Pre-weaning supplementary feed and porcine post-weaning diarrhoea

Attempts were made to induce an intestinal hypersensitivity response to weaner diet by feeding pigs with small quantities of this material before weaning. In two trials using different weaner diets piglets subjected to this regimen showed no significant differences in small intestinal structure, in ability to absorb xylose, in bodyweight gain, in incidence of diarrhoea or excretion of enteropathogens after weaning compared with pigs not given any of the diet before weaning, or fed with a different diet before weaning. When post-weaning diarrhoea occurred it was associated with an earlier, more prolonged and greater proliferation of enterotoxigenic Escherichia coli in the small intestines than occurred in healthy pigs after weaning. The greater proliferation in pigs which developed diarrhoea could not be attributed either to an excessive dietary intake after weaning, or to a specific proliferation of rotaviruses.     

Fine-Scale Spatial Genetic Structure in Perennial Grasses in Three Environments

Past research has shown that changes in grazing-resistance traits may be associated with genetic changes in plant populations. Little is known about spatial genetic relationships within plant populations (spatial genetic structure) and any grazing effects on these relationships. Here we present observations of the fine-scale spatial genetic structure in three grass species in semiarid environments (Arizona, Mexico, and Argentina). In each environment, populations of a dominant grass species were sampled from two sites with contrasting livestock grazing histories. Plant genotypes were described with the use of amplified fragment length polymorphism markers. In Arizona, populations of sideoats grama (Bouteloua curtipendula var. caespitosa Gould and Kapadia) differed in that one has never experienced livestock grazing, whereas cattle have grazed the other. In the other two environments, populations exposed to long-term heavy grazing were examined, along with those that experienced either moderate grazing (Mexico, blue grama [Bouteloua gracilis {Willd. ex Kunt} Lag. ex Griffiths]) or extended exclusion of livestock (Argentina [Poa ligularis Nees ex Steud.]). Based on independent analysis of each population, we observed no differences in average gene diversity between populations of each species. With the use of analysis of molecular variance we found slight but significant genetic differentiation between populations with different grazing histories in Arizona and Argentina. Significant genetic structure was present in all populations and indicated an inverse relationship between spatial and genetic distance. Interestingly, this relationship was most pronounced in the cattle-free sideoats grama population, suggesting larger genetic neighborhood areas in the absence of livestock. Less distinct differences in spatial genetic structure associated with grazing history were evident in the other two species. We hypothesize that livestock grazing may lead to increased homogeneity in genetic structure at the landscape scale. Effectively examining this hypothesis presents many experimental challenges.     

In vitro insecticidal effects of fipronil and beta-cyfluthrin on larvae of the blowfly Lucilia sericata

The insecticidal effects of the phenylpyrazole, fipronil, and a pyrethroid, beta-cyfluthrin, on larvae of the blowfly Lucilia sericata were determined in laboratory assays. When first stage larvae of L. sericata were reared on homogenized pig liver which had been treated with known amounts of test compounds, both fipronil and beta-cyfluthrin induced significant levels of mortality compared to acetone and water controls. However, fipronil was approximately 10 times more toxic than beta-cyfluthrin to L. sericata larvae following ingestion. Beta-cyfluthrin had little effect on mortality until concentrations of approximately 0.5 ppm were reached. In contrast, fipronil effected L. sericata mortality at a concentration of 0.05 ppm and 100% mortality was reached by 0.5 ppm. The lethal concentration (LC50) value for beta-cyfluthrin was 1.56 ppm as compared to 0.14 ppm for fipronil. Following contact of first and third stage larvae with cloth impregnated with known amounts of test compound, the mortality profiles of fipronil and beta-cyfluthrin were similar. At short contact times, the LC50 values for fipronil were lower than those for beta-cyfluthrin. However, at the highest contact time evaluated for the first stage larvae, 300 s, there was a reversal in this trend. The results suggest that the phenylpyrazole fipronil may represent a new potential insecticide for development against blowfly strike of sheep.     

Iron deficiency and pseudo-iron deficiency in hospitalized horses

Values for serum ferritin, serum iron, and serum total-iron binding capacity were determined in 100 hospitalized horses. Six foals had iron deficiency, as indicated by low serum ferritin and iron concentrations. Twenty-eight horses had low serum iron content and normal or high serum ferritin content and were considered to have pseudo-iron deficiency, possibly in response to infection. Ten horses had serum ferritin concentrations that were quite high, probably indicating iron overload.     

A simulation exercise to teach principles of bovine reproductive management

Students in Reproductive Management (a senior-level course with approximately 20 to 50 students per semester) at the University of Missouri-Columbia are required to participate in a simulation exercise that is designed to improve reproductive efficiency in a beef herd. During a simulated 5-yr period, students must 1) improve reproductive efficiency in a beef cow-herd through implementation of reproductive management principles; 2) determine the economic impact of reproductive management decisions in a beef herd; and 3) evaluate the constraints of different geographical locations on approaches to reproductive management. Groups of three to four students are provided with the reproductive and economic records of a farm/ranch located in different parts of North America. Students create reproductive management plans consisting of 1) detailed discussion of farm/ranch environment (climate, terrain, forage and grain availability, and stocking rate; season for breeding and calving; and justification for choice of breed); 2) assessment of current level of reproductive performance; 3) identification and economic justification of specific (measurable) objectives; 4) discussion of alternatives for accomplishing specific objectives; 5) prediction of reproductive performance (pregnancy rate, quantity of calf weaned per cow exposed, and cost per quantity of calf weaned) in response to implementation of specific management practices; and 6) an annual and 5-yr reproductive and economic summary. Students obtain livestock marketing information for their assigned location via the Internet. Spreadsheets were developed to calculate the reproductive efficiency of postpartum cows and replacement heifers based on management decisions made by the groups and to calculate a yearly economic summary for each of the 5 yr. Management decisions are justified in a written report, and oral presentations are given to the class when the project is completed. Greater than 85% of students indicated that the exercise increased their understanding of how management decisions affect reproductive efficiency and profitability in a beef operation and also provided added confidence for students that applied for beef management positions.     

The REFLECT Statement: Methods and Processes of Creating Reporting Guidelines for Randomized Controlled Trials for Livestock and Food Safety

The conduct of randomized controlled trials in livestock with production, health, and food-safety outcomes presents unique challenges that might not be adequately reported in trial reports. The objective of this project was to modify the CONSORT (Consolidated Standards of Reporting Trials) statement to reflect the unique aspects of reporting these livestock trials. A 2-day consensus meeting was held on November 18–19, 2008 in Chicago, IL, to achieve the objective. Before the meeting, a Web-based survey was conducted to identify issues for discussion. The 24 attendees were biostatisticians, epidemiologists, food-safety researchers, livestock production specialists, journal editors, assistant editors, and associate editors. Before the meeting, the attendees completed a Web-based survey indicating which CONSORT statement items would need to be modified to address unique issues for livestock trials. The consensus meeting resulted in the production of the REFLECT (Reporting Guidelines for Randomized Control Trials) statement for livestock and food safety and 22-item checklist. Fourteen items were modified from the CONSORT checklist, and an additional subitem was proposed to address challenge trials. The REFLECT statement proposes new terminology, more consistent with common usage in livestock production, to describe study subjects. Evidence was not always available to support modification to or inclusion of an item. The use of the REFLECT statement, which addresses issues unique to livestock trials, should improve the quality of reporting and design for trials reporting production, health, and food-safety outcomes.