Effects of four mono- and sesquiterpenes on the consumption of alfalfa pellets by sheep

Effects of individual terpenes on alfalfa pellet intake by lambs were examined in four experiments. Forty-five lambs (nine lambs/treatment) were individually fed alfalfa pellets sprayed with either camphene, myrcene, caryophyllene oxide, or beta-pinene at one of five concentrations (one terpene per experiment). Treatments (0, 0.5, 1, 2, and 10x) were multiples of the concentration (x) of a specific terpene in tarbush. Terpenes were applied to alfalfa pellets (0.64 kg x lamb(-1) x d(-1), DM basis), and consumption was measured during a 20-min interval for 5 d. Lambs were maintained and fed alfalfa pellets in one group (except during 20-min tests) at a mean total daily intake of 4.7% of BW (DM basis). Camphene and caryophyllene oxide tended to decrease intake (linear contrasts were P = .0651 and P = .0504, respectively), whereas myrcene and beta-pinene exerted no effect on the consumption of alfalfa pellets by lambs. Camphene and caryophyllene oxide may be involved in the differential herbivory of individual tarbush plants by livestock.     

Effect of individual terpenes on consumption of alfalfa pellets by sheep

We examined effects of individual terpenes on alfalfa pellet intake of lambs in five experiments. Forty-five lambs (nine lambs/treatment) were individually fed alfalfa pellets sprayed with either p-cymene, alpha-humulene, 1,8-cineole, 3-carene, or sabinene at one of five concentrations (one terpene per experiment). Treatments (0, .5, 1, 2, and 10x) were multiples of the concentration (x) of a specific terpene in tarbush that was related to differential herbivory by livestock in previous studies. Terpenes were applied to alfalfa pellets (.64 kg x lamb(-1) x d(-1), DM basis), and consumption was measured during a 20-min interval for 5 d. Lambs were adapted to handling and pen feeding for 10 d and were maintained and fed alfalfa pellets in one group (except during 20-min tests) at a mean total daily intake of 4.7% of BW (DM basis). None of the five compounds decreased alfalfa pellet consumption during the 20-min interval. These five mono- and sesquiterpenes do not seem to be responsible for differential herbivory of individual tarbush plants by livestock.     

Effects of alfalfa maturity on energy utilization by cattle and nutrient digestibility by cattle and sheep.

Two comparative slaughter experiments conducted with growing beef steers (300 kg to 480 kg BW) fed alfalfa cubes demonstrated that animal performance diminished as alfalfa matured. In each trial, ADG (empty BW basis) was 10 to 20% greater from pre-bloom than from early-bloom alfalfa. Net energy for maintenance (Mcal/kg) followed a pattern similar to that of ADG, but NEg (Mcal/kg) did not decrease (P greater than .05) as alfalfa maturity increased. Digestion trials with steers and wethers clearly indicated significant reductions in apparent digestibilities of DM, energy, and cell wall fractions as alfalfa matured. Steers fed at 110% of maintenance in digestion Trails 1, 2, and 3 consistently digested cubed alfalfa to a greater extent than wethers fed the same alfalfa ground and pelleted. Digestion coefficients (percentages) for ADF, cellulose, NDF, and crude fiber were 5 to 14% greater for steers fed cubes than for wethers fed pellets. Regression equations calculated from results of three digestion trials indicate that digestible DM % and DE (Mcal/kg) could be predicted from ADF %, but they were 4 to 5% lower for wethers fed pelleted alfalfa than for steers fed cubes.     

Effects of conditioning and maximal incremental exercise on oxygen consumption in sheep

To assess the suitability of sheep for exercise studies, the effect of incremental exercise and conditioning on oxygen consumption (VO2) was studied. Six sheep were adapted to a treadmill and subsequently trained 8 weeks. The sheep were then studied, in random order, using 3 incremental exercise protocols (EX-1, EX-2, and EX-3). The protocols were chosen to approximate high (EX-1), moderate (EX-2), and low (EX-3) intensity exercise by varying treadmill speed and incline. The sheep were then conditioned for an additional 12 weeks and retested on the EX-2 protocol. During exercise, VO2, gas exchange ratio (R), and rectal temperatures (Tb) were recorded. All 3 protocols resulted in significant increases in VO2, R, and Tb (P less than 0.05). Maximum VO2 for EX-1, 49.9 +/- 5.0 ml/min/kg of body weight, was significantly greater than maximum VO2 for EX-2 and EX-3, 37.8 +/- 6.5 and 42.3 +/- 6.0 ml/min/kg, respectively (P less than 0.05), whereas maximum R and maximum Tb were similar. After the additional 12-week conditioning, time on the treadmill increased 40% from 9.58 +/- 0.87 to 13.4 +/- 0.44 minutes, and maximum VO2 increased 27% to 48.1 +/- 9.1 ml/min/kg. These data indicated that maximum VO2 varied with intensity of the exercise, 12 weeks of maximal exercise conditioning was sufficient to produce a measurable training effect (ie, increase endurance and maximum oxygen consumption) and sheep are suitable for maximal exercise studies where VO2 measurements are desired.     

日粮中添加高微量元素苜蓿青干草对杜泊羊生产性能的影响

通过在杜泊羊的日粮中添加5%～15%的高硒、高硒钴、高硒钴锌以及高硒钴锌铁4种苜蓿Medicago sativa青干草,研究对杜泊羊的采食性能、日增质量和饲料转化等方面的影响。结果表明,和添加普通苜蓿青干草相比,4种苜蓿青干草在添加量为5%～10%的情况下,均能在不同程度上提高羊日增质量,有利于饲料的转化与利用,并且饲喂安全,无副作用。其中添加15%高硒钴锌苜蓿青干草效果最好,日增质量比对照提高了59.4%,饲料转化率（30.72%）比对照提高了59.8%;在日粮中添加10%的高硒钴锌铁苜蓿青干草,效果接近前者,日增质量比对照提高了58.0%,饲料转化率（27.88%）比对照提高了44.7%。     

紫花苜蓿的需水量、耗水量、需水强度、耗水强度和水分利用效率研究

为明确紫花苜蓿Medicago sativa的需水量、耗水量、需水强度、耗水强度和水分利用效率的影响因子和范围,对其进行了较为详尽地探讨.不同气候区域和年份紫花苜蓿的需水量和耗水量不同;增加刈割次数可降低需水量;在一定范围内耗水量随着灌溉量的增加而提高,不同灌溉模式耗水量不同.紫花苜蓿全生长季需水量和耗水量的范围分别为400～2 250和300～2 250 mm.不同气候区域、气候年份、刈割茬次及生长发育阶段紫花苜蓿的需水强度和耗水强度不同;需水强度与大气蒸发力成正相关,耗水强度与土壤含水量成正相关;增加刈割次数可降低需水强度;在一定范围内耗水强度随着灌溉量的增加而提高,不同灌溉模式耗水强度不同.紫花苜蓿全生长季需水强度和耗水强度的范围分别为3～7和2～7 mm/d;短期极端最高需水强度为14 mm/d.不同气候区域、气候年份、灌溉量、灌溉模式、施肥量、施肥模式及刈割茬次紫花苜蓿的水分利用效率不同;建植2年及以上高于建植当年;不同品种差异不显著.在相对正常的田间栽培管理条件下,建植当年紫花苜蓿的生物产量和经济产量(含水量14%)水分利用效率的范围分别为8～12和9～14 kg/(mm·hm2),建植2年及以上者分别为12～25和14～29 kg/(mm·hm2).     

Effect of age of exposure on consumption of a shrub by sheep

We investigated the influence of age of exposure to a specific forage on its consumption by young sheep both during and after that exposure. Prior exposure to the shrub Cercocarpus montanus enhanced subsequent consumption (P less than or equal to .05) of that shrub by lambs and yearlings during two experiments in consecutive years. Effects of prior exposure persisted as long as 9 mo without intervening exposure. Age of exposure influenced consumption in lambs both during the period of exposure (P less than or equal to .0001) and during feeding trials following exposure (P less than or equal to .07) in Exp. 1. Lambs exposed at 1 to 5 wk of age, when they are nonruminant and normally are dependent on the dam, browsed less of the time while at the shrub (P less than or equal to .02) and consumed less of the shrub (P less than .02) at a slower rate (P less than or equal to .03) than did lambs exposed at older ages. Lambs exposed at 4 to 8 wk of age, a period corresponding to the transition from nonruminant to ruminant digestion, consumed more shrub following exposure than did lambs exposed at younger or older ages (P less than equal to .05, unprotected least significant differences test). In Exp. 2, which compared naive yearlings with the experienced yearlings exposed as lambs in Exp. 1 the previous year, age of exposure did not influence consumption by yearling sheep following exposure; however, the number of months that had elapsed from the period of exposure varied from 0 to 13 among experimental groups and may have confounded results. Learning of forages appeared poor among nonruminant lambs; data were inconclusive concerning the efficiency of learning of lambs in the transition to ruminant digestion.     

苜蓿草粉和黄酮对断奶仔猪结肠微生物区系的影响

本试验旨在研究苜蓿草粉和苜蓿黄酮对断奶仔猪结肠微生物区系的影响。选取平均体重为(8.1±0.5) kg和胎次相近的(35±1)日龄"杜×长×大"三元杂交断奶仔猪120头,随机分成5组(每组3个重复,每个重复8头猪):对照组饲喂基础饲粮,试验组分别添加1(Ⅰ组)、2(Ⅱ组)、4(Ⅲ组)g·kg^-1的苜蓿黄酮和50 g·kg^-1的苜蓿草粉(Ⅳ组);预试验期3 d,正式试验期32 d。试验采集的结肠内容物,提取总DNA后在Illumina Miseq平台进行测序。结果表明:1)5个组共产生了484个操作分类单元(operational taxonomic units,OTUs),其中共享327个OTU,占总OTU数量的67.56%,其中Ⅰ组的OTU数量最高。2)物种丰富度ACE指数(community richness the ACE estimator,ACE)呈先上升再下降再上升趋势,其中Ⅰ组显著高于对照组(P<0.05);物种丰富度Chao指数(community richness the Chao estimator,Chao)呈先上升再下降再上升趋势,其中Ⅰ组显著高于对照组(P<0.05)。与对照组相比,Ⅳ组的Sobs(the observed richness,Sobs)、ACE、Chao指数均无显著差异(P>0.05)。各组之间的Shannon指数和Simpson指数均无显著差异(P>0.05)。3)在门水平上,各组间厚壁菌门和拟杆菌门的相对丰度均无显著差异(P>0.05)。在属水平上,各组间梭菌属相对丰度有升高的趋势(P>0.05),其中Ⅰ组和Ⅲ组梭菌属相对丰度显著高于对照组(P<0.05)。与对照组相比,Ⅱ组粪球菌属相对丰度显著提高(P<0.05)。各组间真细菌属相对丰度有升高的趋势(P>0.05),其中Ⅱ组真细菌属相对丰度显著高于对照组(P<0.05)。各组间Anaerotruncus相对丰度有显著差异(P<0.05),其中Ⅱ组和Ⅳ组显著高于对照组(P<0.05);各组间NC2004相对丰度有差异(P>0.05),其中Ⅲ组NC2004相对丰度显著提高(P<0.05)。各组间UCG-014、Erysipelotrichaceae和胃球菌属相对丰度有显著差异(P<0.05)。由此可见,饲粮中添加苜蓿草粉和苜蓿黄酮能够改变结肠微生物细菌组成和结构,进而影响营养物质的消化代谢。     

Effects of cis-beta-ocimene, cis-sabinene hydrate, and monoterpene and sesquiterpene mixtures on alfalfa pellet intake by lambs

The transition of grasslands to shrub-dominated scrubland reduces livestock productivity and contributes to impoverished conditions for humans in arid and semiarid regions worldwide. Many shrubs that are increasing in dominance contain secondary compounds that deter browsing by herbivores. Knowledge concerning the effects of specific compounds in herbivore diets is limited but may provide useful insights into desertification. Flourensia cernua is a dominant shrub in the northern Chihuahuan Desert that contains an abundance of terpenes. Four experiments were conducted to determine the effects of terpenes on intake of alfalfa pellets by lambs. Two individual monoterpenes (cis-beta-ocimene and cis-sabinene hydrate) were examined in Exp. 1 and 2, and mixtures of monoterpenes (borneol, camphene, camphor, 1,8-cineole, limonene, myrcene, and alpha-pinene) and sesquiterpenes (beta-caryophyllene, caryophyllene oxide, alpha-copaene, and alpha-humulene) were examined in Exp. 3 and 4, respectively. Forty-five lambs (9 lambs/treatment) were individually fed treated alfalfa pellets for 20 min each morning for 5 d. Five treatments (0x, 0.5x, 1x, 2x, and 10x; multiples of the concentrations of the same terpenes in F. cernua) were applied to alfalfa pellets (637 g, DM basis) in an ethanol carrier. The experiments were preceded by a 10-d adaptation period of the lambs to untreated pellets. Except during the 20-min test, the lambs were maintained outdoors and fed untreated alfalfa pellets (total mean intake = 4.7% of BW, DM basis). Day x treatment interactions were detected (P < 0.04) in Exp. 1 and 4 because of a greater intake for 0x than for the other treatments on d 1 (Exp. 1) and a lower intake for the 10x treatment on d 1 and 2 (Exp. 4). A trend for decreased intake (g/kg of BW) as the concentration of the sesquiterpene mixture increased was observed in Exp. 3 (P = 0.093 for the linear contrast). Although there was a tendency for the sesquiterpene mixture to decrease intake, cis-beta-ocimene, cis-sabinene hydrate, and the monoterpene mixture did not appear to affect intake by lambs. Thus, sesquiterpenes may exert antiherbivory properties under certain conditions that may contribute to shrub dominance with extended periods of livestock foraging.     

Retention time of macerated alfalfa hay and silage in sheep

Fresh alfalfa was mowed and conditioned mechanically at four levels: a control (rubber rolls), macerated once (a single passage through three finely corrugated rolls set at 1-mm clearance), macerated twice (two passages), and macerated thrice (three passages). Alfalfa was then field-wilted either for 45 h and conserved as chopped silage at 30% dry matter (DM) or for 94 h and stored as baled hay at 85% DM. The eight forage treatments (four mechanical conditioning levels x two conservation systems) were fed to 24 sheep (three replications per treatment) during 5 wk. At the beginning of wk 5, a 15-g sample of chromium-mordanted forage (3.5% Cr) was fed to each sheep, and feces samples were collected at 30 different times over 7 d, between 10 h and 168 h after Cr ingestion. Four models were used to estimate the passage rates, the time delay, and the mean retention time (MRT). A two-compartment time-dependent model and a multicompartment model produced the best fit (average r2 of 0.96) to represent the Cr concentration in the feces over time. When compared with alfalfa hay, alfalfa silage had a higher (P < 0.01) time-dependent turnover rate (0.0949 vs 0.0733/h), a lower (P = 0.03) time delay (9.1 vs 11 h), and a lower (P = 0.04) MRT (57.8 vs 64.4 h). Maceration did not affect significantly (P > 0.10) the time delay or the MRT. However, the MRT of macerated alfalfa hay tended to be higher than the MRT of control hay. Experimental data based on marker concentration in the feces can be used satisfactorily to assess differences in MRT between treatments, but they should be used with caution to estimate the partition of retention time within the gastrointestinal tract.     

Comparison of soybean meal/sorghum grain, alfalfa hay and dehydrated alfalfa pellets as supplemental protein sources for beef cattle consuming dormant tallgrass-prairie forage

Three experiments were conducted to compare soybean meal/sorghum grain (SBM/SG), alfalfa hay or dehydrated alfalfa pellets (DEHY) as supplemental protein sources for beef cattle grazing dormant range forage. In Exp. 1 (35-d digestion study), 16 ruminally cannulated steers were stratified by weight (average BW 259 kg) and assigned randomly within stratification to: 1) control, no supplement; 2) SBM/SG (25% CP) fed at .48% BW; 3) alfalfa hay (17% CP) fed at .70% BW; or 4) DEHY (17.4% CP) fed at .67% BW. Steers receiving protein supplements displayed at least a twofold increase in forage intake (P less than .10). In addition, steers supplemented with DEHY consumed approximately 15% more forage (P less than .10) than SBM/SG- or alfalfa hay-supplemented steers. Digestible DM intake (kg/d), however, was similar between alfalfa hay- and DEHY-supplemented steers and 20% greater (P less than .10) than for SBM/SG-supplemented steers. In Exp. 2, 82 mature, nonlactating Hereford x Angus cows (average BW 489 kg) were assigned randomly to SBM/SG, alfalfa hay or DEHY supplement treatments, which were replicated in three pastures. Cows supplemented with DEHY gained more weight (P less than .05) during the first 84 d of supplementation and displayed the least amount of weight loss at calving (d 127; P less than .05) and just prior to breeding (P less than .10). In contrast, calving interval (361 d) and pregnancy rate (94%) were unaffected (P greater than .10) by dam's previous supplemental treatment. In Exp. 3, one block (pasture) of cows from Exp. 2 was selected at random and grazing behavior was monitored during week-long periods in January and February. A treatment X time interaction (P less than .05) occurred for total time spent grazing; treatments did not differ in January, but cows supplemented with alfalfa hay spent less time grazing in the February grazing period. In conclusion, DEHY and alfalfa hay appear to be at least as effective as SBM/SG as a supplemental protein source for pregnant grazing cows when supplements are fed on an equal CP and ME basis.     

水分和添加剂对苜蓿青贮效果的影响

为研究苜蓿的水分、添加剂对苜蓿青贮发酵品质的影响,通过对头茬苜蓿设置3个水分梯度,并添加4个水平的甲酸、丙酸、双乙酸钠,装入聚乙烯袋抽真空,发酵45 d 后进行营养分析和品质鉴定。结果表明：适宜苜蓿青贮的水分条件为55%,这一水分条件下苜蓿青贮料的 pH、氨态氮、粗纤维最低,可溶性糖、乳酸最高;而3种添加剂对青贮料的影响具体表现为：与对照组相比,能够显著降低苜蓿青贮料的 pH 和氨态氮含量（P 〈0.05）,并且能够很好地保存青贮料中的可溶性糖,通过对灰色关联度分析,甲酸对苜蓿青贮的影响效果最佳,丙酸次之;且55%的水分条件下添加15 mL/kg 的甲酸,青贮效果为最好。     

Effects of supplementing herbaceous forage legume pellets on growth indices and blood profile of West African dwarf sheep fed Guinea grass

Twenty West African dwarf (WAD) rams with average body weight of 12.43?±?0.5 kg were used for the experiment that lasted 84 days to investigate the effects of supplementing herbaceous forage legume pellets on weight change and blood profile of animals fed Panicum maximum basal diet. Sole Panicum maximum served as the control diet and three other experimental diets were P. maximum supplemented with Lablab purpureus pellets, P. maximum supplemented with Calopogonium mucunoides pellets and P. maximum supplemented with Mucuna pruriens pellets constituted the four treatments which were arranged in a completely randomised design. The rams were divided into four groups of five animals each and were balanced for variation in live weight before they were assigned the experimental diets. Panicum maximum was offered to the animals ad libitum and legume pellets were supplemented. Significant differences (P?< 0.05) were observed in weight gain of the rams. Those fed the control diet had the lowest value of 41.88 g/day while rams supplemented L. purpureus pellets had the highest value (83.66 g/day). Haematological parameters, leucocyte values and serum biochemical indices of WAD rams were significantly (P?< 0.05) different across the dietary treatments at the final stage of the trial. The values for red blood cells, haemoglobin concentration, packed cell volume and mean corpuscular haemoglobin decreased slightly in rams supplemented with M. pruriens pellets. Reduction of serum biochemical parameters was also noticed in rams supplemented with M. pruriens pellets. It can be concluded that L. purpureus pellets ranked the best among the herbaceous legume pellets as supplemental feed for West African dwarf sheep resulting in higher weight gain and better feed conversion efficiency with no deleterious effect on blood profile.

     

Influence of alfalfa maturity on feed intake and site of nutrient digestion in sheep

Four wethers fitted with ruminal, duodenal and ileal cannulas were used to study effects of maturity of alfalfa hay on intake, digestion and rate of passage of nutrients in various sites of the digestive tract. Pre-, early-, and mid-bloom hays were harvested from the same field; full-bloom hay was acquired from elsewhere due to wether conditions. Dry matter intake decreased (P less than .05) as intakes of NDF and ADF increased. This was attributed to decreased digestibility and increased retention time of undigested residues. Digestion of OM in the stomach (% of intake) was 44.2, 47.4, 38.8 and 35.1 for pre-, early-, mid- and full-bloom hay, respectively. Digestion of ADF in the stomach was lower for mid-bloom than for pre-and early-bloom hay (P less than .05). Degradation of alfalfa protein in the rumen was 94, 88, 81 and 78% for pre-, early-, mid- and full-bloom hay, respectively. Concentration of ruminal NH3 N, flow of N at the duodenum, fecal N and urinary N decreased of the hay and to N intake. Digestion of N in the small intestine (g/d) decreased as maturity advanced (P less than .05). Duodenal flow of total amino acids was greater (P less than .05) when animals consumed pre-bloom hay than when they consumed more mature hays. Relative feed value calculated from the detergent fiber analysis correlated with actual value determined biologically (r = +.81). Intake and site of nutrient digestion of alfalfa hay were influenced by the stage of maturity at harvest.     

转基因苜蓿对土壤微生物的影响

采用传统的平板计数法和PCR凝胶电泳技术,在大田栽培条件下,以转BADH基因苜蓿和非转基因苜蓿为材料,于2009年和2010年连续2年测定苜蓿根际土壤细菌、放线菌和真菌数量的变化,并对外源基因是否转移到土壤微生物中的可能性进行检测分析。结果表明,在不同年份和不同月份转基因植株与非转基因植株根部土壤3大类微生物(细菌、放线菌和真菌)数量变化趋势一致;二者根部土壤3大类微生物数量无显著差异,2年间转基因苜蓿的土壤3大类微生物数量无显著差异;并利用BADH基因特异引物对土样的总DNA,以及菌株DNA进行PCR扩增,均未检测到外源基因扩增产物。初步研究结果表明,转基因苜蓿对土壤微生物系统尚没有明显的影响。     

锌、铁、钼肥对紫花苜蓿草产量和品质的影响

为了满足紫花苜蓿Medicaco sativa对微量元素的需求,提高其产量和品质,采用田间试验方法,在比较贫瘠的土壤条件下,研究了锌、铁、钼肥单独施用及组合施用对紫花苜蓿草产量及品质影响。结果表明：施用微量元素锌、铁、钼肥均能显著提高紫花苜蓿的草产量,其中铁单施（15 kg/hm2）和锌钼配施（12 kg/hm2,0.5 kg/hm2）处理效果最好,分别增产15.9%和5.9%。微肥对粗蛋白含量没有明显影响,但铁单施、钼单施、锌钼配合施用能显著提高苜蓿粗蛋白产量。微肥能降低粗脂肪含量和产量;对粗纤维含量没有影响,但能提高其产量;对粗灰分和无氮浸出物含量的影响不显著,但能提高其产量;显著降低钙含量,对钙产量无显著影响;能提高磷含量和产量。     

苜蓿施用磷、钾肥效应的研究

采用过磷酸钙与氯化钾进行2因素4水平随机区组施肥试验,结果表明:过磷酸钙600kg hm2与氯化钾100kg hm2施肥处理,苜蓿鲜草产量最高,较对照增产20 0%,纯收入增988元 hm2。新复极差测验表明:不同水平施用过磷酸钙各次刈割鲜草产量及鲜草总产量间差异均达到显著水平(P<0 05),且随着过磷酸钙用量的增加鲜草产量相应地增加。不同水平施用氯化钾与不施氯化钾鲜草总产量差异均达到极显著水平(P<0 01),但施氯化钾150kg hm2与50kg hm2鲜草总产量差异不显著;随着施用氯化钾水平的提高,各次刈割鲜草产量及鲜草总产量均呈先升高后略有下降的趋势,氯化钾施用量以100kg hm2为宜。氯化钾、过磷酸钙及其互作效应均以第1次刈割显著,第2次刈割施肥效应均有所下降,其中氯化钾及氯化钾与过磷酸钙互作效应下降更为明显。增施氯化钾有利于提高苜蓿粗蛋白含量,但粗蛋白含量不随施用量的增加而增加;施过磷酸钙200kg hm2苜蓿粗蛋白含量最高,施400kg hm2苜蓿粗蛋白含量下降。     

水氮互作对河西走廊紫花苜蓿品质的影响

通过研究不同灌溉量(W₁:117 mm;W₂:156 mm;W₃:192 mm)和施氮量(N₁:0 kg·hm^-2;N₂:40 kg·hm^-2;N₃:80 kg·hm^-2;N₄:120 kg·hm^-2)互作条件下河西走廊紫花苜蓿水分利用效率、品质和相对饲用价值的变化特征,旨在确定紫花苜蓿品质最优时的水氮配置模式。结果表明,水氮互作显著影响了紫花苜蓿水分利用效率、粗蛋白质含量、中性洗涤纤维含量和相对饲用价值(P<0.05),但对紫花苜蓿地上生物量、粗脂肪、粗灰分含量和酸性洗涤纤维含量影响不显著。紫花苜蓿水分利用效率、粗蛋白质含量、中性洗涤纤维含量和相对饲用价值随灌溉量和施氮量的增加均呈开口向下的抛物线,最大值出现的组合分别为W₂N₃和W₂N₂,说明只有水氮合理配置才能提高紫花苜蓿品质和相对饲用价值。