Extractability and nutritional value of leaf protein from tropical aquatic plants

In a study conducted on the extraction of protein from the leaves of 30 freshwater aquatic plants, the highest standing crop fresh yield was found inTypha latifolia (2650g/m²). The Bio-Medical Data Processing (BMDP)K-means clustering program withK=2 showed that 11 of the 30 plants had a high protein nitrogen extractability as well as a high nitrogen content of the extracted protein. Among these, leaf protein fromAllmania nodiflora had the highest content of crude protein (62.7%) and β-carotene (782.4 μg/g). Leaf protein prepared fromHygrophila spinosa, Ottelia alismoides andPolygonum barbatum had low in-vitro digestibility. The levels of alkaloids and polyphenols were lower in the extracted protein compared to that present in the original leaf sample.     

Nitrogen and fine root length dynamics in a tropical agroforestry system with periodically pruned Erythrina poeppigiana

The effect of pruning all branches (complete pruning) or retaining one branch (partial pruning) on the dynamics of nitrogen cycling in aboveground biomass, nitrogen supplying power of an amended Eutric Cambisol, and fine root length, was studied in an Erythrina poeppigiana (Walp.) O.F. Cook—tomato (Lycopersicon esculentum Mill.) alley cropping practice in Turrialba, Costa Rica during 1999–2000. Over the 1 year pruning cycle, in which trees were completely or partially pruned four times, respective aboveground biomass production was 4.4 Mg or 7 Mg ha⁻¹ (2-year-old trees) and 5.5 Mg or 9 Mg ha⁻¹ (8-year-old trees); N cycled in aboveground biomass was 123 kg or 187 kg ha⁻¹ (2-year-old trees) and 160 kg or 256 kg N ha⁻¹ (8-year-old trees); mean fine root length was 489 or 821 m (2-year-old-trees), 184 or 364 m per tree (8-year-old-trees). Pruning intensity did not significantly affect net N mineralisation and net nitrification rates during the tomato-cropping season. For the tomato crop, pre-plant mean net N mineralisation rate of 2.5 mg N kg⁻¹ soil day⁻¹ was significantly lower than 16.7 or 11.6 mg N kg⁻¹ soil day⁻¹ at the end of vegetative development and flowering, respectively. Mean net nitrification rates of 3.5, and 4.3 mg N kg⁻¹ soil day⁻¹, at pre-plant and end of vegetative development, respectively, were significantly higher than 0.3 mg N kg⁻¹ soil day⁻¹ at end of flowering. In humid tropical low-input agroforestry practices that depend on organic inputs from trees for crop nutrition, retention of a branch on the pruned tree stump appears to be a good alternative to removal of all branches for reducing N losses through higher N cycling in aboveground biomass, and for conserving fine root length for higher N uptake, although it might enhance competition for associated crops.     

Influence of low phosphorus intake during early lactation on apparent digestibility of phosphorus and bone metabolism in dairy cows

In this study, the effects of reducing the dietary phosphorus (P) supply during the first 4 months of lactation on P balance and bone metabolism were investigated in dairy cows during a full lactation, including the dry period. Twenty-two multiparous cows of the Swedish Red and White Breed were included in the experiment. Eleven cows received a dietary P concentration of 0.43% of DM during the whole lactation (NP), and 11 cows received a dietary P concentration of 0.32% of DM during the first 4 months of lactation, followed by 0.43% of DM during the rest of lactation (LP). Total collection of faeces was carried out during five different stages of lactation, for 5 consecutive days at each occasion. The dynamics of bone metabolism was investigated by monitoring one bone-formation marker, identifying osteocalcin (OC), and one bone-resorption marker identifying C-telopeptide fragments of collagen type I (CTx) in blood plasma. At the two first collection periods, 3–7 and 11–15 weeks after parturition, the apparent digestibility of P was higher in the LP cows (52%) than in the NP cows (42%). During the following collection periods, no difference in the apparent digestibility could be noted between the two groups of cows. Phosphorus retention did not differ between treatments at any collection period. The highest retention was observed during late lactation and during the dry period. The profiles of the bone metabolism markers indicated a net resorption of bone during early lactation, but there were no differences in marker concentrations between the groups during early lactation, indicating that the LP diet did not induce a further elevated net bone resorption.     

Protein quality evaluation of sprouted maize

Protein, lysine, tryptophan, crude fibre (CF) and neutral detergent fibre (NDF) of sprouted, normal and hard endosperm opaque-2 (QPM) kernels increased, whereas in vitro protein digestibility (IVPD) decreased substantially up to five days of germination. Following the removal of radicles alone or both radicles and plumules from sprouted kernels, IVPD improved at all the stages of germination. However, the contents of lysine and tryptophan were not affected significantly. For some stages of germination, these amino acids decreased slightly. In sprouted normal kernels, IVPD was higher whereas protein, lysine and tryptophan content was lower than that of sprouted QPM kernels respectively at all the stages of germination. In four days old sprouted normal kernels, after the removal of both radicles and plumules biological value (BV), net protein utilization (NPU) and utilizable protein (UP) increased over non-sprouted kernels whereas true digestibility (TD) reach at par with non-sprouted kernels.     

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.     

Contribution of Erythrina protein banks and rejected bananas for improving cattle production in the humid tropics

In view of the low pasture productivity in the Central American humid tropics where cattle rearing is a major land-use activity, it is important to examine the potential of alternate feed sources for ruminant feeding. Erythrina berteroana Uban, locally known as poro, and green banana (Musa AAA) fruits have been identified as two such potential sources. The effects of feeding poro as a grazing supplement and diet supplementation with green banana fruits on cattle productivity were evaluated in a long-term trial in Costa Rica. Daily liveweight (LW) gains were measured and samples of all feed material were analyzed for crude protein and in vitro dry matter (DM) digestibility. Pasture availability was high, averaging 0.17 t DM ha day^–1 over the grazing period. The main grass species were Paspalum fasciculatium Poiret, Axonopus compressus Swartz and to a lesser extent African star grass (Cynodon nlemfluensis Vanderyst). DM yields of poro declined significantly with time (> 50%) when it was managed with a two-month resting period but remained higher when subsequently managed with a three-month resting period. Average daily LW gain of animals was 21% to 26% higher with two hours daily browsing of poro than for animals only grazing pasture. Highest liveweight gain was achieved when diets were supplemented with banana and there was no additional benefit when poro was fed in addition to banana. This suggests that fodder banks of poro or supplements with green banana can improve cattle nutrition in the humid tropics.This revised version was published online in November 2005 with corrections to the Cover Date.     

Long-term changes in forest floor processes in southern Appalachian forests

Soil nutrient concentrations decreased in an aggrading southern Appalachian forest over a 20-year period. Construction of nutrient budgets showed significant nutrient sequestration aboveground including increased forest floor mass. We hypothesized that the changes in forest floor mass resulted from decreased litter decomposition rates because of decreased litter quality. In 1992 and 1993, we repeated a litter decomposition experiment conducted in 1969 and 1970 to test this hypothesis. In addition, we examined microarthropod populations and functional groups as litter decomposed. For four of the five species tested, first-year decomposition rates were about the same in both experiments. Initial litter nutrient concentrations of P were lower in all tree species in the most recent sampling. N, Ca, and Mg concentrations also declined in some species. These declines often resulted in decreased nutrient release rates during decomposition. Microarthropod populations differed significantly among litter species, as well as between years (probably resulting from differences in growing-season rainfall). For some litter species we found significant relationships between microarthropod populations and nutrient concentration (primarily C and N); however, most r²-values were low. Data suggest that changes in forest floor mass probably resulted from decreased litter quality and that those changes may have an effect on microarthropod populations.     

Effects of chronic acid fog exposure with soil acidification or nitrogen loading on nutrient status in Abies firma seedlings

To clarify the nutrient status in momi fir (Abies firma Sieb. et Zucc.) seedlings under complex stress conditions of acid fog with soil acidification or nitrogen loading, we exposed seedling shoots to simulated acid fog (pH 3) and simultaneously loaded the soil with acid or excess nitrogen for 17 months. Proton and nitrogen loading reduced K concentration in soil, but these treatments had little effect on the nutrient status of fine roots in momi fir seedlings. Acid fog exposure resulted in reduced concentrations of Mg, Al, and Fe in current-year needles and Mg, Al, Cu, Fe, and Zn in 1-year-old needles. The complex effects of acid fog exposure with proton or nitrogen loading on nutrient status were relatively slight. However, elements such as Al and Cu notably reflect the effects of proton loading. These results show that the nutrient status of trace elements, rather than major elements, in needles of momi fir seedlings is sensitive to exposure to acid fog or proton loading.