On epizootiology and control of lymphoid leukosis in chickens

Sera and organ extracts from ten different commercial stocks of layer chickens were examined for the presence of lymphoid leukosis (LL) viruses. Virus was recovered from 40.8% of the cockerels between three and six weeks of age. Their female hatch mates were examined at the age of 20 months. A mean of 11.3% of these laying hens was positive in the NP activation test. Lymphoid leukosis was successfully controlled in three inbred strains of White Leghorn chickens and in a commercial White Plymouth Rock line. All flocks were kept in a filtered air positive pressure (FAPP) house during the first two months of life and thereafter transferred to a conventional environment. The control method is based on three elements:

• —from an infected flock, hens are selected in whose eggs no avian lymphoid leukosis viruses can be detected by examination of pooled extracts of groups of embryos;

• —only eggs from hens that are shown not to shed congenitally virus in their eggs are used for the production of progeny. The offspring are reared in isolation until two months of age at which time the age-related resistance against tumour formation appears to be sufficiently developed;

• —the chickens are subsequently intramuscularly inoculated with lymphoid leukosis viruses of subgroups A and B and transferred to a conventional chicken house. The inoculated birds become persistently viremic and resist horizontal virus exposure and intramuscular challenge infections.

Horizontal virus transmission was observed to take place when virus-free non-vaccinated chickens were reared in isolation for two months and then exposed under field conditions.Efficiency of virus recovery was considerably improved when washed buffy coat cells were cocultivated with chick embryo fibroblasts or explant cultures were prepared from various tissues before testing with the NP activation test.     

Salinity sensitivity of sorghum at three growth stages

Summary The relative salt tolerance of two sorghum cultivars [Sorghum bicolor (L.) Moench., cvs. Northrup King 265 and Asgrow Double TX] at three different stages of growth was determined in a greenhouse experiment. Plants were grown in sand cultures irrigated four times daily with modified Hoagland's solution. A nonsaline solution and six solutions salinized with NaCl and CaCl₂ (2: 1 molar ratio) provided treatments with osmotic potentials (_s) ranging from –0.05 to –1.05 MPa. The saline treatments were imposed for 30 days beginning at either Stage 1, 4, or 7 as defined by Vanderlip and Reeves (Agron J. 64:13, 1972). The 30-day stages are referred to here as the vegetative, reproductive and maturation stages although the first stage may have included initial panicle differentiation. Both cultivars were most sensitive to salinity during the vegetative stage and least sensitive during maturation. Based on a nonlinear least-squares analysis, grain yield reductions of 50% were predicted at _s=–0.68, –1.02, and –1.14 MPa for NK265 and at –0.62, –1.00, and –1.10 MPa for Double TX when salinized during the vegetative, reproductive, and maturation stages, respectively. Although salinity had no significant effect on mean kernel weights, significant growth stage effects and interaction indicated that kernels were heaviest for plants salinized during the vegetative stage. Stover yields were significantly reduced by salination during the vegetative stage but were unaffected when plants were salinized during the maturation stage. Salination during the reproductive stage also decreased stover yield of Double TX but the effect was smaller than that during the first stage. Stover yield of NK265 was unaffected by salinity at this stage.Mineral analysis of the first leaf below the flag leaf at harvest indicated that both cultivars tended to exclude Na from the upper leaves. Ca and Cl concentrations increased with increased salinity in plants salinized during the maturation stage but salination in earlier stages decreased Ca concentration of this upper leaf at harvest and had no effect on the final Cl concentration. Phosphate and K concentrations decreased when plants were salinized during the third stage but increased when plants were salinized during the vegetative and reproductive stages. Mg was unaffected by salinization during the first and last stage but decreased when plants were salinized,during the reproductive stage. An extensive data base now exists which describes the salt tolerances of many different crops (Maas and Hoffman 1977; Maas 1986). These data express yield responses as a function of the average salt concentration in the rootzone. Generally, these data apply only if salinity is fairly uniform from the seedling stage to maturity. Except for germination, little information exists on the tolerances of crops at different stages of growth. Such information could be invaluable to optimize the use of limited water resources. Knowledge that crops are more tolerant during some stages of growth will improve new strategies for utilizing saline drainage waters (Rhoades 1984).Several studies indicate that tolerances do change as the crop develops and matures, but none of these studies completely separated the effects of duration of treatment from the stage of growth that the crop was treated (Ayers et al. 1952; Kaddah and Ghowail 1964; Kovalskaia 1958; Lunin et al. 1961 a, 1961 b; Maas et al. 1983; Ogo and Sasai 1955; Piruzyan 1959; Verma and Bains 1974). Comparisons of sensitivity during specific phenological stages are confounded when treatment periods are of unequal duration.This study was initiated to determine the sensitivity of grain sorghum [Sorghum bicolor (L.) Moench] to salinity during three 30-day periods of growth. Francois et al. (1984) recently reported that sorghum is a moderately salt-tolerant crop. In field plot tests, grain yields of two cultivars decreased 16% per unit increase in salinity (electrical conductivity of saturated soil extracts from the rootzone) above 6.8 dS/m. They further reported that both cultivars were significantly more tolerant at germination than at later stages of growth. Soil water salinities above 8.2 dS/m delayed germination but full germination occurred within 10 days at salinities up to 22 dS/m. Treatments in the present study were designed to assess plant growth and yield responses to 30-day exposures to salinity beginning at either the 2-leaf stage, at the beginning of rapid culm elongation, or after anthesis.     

Evaluation of the nutritional value of prototype lupin protein concentrates when fed to rainbow trout (Oncorhynchus mykiss)

This study examines the palatability and discrete nutritional evaluation of some prototype lupin protein concentrates (PC) when fed to rainbow trout. Products were developed from both Lupinus angustifolius and Lupinus luteus kernel meals with an increase in protein of 415 g/kg DM to 690 g/kg DM for L. angustifolius and 545 g/kg DM to 750 g/kg DM for L. luteus, respectively. This study completes a three-phase approach to evaluating the nutritional value of these products. The digestibility of energy, nitrogen, phosphorus and organic matter were determined in earlier studies using the diet substitution approach. The apparent digestibility of the energy from the L. angustifolius PC and the L. luteus PC along with the apparent protein digestibility were used to formulate two series of experimental diets to examine both the palatability and discrete nutritional value of the products. Serial inclusion of either PC at 0%, 10%, 20%, 30% and 40% into a typical salmonid diet specification allowed an examination of the palatability of each product. Additional negative controls, based on the 0% diets with inclusion of sulfamerazine sodium, were included in the experiment to demonstrate the capacity of the experiment to detect significant palatability issues. No significant effects of inclusion of either PC on any fish performance criteria, such as feed intake or growth, were identified. In contrast, significant reductions in feed intake and consequently growth were observed from fish fed either of the negative controls. This experiment demonstrated that each PC was highly palatable at inclusion levels up to and including 40% of the diet. Using a protein-limited-restrictively-fed experimental approach the discrete nutritional utilisation of each PC was defined. Growth of fish fed the PC treatments was not significantly different to that of the 0% reference diet. Two control diets with substitutions of cellulose to an equivalent inclusion level to that of the PC have provided an indication of the net benefit of the test ingredients. This experiment demonstrated that each PC provided equivalent nutritional value to the fish at either of the two inclusion levels (20% and 40%) evaluated. These PCs differed in their viscosity and gelling properties which may allow feed manufacturers the opportunity to manipulate the physical attributes of their feeds. Together, these studies clearly show that the prototype PCs have substantial potential as a prospective feed ingredient for the aquaculture sector.     

Factors Associated with Dough Stickiness as Sensed by Attenuated Total Reflectance Infrared Spectroscopy

Attenuated total reflectance (ATR) and Fourier transform infrared (FTIR) spectroscopy have been applied in the characterization of sticky dough surfaces. The characterization provides insight in the chemical distribution of gluten protein, starch, water, and fat during dough kneading. ATR is especially useful for selective sampling of dough surfaces because the depth of penetration of radiation is quite shallow. For dough, it is calculated to be in the order of 0.5–4 μm in the mid‐infrared, ideal for measurements of stickiness effects, where only the dough surface is of interest. To investigate the cohesive and adhesive properties of the individual dough constituents, dough was peeled from the ATR plate to study the material that adhered to it. The infrared spectra obtained indicate that fat and gluten protein appear to be located at the outer sticky dough surfaces, rather than water and starch. In comparison with gluten, the fatty component showed relatively strong adhesive forces to the ATR plate; a high residual fraction was measured after peeling the dough. Gluten proteins display different cohesion and adhesion properties that are strongly dependent on their hydration state. This indicates that the degree of hydration of gluten proteins contributes to the sticky properties of (overkneaded) dough. When analyzing gluten protein in D₂O instead of a dough matrix, more or less similar results were obtained. Significant differences in amide I and amide II intensities were measured for kneaded and stretched gluten protein in comparison to untreated, wet gluten. Besides changes in the vibrational properties of the amide groups, conformational changes in the tertiary protein structure also were observed. It appears that kneading and stretching of dough results in a major decrease in α‐helices content, accompanied by an increase of extended β‐sheet conformations.     

Modelling responses to nutritional, endocrine and genetic strategies to increase fertility in the UK dairy herd

The United Kingdom, as in most countries using intensive dairy management programmes, is facing serious challenges in terms of dairy cow fertility, as highlighted by a rapidly increasing calving interval (CI). A mechanistic, mathematical model is described that predicts the size of the future national dairy herd required to supply domestic requirements and its inherent sustainability in terms of production of replacement female numbers. The results from the model suggest that continuing use of current management strategies may result in the national dairy herd being unsustainable due to increasing CI and reduced fertility in as few as 10 years. Adoption of nutritional, endocrine and genetic techniques that increase fertility can effectively and rapidly reverse this trend and reduce the required size of the national herd, thereby reducing methane emissions from dairy production.     

Death associated with parenteral administration of copper disodium edetate in calves

Copper disodium edetate in recommended doses was apparently responsible for the deaths of one calf and clinical signs of toxicosis in 5 others on one farm, and 7 deaths and clinical signs of toxicosis in a number of others on another ranch. Signs of hyperexcitability, hypermetria, hindlimb weakness, head pressing, depression, and opisthotonos occurred 6 to 24 hours after injections and preceded death by 1 to 2 days. Necropsy and histologic examination revealed massive liver necrosis. High blood concentrations of liver enzymes in affected cattle that did not die indicated that they had liver damage. High blood concentration of iron in cattle that died indicated possible interaction of copper and iron.     

Management of the yellow beet cyst nematode with crop rotation,soil fumigation and granular nematicides

A trail field was managed for six years to test effects of short crop rotations, soil fumigation and granular nematicides on the population dynamics of the yellow beet cyst nematode (Heterodera trifolii f. sp.beta) and sugar-beet yields.In the two-year rotation, the cyst nematode population before planting varied from about the tolerance level (5 eggs per millilitre of soil) to 25 eggs per millitlitre of soil, leading to losses of sugar yield. Soil fumigation with metam-sodium effectively reduced the nematode density before planting, resulting in a 15 and 25% increase in sugar yield in the first two crops, respectively, but was insufficient to protect the third sugar-beet crop from yield-reducing nematode attack. This was attributed to the wet soil at the time of application and accelerated disappearence of the chemical in the soil through biological adaptation to repeated fumigation. Oxamyl or aldicarb granular nematicides applied as a side-dressing to the rows had insufficient effect to protect the sugar-beet from yield-reducing nematode attack. An overall treatment with aldicarb rotavated into the soil, alone and in addition to soil fumigation, increased sugar yield significantly. However in the two-year rotation, yield of the third sugar-beet crop treated with soil fumigation and granular nematicide was still lower than that of the untreated second crop in the three-year rotation.In the three-year rotation, thecyst nematode population before sugar-beet varied from hardly detectable to about the tolerance level. Here sugar-beet could be protected from yield-reducing nematode attack by soil fumigation or an overall treatment with granular nematicide. In the threeyear rotation with soil fumigation an increase ofRhizoctonia crown rot was observed in the second sugar-beet crop.Samenvatting Om de effecten na te gaan van korte rotaties, grondontsmetting en nematicide granulaten op het populatieverloop van de gele bietcystenematode (Heterodera trifolii f.sp.beta) en de opbrengsten van suikerbieten werd gedurende zes jaren een proef uitgevoerd op een natuurlijk besmet perceel van de proefboerderij Vredepeel.In de tweejarige rotatie variëerde de cystenematodepopulatie vóór het bietegewas boven de schadedrempel, wat resulteerde in verlaging van de suikeropbrengst. Grondontsmetting met metam-natrium veroorzaakte een effective vermindering van de dichtheid van de nematoden vóór de bieten en een verhoging van de suikeropbrengst van respectievelijk 15 en 25% bij de eerste twee gewassen, maar was onvoldeende om het derde bietegewas te beschermen tegen een opbrengst verminderende aantasting door nematoden. Dit was een gevolg van natte bodemomstandigheden bij het injecteren en het versneld verdwijenen van het middel door biologische adaptatie van de grond na herhaalde ontsmetting. Nematicide granulaten (oxamyl of aldicarb) naast de rij toegepast hadden onvoldoende effect om de bieten te beschermen tegen een opbrengstverminderende aantasting door nematoden. Een volvelds toepassing van in de grond gefreesde aldicarb alleen en toegevoegd na grondontsmetting verhoodge de suikeropbrengst beduidend. De opbrengst van het derde suikerbietegewas in de tweejarige rotatie was echter na toepassing van grondontsmetting en nematicide granulaten nog beduidend lager dan die van het onbehandelde tweede suikerbietegewas in de driejarige rotatie.In de driejarige rotatie variëerde de cystenematodepopulatie vóór het bietegewas van nauwelijks aantoonbaar tot nabij de tolerantiegrens. Hier kon het suikerbietegewas worden beschermd tegen een eventueel opbrengst verminderende nematodenaantasting door grondontsmetting of volveldstoepassing van nematicide granulaten.