Humoral immune response of the bovine fetus to in utero vaccination with attenuated bovine coronavirus.

A fetal response to in utero vaccination with attenuated bovine coronavirus (9 to 49 days before parturition) was determined in 8 calves, 5 vaccinated and 3 controls. Calves were derived by hysterotomy before parturition and were maintained in a closed gnotobiotic environment. The IgA, IgM, and IgG values and coronavirus-neutralizing antibody titers were higher in the sera and intestinal loop fluid from vaccinated calves than in those from control calves. Sections of ileum and ileal lymph nodes from 1-day-old vaccinated calves, when stained with monospecific anti-bovine IgG, IgM, and IgA had numerous positively stained plasma cells. Positive fluorescence was not detected in comparable tissues from controls. When the 8 calves were given virulent coronavirus orally at 6 days of age, vaccinated calves did not become ill, whereas control calves had diarrhea in 19 to 22 hours. All calves were killed at 10 days of age. Control calves had lesions characteristic of coronavirus infection, and intestinal epithelial cells were positive by fluorescent antibody tests. In vaccinated calves, lesions of coronavirus infection were absent, and results of fluorescent antibody tests were negative. Although in utero vaccination with a coronavirus vaccine stimulated immunity in the newborn calf, the frequency of abortions (2 of 14 cows inoculated intra-amniotically) and premature births (4 of 14) precluded practical application.

Gnotobiotic calves: derivation, maintenance, Thiry-Vella loop preparation, and ethylene oxide gas sterilization.

Twenty-four pregnant Holstein cows were used to develop techniques and procedures to obtain calves by hysterotomy and to maintain them in a closed gnotobiotic environment (sterile plastic-film isolators) for as long as 10 days for infectious disease research. Thiry-Vella loop preparation for obtaining intestinal loop secretions was done in a surgical isolator and was successful in 12 of 14 gnotobiotic calves. Ethylene oxide gas was effective in sterilizing heat-labile and moisture-sensitive instruments and equipment.

Importance of diet of dam and colostrum to the biological antioxidant status and parenteral iron tolerance of the pig.

Fifteen second-parity sows were used to determine the importance of vitamin E (E) and selenium (Se) supplementation of the sow's diet and colostrum consumption by the neonatal pig on tolerance to parenteral iron. Selenium (.1 ppm) and E (50 IU/kg) supplementation of the diet of the sow increased plasma tocopherol and Se concentrations, but did not increase plasma glutathione peroxidase (GSH-Px) activity. Colostrum had greater concentrations of E (primarily alpha-tocopherol) and Se than milk. Plasma biological antioxidant status (tocopherol level and GSH-Px activity) of pigs at birth was very low, but by 2 d of age had increased, especially in alpha-tocopherol (nearly a 20-fold increase). Liveability and body weight gain of pigs were not affected by the pre-colostrum iron injection (200 mg Fe as gleptoferron); however, plasma tocopherol concentrations of Fe-injected pigs were lower and plasma Se concentration and GSH-Px activities were higher at 2 d of age than values of pigs not receiving parenteral Fe. Supplementation of the dam's diet with E and Se maintained high tocopherol and Se levels in her colostrum and milk and a high biological antioxidant status in her pigs throughout the nursing period.

Iron requirements of baby pigs reared in germ-free or conventional environments on a condensed milk diet.

Baby pigs were maintained in either a germ-free or a conventional environment and fed a sterile condensed milk diet (10 micrograms Fe/g milk solids) supplemented with 0, 50 or 100 micrograms Fe/g solids from FeSO4.7H2O or given an im injection of 100 mg Fe from Fe dextran. Pigs were reared on these diets for 4 wk, and weekly measures of gain, food consumption and hematology were taken. The pigs were then killed, and organ weights were taken and tissues analyzed for Fe concentration. All conventional pigs not given supplemental Fe died. None of the unsupplemented pigs raised in the germ-free environmental died. Conventional pigs gained faster and more efficiently and became anemic more rapidly. However, conventional and germ-free pigs were similar in the efficiency with which they incorporated supplemental Fe into hemoglobin or stored Fe in liver and spleen. We concluded from this study that both germ-free and conventional pigs fed a condensed milk diet require 50 to 100 micrograms Fe/g milk solids or more than 100 mg of Fe from Fe dextran once parenterally to maintain desirable hematological traits for 4 wk.

Tetany associated with magnesium deficiency in suckling beef calves.

Sudden death losses occurred in 4-month-old beef calves with clinical signs of muscular dysfunction, including tetanic spasms. Gross lesions were not diagnostic. Microscopic lesions consisted of deposition of calcium salts in the elastic fibers of the arteries in the heart, lungs, and spleen and in the trabeculae of the spleen. Focal areas of interstitial nephritis were characterized by infiltration of lymphocytes and plasma cells. Samples of hay and silage that the cattle were consuming were low in magnesium. Calves with spasms responded to magnesium salts given intravenously, and losses ceased after a magnesium-containing supplement was fed free choice to the calves and cows.

Skeletal muscle function and structure after depletion of creatine.

Experiments were conducted to determine if normal skeletal muscle function and structure are dependent upon their ability to store large quantities of metabolic energy in the form of N-phosphorylcreatine. Muscle levels of creatine and N-phosphorylcreatine were reduced by feeding young male rats diets containing 1 per cent beta-guanidinopropionic acid (beta-GPA). Muscle function was evaluated by monitoring performance during a 4-week, short duration, high intensity exercise program in a control running wheel. Structural effects were determined by histochemistry, morphometric analysis, and routine histologic procedures using light microscopy. Evidence of abnormal creatine metabolism of rats fed beta-GPA included: excessive creatinuria, reduction in urine creatinine, reduced levels of muscle and brain creatine, and a reduced activity of muscle creatine kinase. In separate experiments, beta-GPA inhibited the reaction of creatine with creatine kinase in vitro. When muscle function was evaluated by running, the percentage of expected revolutions for the group of rats fed beta-GPA was below the expected normal values. The white (type II) fibers from the gastrocnemius of exercised rats fed beta-GPA were smaller than fibers from the same muscle areas of rats fed normal diets. The histochemical characteristics of red (type I) and white fibers of all rats tested were within normal limits. It is concluded that feeding beta-GPA will result in structural and functional changes in skeletal muscles of exercised young male rats. These changes are believed to result from the ability of beta-GPA to block creatine entry into muscle and thereby prevent muscle from accumulating and maintaining its normal complement of creatine and N-phosphorylcreatine.