Foliar salt accumulation and injury in crops sprinkled with saline water

Summary Many crops accumulate salts through the leaves when they are wetted by sprinkler irrigation. This accumulation may cause foliar injury and decrease crop yield. This study was conducted to test the salt sensitivity of sprinkled alfalfa, barley, cauliflower, cotton, potato, safflower, sesame, sorghum, sugarbeet, sunflower and tomato. Plants were grown in a greenhouse in covered sand cultures that were trickle-irrigated with nonsaline nutrient solutions. Sprinkling with 15 and 30, and in the case of cotton and sunflower, 30 and 60 meq/l waters (9:1 NaCl:CaSO₄) was begun when plants were 1 to 3 months old and was continued for 4 to 7 weeks at a frequency of 1 h/day, 5 days/week. Except for sorghum, Na⁺ and Cl^– absorption through the leaves was essentially a linear function of salt concentration and duration of sprinkling. Most species absorbed Nat at approximately the same rate as Cl^–; however, in potato and sugarbeet Nat absorption exceeded Cl^–; and in barley and sesame Cl^–; exceeded Na¹. The mean rates of Na⁺ and Cl^–; absorption among species increased in the order: sorghum cotton = sunflower < cauliflower < sesame = alfalfa = sugarbeet < barley = tomato < potato = safflower. Susceptibility to leaf injury among species did not vary in strict relation to rates of salt absorption from 30 meq/l water. Potato and tomato readily absorbed Na⁺ and Cl^–; and quickly exhibited symptoms of leaf tip and margin necrosis. On the other hand, safflower, with one of the highest rates of salt absorption was only slightly injured by sprinkling. Barley readily absorbed salt, particularly Cl^–; and exhibited minor injury symptoms; whereas sesame and alfalfa had intermediate absorption rates but were somewhat more susceptible to injury. Sugarbeet was uninjured by sprinkling but absorbed appreciable amounts of Nat; whereas sorghum developed some necrosis along leaf edges but absorbed very little salt. Cauliflower, cotton, and sunflower absorbed salt slowly and exhibited almost no injury.Supervisory Plant Physiologist, Research Assistant, and Plant Physiologist     

The correlation between serum selenium and blood selenium in cattle.

The selenium (Se) concentration of paired blood and serum samples from cattle was determined by 2 methods: 1) atomic absorption spectroscopy using hydride generation (HG-AAS), and 2) inductively coupled argon plasma emission spectroscopy using hydride generation (ICP). Samples from 327 cattle were analyzed by HG-AAS, and samples from 344 cattle were analyzed by ICP. The data were examined by linear regression analysis, and the technique of inverse prediction was utilized to determine prediction intervals for estimating blood Se concentration from known serum Se concentration. The correlation coefficients, by simple linear regression of serum Se on blood Se, were 0.79 (r2 = 0.62) and 0.88 (r2 = 0.77) for the HG-AAS data and the ICP data, respectively. For the HG-AAS data, the inverse prediction formula for estimating blood Se when serum Se is known, at the 95% prediction interval, was [formula; see text]. For the ICP data, the inverse prediction formula for estimating blood Se when serum Se is known, at the 95% prediction interval, was [formula; see text]. The prediction intervals were quite wide, and the accuracy of estimating blood Se from a known serum Se was not useful for diagnostic purposes. The use of serum Se concentration to assess nutritional status of cattle with respect to Se does not appear to be appropriate.     

Distribution of Salmonella enterica serovars from humans, livestock and meat in Vietnam and the dominance of Salmonella Typhimurium phage type 90

Epidemiologically unrelated non-typhoid Salmonella isolates from humans (n = 56) and animal origin (n = 241, from faeces, carcasses and meat) in Vietnam were investigated. Salmonella Typhimurium, S. Anatum, S. Weltevreden, S. Emek, and S. Rissen were the most prevalent serovars. S. Typhimurium phage type 90 was predominant among S. Typhimurium isolates. The serotype and phage type distribution of the Salmonella isolates was different from that in Europe and America. Many sero- and phage types found in humans were also found in cattle, pigs, and poultry suggesting that food producing animals are an important source of human non-typhoid Salmonella infection in Vietnam.     

Minimizing salt in drain water by irrigation management: Design and initial results of Arizona field studies

Two field experiments were established in the Wellton-Mohawk Irrigation and Drainage District of southwestern Arizona to test the feasibility of decreasing the salt load in drainage water by reduced leaching. Results are given for the initial 2 years of the test for Valencia orange trees (Citrus sinensis L.) and the first year for alfalfa (Medicago sativa L., cv. Hayden).The water application data, substantiated by salinity sensor readings and measures of soil chloride, indicate that the annual evapotranspiration of Valencia orange is approximately 1375 mm on a total area basis. After 2 years, fruit yield and quality and tree growth are not significantly different from flood-irrigated trees that receive 40% more water. If these results persist, the salt load from citrus in the district could be reduced 40 000 Mg annually by reduced leaching. More importantly, because of the salinity of the groundwater pumped for water table control, the salt load exported from the district could be reduced initially by 130 000 Mg annually.Results indicate that the alfalfa experiment was underirrigated the first year and evapotranspiration is about 1950 mm annually. Comparisons indicate that the level basin flood irrigated check yielded 20% more than the experiment and had about 10% leaching, an efficiency that can probably not be improved.     

Preparing Holstein steer calves for the feedlot.

It is increasingly common to raise Holstein steer calves for entry to feedlot production systems rather than more traditional milk-fed veal production systems. Providing adequate nutritional support for the maintenance and growth of Holstein calves is essential in preparing them for a commercial feedlot environment. In this article, the dietary requirements of preruminant calves are reviewed and examples of evaluating milk diets for Holstein calves are detailed. The importance of the transition between milk feeding and grain-forage diets is discussed. Aspects of disease prevention, such as coccidiosis control and colostrum feeding, are also discussed. The reader will gain practical tools to use in preventive medicine programs involving Holstein steers being prepared for commercial feedlots.     

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.     

Intramuscular Selenium Administration in Selenium-Deficient Cattle

Nine recently weaned Hereford heifers were randomly assigned to a control group (n = 3) or a treatment group (n = 6). The animals were selenium (Se) deficient (mean ± SD blood Se concentration = 0.024 ± 0.012 μg/mL). They were maintained on a selenium-deficient diet, and on day 0 of the study the treatment group was given 0.05 mg Se/kg body weight intramuscularly, while the control group received a placebo. The Se concentration of blood, serum, and urine as well as the glutathione peroxidase (GSH-Px) activity of blood and serum was measured over an 84-day period. Peak blood Se and serum Se concentrations (mean ± SD) in the treatment group occurred at 5 hours postinjection and were 0.131 ± 0.028 μg/mL and 0.154 ± 0.027 μg/mL, respectively. The mean blood Se concentration of the treatment group was greater (P < .05) than that of the control group for the first 28 days after injection. The mean serum Se concentration of the treatment group was greater (P < .05) than that of the control group for all times after injection, except for day 56. The mean (±SD) blood GSH-Px activity of the treatment group (12.0 ± 2.3 mU/min/mg hemoglobin) was increased (P < .05) over the control group (2.0 ± 1.4 mU/min/ mg hemoglobin) by day 28 and continued to be greater (P < .05) throughout the 84 day postinjection period. The blood GSH-Px activity and the blood Se concentrations in the treatment group heifers did not reach concentrations considered indicative of Se adequacy (30 mU/min/mg hemoglobin and 0.10 μg/mL, respectively) except briefly, at 5 hours postinjection when the blood Se concentration of the treatment group was 0.131 ± 0.028 μg/mL. The mean serum GSH-Px activity of the treatment group did not differ at any time from that of the control group (P≥ .17). The mean (±SD) fractional excretion (FE) of Se, as an estimate of Se excretion, was greater (P < .05) in the treatment group heifers (n = 5; 6.2 ± 2.5%) than in the control heifers (n = 3; 1.3 ± 0.6%) at 24 hours postinjection. The mean (±SD) weight gain, from day 0 to day 84, for the treatment group heifers was 63.0 ± 18.1 kg and the mean weight gain for the control group heifers was 53.1 ± 7.3 kg at 84 days postinjection and there was no difference between the groups (P < .39). Conclusions drawn from this study include: 1) the increase in blood GSH-Px activity occurs approximately 28 days after Se injection given to Se-deficient heifers, 2) a single label dose of injectable Se does not result in blood Se concentrations or blood GSH-Px activity normally considered to be adequate, 3) the label dose of injectable Se, although therapeutically beneficial for nutritional myodegeneration (NMD), does not seem to be a desired method for long-term Se supplementation of cattle consuming a Se-deficient diet, and 4) blood Se is a better predictor of Se status than serum Se. (Journal of Veterinary Internal Medicine 1993; 7:342–348. Copyright © 1993 by the American College of Veterinary Internal Medicine.)     

Transmission efficiency of five tobravirus strains byParatrichodorus teres

Nematodes from a population of virus-freeParatrichodorus teres were allowed to feed on roots ofPetunia hybrida andNicotiana tabacum cv. White Burley plants infected with five strains of tobacco rattle or pea early-browning tobraviruses and were subsequently tested for virus transmission to roots of virus-freeP. hybrida andN. tabacum cv. White Burley plants. Virus transmission was not correlated with serotypes. Two strains of TRV with different serotypes were efficiently transmitted, whereas two other strains of TRV and one strain of PEBV with serotypes similar to transmitted ones were not transmitted at all. The two efficiently transmitted strains had originally been obtained fromP. hybrida roots which had been exposed to viruliferousP. teres in laboratory bait tests, whereas the three non-transmitted strains had been obtained from infected plant material collected in the field.     

An Actinobacillus pleuropneumoniae arcA deletion mutant is attenuated and deficient in biofilm formation

Actinobacillus pleuropneumoniae is a facultative anaerobic pathogen of the porcine respiratory tract requiring anaerobic metabolic activity for persistence on lung epithelium. The ArcAB two-component system facilitating metabolic adaptation to anaerobicity was investigated with regard to its impact on virulence and colonization of the porcine respiratory tract. Using pig infection experiments we demonstrate that deletion of arcA renders A. pleuropneumoniae significantly attenuated in acute infection and reduced long-term survival on unaltered lung epithelium as well as in sequesters. Contrary to its role in enterobacteria, the deletion of arcA in A. pleuropneumoniae does not affect growth and survival under anaerobic conditions. Instead, other than the parent strain A. pleuropneumoniae DeltaarcA does not show autoaggregation under anaerobic conditions and is deficient in biofilm formation. It is hypothesized that the lack of these functions is, at least in part, responsible for the reduction of virulence.