Utilization of browse supplements with varying tannin levels by Ethiopian Menz sheep: 2. Nitrogen metabolism

The effect of different condensed tannins concentrations on protein metabolism from browse supplements was investigated in a 90-day trial using sixty-six male Ethiopian Menz sheep. Teff straw (Eragrostis tef) was fed ad libitum (control diet), or supplemented with 190 g dried leaves of six Sesbania sesban accessions with increasing levels of condensed tannin (S1, S2, S3, S4, S5 and S6), lablab (Dolichos lablab), tagasaste (Chamaecytisus palmensis), leucaena (Leucaena leucocephala) and goetzei (Sesbania goetzei) in a completely randomized block design. The condensed tannins were highest in goetzei; S6, S5 and leucaena, intermediate in S4, S3, S2 and S1, and lowest in tagasaste and lablab. The supplemented animals had significantly (P < 0.05) higher total dry matter and nitrogen (N) intake than the ones fed teff straw alone. The digestibility of N was lower for the control diet than for any other treatment (P < 0.05). S1 and S2 supplemented diets had significantly higher (P < 0.05) N digestibilities than all other diets. Faecal N, urinary N and urinary N per kg N excreted were significantly different (P < 0.0001) between diets. With increasing tannin levels (among Sesbania accessions) there was a significant decrease (P < 0.05) in urinary N (S1 > S2 > S3 > S4 > S5), and an increase (P < 0.05) in faecal N (S1 < S2 < S3 < S4 < S5). Supplementation increased faecal N output significantly (P < 0.0001) as well as the N retention. Among the forage supplements, N retention was significantly (P < 0.0001) lower in lablab-, tagasaste-, leucaena-, S4- and goetzei-supplemented diets, than for S1, S2, S5 and S6. Apparent nitrogen digestibility was positively correlated (P < 0.001) with the supplement dry matter and crude protein (CP) degradation after 24 h (r = 0.93 and r = 0.85, respectively), the CP content (r = 0.87), and was negatively correlated with acid detergent fibre and neutral detergent fibre (r = –0.87 and –0.87, respectively). The CP degradability characteristics of the forages differed (P < 0.001) in water solubility (93–470 g kg^-1 CP), rate of degradation (2.58–9.73 %/h), lag phase (–1.36–13.37 h), and estimated escape protein (262–619 g kg^-1 CP). With increasing tannin levels (among Sesbania accessions), there was a significant decrease (P < 0.0001) in the rate of degradation (S1 > S2 > S3 > S4 > S5), and an increase in the estimated escape protein. The estimated rumen degradable protein (supplements) varied from 482 to 744 g kg^-1 CP, while intestine digestible protein and the undegradable protein varied from 140 to 314 g kg^-1 CP, hence the browses can supply adequate levels of rumen degradable and bypass protein. This revised version was published online in June 2006 with corrections to the Cover Date.     

Legume forages from pigeon pea, leucaena and sesbania as supplements to natural pastures for goat production in western Tanzania

In two dry and two wet seasons forage of pigeon pea, leucaena and sesbania were fed to growing goats as supplements to natural grazing over a two year period. The supplemented goats gained live-weights faster (P < 0.05) than the control animals. Intakes of pigeon pea (63.1 to 91.4 g/head/day) and leucaena (52.6 to 93.8 g/head/day) were consistently higher (P < 0.05) than that of sesbania (49.7 to 83.4 g/head/day) and this was reflected in liveweight gains in both wet and dry season. Liveweight gains ranged from 25.5 to 43.2, 16.7 to 37.5, 14.4 to 28.3 and 6.7 to 21.6 g/head/day for goats supplemented with pigeon pea, leucaena, sesbania and the control animals respectively. Preliminary cost-benefit analysis of the results indicate that such interventions are likely to be economically attractive and the responses provide a basis for improvement of goat production in the Tabora agro-pastoral systems. This revised version was published online in August 2006 with corrections to the Cover Date.     

Intake,digestibility, nitrogen balance and certain rumen characteristics of Ethiopian Menz sheep fed teff straw supplemented with cotton seed cake,dry sesbania,dry leucaena or fresh leucaena

Twenty five rumen fistulated Ethiopian Menz sheep were used in a completely randomized block design to determine roughage utilization when different types of supplements (sesbania, leucaena, cotton seed cake (CSC)) and forms (fresh or dry leucaena) were fed. The chemical composition, intake, digestibility, nitrogen balance and rumen degradability coefficients were determined. Rumen pH and ammonia-nitrogen (NH₃-N) levels were estimated in samples taken at 1, 2, 3, and 6 h after feeding.There was substitution of teff straw dry matter by the supplements. Fresh leucaena effected the highest substitution. Supplementation enhanced (p<0.05) the dry matter degradation (DD) of teff straw at 6 and 12 hours of incubation but not (p>0.06) for the other incubation times. There were no significant differences (p>0.05) between treatments in the degradation constants: readily soluble component (a) slowly degradable fraction, (b) potential degradability (PD=a+b) and rate of degradation (C) and for rumen NH₃-N concentration, the ranking was CSC > sesbania > dry leucaena > fresh leucaena > teff straw alone (p<0.05). The particularly high substitution rate observed with fresh leucaena might suggest that bulkiness may be a limiting factor in the intake of low quality roughages supplemented with tree leaves. The lower DM and OM digestibilities of the supplemented diets were attributed to substrate preference by rumen cellulolytic bacteria. Excessively high levels of rumen NH₃–N (328 mg/l) in the CSC diet resulted in high urinary nitrogen losses (r ²=0.32;p<0.001) leading to low N balance. This may suggest that for the utilization of poor quality tropical roughages, moderate levels of rumen NH₃–N sustained over a longer period may be needed.     

Effect of pre-feeding forage treatments,harvesting stage,and animal type on preference of tagasaste (<Emphasis Type="Italic">Chamaecytisus palmensis</Emphasis>)

Tagasaste (Chamaecytisus palmensis), a multipurpose fodder tree, is highly productive in the tropical highlands. The forage has high crude protein (CP) concentrations but is reported to have low intake by ruminants. This study investigated the effects of plant harvest stage and feeding management (wilted, dried and fresh) on levels of tannins in tagasaste and on preference and intake by Menz sheep and cattle fed during the dry season. The treatments were (1) fresh tagasaste, (2) wilted tagasaste, (3) dried tagasaste and (4) native hay. There were three preference experiments using sheep (20.2 ± 0.66 kg) to investigate intake under ad libitum or restricted offering of the forages, and to assess effect of harvest age (6- or 10-month regrowth age) on ad libitum intake. In two further experiments ad libitum offerings of the forages were evaluated using young steers (131.2 ± 19.6 kg) and heifers (156.3 ± 5.4 kg). The CP (201 g/kg), hydrolysable tannin (150.2 g/kg) and condensed tannin (8.97abs measured as absorbance at 550 nm wavelength/g NDF) contents of tagasaste forage were not affected by the physical treatments and harvesting stage. When fed ad libitum, sheep preferred (P < 0.01) fresh forage to wilted or dry tagasaste (24.5 vs. 22.9 and 7.9 g dry matter (DM)/kg metabolic body weight (MBW). The restricted offering increased intake of the less preferred dried form. Regrowth age (6 vs. 10 months) did not affect sheep preference. Unlike sheep, steers and heifers preferred (P < 0.01) dried tagasaste rather than the fresh or wilted forage. Animal preference and intake were affected by the preparation method of the forage, but not by regrowth age. Methods to improve intake (for cattle), effects of long-term feeding and evaluation on the subsequent effect of anti-nutritional compounds during digestion and animal performance should be further investigated.     

The effect of browse supplementation on maize husk utilization by goats

The effect of browse supplementation on maize husk (Zea mays) utilization by goats was studied in a 12 week feeding and 2 week digestibility trial. Twenty-four goats were stratified according to their weight, and then randomly allocated to four treatments. Browse supplementation significantly increased (P < 0.05) the total dry matter intake, diet dry matter digestibility and diet organic matter digestibility (P < 0.05) but did not have any significant effect on acid detergent fibre digestibility (P > 0.05). The browse supplemented goats gained more weight than the non browse supplemented goats.     

Relationships between preference, rumen degradability, gas production and chemical composition of browses

The aim of this work was to assess whether degradability, gas production or chemical constituents could predict the preference of browses. Forty tropical browse species leaves with a crude protein (CP) content ranging from 79 to 307 g kg^-1 DM were used for this study. The neutral detergent fibre (NDF) ranged from 220 to 694 g kg^-1 DM, while acid detergent fibre (ADF) ranged from 146 to 523 g kg^-1 DM. The NDF-bound nitrogen (NDFN) and ADF-bound nitrogen were particularly high in Calliandra calothyrsus, Acacia polyacantha, Sesbania sesban, Acacia venosa and Acacia hockii. High levels of tannins were observed in Acacia species especially A. dolichocephala, A. hockii, A. microbotrya and A. salicina. High levels were also observed in Flemingia macrophyla and Leucaena pallida. The browse species differed (P < 0.05) in DM in sacco degradability coefficients. High potential degradability (PD) and effective degradability (ED) were observed in Sesbania spp, Moringa stenopetala, Indigofera arrecta, Chamaecytisus palmensis and Atriplex spp. The browses differed (P < 0.05) in asymptotic gas (Ag) production (ml g^-1 OM), but had similar (P > 0.05) times of incubation at which half of the asymptotic gas had been formed. Preference and DM intake were positively correlated (P < 0.01) to NDFN, but negatively correlated (P < 0.05) to NDF and ADF. The PD and Ag were negatively (P < 0.001) related to NDF, ADF and lignin. Total phenols (TP) and condensed tannins (CT) were negatively (P < 0.05) related to PD, ED and Ag. A positive correlation was observed between CT and NDF-bound condensed tannins (r = 0.55, P < 0.001) and, CT and TP (r = 0.40, P < 0.01). Prediction equations were poor for DM intake and preference, moderate for gas production and good for potential and effective degradabilities. The phenolic components were more related to dry matter degradation and gas production than to preference and dry matter intake. NDFN and Ag made a positive contribution to both preference and DM intake. It was concluded that chemical constitutes such as N, NDF, NDFN, ADF and lignin are essential to predict the nutritive value of browses. This revised version was published online in June 2006 with corrections to the Cover Date.     

Soil fertility changes and response of maize and beans to green manures of leucaena,sesbania and pigeonpea

Three multipurpose tree species (MPTS)-leucaena (Leucaena leucocephala), sesbania (Sesbania sesban var. nubica) and pigeonpea (Cajanus cajan) were pruned at a height of 60 cm above the ground every two months, and resulting plant biomass was incorporated into the soil as green manure. For comparison, maize (Zea mays) stover was also incorporated into some plots, while some other plots were left fallow. Varying quantities of plant biomass which were incorporated into the soil over a period of 12 months caused large changes in major soil plant nutrients, and it substantially improved soil fertility. To test for improved soil fertility, test crops of maize and beans (Phaseolus vulgaris) were grown on the plots after six biomass incorporations of 4806, 13603, 16659 and 7793 kg. ha^–1yr^–1 for pigeonpea, sesbania leucaena and maize, respectively. Responses of the test crops indicated that sesbania and leucaena green manures improved maize stover, cobs and grain yields; and bean haulms and grain yields by 77.6% when compared to fallow plots. Residual effects of green manures still resulted in significant (P < 0.05) yield differences in the test cropin the third testing season. Economic significance of green manures in increasing food crop yields to small scale farmers is discussed.     

Changes in the N and P concentrations,N:P ratios,and tannin content in <Emphasis Type="Italic">Casuarina equisetifolia</Emphasis> branchlets during development and senescence

Changes in the N and P concentrations, N:P ratios, and tannin content in Casuarina equisetifolia branchlets across a coastal gradient were studied at Chishan Forestry Center of Dongshan County, Fujian Province, China. (1) Total phenolics and protein precipitation capacity in young branchlets was significantly higher than in mature and senescent branchlets across a coastal gradient; extractable condensed tannin content was higher in young and mature branchlets than in senescent branchlets. Whereas protein-bound condensed tannins increased with senescence, fiber-bound condensed tannins fluctuated without a consistent pattern; (2) N and P concentrations at various stages of branchlet development across a coastal gradient followed the same order: young branchlets > mature branchlets > senescent branchlets; N:P ratio of young branchlets was the lowest, and increased with maturity and senescence across a coastal gradient; phosphorus resorption efficiency was significantly higher than nitrogen resorption efficiency among corresponding coastal gradients in response to P deficiency (high N:P ratio), but nutrient resorption efficiency was influenced by coastal gradients; (3) significant linear relationships between total phenolics and nutrient contents indicated that polyphenolics had a potential effect on nutrient cycling.     

The effect of feeding maize husk and leucaena as mixture on the voluntary intake of the husk

The effect of feeding maize husk and leucaena as a mixture on voluntary intake of maize husk was studied over a 40-day period. Ten male goats with an average weight of 15 kg were used. The treatments were: (a) maize husk fed in a mixture with leucaena and (b) maize husk plus leucaena offered in separate troughs but at the same time. The maize husk intake and total dry matter intake for the two feeding methods were about the same. Thus total dry matter intake was not affected (P<0.05) by the method of feeding. There was also no significant difference (P<0.05) between the two methods of feeding in the digestibility values. The data were considered to indicate that there were no significant differences in the intake of maize husk when fed in a mixture withLeucaena leucocephala or when offered separately but at the same time.     

The Potential of Albizia lebbeck as a Supplementary Feed for Goats in Tanzania

Forty growing goats (20 males and 20 females) were used in a 90-day growth and intake study to evaluate the potential of Albizia lebbeck (ABC) based concentrate as compared with Gliricidia sepium (GBC), Leucaena leucocephala (LBC), and Moringa oleifera (MBC) based concentrates with cotton seed cake (CSC) as a control. The animals were fed a basal diet of maize stover and supplemented daily with 30 g/kg W^0.75 of ABC, GBC, LBC, MBC, and CSC. They were compounded so as to formulate iso-protein diets. Treatment effects were significant (p<0.05) for growth rates in that with the exception of GBC, goats on CSC exhibited significantly higher gains compared to counterparts in other treatments. The total DM intake was between 50.6 and 52.6 g/kg W^0.75/day and there were no significant (p>0.05) differences among treatments. There were significant differences (p<0.05) among treatments for maize stover intake. CSC based treatment showed the highest intake with insignificant (p>0.05) differences amongst the leaf meal based concentrates. It can be concluded that Albizia lebbeck had similar potential to the other leaf meal based supplements studied but had lower potential compared to a cotton seed cake based supplement, as protein sources for growing goats fed a poor quality basal diet.     

Condensed tannins in Leucaena and their relation to psyllid resistance

Leucaena species and hybrids were examined to determine the relative content of condensed tannins and its relationship to susceptibility to defoliation by the Leucaena psyllid (Heteropsylla cubana). The interspecific Leucaena hybrid KX2 (L. leucocephala × L. pallida) was examined for variability of condensed tannin levels. A broad range of condensed tannin values were found which indicate potential for improved forage value through selection for KX2 trees with lower condensed tannin while maintaining psyllid resistance. A significant correlation was not found linking condensed tannins and psyllid resistance.     

The effect of feeding maize husk and leucaena mixed or separately on the voluntary intake of the husk

The effect of feeding maize (Zea mays L.) husk and leucaena (Leucaena leucocephala) as a mixture or separately on the voluntary intake of maize husk was studied over a 40-day period. Ten male goats with an average weight of 15 kg were used. The maize husk intake and total dry matter intake for the two feeding methods was about the same. Thus, total dry matter intake was not affected (P<0.05) by the feeding method. There was also no significant difference (P<0.05) between the two feeding methods in the digestibility values. The data were considered to indicate that there were no significant differences in the intake of maize husk when fed in a mixture with leucaena or when offered separately but at the same time.     

A seedling inoculation test for screening Sesbania sesban for resistance to the seedling defoliator, Mesoplatys ochroptera

The seedling beetle Mesoplatys chroptera is a serious pest of Sesbania sesban and other Sesbania spp. that are important agroforestry species. Sesbania sesban was compared to Sesbania micrantha, Sesbania goetzi and Sesbania cinerascens, in a seedling inoculation test for resistance to Mesoplatys ochroptera using copulating adult instars as inoculum. The uniform susceptibility of Sesbania sesban including accessions from western Kenya was confirmed. But S. cinerascenswas found to be resistant to the pest. This revised version was published online in June 2006 with corrections to the Cover Date.     

Potential contribution of <Emphasis Type="Italic">Quercus durata</Emphasis> and <Emphasis Type="Italic">Adenostoma fasciculatum</Emphasis> supplemented with <Emphasis Type="Italic">Medicago sativa</Emphasis> on intake and digestibility in sheep and goats

A digestion trial was conducted to estimate the potential contribution of the chaparral browse Quercus durata (leather oak) and Adenostoma fasciculatum (chamise) on intake and nutrient digestion in goats and sheep. Four wether Kiko goats (avg. wt. 22.9 kg) and four wether Targhee sheep (avg. wt. 39.6 kg) were housed in metabolism cages. Alfalfa pellets were used as a dietary supplement. Digestibility of the shrubs was measured by difference and metabolizable energy (ME) and ME intake (MEI) were calculated from digestibility and plants intake values. Oak and chamise had low crude protein (CP) content (6.5 and 4.3% DM) and high content of extractable condensed tannins (17.8 and 9.8% DM). In vitro organic matter digestibility (OMD) and ME for oak and chamise were 35.6 and 33.1% and 5.0 and 4.7 MJ/kg DM, respectively. In vivo OMD (calculated by difference with alfalfa) and MEI, for browse were greater (P < 0.01) for goats fed chamise compared to sheep. In oak, OMD was similar for both animal species but MEI was greater (P < 0.01) for goats. Greater (P < 0.05) DM and CP intakes (per kg BW^0.75) were observed for goats fed either oak or chamise compared with sheep. When an energy source was given as supplement, the potential contribution of chamise and oak to total ME requirements for maintenance was about 58.3 and 60.4% in goats and about 17.1 and 32.9% in sheep, respectively. In consequence, metabolizable energy supplied by these shrubs may not be adequate for maintenance when, during grazing, they are consumed in high proportions with other chaparral plants that may have lower nutritional value than the alfalfa supplemented in this study. Under an appropriate supplementation program, goats could be more effective than sheep to control fuel load in California chaparral, as they consume more chamise and leather oak and obtain more nutrients from them.     

Ruminal Fermentation and Nutrient Digestion in West African Dwarf (WAD) Sheep Fed Leucaena leucocephala Supplemental Diets

Dry season feeding has always posed a problem for ruminant nutrition in sub-Saharan Africa. The availability of browse plants or multi-purpose trees during this period has led to their incorporation in the farming systems. The need therefore to investigate the feeding value and fermentation profiles of WAD sheep fed grass hay with supplemental Leucaena leucocephala formed the objective of this study. Eight 18–24 months old West African Dwarf (WAD) sheep (28.8±4.2 kg body weight) were used in the study. Four of the sheep were fistulated ruminally and rumen pH, ammonia and volatile fatty acid were measured. Dried leaves of L. leucocephala were offered at two levels (25 and 50% of DMI, diets D25% and D50%, respectively) as supplement to a basal hay diet. The basal hay diet without supplement was the control diet. Diet D25% had a higher (p <0.05) ruminal ammonia concentration than the control, while diet D50% had a higher (p <0.05) total volatile fatty acid (VFA) concentration compared to both the control and D25% diets, respectively. Diet D25% had a marginal increase of 6.7% N- retention over the control diet. Organic matter digestibility (OMD) decreased (p <0.05) with level of supplementation. Animals on D50%, D25% and the control diets lost 14, 7.3 and 5%, respectively, of retained energy leading to a negative energy balance. Overall results suggest that a 25% level of supplementation with leucaena gave the best outcome even though a range of 25–50% could be fed during periods of basal diet scarcity.     

Effect of dried Gliricidia sepium leaf supplement on feed intake, digestibility and nitrogen retention in sheep fed dried KW4 elephant grass (Pennisetum purpureum) ad libitum

A feeding experiment was conducted to study the effects of supplementation with dried Gliricidia sepium leaves on dry matter (DM) intake, digestibility and nitrogen retention in sheep fed KW4 elephant grass. Four mature rams were fed elephant grass ad libitum supplemented with four levels of gliricidia leaves (0, 4, 8 and 12 g DM kg⁻¹ lwt day⁻¹) in a 4 × 4 Latin square design. Supplementation with gliricidia leaves decreased elephant grass DM intake (g DM day⁻¹ or g DM kg⁻¹ BW^0.75 day⁻¹). However, the effect of supplementation on total DM intake of the rations was not significant (P >; 0.05). Total crude protein intake significantly (P < 0.001) increased with increasing levels of gliricidia supplementation. Total DM digestibility and body weight changes were significantly (P < 0.05) improved by gliricidia supplementation; with the highest digestibility coefficient (60.5%) and body weight gain (89.3 g/day) obtained at 8 g DM kg⁻¹ lwt day⁻¹. Gliricidia supplementation significantly (P < 0.001) improved nitrogen intake, absorbed nitrogen and retained nitrogen but with no significant difference at 8 and 12 g DM kg⁻¹ lwt day⁻¹ level of supplementation. The highest efficiency of N retention by sheep (44.9%) was obtained at 8 g DM kg⁻¹ lwt day⁻¹ level of gliricidia supplementation. The results indicated that supplemention of KW4 elephant grass with small quantities of gliricidia leaves up to 8 g DM kg⁻¹ lwt day⁻¹ enhance utilisation efficiency of the total ration. Further increases in the level of gliricidia supplementation, under the conditions of this experiment, reduced the intake of elephant grass leading to substitution effects of the basal. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effect of low-protein diet with supplementing different levels of DL-methionine on production performance of minks in growing-furring period

A study was conducted to evaluate production performance of minks in growing-furring period with supplementing DL-Methionine (Met) in low protein diet. Seventy healthy male minks were randomly divided into five groups of 14 minks each. The minks were fed in five kinds of experiment diets (HP, LP, LP+M1, LP+M2 and LP+M3). The dietary protein levels, expressed as percentage of dry matter (DM), were 32% (high protein, HP) and 24% (low protein, LP). LP was supplemented with Met 0.4% (M1), 0.8% (M2) and 1.2% (M3) DM. From mid of September to December 10, apparent digestibility of CP (crude protein), N intake and urinary N excretion were decreased with declining dietary protein levels (p < 0.05) and N retained was the highest in treatment LP+M2. No significant difference was found in total serum protein (TP) and serum urea nitrogen (SUN) among all treatment groups (p > 0.05). Skin length of treatment HP and LP+M2 was higher than that of other groups (p < 0.05). Body length, skin weight, length of guard hair and under hair were not affected by different dietary protein levels (p>0.05). The best performance could be observed in treatment LP+M2. In diet, 24% (DM) protein level with 1.54% Met supplementing was enough for minks during growing-furring period. Dietary protein lowered from 32% to 24% with supplementing Met in diets would result in a 37.9% decrease in urinary N excretion. Furthermore, addition of Met in diets for minks would be beneficial in terms of reducing feed expenses and lessening nitrogen emissions to the environment.     

Effect of diet inclusion of <Emphasis Type="Italic">Tithonia diversifolia</Emphasis> on feed intake,digestibility and nitrogen balance in tropical sheep

Feed intake and digestibility were evaluated in sheep fed low quality Taiwan grass supplemented with Tithonia diversifolia. Four wether hair sheep were housed in metabolic cages and fed with either Control concentrate 20%, Tithonia 20, 35 or 50% in a Latin Square design. Adaptation and, feces and urine collection periods were 14 and 7 days, respectively. Feed intake was increased (P < 0.01) from 58.5 in control to 86.1 g/kg^0.75 in sheep fed Tithonia. NDF intake and digestibility were affected by Tithonia level. Nitrogen intake increased linearly (P < 0.01) with increase in feces and urine excretion. N retention was similar (P > 0.1) among sheep fed Tithonia, but different (P < 0.05) from control. Inclusion of Tithonia foliage at 20% of the DM diet of hair sheep improved their intake of low quality Taiwan grass and nitrogen retention. Higher levels of Tithonia in the diet, however, increase nitrogen loss in feces and urine.     

对印度亚热带潮湿气候中的多种用途树叶作为草料的质量评价(英文)

多种用途树种和灌木在农业系统中有重要的作用,在减少饲料供求矛盾和补充世界各地饲料赤字,提高动物生产力方面有很大的潜力。同时,评价草料各种营养特性,利于生产定量平衡的饲料。评价12种多种用途树种(Acacia auri-culiformis,Albizzia procera,Dalbergia sissoo,Gliricidia macu-lata,Leucaena leucocephala,Samanea saman,Azadirachta in-dica,Eucalyptus hybrida,Gmelina arborea,Michelia champaca,Morus alba,和Tectona grandis)的树叶的营养特性,其中分别包括6种豆科和非豆科树种,指标包括:常规成分,细胞壁成分,总鞣质含量,大量(Ca和P)与微量元素(Fe,Cu,Zn,Mn和Co)含量,干物质体外消化率与有机物消化率以及代谢能量值。结果表明上述各参数都有明显的差异。有机物,粗蛋白质含量,石油醚提取物总量,粗纤维含量,无氮浸出物,总灰分的平均值分别为:(92.02±0.30)%,(16.00±0.74)%,(3.05±0.13)%,(18.97±1.07)%,(54.00±1.12)%和(7.98±0.30)%。豆科树种较非豆科树种有更高的粗蛋白质含量(18.30%和13.70%)。细胞壁成分中的中性洗涤纤维素,酸性洗涤纤维,半纤维,纤维素,酸性木质素含量平均值分别为:(52.48±1.05)%,(31.72±0.97)%,(20.76±0.88)%,(16.97±0.70)%和(9.57±0.62)%。总鞣质含量为(4.22±0.32)%。Ca与P之比合理,多种树种叶中Fe和Mn含量丰富,P,Cu,Zn和Co水平低于标准水平含量。干物质体外消化率与有机物消化率平均值分别为(48.96±1.30)%和(50.69±1.36)%。代谢能量值为(6.95±0.11)MJ·kg-1。粗蛋白质含量与干物质体外消化率与有机物消化率和代谢能量值成正相关;而这三个参数与中性洗涤纤维素,酸性洗涤纤维,和酸性木质素含量成负相关。结果表明:银合欢可作为优良饲料的树种,因为它具有最高的干物质体外消化率与有机物消化率以及代谢能量值(65.20%,67.66%和7.95MJ·kg-1),而Gliricidia maculata,Morus alba,Azadirachta indica,Dalbergia sissoo和Samanea saman可做较好类型饲料的树种,其它树种做饲料质量差。     

Dry-season sesbania fallows and their influence on nitrogen availability and maize yields in Malawi

Nitrogen deficiency is widespread in southern Africa, but inorganic fertilizers are often unaffordable for smallholder farmers. Short-duration leguminous fallows are one possible means of soil fertility restoration. We monitored preseason topsoil (0 to 20 cm) ammonium and nitrate, fallow biomass production and grain yields for three years in a relay cropping trial with sesbania [Sesbania sesban (L.) Merr.] and maize (Zea mays L.). Sesbania seedlings were interplanted with maize during maize sowing at 0, 7400 or 14,800 trees ha^–1, in factorial combination with inorganic N fertilizer at 0 or 48 kg N ha^–1 (half the recommended rate). After maize harvest, fallows were allowed to grow during the seven-month dry season, and were cleared before sowing the next maize crop. Both sesbania fallows and inorganic N fertilizer resulted in significantly greater (P < 0.01 to 0.05) preseason topsoil nitrate-N than following unfertilized sole maize. In plots receiving no fertilizer N, preseason topsoil inorganic N correlated with maize yield over all three seasons (r ² = 0.62, P < 0.001). Sesbania fallows gave significantly higher maize yields than unfertilized sole maize in two of three years (P < 0.01 to 0.05). Sesbania biomass yields were extremely variable, were not significantly related to sesbania planting density, and were inconsistently related to soil N fractions and maize yields. Short-duration fallows may offer modest yield increases under conditions where longer duration fallows are not possible. This gain must be considered against the loss of pigeonpea (Cajanus cajan L. Millsp) harvest in the similarly structured maize-pigeonpea intercrop common in the region.This revised version was published online in November 2005 with corrections to the Cover Date.