Prevalence,geographic distribution and phenotypic differences of Piscirickettsia salmonis EM‐90‐like isolates

Early reports accounted for two main genotypes of Piscirickettsia salmonis, a fish pathogen and causative agent of piscirickettsiosis, placing the single isolate EM‐90 apart from the prototypic LF‐89 and related isolates. In this study, we provide evidence that, contrary to what has been supposed, the EM‐90‐like isolates are highly prevalent and disseminated across Chilean marine farms. Molecular analysis of 507 P. salmonis field isolates derived from main rearing areas, diverse hosts and collected over 6 years, revealed that nearly 50% of the entire collection were indeed typed as EM‐90‐like. Interestingly, these isolates showed a marked host preference, being recovered exclusively from Atlantic salmon (Salmo salar) samples. Although both strains produce undistinguishable pathological outcomes, differences regarding growth kinetics and susceptibility to the antibiotics and bactericidal action of serum could be identified. In sum, our results allow to conclude that the EM‐90‐like isolates represent an epidemiologically relevant group in the current situation of piscirickettsiosis. Based on the consistency between genotype and phenotype exhibited by this strain, we point out the need for genotypic studies that may be as important for the Chilean salmon industry as the continuous surveillance of antimicrobial susceptibility patterns.     

Vitamin A functions and requirements in fish

Vitamin A (VA) is an essential dietary nutrient for fish and plays an important role in a range of physiological processes including vision, reproduction, embryogenesis, growth and differentiation and maintenance of epithelial cells. Knowledge of effects of VA on aquatic organisms is limited, but new information continues to be published. The aim of the present review is to present an overview of the dietary requirements and functions of VA in fish of commercial importance in aquaculture production. The effects of VA on reproduction and early embryonic development are described, and the estimated dietary requirements for VA of several species of fish are discussed. New research findings on how VA requirements vary with the life stages of fish are explored that will expand understanding of the complex role of VA. Sources of VA in feeds are described, and the potential need to consider how changes in fish feed formulations towards higher use levels of sustainable ingredients may affect dietary VA supplementation recommendations is discussed.     

Effect of Mediterranean saltbush (Atriplex halimus) ensilaging with two developed enzyme cocktails on feed intake,nutrient digestibility and ruminal fermentation in sheep

The aim of this study was to assess the effects of feeding Atriplex halimus (AH) silage treated with two developed enzyme cocktails to sheep on feed intake, nutrient digestibility and ruminal fermentation. The AH silage was treated without or with 2 L of ZAD1^® or ZAD2^®/1000 kg with 5% molasses and ensiled for 30 days. Barley grain (300 g/head/day) was fed as an energy supplement once daily at 10.00 hours and AH silage with or without enzyme treatment was offered ad libitum to animals twice daily at 09.00 and 16.00 hours. Sheep were fed on four experimental forage diets comprised of AH silage and barley (D1), AH silage treated with ZAD1^® and barley (D2), AH silage treated with ZAD2^® and barley (D3) and AH silage treated with a combination of ZAD1^® and ZAD2^® (1:1) and barley (D4). Ensiling AH with enzymes reduced its contents of neutral detergent fiber and acid detergent fiber. The dry matter intake of AH of D2, D3 and D4 decreased (P < 0.001) as compared to D1. However, enzyme‐treated diets had greater total digestible nutrients intake (P < 0.001) as compared to D1. The nutrients digestibility for D2, D3 and D4 were higher than those for D1 (P < 0.001), and were higher for D3 as compared to both D2 and D4. Sheep fed on D3 had highest (P < 0.001) ruminal total volatile fatty acids concentration, ammonia nitrogen concentration and microbial protein yield. It could be concluded that AH silage treated with ZAD1^® or ZAD2^® improved digestibility and rumen fermentation in sheep.     

Effect of Stocking Density on Growth,Survival, and Condition of the Mexican Cichlid Cichlasoma beani

The Mexican cichlid Cichlasoma beani is currently exploited regionally as food and can be commercialized in the aquarium trade. Natural populations of C. beani may already be negatively affected by anthropogenic alteration of the areas in which it is distributed. The aim of the present study was to examine the effect on growth, survival, and condition of C. beani cultured in three stocking densities: three (D3), six (D6), and nine (D9) fish per each 40 L tank. At the end of a 6‐wk trial the fish cultured in D3 were longer, heavier, and grew faster than the rest of the treatments but their survival was the lowest compared to D6 and D9. The mortalities were caused by a strong aggressive behavior in D3.     

Genetic diversity in the parental lines and heterosis of the tropical rice hybrids

Genetic diversity within and between the maintainer (B) and restorer (R) lines used in hybrid breeding programs of the Philippine was investigated with information from analysis of pedigree record, quantitative traits and SSR assays. Mean coefficients of coancestry were calculated as 0.11 within R lines, 0.27 within B lines, and 0.04 between R and B lines, indicating greater diversity among R lines than among B lines, and the significant divergence between B and R lines. These results are consistent with those obtained from quantitative trait analysis and SSR marker assays. Relative gene diversity for 37 random SSR markers averaged 0.20 within B lines,0.28 within R lines, and 0.52 between two groups of lines. There were no consistent associations among various genetic diversity measures. Random sets of SSR marker and pedigree based diversity measures had no significant correlation with mid-parent heterosis for grain yield and biomass, indicating that prediction of heterosis for complex traits based on these two genetic diversity estimates is difficult. This revised version was published online in August 2006 with corrections to the Cover Date.     

Growth and development of the arborescent cactus Stenocereus queretaroensis in a subtropical semiarid environment,including effects of gibberellic acid

In Stenocereus queretaroensis (Weber) Buxbaum, an arborescent cactus cultivated in Jalisco, Mexico, for its fruits but studied here in wild populations, stem extension occurred in the autumn at the beginning of the dry season, flowering and fruiting occurred in the spring at the end of the dry season, and new roots grew in the summer during the wet season. The asynchrony of vegetative and reproductive growth reduces competitive sink effects, which may be advantageous for wild populations growing in infertile rocky soils. Seasonal patterns of sugars in the roots and especially the stems of S. queretaroensis were closely related to the main phenological stages, becoming lower in concentration during periods of major stem extension. Cessation of stem extension occurred in 100-year-old plants for which injection of GA(3) reinitiated such growth. Isolated chlorenchyma cylinders had maximum extension in a bathing solution containing 0.1 &mgr;M gibberellic acid.     

Fatty acid profiles, tocopherol contents, and antioxidant activities of heartnut (Juglans ailanthifolia Var. cordiformis) and Persian walnut (Juglans regia L.)

The fatty acid and tocopherol compositions of three heartnut (Juglans ailanthifolia var. cordiformis) varieties (Imshu, Campbell CW1, and Campbell CW3) were examined and compared with those of two Persian walnut (Juglans regia L.) varieties (Combe and Lake). The major fatty acids found in heartnuts and walnuts were identified by gas chromatography as linoleic (18:2n-6), alpha-linolenic (18:3n-3), oleic (18:1n-9), palmitic (16:0), and stearic acid (18:0). Polyunsaturated fatty acids were the main group of fatty acids found in both heartnut and walnut, ranging from 73.07 to 80.98%, and were significantly higher in heartnut than in Persian walnuts (P < 0.001). In addition, heartnuts had significantly higher levels of 18:2n-6 and lower levels of 18:3n-3 compared to the Persian walnuts. gamma-Tocopherol was the main tocopherol homologue present in both types of nuts, followed by delta- and alpha-tocopherol. The highest concentration of gamma-tocopherol was found in Combe Persian walnut at 267.87 mug/g, followed by Lake Persian walnut and Imshu, Campbell CW1, and CW3 heartnut at 205.45, 187.33, 161.84, and 126.46 mug/g, respectively. Tocopherols, particularly the gamma-tocopherol, were found to contribute the most to the strong total antioxidant activities of both walnut and heartnut oils using either the free radical 2,2-diphenyl-1-picrylhydrazyl assay or the photochemiluminescence method.