Einfluss des vegetationsstadiums der luzerne auf die abbaubarkeit des rohproteins im pansen und die in vitro‐verdaulichkeit des nichtabgebauten rohproteins

Es wurde der Einfluß des Vegetationsstadiums der Luzerne auf den Rohproteingehalt, die Löslichkeit des Rohproteins, die Rohfaserfraktionen und die Abbaubarkeit der organischen Substanz und des Rohproteins in situ im Pansen von Bullen untersucht.

Das fortgeschrittene Vegetationsstadium des Luzemebestandes verursachte eine signifikante Erniedrigung des Rohproteingehaltes (P < 0,05). Gleichzeitig sank auch der Anteil des löslichen N am Gesamtgehalt des Stickstoffs. Mit dem Anstieg des NDF‐ und ADF‐Gehaltes (P < 0,01) unter dem Einfluß des Vegetationsstadiums sank die effektive Abbaubarkeit des Rohproteins um etwa 10 % und die effektive Abbaubarkeit der organischen Substanz um etwa 5 %.

Mit Hilfe der in vitro Methode wurde die Verdaulichkeit des im Pansen nicht abbaubaren Rohproteins bestimmt. Die enzymatische Verdaulichkeit (Pepsin, Trypsin, Chymotrypsin) dieser Fraktion war zu Beginn der Blüte des Luzernebestandes mit 75,0 % am höchsten.     

Identification of lucerne stem cell wall traits related to in vitro neutral detergent fibre digestibility

Genetic improvement of forage digestibility, especially utilizing marker assisted selection and recombinant DNA techniques, requires identification of specific biochemical traits and associated genes that impact digestibility. We undertook a study to identify cell wall (CW) traits of lucerne (Medicago sativa L.) stems that were consistently and strongly correlated with in vitro neutral detergent fibre (NDF) digestibility, a measurement that has been shown to correlate with animal performance. Spring and summer harvested lucerne stem material, for 2 years, from 24 individual plants in each of two germplasm sources were analyzed for 16 and 96 h in vitro NDF digestibility, and cell wall concentration and composition (monosaccharide constituents of cellulose, hemicellulose, and pectin; and Klason lignin (KL)) by the Uppsala dietary fibre method using near-infrared reflectance spectroscopy (NIRS). Pearson correlation coefficients were calculated for the relationships among these cell wall traits and with in vitro NDF digestibility. Concentrations of the pectin monosaccharide components were all negatively correlated (r=−0.73 to −0.94) with total cell wall concentration. In contrast, the three most abundant cell wall components glucose (Glc), xylose (Xyl) and Klason lignin were not correlated, or only weakly positively correlated (r<0.35), with cell wall concentration. Cell wall concentration was consistently negatively correlated (r=−0.60 to −0.94) with both 16 and 96 h in vitro NDF digestibility. In contrast, Klason lignin concentration was only marginally correlated (r<0.30) with 16 h in vitro NDF digestibility, but strongly negatively correlated (r=−0.71 to −0.74) with 96 h in vitro NDF digestibility. This is consistent with previous reports which show that lignin affects potential extent of digestion, but not rate. Cell wall glucose and xylose concentrations were inconsistently correlated with fibre digestibility. The monosaccharide components of pectin were consistently positively correlated (r=0.54–0.90) with in vitro NDF digestibility, except for 96 h in vitro NDF digestibility of spring harvested stems. Growth environment (year) and germplasm source had only minor impacts on the preceding correlation patterns, whereas spring versus summer harvests accounted for the inconsistencies observed among correlations for cell wall traits. The results of this study indicate that genetic improvement of fibre digestibility of lucerne stems should target genes that reduce total cell wall concentration, perhaps by reducing the rate of xylem tissue deposition during maturation, and reduce Klason lignin and increase pectin concentrations in the cell wall to improve potential extent and rate of fibre digestibility, respectively.     

The evaluation of pollen quality,and a further appraisal of the fluorochromatic (FCR) test procedure

Summary Methods currently available for evaluating pollen quality in vitro include, (a) tests of germinability; (b) tests of the stainability of the vegetative cell contents; (c) tests for enzyme activity, and (d) the fluorochromatic procedure (FCR), which tests principally the integrity of the plasmalemma of the vegetative cell. Using germinability in vitro as a standard, a comparison has been made between histochemical methods of classes (b), (c) and (d) in application to various pollens, immature, mature, and treated in ways known to affect viability and membrane state. Predictably, the lowest correlation was obtained with tests of stainability. The highest was given by the FCR, which generally provided an excellent guide to potential germinability. The FCR procedure is subject to various limitations, however, (a) A high correlation between FCR and germinability can only be expected when mature, ripe pollen is used; with immature pollen, the FCR will predict excessively high potential germinability. (b) The FCR may also predict a higher potential level of pollen function than in vitro germinability when the germination medium is sub-optimal. In this situation, however, it will generally give a better guide to fertilising capacity, (c) The FCR is not a test of pollen viability. Like germinability in vitro, it can yield a negative score with pollen which is nevertheless capable of functioning. For example, false negatives will be obtained with some species if the pollen is not properly pre-conditioned by rehydration before testing, an important point in monitoring stored pollen. The paper includes a brief discussion of the rationale of pollen testing.     

Defining phosphorus efficiency in plants

The many different definitions for "nutrient efficiency" make the use of the term ambiguous. We evaluated nutrient efficiency using data from a study of response to phosphorus (P) supply in white clover (Trifolium repens L.) and lucerne (Medicago sativa L.). Application of various criteria identified in the literature as measures of nutrient efficiency did not clarify differences between purportedly P efficient and inefficient germplasm. Germplasm differed in maximum shoot and total dry mass and in solution P concentration ([P]_s) required to achieve 80% maximum yield, but not in P concentration of tissue ([P]_t), internal P utilization, or P uptake per unit of fine root dry mass. Differences in yield may have resulted from factors other than efficient use of P. To reduce the confounding effects that other factors have on nutrient efficiency, it is essential that equivalent yields of germplasm be demonstrated where nutrients are not limiting. Mechanisms that enable enhanced nutrient efficiency can be identified less ambiguously using this approach.Joint contribution of the Minn. Agric. Exp. Stn. and the USDA-ARS     

Effects of ensiled forage legumes on performance of store finishing lambs

Male Beulah speckled face lambs (initial live weight (LW) 28.8 ± 0.31 kg) were allocated to three dietary treatments to evaluate the performance of store lambs of a hill breed when offered ensiled lucerne (Medicago sativa), red clover (Trifolium pratense) or ryegrass. Second-cut silage bales (wilted and inoculated) were prepared from 3-year old lucerne and red clover stands and a 1-year old ryegrass sward. All the lambs were group-housed and offered ad libitum ryegrass silage during a 3-week co-variate period. This was followed by a week of dietary changeover period, after which the lambs were housed individually and offered their treatment diet ad libitum. All the lambs received a flat rate supplement of pelleted molassed sugarbeet (250 g fresh weight/day). Individual intakes were determined daily, and weekly measurements of LW and body condition score (CS) were made. Additional measurements were taken by scanning the lambs for depth of Longissimus dorsi (LD) muscle and subcutaneous fat. Over an experimental period of 7 weeks, the lambs offered red clover silage had a higher voluntary silage dry matter (DM) intake, total DM intake and metabolisable energy (ME) intake (P < 0.001) than lambs offered either lucerne or ryegrass silage. This resulted in a faster (P < 0.001) growth rate and increase (P < 0.001) in CS, with no difference between lucerne and ryegrass silages. The feed conversion efficiency (FCE) was 8.0 ± 0.61 kg feed/kg gain for lambs fed red clover silage, compared with 16.6 ± 2.82 and 10.6 ± 1.94 kg feed/kg gain for lucerne and ryegrass silage, respectively. The CP intake was higher (P < 0.001) for lambs fed the lucerne and red clover silages than for the ryegrass silage treatment. The concentration of plasma total protein (TP) was higher (P < 0.05) for lambs offered ryegrass silage versus lucerne and red clover silage. Urea concentrations were highest for lambs fed lucerne silage and lowest for those fed ryegrass silage (P < 0.05). The glucose concentration was higher (P < 0.05) for lambs offered red clover silage, whereas non-esterified fatty acids (NEFA) concentration was higher (P < 0.05) for lambs offered lucerne silage. Substituting ryegrass silage with red clover silage has the potential to improve the performance of finishing store lambs.     

黄土高原苜蓿-冬小麦轮作系统土壤水分时空动态及产量响应

2 0 0 1～ 2 0 0 3年在甘肃庆阳黄土高原连续 3 a研究了紫花苜蓿 -冬小麦轮作系统中土壤 0～ 3 0 0 cm剖面水分动态特征 ,作物产量及其含 N量。处理包括 4龄苜蓿草地 (L C)、4龄苜蓿草地后茬持续休闲 (L F)、4龄苜蓿草地休闲 4个月后种植冬小麦(L Fl W) ,和 4龄苜蓿草地休闲 1个月后种植冬小麦 (L Fs W)。结果表明 ,种植 4a苜蓿后春季翻挖实施休闲至冬小麦播种(L Fl W)的 4个月期间 ,降雨的入渗深度为 150 cm,而苜蓿秋季翻挖休闲至小麦播种 (L Fs W)的一个月间 ,降雨在土壤内的入渗深度为 90 cm,不同休闲长度对头茬冬小麦土壤 0～ 90 cm水分贮存量无显著影响 ,亦不影响头茬冬小麦的出苗和出苗数。苜蓿后茬完全休闲 (L F)一个生长季后 ,60～ 90 cm土壤水分含量达田间最大重力持水量 (Drainage U pper L imit DU L )的 93 % ,0～ 3 0 0cm剖面土壤贮水量达 670 mm ,是剖面田间最大重力持水量 (DUL )的 78% ;L Fl W和 L Fs W处理下头茬小麦籽粒产量之间差异显著 (P<0 .0 5) ,收获指数和千粒重等指数无显著差异 ;L Fl W和 L Fs W处理中获得的二茬小麦产量无显著差异 ;连续种植苜蓿与种植小麦有接近的生物量 ,但苜蓿地植物总 N的输出量较小麦田高 2～ 3倍。由于黄土高原降雨变率大 ,因此预测土壤含水量动态有     

Nitrogen-induced boron deficiency in lucerne

Summary In a glasshouse experiment with a boron deficient soil the application of nitrogen was found to decrease the boron concentration and boron uptake by lucerne (Medicago sativa). Without added boron, nitrogen applications killed the lucerne, probably by inducing severe boron deficiency. With added boron, the lowest rate of nitrogen application increased lucerne yield but further additions depressed yields. The effect was due to a physiological interaction rather than an effect of the nitrogen on the availability of the boron in the soil.     

Water relations and adaptations to increasing water deficit in three perennial legumes, Medicago sativa, Dorycnium hirsutum and Dorycnium rectum

Dorycnium hirsutum (L.) Ser. and Dorycnium rectum (L.) Ser. are Mediterranean perennial legumes that may have potential as alternative forage plants to Medicago sativa (lucerne, alfalfa) for low rainfall dryland agriculture. Strategies for surviving periods of water deficit are vital for perennial plants in water-limited environments. This experiment compared leaf physiological and morphological adaptations to increasing water deficit among D. hirsutum, D. rectum and M. sativa. Plants were grown in the glasshouse in large pots (7.8 L, 1 m deep, 10 cm diameter) containing a sandy clay loam (14% available water content) to limit differences between root foraging among the species. Watering was withheld for 21 days and predawn and midday leaf water and osmotic potential were determined. Mid-morning rates of gas exchange were measured at five times as soil water was depleted. After 35 days of withholding water, plant recovery was measured. D. hirsutum and M. sativa reduced stomatal conductance at leaf water potentials below −1.8 MPa and water-stressed D. hirsutum osmotically adjusted by up to 0.68 MPa. D. rectum differed from the other species; leaf water potential was maintained at high levels until soil water content had reached low levels, and reductions in stomatal conductance and photosynthesis were not associated with leaf water potential. D. hirsutum and M. sativa displayed leaf morphological adaptations that may contribute to greater resistance of water deficit. Only one of five D. rectum plants survived the water-stress treatment compared to five of five for D. hirsutum and four of five for M. sativa. The water relations and physiology of D. hirsutum observed in this study suggest that it possesses adaptations suitable for arid environments. On the other hand, the poor survival and water relations of D. rectum indicate that it is poorly adapted to situations where water deficit is common.     

Untersuchungen zum Einfluß der Häufigkeit der Kontrollwägungen auf das Versuchsergebnis bei Mastschweinen

Abstract

In Silierversuchen mit 2 1-Glasgefäßen erfolgten in zwei Versuchsjahren (1988, 1989) Untersuchungen der Wirkung von Zellulase des Stammes Penicillium janthinellum für die Silierung von Luzerne (Medicago sativa). Mit dem Enzymzusatz wurden gute bis sehr gute Siliererfolge bei Reduzierung der Gärverluste erreicht. Durch Differenzierung der vergärbaren Kohlenhydrate im Ausgangsmaterial und den Silagen konnte nachgewiesen werden, daß Glucose und Fructose vollständig und Xylose nicht fermentiert worden sind sowie eine Zuckernachlieferung infolge des Enzymeinsatzes gegeben war.

The effect of cellulase of the strain Penicillium janthinellum for ensilaging lucerne (Medicago sativa) was proved in two experiments conducted throughout consecutive years (1988 and 1989) with 2 1-glass containers. Good and very good ensilaging successes, accompanied with considerable reductions of fermentation losses, were achieved by addition of cellulase. It was demonstrated by means of differentation of the fermentable carbohydrates in the ensilaging material and in the silages that glucose and fructose were fermented completely and xylose was not fermented. A deposit of sugar resulted from the cellulase addition.     

Non random chloroplast DNA hypervariability in Medicago sativa

Two hypervariable regions of the alfalfa (Medicago sativa L) chloroplast genome were used to describe levels of genetic relatedness among populations. PCR primers were developed to amplify the hypervariable regions. The frequency of occurrence of fragments of like size between populations was used to develop a measure of genetic relatedness. Relationships among 135 alfalfa accessions were investigated with principal component and cluster analyses, based on the genetic distance measures. Distinct clusters were taken as an indication of genetically distinct lineages. The populations investigated represented collections from world regions defined as the centers of origin of specific alfalfa germplasm sources, or else represented collections of introduced, and naturally adapted, accessions from agriculturally advanced regions. In general, this analysis indicated that the accessions from regions of origin of germplasm sources were largely homogeneous, while accessions from areas of introduction were much more diverse. In some cases, the accessions from a region of origin formed distinct clusters, suggesting that divergence has resulted in genetically distinct lines persisting in the original region of origin. Investigation of the stability of the marker fragments through vegetatively, and sexually, propagated plants indicated stable transmission through the sexual phase. However, one of the two regions underwent a deletion of 145 bp of one copy of a tandemly repeated 146 bp region in the equivalent of 80 years of vegetative growth. Received: 18 November 1999 / Accepted: 31 March 2000