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Biomedical subjects

D A Todhunter

Publications and source records attributed to D A Todhunter.

45 records · Page 3Linked to original sources
PubMed1985

Environmental mastitis: cause, prevalence, prevention.

Rate of intramammary infection by coliform bacteria and species of streptococci other than Streptococcus agalactiae (environmental pathogens) was studied in a dairy herd in total confinement. Rate was higher during the dry period than during lactation and increased progressively as parity increased. Rate was maximal during summer and coincided with maximum exposure to coliforms in bedding. Streptococcal infections were longer than coliform. Approximately 59% of streptococcal infections and 69% of coliform infections were present for 30 lactation days or less. Percent quarters infected by day of year varied between .7 and 3.0% for coliform bacteria and between 1.6 and 4.7% for streptococci. Approximately 81% of coliform infections and 53% of streptococcal infections during lactation were clinical. Clinical cases were highest during the first 76 days of lactation and during summer. Only 6.7% of coliform infections resulted in acute coliform mastitis, and all acute cases were during summer or early lactation. Dry cow therapy reduced rate of streptococcal infection during the early dry period but was without effect during the prepartum period. There was no effect of dry cow therapy on coliform infection rate during the dry period. Problems associated with prevalence and control of environmental mastitis were discussed.

Animals↗
PubMed1985

In vitro growth of mastitis-associated streptococci in bovine mammary secretions.

Cell-free, fat-free mammary secretions were tested in vitro for ability to support growth of streptococci associated with mastitis. Secretions were obtained prior to drying off, during the dry period, at calving, and during lactation from four cow treatment groups. Treatment groups were dry cow therapy, dry cow therapy and mammary glands subjected to induced inflammation 7 d post-drying-off, no dry cow therapy and no induced inflammation, no dry cow therapy but mammary glands subjected to induced inflammation. Growth of Streptococcus uberis, Streptococcus faecalis, and Streptococcus agalactiae in secretions from nonlactating glands was unaffected by induced inflammation. Growth of Streptococcus bovis was significantly inhibited in secretion obtained 14 d after induced inflammation. Dry cow therapy had no effect on streptococcal growth in secretion obtained 7 d after therapy. Streptococcal growth was greatest in secretions from involuted glands, and there was little or no evidence for growth inhibitory factors in cell-free, fat-free secretions obtained during the dry period. Milk from lactating glands inhibited streptococcal growth, and the inhibitory factor was presumptively identified as lactoperoxidase. Apolactoferrin, immunoglobulin, or both had little effect on streptococcal growth.

Animals↗
PubMed1985

Effects of vitamin E and selenium deficiencies on rat immune function.

The effects of dietary restriction of vitamin E and selenium were studied in male Long-Evans hooded rats. Weanling animals were maintained for 5-6 weeks on torula yeast-based diets, with or without the addition of vitamin E (150 IU/kg) or selenium (0.5 mg/kg), to form the following dietary groups: +E, +Se; +E, -Se; -E, +Se; -E, -Se, and a fifth group pair-fed with the -E, -Se group. This latter group exhibited a decreased rate of growth similar to the -E, -Se group. Lymphocyte blastogenesis in response to mitogens was decreased in animals fed the diets deficient in either vitamin E or selenium, and also in the pair-fed group. Very marked suppression of mitogen responses was seen in the doubly deficient group, as well as a greater loss of viability during culture. Spleen cell-mediated antibody-dependent lysis of chicken erythrocytes was increased in the doubly deficient group, although this difference could be abolished by the addition of catalase, but not indomethacin, to the culture medium. Dietary deficiency of vitamin E and selenium had no discernible effects on alveolar macrophage function, as measured by cell-mediated antibody-dependent cytolysis, killing of Staphylococcus aureus or regulation of T-lymphocyte blastogenesis.

Animals↗
PubMed1984

Effect of vitamin E and selenium supplementation on incidence of clinical mastitis and duration of clinical symptoms.

Incidence of clinical mastitis and duration of clinical symptoms for complete lactations were evaluated for 80 cows randomly assigned to one of four groups: vitamin E supplemented- and selenium injected, selenium injected, vitamin E supplemented, and controls. Vitamin E supplementation and selenium injection were during the dry period. Log-linear analysis of incidence data revealed a significant 37% reduction of clinical mastitis by vitamin E. Incidence was not affected by selenium alone, nor was there any evidence for interaction of vitamin E with selenium on incidence. However, duration of clinical symptoms (calendar months clinical/quarter lactating) was reduced by 46% for the selenium group, 44% for the vitamin E group, and 62% for the vitamin E-selenium group as compared to controls. We conclude that dairy cow diets deficient of vitamin E may elevate incidence of clinical mastitis. Selenium deficiency may result in greater duration of clinical symptoms, and selenium may interact with vitamin E. Coliform bacteria and species of streptococcus other than Streptococcus agalactiae were isolated from 70% of the clinical cases.

Animals↗
PubMed1984

Immune response of pregnant cows to bovine rotavirus immunization.

Fifteen pregnant Holstein cows were freely assigned to 3 experimental groups (5 cows in each group). Cows in group I were inoculated IM and intramammarily (IMm) with Ohio Agricultural Research and Development Center (OARDC) tissue culture-propagated modified-live Nebraska calf diarrhea bovine rotavirus with added adjuvant (OARDC vaccine-immunized cows). Group II cows were given IM injections of a commercial modified-live rotavirus-coronavirus vaccine (commercial vaccine-immunized cows), and the remaining 5 cows were noninoculated controls (group III). Rotavirus antibody in colostrum and milk was mainly associated with immunoglobulin (Ig)G1, and less so with IgG2, IgA, and IgM, as analyzed by the enzyme-linked immunosorbent assay (ELISA), using monospecific anti-bovine IgG1, IgG2, IgM, and IgA sera. In serum, the rotavirus antibody was distributed almost equally between IgG1 and IgG2. The same relationships appeared in both immunized and nonvaccinated cows. All OARDC vaccine-injected cows had virus-neutralization (VN) and ELISA IgG1 rotavirus antibody titers in serum and mammary secretions at significantly increased levels (at least 100-fold; P less than 0.05) compared with the titers in groups II (commercial vaccine-immunized cows) and III (controls). Serum, colostrum, and milk antibody titers from these latter 2 groups did not differ statistically. The ELISA IgG2, IgA, and IgM rotavirus antibody titers also were significantly greater in mammary secretions from OARDC vaccine-immunized cows than in groups II and III cows. There was a high correlation between ELISA IgG1 and VN rotavirus antibody titers for all samples tested (r = 0.97, P less than 0.001), but ELISA IgG1 antibody titers were consistently higher than VN titers. The ELISA IgG1 and VN antibody titers of milk samples collected from cows 30 days after parturition were higher from the OARDC vaccine-immunized cows (ELISA IgG1, geometric mean titer (GMT) = 3,511; VN GMT = 1,689) than were titers from the group II cows (ELISA IgG1 GMT = 39; VN GMT = 33) or group III cows (ELISA IgG1 GMT = 21; VN GMT = 19). These results indicate that IM plus IMm immunization of pregnant cows, using modified-live bovine rotavirus with added adjuvant, may significantly enhance serum, colostrum, and milk rotavirus antibody titers, whereas IM vaccinal inoculation of pregnant cows with a commercial modified-live rotavirus-coronavirus vaccine may not.

Adjuvants, Immunologic↗
PubMed1981

Selenium content and glutathione peroxidase activity in tissues of young cattle fed supplemented whole milk diets.

Three groups of 5 calves each were fed (from birth to 12 weeks of age) 3 vitamin-mineral supplemented whole milk diets differing only in their selenium (Se) content (0.03, 0.23, and 0.53 microgram/g of solids). Glutathione peroxidase (GSH-Px) activities and Se concentrations were determined in blood at weekly intervals and in selected tissues after 12 weeks. There were marked differences among the tissues in GSH-Px activity, most notably in the liver, lungs, and adrenal glands, depending on whether H2O2 or cumene hydroperoxide was used to assay the enzyme. Tissues having the highest GSH-Px activity on a weight basis, when assayed with the H2O2 substrate, were erythrocytes and testes. Enzyme activity in thymus, brain, striated muscle, adipose tissue, and blood plasma was lowest among the tissues analyzed. The Se concentration on a fresh tissue-weight basis was highest in kidney cortex, intermediate in kidney medulla, testes, liver, and spleen, and lowest in striated muscle, adipose tissue, and blood plasma. The Se concentration was increased in liver, kidney cortex, spleen, and heart, with increasing increments of dietary Se, whereas differences were not observed in testes and adipose tissue.

Animal Feed↗
PubMed1981

Distribution of selenium-dependent and nonselenium-dependent glutathione peroxidase activity in tissues of young cattle.

Separation by gel-filtration chromatography and enzyme assay with H2O2 and an organic hydroperoxide substrate were used to identify selenium (Se)-dependent and non-Se-dependent glutathione peroxidase (GSH-Px) in tissues of calves fed supplemented whole milk diets differing only in their Se content (0.03, 0.23, and 0.53 microgram/g of total solids). Spleen, cardiac muscle, erythrocytes, brain, thymus, adipose tissue, and striated muscles of calves were found to contain only the Se-dependent GSH-Px. Tissues having both enzymes included liver, lungs, adrenal glands, testes, kidney medulla, and kidney cortex. Hepatic tissue contained the highest percentage of non-Se-dependent GSH-Px activity of the calf tissues. For those tissues having Se-dependent and non-Se-dependent GSH-Px activity, the Se-dependent enzyme activity was generally lower for calves fed 0.03 microgram of Se/g of total solids as compared with activity in calves fed larger amounts of Se. The tissue ranking of non-Se-dependent GSH-Px activity, as a percentage of total GSH-Px activity, was not changed by differences in the Se content of the diets fed to the calves.

Animals↗
PubMed1980

In vivo incorporation of tritium from 3H2O into pulmonary lipids of meal-fed and starved rats.

In vivo fatty acid synthesis, as measured by tritium incorporation from 3H2O into fatty acids, was examined in the lungs of meal-fed and starved rats. In meal-fed animals, 74% of the radioactivity isolated from pulmonary lipids was found in the phospholipid fraction, with phospholipid fatty acids accounting for approximately 89% of total radioactivity in this fraction. Starving rats for 72 h markedly reduced in vivo 3H2O incorporation into pulmonary lipids. Intraperitoneal injection of (-)-hydroxycitrate prior to 3H2O administration also markedly reduced isotope incorporation into pulmonary lipid fractions of fed rats. These studies demonstrated net in vivo synthesis of fatty acids in pulmonary tissue of rats using a method that is not complicated by potential differences in metabolic pool sizes or peculiarities of specific carbon substrate sources. Synthesis of fatty acids in vivo was affected by the nutritional state of the animal and citrate appears to be a significant source of cytoplasmic acetyl-CoA for de novo pulmonary lipogenesis in the fed rat.

Animals↗