Feed intake, nutrient digestibility and ruminal fermentation activities in sheep-fed peanut hulls treated with Trichoderma viride or urea

This study aimed to assess impacts of fungal treatment on the nutritional value of peanut hulls (PH) or urea at the rate of 5 kg/100 g of PH. Fermented sugar beet pulp inoculated with Trichoderma viride was supplemented to PH at rates of 5.0, 10.0 and 15.0 g/100 g air dry of PH and mixed well before aerobic incubation for 21 days. Organic matter (OM) content of PH declined with increased levels of fermented sugar beet pulp inoculums, while crude protein (CP), ether extract (EE), and ash increased. Fiber contents were decreased with both treatments of fermented sugar beet pulp and urea. Total N of PH increased with urea treatment, which reduced the true protein N to total protein N ratio. In sacco degradabilities of dry matter (DM), OM, and CP with urea treatment increased compared with fungal treatment. The DM intake of peanut hulls treated with fungus (PHF) was higher (P?<?0.05) than with peanut hulls treated with urea (PHU). Digestibility of OM, CP, neutral detergent fiber, and non-fiber carbohydrate by native breed Ossimi sheep with PH were higher (P?<?0.05) than with PH or urea treated PH. The intakes, losses, and balance of N increased (P?<?0.01) with PHF versus PH feeding. Feeding PHF increased (P?<?0.01) ruminal concentrations of NH₃-N, acetic acid, butyric acid, and the acetic to propionic acid ratio. Bacterial and protozoal counts increased (P?<?0.05) with feeding PHF or PHU versus PH. Overall, this fungal treatment of peanut hulls created a higher nutritive value feed for ruminants.     

Clonal population structure and introductions of the chestnut blight fungus, <Emphasis Type="Italic">Cryphonectria parasitica</Emphasis>, in Asturias,northern Spain

To understand the history of introductions of the chestnut blight fungus, Cryphonectria parasitica, in the Principality of Asturias in northern Spain, we conducted an extensive survey of chestnut blight and collected C. parasitica from 216 sites. All 778 isolates were assayed for vegetative compatibility (vc) type, whereas a subsample of 301 isolates was assayed for mating type, and 189 isolates were genotyped at 16 microsatellite markers. We found low diversity for all markers. Nearly all isolates (95%) were compatible with vc type EU-1 and had the same microsatellite multilocus haplotype, or differed from the most common type by mutation at one locus. Approximately 5% of the isolates were vegetatively compatible with EU-13 and only two isolates (< 1%) were compatible with EU-3; five different microsatellite haplotypes were found among isolates in these latter two vc types. The overall mating-type ratio was 218 MAT-1: 81 MAT-2, with both mating types represented in each of the three vc types. Microsatellite haplotypes based on ten markers used in France showed that most isolates in Asturias were either identical to or only one marker different from one of the seven most common genotypes in France, RE103. Based on these ten markers alone, the population of C. parasitica in Asturias, would appear to have been founded by a single genotype from the C1 lineage (to which RE103 belongs) found in eastern France and northern Italy. However, additional genotyping by vc types suggests the introduction of multiple genotypes, with different vc types. The exact source for introduction into Asturias cannot be determined without additional genotyping of isolates from other locations. Regardless of their origin, the low diversity of vc types makes this population ideal for deploying hypovirulence because there will be few barriers for virus transmission between individuals.     

Early season nitrogen accumulation in winter wheat

Cereal rye (Secale cereale L.) is widely used as a winter cover crop to conserve soil residual nitrogen (N) in the mid‐Atlantic region of the United States. Cereal rye, however, has agronomic drawbacks that may make other winter small grain crops more desirable alternatives. Winter wheat (Triticum aestivum L.) is a small grain that could substitute for cereal rye as a cover crop because it would give growers the flexibility of using it as a cover crop or growing it to maturity. There is currently little information on early season N accumulation of winter wheat cultivars, which is critical for the success of a small grain cover crop. To determine the degree of variation in early season N accumulation and early season biomass yield in soft red winter wheat in the mid‐Atlantic region, twenty‐five commercially available cultivars were evaluated at Beltsville, MD in the 1996/1997 and 1997/1998 growing seasons. Acereal rye cultivar ("Wheeler") was included as a cover crop control. Samples of plant tissue were taken at Feekes growth stage 5 and at physiological maturity each year. There were significant differences among cultivars for early season N accumulation and biomass yield. A large group of wheat cultivars had similar early season N accumulation and biomass yield as the cereal rye cover crop control. This suggests that some cultivars of winter wheat may be as effective as cereal rye as a winter cover crop. Early season N accumulation was highly correlated (r=0.90***) with early season biomass yield rather than with plant N content. These results indicate that soft red winter wheat has potential as a dual grain and cover crop and could be considered an alternative to cereal rye as a winter cover crop for conserving residual soil nitrogen in the mid‐Atlantic region of the United States.     

Pathogenicity of phylogenetic species in the Fusarium graminearum complex on soybean seedlings in Argentina

Soybean (Glycine max L.) is one of the main crops in Argentina. Most of the studies of pathogenicity in the Fusarium graminearum complex have focused on strains isolated from wheat and maize, and there is little information on strains isolated from soybean. Our objective in the present study was to compare the pathogenicity among soybean isolates of different phylogenetic species within the Fusarium graminearum complex on soybean seedlings under controlled conditions. Six strains representing three different phylogenetic species (F. graminearum, F. meridionale and F. cortaderiae) were identified by partial sequencing of the Translation Elongation Factor -1α gene (TEF-1) and evaluated for pathogenicity. All six strains reduced emergence, mainly by causing pre-emergence damping-off, seedling height and root dry weight and produced abnormal seedlings. The mean disease severity averaged across all isolates was approximately 3.0 in a 0–4 rating scale where 0?=?healthy seedling and 4?=?dead seedling. Significant differences in pathogenicity were observed among F. graminearum, F. meridionale and F. cortaderiae. These results are consistent with the hypothesis that different phylogenetic species within the Fusarium graminearum complex isolated from soybean are pathogenic under controlled conditions to soybean seedlings in Argentina. The present study demonstrates for the first time the pathogenic effect of F. meridionale on soybean in Argentina.     

Effect of ruminally protected methionine on body weight gain and growth of antlers in red deer (<Emphasis Type="Italic">Cervus elaphus</Emphasis>) in the humid tropics

Sixteen male red deer (Cervus elaphus), with an initial weight of 93.83 ± 4.38 kg were used to study the effect of the dietary level of ruminally protected methionine (RPM) on growth, antler morphometry and serum metabolites. The deer were allowed to graze and were individually supplemented with concentrate to provide 0, 2.5, 3.5 or 4.5 g/day of RPM for 65 days. There was a quadratic effect on daily weight gain (0.163, 0.098, 0.147 and 0.172 kg/day; P < 0.005) and antler beam length (59.7, 63.6, 63.0 and 57.2 cm; P < 0.02) for RPM levels of 0 to 4.5 g/day, respectively. The brow tine length and the number of points were similar across all treatments. Serum glutamic pyruvate transaminase (SGPT) was reduced (quadratic effect; P < 0.02; 22.0, 29.6, 18.0 and 17.8 IU/l) to RPM levels of 0 to 4.5 g/day, respectively, whereas other metabolites (glucose, cholesterol, urea, creatinine, total protein and serum glutamic oxaloacetic transaminase [SGOT]) were unchanged. Increasing the RPM dose did not affect weight gain or antler growth. Methionine supplementation reduced the activity of SGPT.     

Microhabitat use, not temperature, regulates intensity of Gyrodactylus cichlidarum long-term infection on farmed tilapia--are parasites evading competition or immunity?

Gyrodactylids (Monogenea) are ectoparasites of fish, some of which negatively affect commercially valuable fishes. Temperature strongly regulates population dynamics of these viviparous flatworms in farmed and wild fish populations, with most gyrodactylid species showing positive temperature-abundance associations. In agreement with epidemiological theory, numerous laboratory studies demonstrate that these parasites cannot persist in confined fish populations without periodic introduction of susceptible hosts. Extinction of gyrodactylid populations is due to host immunity, which develops in several fish species. In this one-year study, we followed populations of the recognized pathogen Gyrodactylus cichlidarum infecting four genetic groups of confined tilapia (wild type Nile tilapia Oreochromis niloticus niloticus, red O. n. niloticus, Mozambique tilapia O. mossambicus and a red synthetic population called Pargo-UNAM) kept under farming conditions and subject to natural environmental fluctuations. Based on the antecedents given, we postulated the following three hypotheses: (1) parasite abundance will be regulated by water temperature; (2) parasites will induce host mortality, particularly during periods of rapid infrapopulation growth; and (3) gyrodactylid populations will eventually become extinct on confined fish hosts. We disproved the three hypotheses: (1) parasite numbers fluctuated independently of temperature but were associated to changes in microhabitat use; (2) although gyrodactylid populations exhibited considerable growth, no evidence was found of negative effects on the hosts; and (3) infections persisted for one year on confined fish. Microhabitat use changed over time, with most worms apparently migrating anteriorly from the caudal fin and ending on the pectoral fins. Gyrodactylid populations followed similar trajectories in all fish, aggregating and dispersing repeatedly. Several instances were found where increased parasite dispersion coincided with increased intensity of infection; as well as the opposite, where increased aggregation coincided with parasite population declines. Three alternative explanations could account for these observations: that parasites (1) experience differential mortality on different anatomical regions of the fish; (2) migrate to avoid intraspecific competition; and (3) migrate to escape localized immune responses induced by infection. Our data do not allow us to demonstrate which of these alternatives is correct, so we discuss the merits of each. We provide circumstantial evidence in support of the third explanation, because as shown in other fish host-gyrodactylid interactions where immune responses have been characterized, in this study worms progressively moved away from fins with high mucus cell density to those with low density - what would be anticipated if immune defenses occur and reach the fish surface through mucus.     

Selenium species in selenium-enriched and drought-exposed potatoes

The aim of this work was to study selenium (Se) speciation in the potato ( Solanum tuberosum L.) cultivar Desiree, enriched in Se by foliar spraying with a water solution containing 10 mg of Se/L in the form of sodium selenate. Four combinations of treatments were used: well-watered plants with and without Se foliar spraying and drought-exposed plants with and without Se foliar spraying. Water-soluble Se compounds were extracted from potato tubers by water or enzymatic hydrolysis with the enzyme protease XIV, amylase, or a combination of protease XIV and amylase. Extraction was performed using incubation at a constant temperature and stirring (37 degrees C at 200 rpm) or by ultrasound-assisted extraction (300 W), using different extraction times. Separation of soluble Se species (SeCys2, SeMet, SeMeSeCys, selenite, and selenate) was achieved by ion-exchange chromatography, and detection was performed by inductively coupled plasma-mass spectrometry (ICP-MS). Results showed that the concentration of selenate extracted was independent of the enzymatic extraction technique (approximately 98 ng/g for drought-exposed and 308 ng/g for well-watered potato tubers), whereas the extraction yield of SeMet changed with the protocol used (10-36%). Selenate and SeMet were the main soluble Se species (representing 51-68% of total Se) in potato tubers, regardless of the growth conditions.