Virus interference between H7N2 low pathogenic avian influenza virus and lentogenic Newcastle disease virus in experimental co-infections in chickens and turkeys

Low pathogenicity avian influenza virus (LPAIV) and lentogenic Newcastle disease virus (lNDV) are commonly reported causes of respiratory disease in poultry worldwide with similar clinical and pathobiological presentation. Co-infections do occur but are not easily detected, and the impact of co-infections on pathobiology is unknown. In this study chickens and turkeys were infected with a lNDV vaccine strain (LaSota) and a H7N2 LPAIV (A/turkey/VA/SEP-67/2002) simultaneously or sequentially three days apart. No clinical signs were observed in chickens co-infected with the lNDV and LPAIV or in chickens infected with the viruses individually. However, the pattern of virus shed was different with co-infected chickens, which excreted lower titers of lNDV and LPAIV at 2 and 3 days post inoculation (dpi) and higher titers at subsequent time points. All turkeys inoculated with the LPAIV, whether or not they were exposed to lNDV, presented mild clinical signs. Co-infection effects were more pronounced in turkeys than in chickens with reduction in the number of birds shedding virus and in virus titers, especially when LPAIV was followed by lNDV. In conclusion, co-infection of chickens or turkeys with lNDV and LPAIV affected the replication dynamics of these viruses but did not affect clinical signs. The effect on virus replication was different depending on the species and on the time of infection. These results suggest that infection with a heterologous virus may result in temporary competition for cell receptors or competent cells for replication, most likely interferon-mediated, which decreases with time.     

Extracellular proteins of Clostridium chauvoei are protective in a mouse model

The anaerobic bacillus Clostridium chauvoei is the causative agent of blackleg, a lethal disease that has an important impact on the sheep and cattle industry worldwide. Immunity to C. chauvoei is considered to be mainly anticellular, and for this reason there is scarce information about the immunogenicity of extracellular proteins. In this work variations in protein profiles, immune response by ELISA and protective capacity of culture supernatants of three C. chauvoei strains, collected at different growth phases, are reported. Sera raised against extracellular antigens also recognised cellular antigens of the same molecular masses. Partially purified cell-free supernatants and those concentrated 10 times by ultrafiltration (C-CFS), obtained at the early stationary phase of growth, induced a strong immunoprotective response, even at low doses, that was more marked for C. chauvoei strain ATCC 10092 (p < or = 0.05). With C-CFS formulations, a clear relationship was observed between IgG titres, protective capacity and concentration of the antigen doses, indicating a specific immune response.     

Effects of dietary arginine on hematological parameters and innate immune function of channel catfish

The effects of elevated dietary arginine on the hematology and immune function of juvenile channel catfish Ictalurus punctatus were evaluated by means of in vivo and in vitro experiments. Healthy juvenile channel catfish (average weight, 34.8 g) were fed casein-gelatin-based diets containing 28% crude protein and supplemented with crystalline L-arginine (ARG) at 0.5, 1, 2, or 4% of diet. An intact-protein diet containing 1.3% arginine also was included to investigate the effects of amino acid form (crystalline-free amino acids versus intact protein). Each purified diet was fed to apparent satiation to triplicate groups of fish for 6 weeks. At the end of the experimental feeding period, the fish were injected intraperitoneally with two doses (3 d apart) of 2 mg lipopolysaccharide/kg body weight. Six days after the initial injection, the fish were anesthetized and tissue samples were obtained to evaluate hematological and humoral and cellular immune parameters, including phagocytic activity of peritoneal macrophages, hemoglobin, hematocrit, mean corpuscular volume (MCV), blood cell counts, plasma protein, and hepatic superoxide dismutase activity. High dietary levels (4% ARG) resulted in significantly higher levels of hemoglobin, hematocrit, and circulating erythrocytes. Dietary ARG did not significantly affect MCV and the number of circulating leukocytes, lymphocytes, eosinophils, and monocytes. In vitro, a moderate level (2 mM) of ARG in the culture media was found to be ideal in significantly enhancing phagocytosis. This study demonstrates that some aspects of the immune system of channel catfish are sensitive to changes in dietary ARG.     

Determination of in vitro digestibility of forage species used in ruminant feeding

Within the evaluation of the quality of forage resources, the main parameter that defines it is the digestibility of dry matter, which together with the amount of neutral and acidic detergent fibers and crude protein constitutes the basic information to assess forages which are supplied in the diet of the cattle. This research was carried out at the University of Los Llanos (Villavicencio, Colombia), and its objective was to determine the digestibility of three forages in cattle through three different in vitro techniques: inoculation with ruminal fluid and with feces and enzymatic digestibility technique, making the comparison with the in situ technique in order to validate the techniques and equipment that are being used for these procedures. The following species were evaluated: Pennisetum purpureum (PP), Tithonia diversifolia (TD), and Bauhinia variegata (BV), assessing the curve and rate of degradation of dry matter (DM), neutral detergent fiber (NDF), and total protein (TP) (0 to 72 h). A design of repeated measures was used, under which the analysis of variance was carried out to determine the ranges of deviation between the techniques and thus establish the trend of the data; the variables evaluated were the DM, NDF, and TP digestibilities of the three forages using the four techniques (three in vitro and one in situ). After verifying the differences between the variances of the digestibilities and checking the sphericity assumption with the Mauchly test, multiple comparisons were made with the Bonferroni test with a significance of 5%. The digestibility of DM, NDF, and TP varied between 38.62 and 44.22, 54.18 and 66.97, and 47.54 and 57.05%; 49.07 and 70.70, 72.52 and 75.44, and 62.61 and 74.02%; 29.93 and 34.84, 26.21 and 70.88, and 25.67 and 50.60% respectively in forages PP, TD, and BV, depending on the technique used for their estimation. Despite finding statistically significant differences between several of the comparisons made in the digestibility techniques, a high coefficient of determination and a high correlation between the in vitro estimations with respect to the in situ estimation were found; therefore, it is possible to use these techniques routinely thus avoiding the need to have cattle with fistulae to perform digestibility tests, with enzymatic digestibility technique being the most practical one.

     

Use of sewage sludge in silvopastoral systems under Pinus radiata D. Don: soil,tree growth,and pasture production

Agroforestry Systems - Short-term production in silvopastoral systems is often limited due to inappropriate soil-fertility management. Sewage sludge fertilisation could enhance productivity of...     

Do pine plantations provide mycorrhizal inocula for seedlings establishment in grasslands from Patagonia,Argentina?

We investigated if Pinus ponderosa plantations in Patagonia are able to produce viable mycorrhizal inocula towards adjacent grasslands, which only harbor endomycorrhizal vegetation. We hypothesized that these inocula have the potential to contribute to the establishment of naturally disseminated seedlings. Also, we determined the main fungal taxa involved in this process. Seven plantations in the onset of their reproductive phase and located in the Patagonian native forest/steppe ecotone (Argentina) were selected. Soil samplings were obtained at nine points along a 450 m long, W-E transect established in each plantation. Soil bioassays were performed in a greenhouse, with P. ponderosa seedlings acting as hosts for mycorrhizal inocula present in soil samples, during 12 months. Mycorrhization percentage, morphotype richness and morphotype composition was determined through morphological evaluation. Viable ecto- and ectendomycorrhizal inocula were found disseminated outside plantations. The amount of mycorrhizal inoculum followed a decreasing function with distance to plantation edges. Mycorrhizal fungal genus Rhizopogon and “E-strain” mycorrhizal types appeared as pioneering taxa regarding seedlings colonization, being the most persistent and frequent symbionts found. Plantations, thus, facilitate the surrounding terrain for newcoming seedlings through the dispersion of mycorrhizal fungal inocula.     

A comparative physiologico-genetical study of activities of some enzymes in a heterotic single cross hybrid of maize (Zea mays L.)

Summary In field trials conducted over three growth seasons I studied the differences in activities of the enzymes: polyphenoloxidase, ascorbateoxidase and peroxidase, with a heterotic single-cross hybrid of maize and its pollen-sterile analogue. Additional observations were made for differences between the single-cross hybrids and their parental lines. The samples (staminate spikelets) were taken at random just before and after tasselling. Significant differences could be established concerning the object set. Comparison of the self-pollinating line of maize with the pollen-sterile analogue revealed the down ward trend in peroxidase (P) activity with the pollen-sterile line; the upward trend in polyphenoloxidase (PPO) activity and the downward trend in ascorbateoxidase (A) activity were observed with the pollen-sterile line before tasselling. After tasselling, activity of PPO showed a downward and that of A an upward trend. The single-crospollen-sterile hybrid revealed, compared to the parental lines, an upward trend in its PPO and A activities before tasselling and a downward trend in the same enzymes after tasselling; while activity of P in this single-cross, pollen-sterile hybrid indicated the downward trend in general. Compared with the parental forms, the pollen-fertile hybrid of maize showed a trend towards lower activities of the studied enzymes for all seasons and periods under observation. Comparing results in the single-cross hybrids there was an indication of higher activities of PPO and A in the pollen-sterile analogue; whereas the same analogue revealed a lower activity of P before tasselling and higher value after tasselling.     

Saliva chromogranin A in growing pigs: A study of circadian patterns during daytime and stability under different storage conditions

Salivary chromogranin A (CgA) is considered to be a biomarker of activation of the sympatho-adrenomedullary system, and has recently been proposed as a useful indicator of the acute stress response in pigs. The aim of the present study was to determinate whether salivary CgA concentrations in healthy growing pigs exhibits any circadian pattern during the daytime, and to evaluate its stability under different storage conditions. A total of 80 pigs (40 in spring and another 40 in autumn) of two different ages and genders were used. To establish the circadian pattern, saliva samples were collected at 07.00, 11.00, 15.00 and 19.00 h on two consecutive days. Pooled samples were used for the stability study and were measured on the day of sampling and periodically for up to 360 days later. Samples were stored at 4 °C, ?20 °C or ?80 °C and the effect of repeated freezing and thawing was also evaluated.No circadian pattern was detected for salivary CgA in either season and there were no significant effects of gender or age. However, mean salivary CgA concentrations were significantly higher (P < 0.0001) in the pigs sampled in autumn, compared to those sampled in the spring. Short term storage at 4 °C is recommended for up to 2 days, whereas frozen samples can be stored for 1 year at ?20 °C or ?80 °C, without substantial reduction in CgA values. In addition, samples can be frozen and thawed up to seven times without significant loss of the biomarker.