NOTE ON THE SPIKE-HEEL LARKS OF THE CAPE PROVINCE

This study investigates the possibility of hybridisation between introduced domestic Helmeted Guineafowl Numida meleagris, derived from the West African subspecies N. m. galeata, and South African guineafowl, N. m. coronata. There is putative morphological evidence of such hybridisation in wild populations and it is known that domestic guineafowl do not survive well in the wild. Molecular analysis of the control region of mtDNA confirmed the occurrence of the domestic guineafowl haplotype in individuals present in wild populations from KwaZulu-Natal, but not in birds from populations from the Free State. Thus, despite the absence of the availability of bi-parentally inherited nuclear DNA marker, the presence of the domestic haplotype in individuals of both wild and intermediate phenotype (between wild and domestic birds) suggests that there is hybridisation in the wild between domestic and wild guineafowl. To avoid potential negative affects associated with outbreeding depression, we argue for careful control of releases of domestic guineafowl into the wild. This study investigates the possibility of hybridisation between introduced domestic Helmeted Guineafowl Numida meleagris, derived from the West African subspecies N. m. galeata, and South African guineafowl, N. m. coronata. There is putative morphological evidence of such hybridisation in wild populations and it is known that domestic guineafowl do not survive well in the wild. Molecular analysis of the control region of mtDNA confirmed the occurrence of the domestic guineafowl haplotype in individuals present in wild populations from KwaZulu-Natal, but not in birds from populations from the Free State. Thus, despite the absence of the availability of bi-parentally inherited nuclear DNA marker, the presence of the domestic haplotype in individuals of both wild and intermediate phenotype (between wild and domestic birds) suggests that there is hybridisation in the wild between domestic and wild guineafowl. To avoid potential negative affects associated with outbreeding depression, we argue for careful control of releases of domestic guineafowl into the wild.     

The effects of agriculture and the availability of edge habitat on populations of Helmeted Guineafowl Numida meleagris and on the diversity and composition of associated bird assemblages in KwaZulu-Natal province, South Africa

We investigated the effects of agriculture and the availability of edge habitat on populations of Helmeted Guineafowl Numida meleagris and associated avian diversity and species composition in woodland and grassland biomes in the Midlands of KwaZulu-Natal province, South Africa. Study sites within woodland biome had greater species diversity than those in grassland, whereas adjacent, high-quality, protected habitat in grassland sites, enhanced diversity within this biome. Both guineafowl populations and overall avian diversity declined with increasingly intensive agriculture and disappearance of edge habitat and associated, optimally fragmented habitat mosaic. Furthermore, traditional agriculture in the form of contouring in a pesticide-free environment, resulted in extensive edge habitat that appeared to provide additional food and cover for birds. This, in turn, caused an increase in overall bird diversity, and in guineafowl populations in particular. The widespread decline in Helmeted Guineafowl populations in the Midlands that started in the 1980s, and possibly the decline in species associated with this variegated landscape, was therefore caused by the loss of the habitat mosaic to intensive, modern, monoculture, crop agriculture. Maintaining species diversity and healthy guineafowl populations within these habitats requires the persistence or re-creation of a habitat mosaic and the resulting edge habitat on a landscape scale.     

Habitat preferences of Helmeted Guineafowl Numida meleagris in the Krugersdorp Game Reserve,Gauteng province,South Africa

Field surveys were conducted in the Krugersdorp Game Reserve, Gauteng province, South Africa, during 1978–1981 to study the habitat preferences of Helmeted Guineafowl Numida meleagris. The study area was traversed with a vehicle in the late afternoons on a set route (12 km) and at least one observation was conducted each month during the three-year period. With the aid of binoculars all guineafowl that were sighted were counted and recorded on a map. The purposes were to (1) describe the habitat preferences of guineafowl and (2) to demonstrate that weeds attracted guineafowl during winter and can be retained in modified landscapes (e.g. farms) to provide important microhabitats. The highest mean monthly density across five habitat categories throughout the year was recorded in old vegetable gardens. The old vegetable gardens of c. 35 ha attracted more than 60% of the guineafowl population from April to October, which was mainly during winter when the birds scratched actively in weedy patches.     

Roosting requirements of Helmeted Guineafowl Numida meleagris on Highveld grain and livestock farms with alien tree groves,Gauteng province,South Africa

This study describes the relationship between Helmeted Guineafowl Numida meleagris and invasive alien trees on livestock and maize farms south-east of Johannesburg, Gauteng province, South Africa. The dependence of the birds on alien trees affects strategies for the removal of these trees. During June to December 2014, Helmeted Guineafowl were recorded weekly on maps along a 42 km transect. Since Helmeted Guineafowl live in cohesive social groups of 15–20 birds, they roost communally in one or two trees during winter rather than spreading across an entire tree grove. The distribution of alien trees across the landscape in patches has enabled Helmeted Guineafowl flocks to reach new feeding patches near to roosting trees, as old feeding patches are depleted. One Helmeted Guineafowl flock of 15–20 birds requires ～0.09 ha covered with mature alien trees for roosting. Suggestions are presented relating to the reduction of alien trees in compliance with the Conservation of Agricultural Resources Act 43 of 1983 and conservation of Helmeted Guineafowl.     

Actual and perceived collision risk for bird strikes at Namibian airports

At Namibia’s two major airports, Hosea Kutako International and Eros (domestic), 117 bird strike collision incidents were recorded between 2006 and 2010. A risk assessment, which included a proposed risk weighting methodology, was conducted at Hosea Kutako and Eros airports, which estimated the probability of an accident/collision as well as the consequence of such a collision. The assessment included surveys of bird occurrence frequencies as well as pilot interviews. The results of the risk assessments were compared with actual bird strike incidences for each species, frequency of occurrence of birds and pilot perceptions of species risk, in order to find whether risk assessment and pilot perception are reliable measures of potential bird strike incidence. White-backed Vulture Gyps africanus and Helmeted Guineafowl Numida meleagris were the highest risk species at both airports. They were also, after Crowned Lapwing Vanellus coronatus, the species most often observed by pilots. Bird strike records showed that Crowned Lapwing and Helmeted Guineafowl were also the most frequently struck birds at both airports. The study illustrates how combining risk assessment, pilot perception and bird strike history can benefit bird strike minimisation plans at airports through the rapid identification of priority bird species.     

Effect of extrusion on trypsin inhibitor activity and nutrient digestibility of diets based on fish meal,soybean meal and white flakes

Abstract

The effects of moist extrusion processing of diets containing fish meal (FM) and conventional defatted soybean meal (SBM) or untoasted defatted soybean meal (white flakes [WF]) on amino acid composition, trypsin inhibitor activity (TIA), and apparent total tract digestibility of nutrients were studied. Three diets with the nutritional characteristics of feeds for salmonid fish were formulated: one control based on FM as protein source and two others where 40% of total amino acids from FM were substituted by either SBM or WF. Each diet was fed to mink either as an unextruded mixture of the ingredients or as extruded pellets in order to determine the effect of extrusion processing. Extrusion did not change the amino acid composition of the diets significantly, but reduced the TIA of both diets containing soy products by approximately 76%. Intake of the unextruded WF diet was only one-third compared with the other diets. The dry matter concentration in faeces from mink fed diets containing soy products was significantly lower than in mink fed the FM diet. Digestibility of crude protein, all amino acids and fat was lower, but starch higher, in the unextruded WF diet than in the FM and SBM diets, whereas no significant differences were found among the extruded diets. Extrusion of the WF diet increased digestibility of protein and all amino acids. The greatest increase in digestibility after extrusion of the WF diet was observed for cysteine followed by tryptophan. Extrusion of the FM and SBM diets had no significant effect on amino acid digestibility. Digestibility of starch was, in general, increased by extrusion. It is concluded that the heat treatment involved in typical moist extrusion processing used for fish feed may be sufficient to inactivate most of the TIA in unheated soybean meal, and to increase digestibility of the protein in WF to approximately the same level as found for SBM and FM. Still, extrusion is a lenient process with minor effects on nutrient digestibility of diets containing fish meal or toasted soybean meal as major protein sources.     

Influence of feed provisioning prior to digesta sampling on precaecal amino acid digestibility in broiler chickens

A regression approach was applied to determine the influence of feed provisioning prior to digesta sampling on precaecal (pc) amino acid (AA) digestibility in broiler chickens. Soybean meal was used as an example test ingredient. Five feed-provisioning protocols were investigated, four with restricted provision and one with ad libitum provision. When provision was restricted, feed was provided for 30 min after a withdrawal period of 12 h. Digesta were sampled 1, 2, 4 and 6 h after feeding commenced. A diet containing 300 g maize starch/kg was prepared. Half or all the maize starch was replaced with soybean meal in two other diets. Average pc digestibility of all determined AA in the soybean meal was 86% for the 4 and 6-h protocols and 66% and 60% for the 2 and 1-h protocols, respectively. Average pc AA digestibility of soybean meal was 76% for ad libitum feed provision. Feed provisioning also influenced the determined variance. Variance in digestibility ranked in magnitude 1 h > ad libitum > 2 h > 6 h > 4 h for all AA. Owing to the considerable influence of feed-provisioning protocols found in this study, comparisons of pc AA digestibility between studies applying different protocols prior to digesta sampling must be treated with caution. Digestibility experiments aimed at providing estimates for practical feed formulation should use feed-provisioning procedures similar to those used in practice.     

Transgenic soybean plants overexpressing <Emphasis Type="Italic">O</Emphasis>-acetylserine sulfhydrylase accumulate enhanced levels of cysteine and Bowman–Birk protease inhibitor in seeds

Soybeans provide an excellent source of protein in animal feed. Soybean protein quality can be enhanced by increasing the concentration of sulfur-containing amino acids. Previous attempts to increase the concentration of sulfur-containing amino acids through the expression of heterologous proteins have met with limited success. Here, we report a successful strategy to increase the cysteine content of soybean seed through the overexpression of a key sulfur assimilatory enzyme. We have generated several transgenic soybean plants that overexpress a cytosolic isoform of O-acetylserine sulfhydrylase (OASS). These transgenic soybean plants exhibit a four- to tenfold increase in OASS activity when compared with non-transformed wild-type. The OASS activity in the transgenic soybeans was significantly higher at all the stages of seed development. Unlike the non-transformed soybean plants, there was no marked decrease in the OASS activity even at later stages of seed development. Overexpression of cytosolic OASS resulted in a 58–74% increase in protein-bound cysteine levels compared with non-transformed wild-type soybean seeds. A 22–32% increase in the free cysteine levels was also observed in transgenic soybeans overexpressing OASS. Furthermore, these transgenic soybean plants showed a marked increase in the accumulation of Bowman–Birk protease inhibitor, a cysteine-rich protein. The overall increase in soybean total cysteine content (both free and protein-bound) satisfies the recommended levels required for the optimal growth of monogastric animals.     

黄颡鱼对四种动物性蛋白原料在不同制粒工艺下的表观消化率研究

实验以三氧化二铬(Cr₂O₃)为外源指示剂,采用“70%基础饲料+30%实验原料”的方法配制实验饲料,测定了初始体质量为(28.68±0.49) g的黄颡鱼(Peltobagrus fulvidraco)对国产鱼粉、进口鱼粉、进口鸡肉粉和脱脂黄粉虫粉在膨化制粒和非膨化制粒两种工艺下的干物质、粗蛋白、粗脂肪和氨基酸表观消化率。结果显示,在非膨化制粒工艺下,黄颡鱼对进口鸡肉粉的干物质表观消化率显著高于另外3种原料(P<0.05),黄颡鱼对黄粉虫粉蛋白消化率最低(P<0.05),黄颡鱼对进口鸡肉粉脂肪表观消化率显著高于国产鱼粉和进口鱼粉(P<0.05); 在膨化制粒工艺下,进口鸡肉粉的干物质表观消化率显著低于另外3种原料(P<0.05),国产鱼粉和进口鱼粉的粗蛋白质消化率达94%以上,显著高于另外两种原料(P<0.05),但进口鸡肉粉的脂肪表观消化率显著低于其他原料(P<0.05)。在非膨化制粒工艺和膨化制粒工艺下国产鱼粉、进口鱼粉和黄粉虫粉的干物质表观消化率无显著性差异,但在非膨化制粒工艺下进口鸡肉粉的干物质表观消化率显著高于膨化制粒工艺(P<0.05)。对于国产鱼粉、进口鱼粉和黄粉虫粉而言,非膨化制粒工艺的蛋白消化率显著低于膨化制粒工艺(P<0.05),而鸡肉粉则相反。膨化加工工艺进口鱼粉的脂肪表观消化率显著高于非膨化加工工艺(P<0.05),而膨化加工工艺的黄粉虫脂肪表观消化率显著低于非膨化加工工艺(P<0.05)。氨基酸的消化率结果与粗蛋白的表观消化率变化趋势基本一致。由此可知,对于黄颡鱼饲料,国产鱼粉和进口鱼粉是最佳的蛋白质来源,进口鸡肉粉和黄粉虫亦可以作为其优质的蛋白质来源。对于进口鱼粉、国产鱼粉和黄粉虫粉,膨化制粒工艺更有利于黄颡鱼对其干物质、蛋白、脂肪和氨基酸等营养元素的消化利用,而对于进口鸡肉粉,非膨化制粒工艺更有利于黄颡鱼对营养元素的消化利用。     

Nutritional evaluation of the white-rot fungus Sporotrichum pulverulentum as a feedstuff to rats,pigs, and sheep

The production of single-cell protein (SCP) based on cheap carbon sources such as spent liquor from paper mills is of interest for different reasons. The White-rot fungus (Sporotrichum pulverulentum) has earlier been shown to degrade cellulose and lignin. The nutritive value of this fungus was investigated with rats, pigs, and sheep. The effect of different drying process was evaluated on rats. Experiments with piglets, growing pigs, and sheep were aimed at getting primary information on nutritive parameters with domestic animal species, Chemical analysis of S. pulverulentum showed that the sum of the amino acids corresponded to 70% and ammonia, GABA, and glucosamine to 20% of its crude protein content. Differences between drying treatments in their effect on protein digestibility were not noted. From a protein quality viewpoint, a tendency toward superiority was noted for two of the drying processes. The amino acid digestibility of S. pulverulentum was inferior to values for soybean oil meal given in textbooks. The piglet experiment confirmed the lower nutritive value of S. pulverulentum compared with soybean oil meal. in the piglet stage a content of metabolizable energy of S. pulverulentum was found which corresponded to 60% of that for soybean oil meal. With increasing age the ability of pigs to utilize the fungus increased. The limited nutritive value for monogastric animals is most certainly caused by the cell-wall structure of S. pulverulentum with poor digestibility of the carbohydrates. The experiment with sheep showed more satisfactory results than with monogastric species, with digestibility of crude protein of 82% and a content of metabolizable energy of 70% of soybean oil meal.     

Standardised ileal crude protein and amino acid digestibilities in protein supplements for piglets

Standardised ileal digestibilities (SID) of crude protein and amino acids (AA) originating from 24 different feed ingredients, including 11 feed ingredients produced from soybeans, seven by-products of starch processing, four whey products and two fish meals, were determined in piglets by means of the difference method. For the indispensable AA, the highest SID values were obtained in three out of four whey proteins (SID ≥90% for most indispensable AA), one out of two fish meals (SID ≥86%), soy protein concentrate, hydrolysed soy protein isolate (SID ≥86% for most indispensable AA), and by-products of starch processing (SID ≥84% for most indispensable AA). The lowest SID values were obtained in extruded soybeans and microbially fermented soy protein (SID ≤78% for most indispensable AA), whereas the SID values for high-protein soybean meal were intermediate (SID 80–89% for indispensable AA except for Thr). The SID values in the three enzymatically fermented soy proteins (SID 80–94% for most indispensable AA) were similar to those in high-protein soybean meal and soy protein concentrate. The results of the present study indicate that SID values of AA in feed ingredients for piglets differ considerably from those reported for grower-finisher pigs, thus there may be a need for separate feed tables for piglets.     

Effect of extrusion on trypsin inhibitor activity and nutrient digestibility of diets based on fish meal, soybean meal and white flakes

The effects of moist extrusion processing of diets containing fish meal (FM) and conventional defatted soybean meal (SBM) or untoasted defatted soybean meal (white flakes [WF]) on amino acid composition, trypsin inhibitor activity (TIA), and apparent total tract digestibility of nutrients were studied. Three diets with the nutritional characteristics of feeds for salmonid fish were formulated: one control based on FM as protein source and two others where 40% of total amino acids from FM were substituted by either SBM or WF. Each diet was fed to mink either as an unextruded mixture of the ingredients or as extruded pellets in order to determine the effect of extrusion processing. Extrusion did not change the amino acid composition of the diets significantly, but reduced the TIA of both diets containing soy products by approximately 76%. Intake of the unextruded WF diet was only one-third compared with the other diets. The dry matter concentration in faeces from mink fed diets containing soy products was significantly lower than in mink fed the FM diet. Digestibility of crude protein, all amino acids and fat was lower, but starch higher, in the unextruded WF diet than in the FM and SBM diets, whereas no significant differences were found among the extruded diets. Extrusion of the WF diet increased digestibility of protein and all amino acids. The greatest increase in digestibility after extrusion of the WF diet was observed for cysteine followed by tryptophan. Extrusion of the FM and SBM diets had no significant effect on amino acid digestibility. Digestibility of starch was, in general, increased by extrusion. It is concluded that the heat treatment involved in typical moist extrusion processing used for fish feed may be sufficient to inactivate most of the TIA in unheated soybean meal, and to increase digestibility of the protein in WF to approximately the same level as found for SBM and FM. Still, extrusion is a lenient process with minor effects on nutrient digestibility of diets containing fish meal or toasted soybean meal as major protein sources.     

Nutritional assessment and fate of dna of soybean meal from roundup ready or conventional soybeans using rats

This study was conducted to compare the safety of soybean meal prepared from genetically modified (GM) glyphosate-tolerant (Roundup Ready; RR) soybeans and conventional soybeans. Eighty Sprague-Dawley rats (40 males and 40 females) were randomly allotted to one of four groups according to sex and body weight for a 13-week feeding experiment. The rats were fed corn-based diets containing 60% conventional soybean meal, a mixture of 30% conventional and 30% RR soybean meal, 60% or 90% RR soybean meal. All diets were adjusted to an identical nutrient level except the 90% RR diet. The two soybean meals were similar in chemical analysis and amino acid composition. During the 13-week growth trial, body weight (P?P?cp4 epsps gene specific for the GM constructs from RR soybean meal or a 407?bp of lec gene from endogenous soybean DNA could not be detected in investigated masseter muscle samples. No adverse effects of glyphosate-tolerant soybean meal on rats were seen even at levels as high as 90% of the diet.     

Effects of exogenous enzymes on apparent nutrient digestibility in rainbow trout (Oncorhynchus mykiss) fed diets with high inclusion of plant-based protein

Plant-based protein ingredients are increasingly used in feed for carnivorous fish as replacement for fish meal. This study investigated if supplementing diets with high inclusion levels of plant-based protein with three different enzymes could improve the apparent nutrient digestibility in juvenile rainbow trout (Oncorhynchus mykiss). Three diets with high inclusion levels of either de-hulled, solvent extracted soybean meal (344 g/kg), sunflower meal (246 g/kg), or rapeseed meal (264 g/kg) were produced and feed batches were coated post-extrusion with the different enzymes: β-glucanase at 67 mg/kg, xylanase at 208 mg/kg, protease at 228 mg/kg, or a combination of the three enzymes at the same doses. Three consecutive digestibility trials were carried out using a flow-through, modified Guelph System. Each trial was designed to include five dietary treatment groups: a non-supplemented control diet and 4 diets supplemented with either β-glucanase, xylanase, protease or a combination of the three enzymes. Diets were fed to triplicate tanks and two faecal sampling periods for digestibility measurements for each tank were scheduled. Each experiment comprised a 10-day digestibility trial succeeded by a water sampling period for measuring the dissolved nitrogen (N) output. Each experiment lasted 17–19 days in total.Apparent digestibility coefficients (ADCs) of protein, fat, ash, phosphorus and dry matter (DM) were derived from the three digestibility trials, along with calculations of the specific growth rate (SGR, %/d) and feed conversion ratio (FCR). Nitrogen mass-balance and energy retention were evaluated for each dietary treatment group to elucidate on the utilization of digested nutrients and energy.Enzyme supplementation had only moderate effect on apparent nutrient digestibility in the sunflower and rapeseed experiments, while β-glucanase and protease improved the apparent digestibility of all dietary nutrients in the soybean experiment (P<0.05). The effect was more pronounced for lipid than for other nutrients. β-Glucanase had a positive effect on energy retention in the soybean experiment (P<0.05), while there were no effects on nitrogen retention or fish performance in any of the three experiments (P>0.05) during the short feeding periods. The study thus provides preliminary results on the potential of β-glucanase and protease to increase apparent nutrient digestibility of soybean meal in fish feed.     

From sulfur to homoglutathione: thiol metabolism in soybean

Sulfur is an essential plant nutrient and is metabolized into the sulfur-containing amino acids (cysteine and methionine) and into molecules that protect plants against oxidative and environmental stresses. Although studies of thiol metabolism in the model plant Arabidopsis thaliana (thale cress) have expanded our understanding of these dynamic processes, our knowledge of how sulfur is assimilated and metabolized in crop plants, such as soybean (Glycine max), remains limited in comparison. Soybean is a major crop used worldwide for food and animal feed. Although soybeans are protein-rich, they do not contain high levels of the sulfur-containing amino acids, cysteine and methionine. Ultimately, unraveling the fundamental steps and regulation of thiol metabolism in soybean is important for optimizing crop yield and quality. Here we review the pathways from sulfur uptake to glutathione and homoglutathione synthesis in soybean, the potential biotechnology benefits of understanding and modifying these pathways, and how information from the soybean genome may guide the next steps in exploring this biochemical system.     

不同饲料原料对黄颡鱼表观消化率及消化酶活性的影响

实验研究黄颡鱼(Pelteobagrus fulvidraco)对分别含有豆粕、发酵豆粕、菜粕和发酵菜粕的4种饲料以及这4种原料的干物质、蛋白、能量及氨基酸的表观消化率, 为黄颡鱼饲料的配制提供科学依据, 同时测定不同原料对消化道胰蛋白酶、糜蛋白酶及淀粉酶活性以及血液指标谷丙转氨酶、谷草转氨酶、总蛋白及碱性磷酸酶的影响。结果显示: 黄颡鱼对4种原料的干物质的表观消化率有显著差异, 其利用率由高到低依次为豆粕、发酵豆粕、菜粕及发酵菜粕(P<0.05)。黄颡鱼对发酵菜粕的蛋白质表观消化率显著低于其他3种原料(P<0.05), 而4种原料能量的表观消化率没有显著性差异(P>0.05)。黄颡鱼对各原料蛋氨酸和组氨酸的表观消化率没有显著性差异且低于83%(P>0.05), 而对各原料中其他氨基酸的表观消化率均有显著性差异, 在85%—98%之间, 发酵菜粕各氨基酸的表观消化率显著低于其他3种原料(P<0.05)。胰蛋白酶活力在菜粕组显著高于其他原料组(P<0.05), 活力呈现出前肠>中后肠>胃的趋势, 糜蛋白酶活力在不同原料间无显著差异, 糜蛋白酶活力呈现胃>前肠>中后肠的趋势, 淀粉酶活性呈现前肠>胃>中后肠。血液指标谷草转氨酶在豆粕组显著高于其他原料组(P<0.05), 菜粕与发酵菜粕组最低, 而谷丙转氨酶、总蛋白、碱性磷酸酶在各原料组间没有显著性差异(P>0.05)。综上所述, 豆粕、发酵豆粕、菜粕和发酵菜粕均可以作为黄颡鱼饲料中优质的蛋白源。     

New fermentation technique for complete digestion of soybean protein

The aim of this study was to develop a new fermentation method in order to improve the digestion of soybean protein, and to promote normal fermentation of soybean. A proximate composition, such as moisture, pH, and reducing sugar, of fermented soybeans by the new fermentation was similar to those of controls. Neutral protease activity, the most important factor for fermented soybean products, was the highest, having about 636 U/g at 54 h fermentation. The content of total free amino acid was almost 3-18 times higher than controls. The three-step fermented soybeans can be used as a functional food ingredient for human consumption, with higher protein digestibility.     

The influence of crop rotation and soil fumigation on a mycorrhizal fungal community associated with soybean

Population densities of mycorrhizal fungal propagules in a western Kentucky field highly productive for soybean were measured by bioassay throughout a soybean production season. The primary experimental variables were crop rotation (soybeans in 1985, then 2 years in corn, milo, fescue, or soybean, then soybean in 1988 on all plots when populations of propagules were determined) and soil fumigation with 67% methyl bromide/33% chloropicrin. Of the 20 species in three genera found, Glomus predominated both in terms of number of species and population densities. Most species of Glomus occurred at higher population densities in rotated plots than in continuous soybean plots. In continuous soybean plots, species of Gigaspora made up a much higher proportion of the mycorrhizal fungal community than in rotated crops. Species richness and diversity were lower, and dominance and equitability higher, in nonfumigated continuous soybean plots than in rotated plots early in the season, but the differences were not present at the end of the season. Soil fumigation killed most propagules in the upper 15 cm of soil, but after production of a crop of soybeans, populations of total propagules and most Glomus spp. recovered to prefumigation densities. However, Gigaspora margarita and Gigaspora gigantea did not recover similarly. Fumigation reduced species richness and diversity and increased dominance, but the effects were ameliorated by the end of the season. Colonization of roots was low during vegetative growth but increased rapidly after the onset of soybean reproduction. There was no evidence for mutualism during the early half of the season, perhaps due to high soil P and low dependency of soybean. Fumigation increased soybean yields. A stable mycorrhizal fungal community appeared to become established with continuous soybean production, and both crop rotation and soil fumigation disrupted the community.     

长吻对鱼粉等六种商品饲料中粗蛋白和能量的消化率

本试验以三氧化二铬（Ｃｒ２Ｏ３）为指示物测定Ⅰ龄长吻对鱼粉、猪血粉、豆饼粉、菜籽饼粉、小麦粉和玉米蛋白粉等六种商品饲料原料粗蛋白和总能量的消化率。试验饲料由参考饲料和试验原料以７０∶３０的比例混合挤压制成颗粒饲料。试验鱼粪便样品用虹吸方式收集,并将测试的消化率结果经过降低１０％的校正。由此所得消化率值更能反应长吻的消化生理状况。另外本文对六种饲料的消化率结果进行了讨论。     

Apparent digestion coefficients for dry matter, protein and essential amino acids in terrestrial ingredients for Pacific shrimp Litopenaeus vannamei (Decapoda: Penaeidae)

Protein quality mainly depends on the essential amino acid (EAA) profile, but also on its bioavailability, because EAA digestibility is generally lower than the analyzed amounts. This information is needed in the aquaculture industry for aquafeed formulation. For this purpose, the apparent digestibility coefficients of dry matter, protein, and essential amino acids of eight feedstuffs of terrestrial origin were determined for the juvenile whiteleg shrimp Litopenaeus vannamei (15-19 g), using 1% chromic oxide as an inert marker. A reference diet was formulated and produced in the laboratory. Eight experimental diets were prepared each with 30% of one of the experimental ingredients added to the reference diet: casein, porcine byproduct meal poultry byproduct meal, corn meal, wheat gluten meal, soybean paste, sorghum meal, and wheat meal. The experiment consisted of a single-factor, completely randomized design with three replicates per treatment. Samples of ingredients, diets and feces were analyzed for nitrogen and amino acids. For amino acid assay, we used reverse-phase high performance liquid chromatography. To avoid partial loss of methionine and cystine, samples of ingredients, diets, and feces were oxidized with performic acid to methionine sulfone and cysteic acid prior to acid hydrolysis. The apparent dry matter and protein digestive utilization coefficients varied from 68% to 109% and from 70% to 103%, respectively. Apparent digestibility of protein for casein, soy paste, wheat meal and wheat gluten were very high (over 90%), corn gluten and poultry byproducts meal showed high protein digestibility (over 80%), but porcine byproducts meal and sorghum meal had low digestibility (76% and 70%, respectively). There was a reasonable, but not total, correspondence between apparent protein digestibility and average essential amino acid digestibility coefficients, except for arginine in corn gluten, phenylalanine and leucine in sorghum meal, phenylalanine in soy paste and lysine in wheat meal and poultry by-product meal. The most digestible feed ingredients for whiteleg shrimp were: wheat gluten, wheat meal and soy paste; poultry byproduct meal and corn gluten were less digestible and the lowest digestibility occurred in porcine byproduct meal and sorghum meal. Feedstuffs exhibited great variability in dry matter, protein and amino acid digestive utilization coefficients, which should be considered when formulating shrimp feeds.