Total weed density increased after 1 yr of no-tillage and after 2 yr of conventional tillage in a 4-yr experiment with repeated assignment of the same treatment to the same plots. Large crabgrass, goosegrass, and carpetweed densities were higher in the no-tillage compared with the conventional-tillage treatment in at least 1 yr whereas common lambsquarters density was greater in the conventional-tillage treatment the last year of the experiment. Within the no-tillage treatment, rye or hairy vetch residue reduced total weed density an average of 78% compared to the treatment without cover crop when cover crop biomass exceeded 300 g m–2and when residue covered more than 90% of the soil. Goosegrass, stinkgrass, and carpetweed densities were reduced by cover crop residue in at least 1 yr whereas large crabgrass was unaffected. Common lambsquarters density increased where rye was grown as a cover crop prior to conventional tillage. Despite differences in weed density among treatments, weed biomass was equivalent in all treatments during the last 2 yr.

Six multicatheterized beef steers (421 +/- 21 kg BW) were used to predict the effect of dietary concentrate level on blood flow and net flux of urea and other metabolites across splanchnic tissues. Diets ranged from 0% (switchgrass hay) to 90% concentrate (10% switchgrass hay, 89% cracked corn, 1% urea). Daily DMI varied from 8.01 to 5.34 kg/d. Nitrogen intake (99 g/d) and calculated ME intake (16.8 Mcal/d) were equal among diets. As dietary concentrate increased from 0 to 90%, liver blood flow decreased from 850 to 795 L/h, portal-drained visceral (PDV) blood flow decreased from 750 to 620 L/h, and mesenteric-drained visceral (MDV) blood flow decreased from 270 to 250 L/h. Liver release of urea N was 94 mmol/h when dietary concentrate was less than 20%, then increased to 146 mmol/h at 55% concentrate. Urinary excretion of urea N was 13 mmol/h or less when dietary concentrate was 20% or less, increased to 53 mmol/h at 55% concentrate, then continued to increase to 76 mmol/h at 90% concentrate. Transfer of urea N to PDV ranged from 71 to 91 mmol/h and transfer to MDV ranged from 0 to 10 mmol/h among diets. As dietary concentrate increased from 27 to 63%, VFA release by PDV decreased, net MDV and splanchnic release of glucose increased, and splanchnic tissues switched from net uptake to net release of L-lactate. Net PDV release or liver removal of ammonia or alpha-amino N and net liver release of glucose were not affected. We conclude that the liver responded to changes in the percentage of dietary concentrate by altering urea production and by altering the role of lactate in intermediary metabolism.

No abstract

Dual-energy x-ray absorptiometry (DXA) was evaluated as a method for measuring body composition of pigs. Forty-eight female pigs (10.2 to 60.5 kg) were killed and the whole bodies scanned on a DXA instrument. The DXA measurements provided readings of total tissue mass, percentage of fat, fat tissue mass, lean body mass, and bone mineral content. By chemical analysis, the whole body fat content of the pigs ranged from 9.3 to 24.3%, giving rise to DXA RST values (ratio of attenuation coefficients) ranging from 1.386 to 1.334. The average percentage body fat measured by DXA (18.2 +/- .9%) was not significantly different (P = .76) from the results by chemical analysis (17.8 +/- .6%); however, concordance correlation analysis revealed unacceptable accuracy in the DXA measurement due to a negative bias for smaller percentages and a positive bias for larger percentages. Total body fat measured by the two methods was also highly correlated (r = .989), and the average for DXA (7.31 +/- .62 kg) was not significantly different (P = .89) from the value for the chemical method (7.20 +/- .50 kg). The relationship between the DXA estimate of lean body mass and the amount of protein in the body by chemical analysis was described by the equation: kg protein = .227.kg DXA lean -1.28, with a correlation coefficient (r) of .968. The DXA measurements of total tissue mass and actual body weights were highly correlated (r = .999), with an acceptable concordance at the .05 level. Scans were also analyzed for regional composition of the front and back legs. It was generally difficult to determine anatomically how well soft tissue described by DXA regions corresponded to those dissected. The DXA and chemical results for regional analysis of back legs were in better agreement than those for the front legs. These results indicate that DXA may be used as a reliable method for measuring body composition of pigs, but needs more extensive calibration and may be more appropriate for total body rather than regional analysis.

No abstract

Occurrence rates and determinants of infection with herpes simplex virus types 1 and 2 (HSV-1 and HSV-2) were measured in first- and fourth-year undergraduate students at a state university. This cross-sectional multistage probability sample survey included sociodemographic characteristics, sexual behavior patterns, disease history, and HSV type-specific antibody status. The prevalence of HSV-1 antibody was 37.2% in freshmen and 46.1% in fourth-year students; that for HSV-2 antibody was 0.4% and 4.3%, respectively. A history of cold sores was obtained in 25.6% of the freshmen; none had a history of manifest genital herpes. A history of cold sores was obtained in 28% and a history of genital herpes in 1.1% of the fourth-year students. The case-weighted prevalence of HSV-1 and HSV-2 antibodies was found to be significantly elevated for a number of student characteristics. However, multiple logistic regression analyses indicated that the significant predictors of HSV-1 antibodies in this population were female gender, black race, first intercourse at age less than or equal to 15 years, total years of sexual activity, history of a partner with oral sores, and a personal history of a non-HSV sexually transmitted disease (STD). Predictors of HSV-2 antibody were black race, duration of sexual activity, and history of a non-HSV STD.

No abstract

The objectives of this study were 1) to quantify daily patterns of plasma flow and metabolite flux through portal-drained viscera (PDV) and liver in cattle fed twice daily and 2) to identify an interval for blood sampling that would approximate the average daily plasma flow and nutrient flux values. Data are from three experiments in which multicatheterized cattle were fed at or near ad libitum intake twice daily. Five lactating primiparous Holstein cows (506 kg, fed at 0730 and 1930) ate 17.3 kg DM/d as chopped alfalfa hay:corn grain plus supplement (urea and minerals) 50:50 (Exp 1). Five beef steers (474 kg, fed at 0900 and 2100) ate 8.3 kg DM/d as chopped switchgrass hay:corn grain plus supplement 37:63 (Exp 2). Six beef steers (306 kg fed at 0900 and 2100) ate 6.9 kg DM/d as chopped alfalfa hay (Exp 3). Plasma flow (by dilution of para-aminohippurate) was measured hourly for 24 h. Plasma flows (mean +/- SE) through PDV were 1,264 +/- 147, 538 +/- 56, and 499 +/- 26 L/h for Exp. 1, 2, and 3, respectively. Corresponding liver flows were 1,662 +/- 216, 642 +/- 41, and 591 +/- 30 L/h. The within-animal differences from their respective daily means were estimated as a function of time of day using nonparametric smoothing. Across experiments, PDV and liver flows were above the daily mean from 1200 to 1400, were not different from the daily mean from 1600 to 1700, and were below the daily mean from 1930 to 2130. Metabolites measured were ammonia, urea, alpha-amino N, and glucose. In general, metabolite flux was not different from the average daily mean values between 1200 and 1600. Blood sampling over 12 h or one 12-h feeding cycle is sufficient for daily plasma flow and metabolite flux estimation in cattle fed twice daily.