Determination of oxytetracycline in bovine kidney and medicated milk replacer by liquid chromatography.

Improvements and optimization of AOAC INTERNATIONAL Official Method 995.09 for the detection of oxytetracycline in bovine kidney at the new U.S. tolerance of 12 ppm are reported. Recoveries from kidney fortified at 4 concentrations over the range of 3-40 ppm averaged 84-98%. Results from the kidney of a calf fed medicated milk replacer containing oxytetracycline are also reported. Additionally, adaptation of this method to the detection of oxytetracycline in medicated milk replacer is discussed.

Challenge differentially affects cytokine production and metabolic status of growing and finishing swine.

Growing (35 kg body weight) and finishing (85 kg body weight) swine challenged with endotoxin (Escherichia coli O55:B5) at a dose of either 2 or 20 microg/kg produced tumor necrosis factor (TNF)alpha in a dose-response relationship as measured by bioassay. Peak TNFalpha plasma levels were observed 1-2 hr post-challenge, returning to basal values 4 hr post-challenge. However, both an enzyme-linked immunosorbent assay specific for swine TNFalpha and total human TNFalpha demonstrated no dose-response relationship; peak plasma levels of immunoreactive TNFalpha were also observed 1-2 hr post-challenge. Maximal plasma interleukin-6 levels occurred 1-2 hr post-challenge and remained elevated through 8 hr post-challenge; there was no effect of lipopolysaccharide dose or metabolic status. Although the metabolic status of the animals also affected glucose levels, with growing animals exhibiting greater sensitivity compared with finishing animals, endotoxin-induced decreases in blood glucose levels were primarily dose-dependent. In contrast, changes in plasma urea nitrogen and free fatty acid (FFA) levels were strictly related to the metabolic status. Urea nitrogen levels were unchanged in growing swine, whereas they were increased in finishing swine and remained elevated 24 hr post-challenge. FFA levels in growing and finishing swine increased 3-6 hr post-challenge. FFA levels returned to basal values for finishing swine 24 hr post challenge, but in growing swine remained elevated 24 hr post-challenge. Plasma aspartate transaminase levels were increased through 24 hr post-challenge; animals given a dose of 20 microg/kg exhibited the greatest increase. Similarly, swine challenged with a dose of 20 microg/kg also exhibited the greatest increase in levels of conjugated bilirubin; there was no effect on unconjugated (free) bilirubin. These results demonstrate that endotoxin challenge of swine result in a pattern of changes that are dependent on both the dose of endotoxin used and the metabolic status of the animal examined.

Effect of recombinant growth hormone and chromium picolinate on cytokine production and growth performance in swine.

The effect of dietary chromium picolinate (CrP) and recombinant porcine growth hormone, somatotropin (rPST) administration on growth performance and cytokine production in Landrace-Poland China gilts was determined using a 2 by 2 treatment array. Treatments were: (1) control (basal diet), (2) CrP-supplemented diet (basal diet + 300 micrograms Cr3+/kg diet as CrP), (3) rPST (100 pg/kg body weight/day), and (4) rPST+CrP. CrP-supplemented diets were fed beginning at 20 kg body weight through 90 kg. Administration of rPST was begun at 60 kg weight and continued through 90 kg. All rPST treated pigs demonstrated improvements in growth performance versus controls. Pigs given CrP-supplemented diets showed no differences in growth performance. At 90 kg, pigs were challenged with endotoxin (lipopolysaccharide, 0.2 microgram/kg i.v.). Blood samples were collected at 0, 1, and 3 h postchallenge. Plasma IL-6 levels increased from 23 U/ml at time 0 to 1,927 U/ml at 3 h for control swine. Swine from the CrP treatment group had IL-6 levels of 8,130 U/ml at 3 h post-LPS. There were no differences in plasma IL-6 from pigs in the rPST and rPST+CrP treatment groups compared to the controls. Endotoxin challenge had no effect on either blood glucose levels or induction of TNF-alpha in any treatment group. PBMC from CrP-treated animals produced more IL-2 than peripheral blood mononuclear cells from all other groups.