‐dependent reduction in soluble‐N, NH₃‐N and a large increase in true protein content and N bound with neutral detergent fibre (NDF‐N), which indicates an effective proteolysis reduction during ensiling. Also, the rumen undegradable protein (RUP) increased linearly (P < 0.01) with CT inclusion. However, a linear decrease (P < 0.02) of 5%, 13% and 22% of IVOMD was observed for the silages L40, L80 and L120 respectively. The results obtained suggest that C. ladanifer CT can be used as silage additives to reduce proteolysis of high‐protein forages during ensiling. A level of CT of 40 g/kg DM seems to be the best compromise between the gains achieved by the protection of CP degradation in silo and in the rumen and the losses associated with the depression of the digestion and absorption.     

Silage additives to reduce protein degradation during ensiling and evaluation of in vitro ruminal nitrogen degradability

Despite the high degradability of their proteins, grass and legume silages represent an important option to reach more sustainable livestock systems. To improve the nitrogen use efficiency of these crops, this study assessed the potential of several additives (chestnut tannins, oak tannins, zeolite, erythritol by‐product solution and wood molasses) to reduce proteolysis in the silo and in vitro nitrogen degradability. Ryegrass (Lolium multiflorum) and red clover (Trifolium pratense) were ensiled in varying proportions in laboratory‐scale silos made of vacuum‐packed plastic bags. Dry‐matter content, chemical composition, pH, ammonia and volatile fatty acids content were analysed after 34 days of ensiling. Ruminal nitrogen degradability was assessed in vitro (Aufrère & Cartailler, 1988 ). We observed that the proportion of ammonia in silage was reduced by the addition of oak tannin (?12%) and zeolite (?16%). The addition of zeolite lowered in vitro organic matter digestibility. Rapidly degradable nitrogen (1‐hr degradability) was reduced in vitro by both tannins (?6.8% for chestnut and ?6.6% for oak) and zeolite (?5.8%), but total degradable nitrogen (24‐hr degradability) was only reduced by oak (?6.5%) and chestnut tannins (?7.3%). It suggests that tannins protected proteins from plant and bacterial enzymes by forming a complex that better resists silage fermentations and in vitro protease action. The reduction effects on proteolysis in the silo and on in vitro ruminal nitrogen degradability are limited individually but could be cumulative. Erythritol by‐product solution and wood molasses had no effect on silo or in vitro proteolysis.     

Differences in the crude protein fractions of lucerne leaves and stems under different stand structures

Protein degradability in forage legumes is of global importance because utilization efficiency of forage has economic and environmental consequences. However, there are no published studies on the effect of legume stand structure on differences in crude protein (CP) fractions. The main objective of the present research was therefore to investigate differences in CP fractions in leaves and stems of lucerne (Medicago sativa L.) during the growing season. Stand traits were measured over 2 years, and forage was sampled at the early bud and early flower stages in the first, second and third cuts. Stems had significantly higher concentrations (in g kg^?1 CP) of non‐protein (fraction A: 430 g kg^?1 CP) and indigestible nitrogen (fraction C: 92 g kg^?1 CP) than leaves and had lower relative content of true protein (fraction B: 478 g kg^?1 CP). In the total forage (stems and leaves combined), about 80% of the variation in CP fractions was explained by year, cut and maturity. Year was the most important factor, particularly for the B fractions. Cut was the second‐most important factor; its main effect was that the relative abundance of fraction A declined from 394 g kg^?1 CP in the first cut to 293 in g kg^?1 CP the third cut. Maturity increased the amounts of indigestible fraction C and protein fractions B₁ and B₃. This was associated with the leaf weight ratio, which had an inverse relationship with maximal stem length and dry matter yield. Variation partitioning showed that 75% of CP fraction variability associated with cut, maturity and year could be explained by the evaluated stand traits. This research has highlighted the need to consider plant morphological traits when legume CP fractions are evaluated.     

Effects of formic acid and potassium diformate on the fermentation quality,chemical composition and aerobic stability of alfalfa silage

The objective of this study was to evaluate the efficacy of potassium diformate (KDF) as a potential additive for alfalfa silage. Fresh alfalfa was untreated or treated with formic acid (4 g/kg fresh weight, FW) or three concentrations of KDF (4, 5.5 or 7 g/kg FW). After 60 days of ensiling, the addition of formic acid and greater levels of KDF (5.5 and 7 g/kg) effectively reduced silage pH and inhibited the undesirable bacteria, indicated by lower butyric acid, ethanol, ammonia N concentrations and microbial populations (including enterobacteria, yeasts, moulds and clostridia). Additives decreased the dry‐matter loss, and more water‐soluble carbohydrates were preserved in the silages with formic acid or potassium diformate than in the control. Alfalfa silages treated with formic acid at 4 g/kg FW or potassium diformate at 5.5 or 7 g/kg FW were classified as the highest quality silage based on the higher Flieg's point (above 70) and remained stable for more than 9 days during aerobic exposure. Potassium diformate is recommended as an effective additive for alfalfa silages at a level of 5.5 or 7 g/kg FW under the humid and hot conditions of southern China.     

Volatile fatty acid proportions and microbial protein synthesis in the rumen of cattle receiving grass silage ensiled with different rates of formic acid

Timothy–meadow fescue herbage was ensiled with formic acid (FA) (expressed as 100% solution) at the rates of 0, 2, 4 or 6 L t^?1. The silages were fed along with concentrates to bulls fitted with cannulae in the rumen and duodenum. The ration comprised grass silage (700 g kg^?1), barley (240 g kg^?1) and rapeseed meal (60 g kg^?1). The application rate of FA had no effect on the site or extent of the digestion of dietary organic matter (OM) and neutral‐detergent fibre. The flow of total N at the duodenum increased linearly (P < 0·05) with application rate of FA, reflecting mainly an increased (P < 0·01) flow of microbial N. The apparent efficiency of net microbial protein synthesis in the rumen increased (P < 0·05), the proportion of propionate in the volatile fatty acids (VFA) in the rumen was not affected (P > 0·05) but that of butyrate increased (linear and quadratic effects, P < 0·01) with increasing rate of FA. It is concluded that an increase in the rate of FA at ensiling leads to a higher utilization of energy and/or protein‐yielding substrates for rumen microbes and to a modified rumen VFA pattern with an increased proportion of butyrate.     

Protein degradation and fermentation characteristics of unwilted red clover and alfalfa silage harvested at various times during the day

Extensive proteolysis during fermentation of high‐protein legumes reduces dietary N‐use efficiency in ruminants. Research has demonstrated that enhancing the level of fermentable carbohydrates in crops entering the silo may reduce protein degradation by increasing the rate of decline in pH. The objective was to evaluate whether delaying cutting time during the day, to allow accumulation of total non‐structural carbohydrates (TNC), would inhibit proteolysis in the silo. Red clover (Trifolium pratense L.) and alfalfa (Medicago sativa L.) were harvested at 06.00, 10.00, 14.00 and 18.00 hours in 1993, 1994 and 1995, and ensiled without wilting. TNC accumulated in fresh forage during the day, with starch accounting for more than 0·50 of the daily change in TNC in fresh herbage of both species, except in red clover in 1995. The level of TNC in fresh forage did not consistently affect the extent of protein degradation in either species and, in all instances, alfalfa underwent more extensive proteolysis than red clover. Silage pH typically decreased and starch concentration increased as cutting time was delayed from 06.00 to 18.00 hours. Although the extent of proteolysis was largely unaffected by inherent increases in TNC, harvesting in the afternoon did provide several benefits including increased dry‐matter content, lower silage pH and higher starch concentrations. Effluent production is a concern in any unwilted silage system; there was therefore an added advantage of lower moisture content from cutting in the afternoon.     

Effects of applying Lactobacillus plantarum and Chinese gallnut tannin on the dynamics of protein degradation and proteases activity in alfalfa silage

The effects of Lactobacillus plantarum (LP) and Chinese gallnut (Rhus chinensis Mill) tannin on the fermentation quality, nitrogen distribution, protein fractions and proteases activity of alfalfa (Medicago sativa) silage were studied. Additives added to alfalfa forage (approximately 40% DM) were LP (1 × 10⁶ cfu/g FW) plus sucrose (4 g/kg FW) (LP + S), LP (1 × 10⁶ cfu/g FW) plus commercial cellulase (0.1 g/kg FW) (LP + C) and Chinese gallnut tannin at two levels (20 and 50 g/kg DM) (TA 2% and TA 5%). The control was sprayed with the same volume of distilled water. Silage was sampled and analysed on days 1, 3, 5, 7, 14, 21, 28 and 35. The results showed that the degradation of protein to nonprotein nitrogen took place mainly during the first 3 days, while the degradation of peptides and free amino acids occurred throughout the ensiling process. All additives lowered nonprotein nitrogen and free amino acids nitrogen proportion during the ensiling. Additive TA 5% was the most effective to inhibit proteolysis among the four additives, followed by LP + S. They inhibited the activities of all three plant proteases and decreased production of nonprotein nitrogen, free amino acids and ammonia nitrogen during the ensiling process.     

大豆品种早12花序分化形成期间的顶芽内源激素变化

大豆花序分化形成期间,顶芽内源玉米赤霉烯酮（ＺＥＮ）含量先降后升;异戊烯基腺嘌ｉＰＡｓ）含量在花序发育后期迅速增加,说明ＺＥＮ与ｉＰＡｓ可促进花序的发育。植株的脱落酸（ＡＢＡ）含量短日（ＳＤ）处理始终比连续照光处理低,表明ＡＢＡ可抑制花芽的形成与分化。     

The effect of different additives on the fermentation quality, aerobic stability and in vitro digestibility of pea/wheat bi-crop silages containing contrasting pea to wheat ratios

Studies were conducted to compare the effects of using two microbial inoculants, a sulphite salt‐based additive, formic acid and quebracho tannins, on the fermentation quality, nutritive value and aerobic stability of pea/wheat bi‐crop silages. Spring peas (Pisum sativum var. Magnus) and spring wheat (Triticum aestivum var. Axona) were drilled together at rates that gave high (HP/W; 3:1) or low (LP/W; 1:3) pea to wheat ratios. The peas and wheat were harvested at the yellow wrinkled pods and late milk/early dough maturity stage, respectively, and conserved in 1·5‐kg polyethylene bag, laboratory silos. The bi‐crops were conserved without treatment (control) or treated with either of two lactic acid bacteria‐based inoculants [Lactobacillus buchneri; applied at 10⁵ colony‐forming units (CFU) g^–1 fresh weight (FW) or Lactobacillus plantarum (applied at 10⁶ CFU g^–1 FW)], sulphite salts (applied at the rate of 1 ml sulphite solution kg^–1 FW), quebracho tannins (applied at 16 g kg^–1 FW) and formic acid (applied at 2·5 g kg^–1 FW). Six replicates were made for each treatment, and the silos were opened after 112 days of ensilage. The level of peas in the bi‐crop influenced the effectiveness of the additives. With the exception of sulphite salts, all the additives significantly reduced the soluble nitrogen (N) and ammonia‐N concentrations of all the silages. The ratio of lactic acid to acetic acid was generally lower in the LP/W silages than in the HP/W silages, and the additive treatments only increased the in vitro digestible organic matter in dry matter of the LP/W silages. Of all the additives evaluated, formic acid resulted in the least aerobic spoilage in HP/W bi‐crop silages. However, in the LP/W bi‐crops, additive treatment was not necessary for ensuring aerobic stability.     

Effects of propionic acid and Lactobacillus buchneri (UFLA SIL 72) addition on fermentative and microbiological characteristics of sugar cane silage treated with and without calcium oxide

The objective of this work was to evaluate the effects of a new strain of Lactobacillus buchneri (UFLA SIL 72) isolated from sugar cane (Saccharum spp.) silage and the addition of propionic acid [1% based on fresh matter (FM)] to silages treated with and without calcium oxide (1% of FM) at 60 and 170 d of ensiling. A randomized block design with a 2 × 2 × 2 × 2 factorial arrangement of treatments was used to analyse the results. The use of calcium oxide reduced the ethanol content and neutral detergent fibre in all silages, increased pH values and favoured the growth of clostridia and yeasts. The addition of propionic acid reduced the yeast population, but it was not able to reduce ethanol content of silage. The addition of L. buchneri resulted in silages with higher concentration of propionate, reduced the levels of ethanol and reduced the population of clostridia in all silages. The use of calcium oxide is not recommended for silage of sugar cane.     

Effect of wilting,silage additive,PEG treatment and tannin content on the distribution of N between different fractions after ensiling of three different sainfoin (Onobrychis viciifolia) varieties

Sainfoin (Onobrychis viciifolia) is a tanniniferous, leguminous plant that has potentially beneficial effects on protein utilization in ruminants. As ensiling causes protein breakdown and elevated levels of buffer soluble N (BSN), we studied the distribution of N before and after ensiling sainfoin. Three varieties of sainfoin were either direct‐cut and frozen directly or wilted and frozen before later ensiling in mini‐silos with and without acidification with Promyr (PM; an acidifying commercial mixture of propionic and formic acid) and with or without polyethylene glycol (PEG). Extractable tannins (ET) and protein‐bound tannins (PBT) were measured with an HCl/butanol method in an attempt to correlate tannin levels to N fractions. The sainfoin silages showed good ensiling characteristics and had relatively high concentrations of undegraded protein. The effect of wilting on BSN levels (g/kg N) was dependent on sainfoin variety (P < 0·001). PEG increased and PM decreased the level of BSN in the silages (P < 0·001). PM treatment also produced less non‐protein N and ammonia‐N (P < 0·05) as compared with no additive. Addition of PEG to the silage increased the BSN‐proportion 1·8‐ and 2·6‐fold for both DM stages. A strong tannin‐protein binding effect is, therefore, confirmed in sainfoin. However, correlations between tannin levels (ET and PBT) and BSN were poor in the (non‐PEG) silages, indicating either that the HCl/butanol method is unsuitable for measuring tannin in silages or that qualitative attributes of tannins are more relevant than quantitative. The HCl/butanol method seems therefore not to be useful to predict degradation of protein in sainfoin silages.     

The effects of stage of growth and additives with or without cellulase on fermentation and in vitro degradation characteristics of Leymus chinensis silage

This study evaluated the effects of different combinations of added lactic acid bacteria and cellulase applied at two growth stages on chemical composition and in vitro rumen digestibility of Leymus chinensis silage. Fresh grass was harvested at early heading stage (S1) and late heading stage (S2), respectively, and ensiled with five additives: 200 U cellulase (C) kg^?1 fresh matter (FM), 1 × 10⁵ colony‐forming units (cfu) Lactobacillus plantarum (LP) g^?1 FM, 1 × 10⁵ cfu Lb. casei (LC) g^?1 FM, LP+C, LC+C and a control (CK). Four replicates of each treatment were weighed into 5‐L plastic buckets, and the mini silos were stored at ambient temperature (~30°C) for 60 d. Leymus chinensis harvested at S2 showed relatively higher neutral detergent fibre content, coliform bacteria count and lower crude protein content than S1. All additives decreased the pH and ammonia nitrogen (NH₃‐N) content of L. chinensis silage (P < 0·001) except C. LP+C and LC+C decreased fibre content and increased water‐soluble carbohydrate content (P < 0·001). The silages were further anaerobically incubated in vitro at 39°C for 48 h with buffered rumen fluids of lactating cows. Leymus chinensis harvested at S2 showed lower in vitro dry‐matter disappearance, NH₃‐N, total volatile fatty acid (VFA) content and higher average gas production rate (P < 0·05) than S1. In conclusion, Leymus chinensis should not be harvested too late. Compared with other treatments, a combination of Lb. casei (LC) with cellulase resulted in better fermented silage, but further testing is needed to confirm its efficacy.     

Wide variation in nitrification activity in soil associated with different forage plant cultivars and genotypes

There is a growing interest in using plants to manipulate the nitrification rate in soils with the object of reducing losses of nitrogen from the soil–plant system – lower rates of nitrification being associated with reduced leaching of nitrate and reduced emissions of nitrous oxide. Here we screened the potential nitrification rate in soil associated with 126 cultivars from 26 species representing three functional groups used in temperate managed grassland. Plants were grown in pots, and the nitrification was measured using two approaches: (i) a measure of potential nitrification carried out in the laboratory on soil samples and (ii) a measure of nitrification in the presence of the growing plants using the ratio of nitrate to ammonium () measured on in situ ion exchange membranes after the application of urine. There was about a twofold difference among cultivars in nitrification measured using the potential assay and a 10‐fold difference using the ratio approach. The ranking of nitrification was different using the two approaches perhaps suggesting that the presence of plants in the ratio approach had an effect on the outcome although further work will be necessary to confirm this. Irrespective of the method used, the results demonstrate substantial differences between cultivars but also within cultivars offering the possibility of selection to enhance plant effects on nitrification.     

不同年代育成大豆叶片氮含量的变化及其与净光合速率的关系

为了解大豆品种遗传改良过程中叶片氮含量的变化及其与净光合速率的关系,对吉林省1923年-2004年间育成的21个大豆品种的叶片氮含量和光合特性进行了研究。结果表明,叶片氮含量与育成年代在R2期和R6期呈极显著或显著正相关,但在R4期呈不显著负相关。在R2期和R6期,大豆品种间叶片单位叶面积氮含量增长率明显大于净光合速率增长率,导致了氮素光合利用效率与育成年代呈极显著或显著负相关;在R4期,现代品种叶片单位叶面积氮含量低于老品种,而净光合速率仍高于老品种,导致了氮素光合利用效率与育成年代呈显著正相关。叶片氮含量高,叶绿素含量就高,净光合速率也高,但氮素光合利用效率却低;可将R4期氮素光合利用效率作为高产品种选育的一个指标。       

Effect of different Cs concentrations on overall plant growth and Cs distribution in soybean

The absorption and dynamics of Cs in crops can be measured and examined using not only ¹³⁷Cs but also ¹³³Cs, a stable isotope which can be analyzed in a regular laboratory. When ¹³³Cs is used, however, the concentration of added ¹³³Cs must be set higher than that in the soil solution due to the detection sensitivity of inductively coupled plasma optical emission spectrometry (ICP-OES). There is concern that such high Cs concentrations may adversely affect crops and interfere with Cs dynamics. Using soybean as a test product, we first examined the initial growth of soybean cultivated under exposure to solutions with different ¹³³Cs concentrations. In combination with each ¹³³Cs concentration, two potassium (K) concentrations were tested. Results show that at both K concentrations, growth was inhibited under ¹³³Cs concentrations higher than 1 × 10^?3 mol L^?1. Soybeans cultivated at ¹³³Cs concentrations higher than 1 × 10^?6 mol L^?1 can be subject to ICP-OES for measuring ¹³³Cs concentrations in the plant tissue. Next, soybeans cultivated under different ¹³³Cs concentrations throughout growth were examined for Cs distribution in the plants. The distribution patterns of Cs in soybean plants cultivated at ¹³³Cs concentrations equivalent to those found in the soil were almost identical to those in plants cultivated at measurable ¹³³Cs concentrations (1 × 10^?6–1 × 10^?4 mol L^?1) as measured with ICP-OES. Therefore, in our investigation, ¹³³Cs distribution in soybean plants treated with up to 1 × 10^?4 mol L^?1 was considered equivalent to that in plants cultivated in the field.     

Effect of ensiling field bean, field pea and common vetch in different proportions with whole-crop wheat using formic acid or an inoculant on fermentation characteristics

Whole‐crop field bean (FB), field pea (FP) and common vetch (CV) [155, 213 and 238 g dry matter (DM) kg^?1] were ensiled in 1·5 L laboratory silos with whole‐crop wheat as mixtures of 0, 0·25, 0·50, 0·75 and 1·00 of fresh weight (FW). Silages were ensiled (i) without additive, and (ii) with formic acid (FA) (4 L t^?1) or (iii) an inoculant (Lactobacillus plantarum, 10⁶ colony‐forming units g^?1 FW) as additives. The concentrations of water‐soluble carbohydrates in herbage of whole‐crop FB, FP, CV and wheat were 93, 157, 67 and 114 g kg^?1 DM and the buffering capacities were 588, 710, 755 and 429 mEq kg^?1 DM respectively. Field bean and FP silages were mainly well preserved with low pH values and moderate fermentation losses, except for FB‐only silage without additive which had a high butyric acid concentration. Common vetch silages had higher pH values and were less well fermented compared to the silages of the other legumes. For all legumes, FA reduced ammonia‐N concentrations more effectively compared to other additive treatments. In conclusion, in FB and FP silages the use of FA or an inoculant, as additives, ensured good preservation up to a proportion of legume in the herbage of 0·75. With all legume silages, and with those containing CV, only FA, as an additive, adequately restricted protein breakdown.     

Effects of different rates and timing of application of nitrogen as slurry and mineral fertilizer on yield of herbage and nitrate-leaching potential of a maize/Italian ryegrass cropping system in north-west Portugal

Efficient use of cattle-slurry to avoid nitrogen (N) leaching and other losses is important in designing intensive dairy systems to minimize pollution of air and water. The response in dry-matter (DM) yield of herbage and nitrate-leaching potential to different rates and timing of application of N as cattle slurry and/or mineral fertilizer in a double-cropping system producing maize ( Zea mays L.) silage and Italian ryegrass ( Lolium multiflorum Lam.) was investigated in north-west Portugal. Nine treatments with different rates and combinations of cattle slurry, and with or without mineral-N fertilizer, applied at sowing and as a top-dressing to both crops, were tested and measurements were made of DM yield of herbage, N concentration of herbage, uptake of N by herbage and amounts of residual soil nitrate-N to a depth of 1 m, in a 3-year experiment. Regression analysis showed that the application of 150 and 100 kg of available N ha⁻¹ to maize and Italian ryegrass, respectively, resulted in 0·95 of maximum DM yields of herbage and 0·90 of maximum N uptake by herbage. Residual amounts of nitrate-N in soil after maize ranged from 48 to 278 kg N ha⁻¹ with an exponential increase in response to the amount of N applied; there were higher values of nitrate-leaching potential when mineral-N fertilizer was applied. The results suggest that it is possible in highly productive maize/Italian ryegrass systems to obtain high DM yields of herbage for maize silage and Italian ryegrass herbage with minimal leaching losses by using slurry exclusively at annual rates of up to 250 kg available N ha⁻¹ (equivalent to 480 kg total N ha⁻¹) in three applications.     

The influence of different nitrogen treatments on the size distribution of protein fractions in hard and soft wheat

The relative quantity of specific proteins, protein subunits, as well as amount and size-distribution of polymeric proteins in wheat kernels may vary due to environmental conditions. In this study, the effect of different nitrogen treatments on polymeric and monomeric proteins in wheat was determined. Two soft white biscuit wheat cultivars, a cracker wheat and a hard red bread wheat were planted under irrigation in a randomized complete block design with three replications in two successive years at six different nitrogen treatments. SE-HPLC was used to determine the amount of monomeric and polymeric proteins, and various quality characteristics were measured after harvesting. The large and small SDS-extractable polymeric proteins were not influenced by different N levels. There was a strong cultivar influence, where some cultivars had a larger reaction to N treatments than others. The later application (at flag leaf stage) of nitrogen did not increase the protein fractions. The total amount of N given seemed to have a greater influence on the protein fractions than the timing of the fertilizer application. The lowest N treatment consistently gave the lowest flour protein content value. There was a strong correlation between flour protein content and large monomeric proteins.     

香蕉果实采后成熟过程中苹果酸脱氢酶(MDH)及苹果酸含量的变化

以巴西香蕉果实为材料,研究果实采后正常成熟过程中乙烯释放速率,苹果酸脱氢酶(MDH)活性,苹果酸、淀粉以及可溶性总糖含量的变化。结果表明：香蕉果实采后成熟过程中乙烯释放速率在采后10 d开始增加,到采后14 d达到高峰;MDH酶活性在采后10 d迅速增强,到采后16 d达到峰值;苹果酸含量在果实成熟早期上升,晚期下降,可溶性总糖含量逐渐增加,而淀粉含量持续下降。推测MDH通过改变香蕉品质而参与果实成熟。     

Winter wheat genotypes under different levels of nitrogen and water stress: Changes in grain protein composition

Hard white winter wheat with superior and consistent quality is preferable for Asian markets. This study investigated the combined influences of moisture deficit during grain-fill and N management on protein quality, dough rheological properties, and protein molecular weight distributions in soft and hard winter wheats. Genotypes were grown under an irrigation gradient and two N-fertilization levels. Grain polyphenol oxidase (PPO) activity, SDS sedimentation, and Mixograph analyses were evaluated. Flour protein composition was characterized using SE-HPLC. Moisture stress during grain-fill increased flour protein content. N fertilization increased flour protein content. No significant correlation was found between flour protein and PPO. Changes in protein composition were related to general increases in protein content, regardless if the result of reduced irrigation or increased fertilization rate. The percentage of monomeric proteins increased more than the polymeric proteins as flour protein increased. Similarly, SDS sedimentation volume increased as a function of protein content. As expected, subunit GluD1 5+10 was associated with larger sedimentation volume and higher dough strength in genotypes as compared to those with subunit GluD1 2+12. Biplot analyses showed that genotypes of similar protein quality and composition responded similarly to N and irrigation treatments.