Biomedical subjects

B A Mallard

Publications and source records attributed to B A Mallard.

At least 37 records · Page 2Linked to original sources

PubMed1997

Effects of growth hormone, insulin-like growth factor-I, and cortisol on periparturient antibody response profiles of dairy cattle.

The objectives of this study were to determine hormone and antibody response profiles from the prepartum period to peak lactation, and evaluate potential immunomodulatory effects of the classic endocrine hormones, growth hormone (GH), insulin-like growth factor-I (IGF-I) and cortisol. Specifically, 33 Holstein cows were immunized with ovalbumin (OVA) and Escherichia coli J5 at weeks -8 and -3 prior to parturition. At parturition (week 0), cows received an additional immunization of OVA. Blood was collected at weeks -8, -3, 0, 3 and 6 relative to parturition and various samples were used to determine plasma hormone concentration, serum immunoglobulin (Ig), and specific antibody response to OVA and E. coli. Colostrum and milk samples were also collected post-parturition to monitor local immunoglobulin and antibody responses. Results indicated that not all periparturient cows exhibited depressed immune response, and that antibody response to OVA could be used to partition cows into 3 groups recognizing animals with sustained measurable antibody response before and after parturition (Group 1), animals which responded poorly to immunization at parturition (Group 2), and animals which did not respond to immunizations at week -3 or parturition (Group 3). Cows with the highest antibody response to OVA (Group 1) also tended (P < or = 0.10) to have the highest response to E. coli J5 at parturition and had the lowest incidence of disease, particularly mastitis. Antibody response to OVA measured in milk tended to be higher in Group 1 cows, particularly at week 0 (P < or = 0.06) compared to cows of Group 3. IGF-I was higher (P < or = 0.05) in cows of Group 1 than Group 3 at peak lactation (week 6).

Animals↗

PubMed1997

Effects of peripartum stress and health on circulating bovine lymphocyte subsets.

Alterations in the proportions of peripheral blood lymphocyte subsets was monitored using flow cytometry, before, during and after the peripartum period (week-8 to week (wk) 16) of dairy cows, when pregnancy and lactational stresses prevail and disease incidence is highest. A health code was assigned to each animal at each sampling time, and a subset of non-pregnant, non-lactating (NPNL) cows were sampled for comparisons, and to examine the effect of pregnancy and lactation only, on lymphocyte subset proportions. Results were expressed as the percentage of positive stained cells expressing CD2, CD4, CD8, WC1(gamma delta), IgM and class II major histocompatibility complex (MHC-II) molecules, as determined by flow cytometry. Comparisons of subset proportions were made across time and between health status categories. Mean fluorescence intensity (MFI) values were also examined across the periparturient period for CD2, CD4, CD8 and gamma delta T cell subsets. All T cell subsets varied significantly during the perparturient period in healthy cows, especially around parturition. B cell and MHC-II+ populations remained relatively constant until after calving and then significantly (P < or = 0.06) decreased. Compared to NPNL cows, all T cell subsets were significantly lower in healthy cows at most time points, whereas B cell and MHC-II+ cells were comparable to the NPNL values. CD2, CD4, and CD8 subsets decreased significantly at wk-3 and returned to initial subset proportions by wk 16. Conversely, the WC1 population increased at wk-3 relative to calving but declined to approximate initial proportions at calving. Health status had no significant overall effect on any subset unless it was separated by weeks in which case there were interactions between health and week for CD2 and CD8. Results indicate that variations in T lymphocyte subsets and in the concentrations of surface marker molecules (MFI) occur more as a result of pregnancy and lactation than health status in the dairy cow and that these factors have the least influence upon B cell and MHC-II+ populations during the periparturient period.

Animals↗

PubMed1997

Antibody response to Actinobacillus pleuropneumoniae antigens after vaccination of pigs bred for high and low immune response.

To enhance inherent general resistance to infectious diseases an indirect strategy of selective breeding for multiple immune response traits representing both antibody and cell-mediated immune response has been pursued over several generations in pigs. High and low response lines differ significantly not only in response to antigens included in the estimated breeding values upon which the selection was based, but also to other antigens. To test whether or not the lines also differed in antibody response to vaccination, high and low response pigs were given a commercial Actinobacillus pleuropneumoniae vaccine, and their serum antibody to three constituent antigens, carbohydrates (CHO) 1 and 5 and lipopolysaccharide (LPS) 1 was measured by enzyme immunoassay. The high line had significantly (P < or = 0.05) more antibody to all antigens except at day 28 to CHO antigen 5. The frequency of non-response to vaccination was also less in the high response pigs to CHO antigen 1 (P < or = 0.01) and to the LPS antigen (P < or = 0.06) but not to the CHO antigen 5. Based upon these observation it is concluded that the high immune response pigs are more responsive to the commercial vaccine than are the low response pigs and that the strategy of altering population immune response by multi-trait selective breeding may be useful in facilitating vaccine-based health management programs for livestock.

Actinobacillus pleuropneumoniae↗

PubMed1997

Antibody- and cell-mediated immune responses of Actinobacillus pleuropneumoniae-infected and bacterin-vaccinated pigs.

Current porcine pleuropneumonia bacterins afford only partial protection by decreasing mortality but not morbidity. In order to better understand the type(s) of immune response associated with protection, antibody- and cell-mediated immune responses (CMIR) were compared for piglets before and after administration of a commercial bacterin, which confers partial protection, or a low-dose (10(5) CFU/ml) aerosol challenge with Actinobacillus pleuropneumoniae CM5 (LD), which induces complete protection. Control groups received phosphate-buffered saline or adjuvant. Serum antibody response, antibody avidity, delayed-type hypersensitivity (DTH), and lymphocyte blastogenic responses were measured and compared among treatment groups to the lipopolysaccharide (LPS), capsular polysaccharide (CPS), hemolysin (HLY), and outer membrane proteins (OMP) of A. pleuropneumoniae. Peripheral blood lymphocytes and sera were collected prior to and following primary and secondary immunization-infection and high-dose A. pleuropneumoniae CM5 (10(7) CFU/ml) aerosol challenge. Serum antibody and DTH, particularly that to HLY, differed significantly between treatment groups, and increases were associated with protection. LD-infected piglets had higher antibody responses (P < or = 0.01) and antibody avidity (P < or = 0.10) than bacterin-vaccinated and control groups. Anti-HLY antibodies were consistently associated with protection, whereas anti-LPS and anti-CPS antibodies were not. LD-infected animals had higher DTH responses, particularly to HLY, than bacterin-vaccinated pigs (P < or = 0.03). The LD-infected group maintained consistent blastogenic responses to HLY, LPS, CPS, and OMP over the course of infection, unlike the bacterin-vaccinated and control animals. These data suggest that the immune responses induced by a commercial bacterin are very different from those induced by LD aerosol infection and that current bacterins may be modified, for instance, by addition of HLY, so as to stimulate responses which better reflect those induced by LD infection.

Actinobacillus Infections↗

PubMed1996

Effects of chromium on health status, blood neutrophil phagocytosis and in vitro lymphocyte blastogenesis of dairy cows.

The objective of this study was to determine the effects of supplemental dietary chromium (Cr) on health status and mastitis-related parameters, as well as neutrophil phagocytic activity of dairy cows during late pregnancy and early lactation. In addition, possible interactions and involvements of Cr with insulin, cortisol, somatotropin (rBST) and insulin-like growth factor-1 (IGF-1) were directly investigated in vitro based on blastogenic responses using peripheral blood lymphocytes (PBL) of eight cows fed the control diet. Forty pregnant Holsteins, 18 primiparous and 22 multiparous, at week (wk) 6 before the expected calving dates were randomly assigned to treatments: control and supplemental chelated Cr (0.5 ppm) in the diet. All cows were managed in a normal production operation and health status was assessed by recording the incidence of health problems during the experimental period of wks 6 before and 16 after calving (-6 to 16 wks). Mastitis-related parameters included somatic cell counts (SCC), bacterial colony counts of milk samples from each mammary gland quarter of all cows during wk 1 to wk 8 postpartum. Peripheral blood neutrophil phagocytic function of eight cows fed either control or supplemental Cr diet was determined by the ability to take up uniform fluorescent beads measured by flow cytometry. Supplemental Cr had no effect (P > 0.10) on health status of cows during late pregnancy and early lactation, or on SCC and bacterial colonies of quarter milk samples from early lactation (wks 1 to 8). Supplemental Cr also did not affect neutrophil phagocytic function of cows from 6 wks prepartum to 6 wks postpartum. However, in the in vitro study of PBL (from control animals, not fed Cr diet) blastogenesis with addition of insulin or cortisol at two levels (0.05 and 0.5 ng ml-1), insulin and cortisol enhanced or had no effect on PBL proliferations with or without concanavalin A (con A) simulation. However, further Cr addition in the culture medium containing supplemental insulin or cortisol, particularly CrCl3, additively increased (P < 0.05) BPL blastogenic activities with or without con a stimulation. Conversely, addition of rBST or IFG-1 (0.5 and 5.0 ng ml-1) in the culture medium enhanced PBL proliferation, but addition of Cr gave no additional effect. These results indicated that supplemental Cr had no beneficial effect on health status, mastitis-related parameters or neutrophil phagocytic activity of dairy cows. However, in vitro study confirmed and extended our previous observations that Cr has an effect on lymphocyte proliferation and this may associate with insulin or cortisol actions.

Animal Feed↗

PubMed1996

Construction of an internal control to quantitate multiple porcine cytokine mRNAs by RT-PCR.

A multiple internal control was constructed to be used as an exogenously added control in reverse transcription polymerase chain reaction (RT-PCR) for pig cytokines. It consists of 5' and 3' primer sequences in the order of beta 2 microglobulin (beta 2-m), IL-1, IL-4, IL-6, IL-8, IL-2, IL-10, TNF-alpha, TNF-beta and IFN-gamma. Construction was accomplished by overlapping and extension PCR (OE-PCR) utilizing short oligonucleotides. The primers were designed to give two products of different sizes on co-amplification of control and target RNAs by RT-PCR in a single tube. This permits analysis of message for several cytokines using a single exogenously added competitive template. Incorporated endonuclease sites allow construct modification by oligonucleotide addition.

Animals↗

PubMed1996

Effects of supplemental chromium on production of cytokines by mitogen-stimulated bovine peripheral blood mononuclear cells.

This study determined whether supplementing the diets of dairy cows during the peripartum period with organic trivalent Cr influenced the capacity of their peripheral blood mononuclear cells to produce activation cytokines in response to stimulation with mitogens in vitro. Nine cows were fed 0.5 ppm of Cr/d per cow from 6 wk prepartum to 16 wk postpartum; 10 other periparturient cows served as unsupplemented controls. Mononuclear leukocytes, enriched from peripheral blood during wk 0, 2, 4, and 6 of lactation, were cultured with or without the T-lymphocyte mitogen, concanavalin A. Culture supernatants, harvested at 24, 48, or 72 h, were assayed for interleukin-2, interferon-gamma, and tumor necrosis factor-alpha. The cytokines were barely detectable in the supernatants from the unstimulated cultures, but supernatants from mitogen-stimulated cultures contained higher concentrations of each cytokine. For cows fed Cr, concentrations of all three cytokines in the culture supernatants of the mitogen-stimulated mononuclear cells decreased significantly relative to values for unsupplemented cows, particularly around peak lactation for the 24- and 48-h cultures. Theses results extended our previous observations and supported the hypothesis that organic Cr is immunomodulatory in high producing cows.

Animals↗

PubMed1996

Effect of supplemental chromium on antibody responses of newly arrived feeder calves to vaccines and ovalbumin.

Two trials were conducted to investigate the effects of supplemental chromium (Cr) from organic sources (Cr chelate and high Cr yeast) on antibody responses of newly arrived feeder calves following vaccination with infectious bovine rhinotracheitis (IBR), para-influenza-3 (PI3), bovine respiratory syncytial virus (BRSV), bovine viral diarrhea (BVD) and Pasteurella haemolytica and ovalbumin (OVA). Using cross bred steer calves purchased at sales in Ontario, vaccines and OVA were given on d 0 and 21 after arrival in the feedlot. Immune responses of calves were measured as serum specific antibody titres against all antigens on d 0 and 28 or d 35. The anti-OVA antibody responses (trial 2) were further investigated by measuring antibody concentrations of calves weekly until d 55 after arrival in the feedlot. Supplemental Cr (0.14 ppm) from an amino acid-chelated source had no effect on antibody responses to IBR, P13 and BRSV, but enhanced (P < 0.05) antibody titres of calves in response to the BVD vaccine on d 28 or d 35. Supplemental Cr from Cr yeast had no effect on antibody titres of calves to any vaccines. Chromium from both sources (trial 1 and 2) had no effect on antibody responses of calves following vaccination with P. haemolytica. However, supplemental Cr (0.75 ppm) from Cr yeast enhanced (P < 0.05) serum antibody responses of calves to OVA during the primary response (d 14) and secondary response (d 35) following immunization. These data confirmed our previous finding that supplemental Cr can enhance humoral immune response of market-transit stressed calves, but its enhancement on vaccine efficacy was antigen-dependent and variable.

Animal Feed↗

PubMed1996

Homologues of murine Vh11 gene are conserved during evolution.

Since the murine Vh11 gene family shows 75% homology with group III VH gene families and is preferentially expressed in B-1 lymphocytes, we have analyzed if corresponding Vh11 genes existed across phylogenetically distant mammalian lineages. In a Southern blot, homologues of the murine Vh11 gene were detected in the genomic DNA from rats, pigs, sheep, cattle, horses, dogs and man. These observations suggest conservation of corresponding sequences of the Vh11 gene family during evolution, similar to group III VH genes, either because of strong selection pressures essential for species fitness and survival or molecular drive leading to these consequences.

Animals↗

PubMed1995

Interferon induction in swine lymphocyte antigen-defined miniature pigs.

Interferon was induced in two groups of swine lymphocyte antigen (SLA)-defined miniature pigs with polyinosinic: polycytidylic acid complexed with poly-L-lysine and carboxymethylcellulose. The group 1 pigs were low antibody-response phenotypes (SLAa/a, SLAa/c, SLAc/c), and the group 2 pigs were high antibody-response phenotypes (SLAd/d, SLAd/g, SLAg/g). Six hours after induction the antiviral tires were not influenced by the SLA group, but higher titres were observed in females. Higher antiviral titres were found in group 2 pigs before treatment and 24 hours after treatment, and higher titres were found in female pigs. The antiviral titres before and after treatment were also influenced by the sire. Group 2 pigs had a lower total leucocyte counts before treatment, and there was a significant reduction in leucocyte numbers in both groups six hours after induction, due mainly to a large reduction in lymphocyte counts.

Animals↗

PubMed1995

Immunomodulatory activity of blood serum from chromium-supplemented periparturient dairy cows.

Our previous research showed enhanced immune responses, including mitogen-induced blastogenesis of peripheral blood mononuclear cells from feedlot calves and periparturient dairy cows supplemented with dietary chromium (Cr). The objective of the present study were to test whether blood sera from Cr-supplemented periparturient cows contained immunomodulatory activity for mitogen-stimulated peripheral blood mononuclear cells and, if so, to determine if this activity was explicable by differences in blood profiles of some glucose-regulating hormones (insulin, cortisol, growth hormone, insulin-like growth factor I, and tumor necrosis factor-alpha) between Cr-supplemented and unsupplemented (control) animals. Blood sera from ten unsupplemented cows and nine Cr-supplemented cows (0.5 ppm day-1) were collected weekly from 2 weeks before to 6 weeks after parturition, and were used to supplement (1, 10, and 20% vol/vol) culture medium supporting concanavalin A (Con A) stimulated mononuclear cells enriched from blood of four nulliparous donor cows. Hormone concentrations were determined using radioimmunoassays. Con A-induced blastogenesis was enhanced when 1, 10, and 20% sera from Cr-supplemented cows was added to the mononuclear cell cultures, and this was particularly evident around parturition. Conversely, peripartum sera from unsupplemented cows depressed Con A-induced blastogenesis. Except for a marginal rise in blood cortisol 2-4 weeks after parturition, no significant effects of Cr supplementation on other hormones (insulin, growth hormone, insulin-like growth factor I, tumor necrosis factor-alpha) were observed. These observations suggest that factors in peripheral blood serum from Cr-supplemented cows, other than absolute concentrations of the glucose-regulating hormones studied, modulate Con A-induced blastogenesis of mononuclear leukocytes.

Adjuvants, Immunologic↗

PubMed1995

Differences in bovine lymphocyte antigen associations between immune responsiveness and risk of disease following intramammary infection with Staphylococcus aureus.

This study evaluated the relationships between immune response, disease resistance, and bovine leukocyte antigens, BoLA, in Holstein cows following intramammary challenge with Staphylococcus aureus. This investigation was to determine whether immune responsiveness differed between these cows and whether differences were related to expression of class I BoLA antigens, which might explain the increased resistance or susceptibility to S. aureus mastitis. Antibody responses to S. aureus in milk and serum, total IgG1 in milk, and blastogenic responses with and without concanavalin A were evaluated. The CA42 allele, previously associated with increased risk of infection, was relatively uninformative for the immune response parameters examined. Other alleles, such as W3, were associated with higher milk antibody responses to S. aureus and higher milk IgG1 postchallenge. Alleles W7, W4, and W26 were associated with lower milk IgG1 and lower antibody titers in serum postchallenge. The association reported between allele CA42 and increased risk of S. aureus mastitis did not relate to lower antibody or blastogenic responses by these cows; however, indicators of innate resistance were not examined. In addition, the different associations detected between milk and serum emphasize the importance of considering mucosal immunity and unique immunological compartments when searching for relevant genetic markers of disease resistance.

Animals↗

PubMed1995

The influence of supplemental chromium and vaccines on the acute phase response of newly arrived feeder calves.

The acute phase response as indicated by serum haptoglobin and total haemolytic complement activity (CH50) was measured in 72 cross-bred steer calves purchased at sales in Ontario. During the 28 day (d) trial, 18 steers were randomly assigned to each of the following groups: 1) control; 2) vaccinated (Infectious Bovine Rhinotracheitis, Parainfluenza-3, Bovine Viral Diarrhea, Bovine Respiratory Synctial Virus vaccine plus Pasteurella haemolytica vaccine); 3) supplemental chelated Cr (0.14 mg/kg); and 4) Cr plus vaccines. Haptoglobin concentrations were low at arrival, increased (P < 0.05) on day 7, and returned to near initial levels (P > 0.05) by day 14. Supplemental Cr reduced (P < 0.05) haptoglobin on day 7 when morbidity was highest. Following antibiotic treatment for respiratory disease haptoglobin was lower (P < 0.05) than during morbidity; however, during morbidity, haptoglobin concentrations were not greater in sick calves (P > 0.05) than in healthy calves. Complement activity was lowest on day 7 (P < 0.05) and peaked on day 14 (P < 0.05). Complement activity tended to be lower on day 7 for vaccine, Cr, and Cr+ vaccine groups; however, the difference from controls was not significant (P > 0.10). Complement activity did not increase on day 14 (P > 0.05) with Cr supplementation as in other treatments. Morbid calves had lower (P < 0.05) CH50 activity than healthy calves on day 14. Following antibiotic treatment, the Cr-supplemented group had higher (P < 0.05) CH50 than during morbidity. In general, chromium supplementation reduced the acute phase response in newly arrived feeder calves.

Acute-Phase Reaction↗

PubMed1994

Workshop: genetic improvement of resistance to mastitis of dairy cattle with special emphasis on somatic cell count.

A scientific workshop was held with specific emphasis on genetic improvement of resistance to mastitis based on SCC. The first objective was to present current knowledge of physiological and genetic aspects of resistance to mastitis. The second objective was to provide a forum for discussion of various strategies for genetic improvement of resistance to mastitis with particular emphasis on use of genetic evaluations for SCC. Contributions covered physiological, immunological, and genetic aspects of resistance to mastitis and SCC, as well as developments in genetic evaluation for SCC.

Animal Husbandry↗

PubMed1994

Genetic impact on the risk of intramammary infection following Staphylococcus aureus challenge.

This study evaluated relationships among intramammary challenge with Staphylococcus aureus, SCC, and susceptibility to infection and determined the genetic contribution to susceptibility of infection with special emphasis on bovine lymphocyte antigens. Intramammary challenge with S. aureus Newbould 305 was used as a model for natural infection. A total of 124 cows were challenged in all quarters with 600 cfu of S. aureus Newbould 305 in 2 ml of PBS solution. Quarter milk samples for bacteriology and SCC were taken at three times both before and after challenge. Lymphocytes were separated from whole blood and tested with a standard microlymphocytotoxicity test to determine the presence of bovine lymphocyte antigens class I alleles. One hundred and thirteen cows were negative for S. aureus at challenge, and 11 cows exhibited positive S. aureus counts in one or more quarters at challenge. Fifty-three percent of quarters from the 124 cows challenged became infected after challenge. Nineteen cows had no quarters infected; 19 cows, one; 26 cows, two; 25 cows, three; and 24 cows had four quarters infected after challenge. Average SCC before challenge was 181,000 and after challenge was 758,600. The SCC prior to challenge of cows that resisted infection were higher than prior SCC of cows that became infected (282,000 and 91,000, respectively). The reverse was true after challenge. Presence of the bovine lymphocyte antigens class I allele CA42, instead of EU28 (based on gene substitution), increased susceptibility to S. aureus infection. Heritability estimates of S. aureus susceptibility after experimental challenge were low and unstable.

Alleles↗

PubMed1994

Effects of supplemental chromium on antibody responses of newly weaned feedlot calves to immunization with infectious bovine rhinotracheitis and parainfluenza 3 virus.

The objective of this study was to determine the effect of supplemental dietary chromium (Cr) on antibody responses of feedlot calves. Fifty-five newly weaned calves were divided into two groups, 28 that received supplemental Cr and 27 that did not, and were immunized with a commercial vaccine against bovine infectious rhinotracheitis virus (IBR) and bovine parainfluenza virus type 3(PI-3). Sera harvested from blood sampled preimmunization, and at days 14 and 28 postimmunization (PI), were assayed for anti-IBR and anti-PI-3 antibody titers. Individual calves were also scored as seroconverters if day 14 or 28 PI titers were > or = 3 times the value of the preimmunization titer. Thirty-five calves did not seroconvert to either antigen. Of 20 IBR seroconverters, 15 calves were from the Cr-supplemented group while only five calves were controls (p = 0.007). There was no treatment difference in the number of PI-3 seroconverters. Least squares analysis of actual antibody titers revealed that Cr supplementation increased the magnitude of the peak antibody response to the IBR (p = 0.003), but had no effect on anti-PI-3 antibody titers. These data confirmed and extended our previous observations that supplemental Cr can be immunomodulatory in cattle.

Analysis of Variance↗

PubMed1993

Effect of selection of swine for high and low immune responsiveness on monocyte superoxide anion production and class II MHC antigen expression.

Monocyte function was investigated in second (G2) and third (G3) generation pigs selected for high and low antibody and cell-mediated immune responsiveness. In groups of pigs from the high-and low-immune response lines, monocyte release of superoxide anion (O2-) was assayed in response to phorbol 12-myristate-13-acetate and expression of the Class II-MHC (MHC-II) antigens SLA-DR and SLA-DQ, determined using flow cytometry. Analysis of variance using a linear model demonstrated no significant intergroup differences in O2- production by lymphokine-activated monocytes from G2 pigs. In G3 pigs, there were no significant intergroup differences in the percentage of MHC-II+ cells or in the density of expression of either SLA-DR or SLA-DQ. In individual pigs, monocyte SLA-DR and SLA-DQ expression was similar in terms of the percentage of MHC-II+ cells and in the magnitude of MHC-II expression. Litter contributed significantly to variation in monocyte O2- production in G2 pigs (P < or = 0.005) and SLA-DQ (P < or = 0.01) expression. Although the lines differed significantly in correlates of antibody and cell-mediated immune response, there was no apparent effect of selection for high and low immune responsiveness in swine on monocyte O2- production and MHC-II expression.

Animals↗

PubMed1993

Effects of supplemental chromium on immune responses of periparturient and early lactation dairy cows.

The objective of the present study was to determine the effects of supplemental dietary chromium on immune responses of dairy cows subjected to physical and metabolic stresses associated with late pregnancy, calving, early lactation, and peak milk yield. Nine periparturient dairy cows were supplemented with chelated Cr (.5 ppm/d) from 6 wk prepartum (wk -6) through 16 wk postpartum (wk 16), and 10 cows were unsupplemented controls. To assess humoral immune responses, all cows were immunized with ovalbumin (OVA; s.c.) and human erythrocytes (HRBC; i.v.) on wk -2 and 2, and sera from weekly blood samples were assayed for content of antigen-specific antibody. Cell-mediated immunity was assessed in vitro using antigen (OVA)- and mitogen-stimulated peripheral blood mononuclear cell (PBMC) blastogenesis of cells collected biweekly from wk -2 and 6. Supplemental Cr caused anti-OVA antibody responses (P < .01) and mitogen-stimulated blastogenic responses of PBMC (P = .05) to be elevated, was associated with lowered OVA-stimulated blastogenic responses of PBMC (P < .01), and had no overall effect on antibody responses to HRBC (P > .10) relative to responses of control cows. These results confirmed and extended our previous observations that supplemental Cr can alter specific immune responses of stressed cattle.

Analysis of Variance↗