Influence of isoprinosine on bovine herpesvirus type-1 infection in cattle

A study was conducted to determine the in vivo efficacy of isoprinosine (ISO) in calves infected with bovine herpesvirus type-1 (BHV-1). Calves were infected with BHV-1 on day 0 and received ISO daily for 14 days. Clinical signs of disease, shedding of BHV-1, lymphocyte proliferative responses to mitogens, interleukin-2 production, and alveolar macrophage bactericidal activity were monitored during the study. Rectal temperatures were increased (P less than 0.05) in BHV-1 and ISO-BHV-1 calves at days 3 to 7 postinfection (PI). Isoprinosine did not influence BHV-1 shedding in calves. Lymphocyte proliferative responses to phytohemagglutinin (PHA) were lower (P less than 0.01) in BHV-1 calves when compared to control or ISO calves at day 4 PI, but ISO did not ameliorate this effect. Interleukin-2 activity was greater (P less than 0.05) in ISO-BHV-1 calves on days 4 and 8 PI in PHA-stimulated lymphocytes and on day 8 PI in concanavalin A-stimulated lymphocytes when compared to control, ISO or BHV-1 calves. Isoprinosine treatment of BHV-1-infected calves tended to decrease alveolar macrophage bactericidal activity. These data suggest that ISO does not reverse BHV-1 suppression of lymphocyte proliferation, but may enhance IL-2 production in BHV-1 infected calves.     

Whole blood leukocyte vs. separated mononuclear cell blastogenesis in calves: time-dependent changes after shipping.

The blastogenic response of peripheral blood mononuclear cells to mitogenic stimulation by concanavalin A was lower (P less than 0.01) after transporting 60 dairy calves 480 km than it was either one or two weeks later. The response was similar for phytohemagglutinin. There was a decrease (P less than 0.05) in the number of peripheral blood monocytes and neutrophils two weeks after shipping. The transportation of calves did not affect plasma IgG1 or IgM level. The mitogenic stimulation of peripheral blood leukocytes by both phytohemagglutinin and concanavalin A in whole blood cultures was more variable than with the culture of peripheral blood mononuclear cells. Technique variation, which was defined as the coefficient of variation among quadruplicate cultures, was greater than 20% for while blood assays and less than 10% for cultures of peripheral blood mononuclear cells. The variation among different calves tested at the same time and the variation within single calves tested at different times were also lower in peripheral blood mononuclear cell cultures than in whole blood mononuclear cell cultures than in whole blood assays. It is suggested that the variation among replicate cultures be reported in blastogenesis studies.     

Shipping suppresses lymphocyte blastogenic responses in Angus and Brahman X Angus feeder calves

An experiment using 40 Angus or Brahman X Angus preconditioned feeder calves was conducted to evaluate the influence of shipping on cellular immune reactivity. Steers were allotted on the basis of weight and breed to a control or shipped group. Shipped steers were trucked 700 km to a feedlot; control steers remained at the ranch of origin. Total and differential leukocyte counts, phytohemagglutinin skin-test responses, lymphocyte blastogenic responses, monocyte phagocytic function, packed cell volumes and concentrations of plasma cortisol were determined before, immediately after and 1 wk after shipment. At unloading, total leukocytes were increased (P less than .05) in shipped Angus steers. Shipped steers also had higher (P less than .01) numbers of neutrophils. Skin-test responses to phytohemagglutinin were higher (P less than .05) in Angus than in Brahman X Angus steers, but shipping did not influence the reaction. Lymphocyte blastogenic responses were lower (P less than .05) in shipped steers; however, cortisol levels in plasma were not elevated (P greater than .10) in shipped calves. Monocyte phagocytosis and packed cell volume were not influenced by shipping. These data suggest that shipped steers have suppressed lymphocyte blastogenic responses.     

Effects of ketoprofen alone or in combination with local anesthesia during the castration of bull calves on plasma cortisol,immunological, and inflammatory responses

To determine the effects of the anti-inflammatory ketoprofen, alone or with local anesthesia (LA) during castration on cortisol, immune, and acute phase responses, 40 Friesian calves (215 +/- 3.5 kg) were assigned as follows: 1) control, 2) surgical castration (SURG), 3) SURG following ketoprofen (3 mg/kg BW i.v.; SURG + K), 4) SURG following LA (9 mL of 2% lidocaine hydrochloride to each testis; SURG + LA), or 5) SURG following LA and K (SURG + LA + K). Total cortisol response was greater (P < 0.05) in SURG, SURG + LA, and SURG + K + LA calves than in control calves and was not different between control and SURG + K calves. The interval to peak cortisol was longer (P < 0.05) for SURG + K + LA calves than for either SURG or SURG + K calves. On d 3, KLH-induced interferon-gamma production was lower (P < 0.05) in SURG calves than in control calves, whereas concanavalin A-induced interferon-gamma production was lower (P < 0.05) in all castration groups than in control. On d 1 after surgery, fibrinogen was higher (P < 0.05) in SURG and SURG + LA calves than in control calves, whereas SURG + LA + K calves had lower (P < 0.05) fibrinogen than did SURG calves. Haptoglobin was higher (P < 0.05) in SURG calves on d 1, 3, and 7 than in control calves. On d 1 after surgery, SURG + K and SURG + LA + K calves had lower (P < 0.05) haptoglobin concentrations than SURG calves, whereas SURG + K calves had lower (P < 0.05) levels than SURG calves on d 3. In conclusion, surgical castration induced a significant elevation in cortisol secretion; the rise in cortisol was reduced to control levels by the administration of ketoprofen but not local anaesthetic. Thus, systemic analgesia using ketoprofen is more effective than local anesthesia during castration to alleviate the associated stress response.     

Decreased mononuclear cell response to mitogens in artificially reared neonatal pigs.

The influence of two rearing methods for neonatal pigs on mononuclear cell responses to mitogens was studied. Littermate pigs were reared artificially or on the sow. Artificially reared pigs displayed a leukocytosis (P less than 0.05) characterized by an increase (P less than 0.05) in mature and immature neutrophils. Skin-test responses to intradermal injections of phytohemagglutinin were less (P less than 0.05) in artificially reared pigs than in sow-reared controls. Lymphocyte proliferative responses to mitogenic stimulation were approximately 50% lower (P less than 0.05) in artificially reared pigs than in sow-reared pigs. These data suggest that artificial rearing lowers in vivo and in vitro lymphocyte responses in neonatal pigs.     

In vitro lymphocyte proliferative responses and gamma-interferon production as measures of cell-mediated immunity of cattle exposed to Pasteurella haemolytica.

Cell-mediated immune mechanisms may play a role in the pathogenesis and prevention of pneumonia in cattle caused by Pasteurella haemolytica serotype A1. To determine the circumstances required to stimulate and identify cell-mediated immune responses, calves were vaccinated with a commercial P. haemolytica bacterin or a live commercial P. haemolytica vaccine, or were infected intratracheally with virulent P. haemolytica. All calves were challenge-exposed intratracheally with P. haemolytica 31 d after vaccination or prior infection. Peripheral blood mononuclear cells and mediastinal and superficial cervical lymph node cells were stimulated with antigens prepared from P. haemolytica to evaluate in vitro proliferative responses and gamma-interferon production as measures of cell-mediated immunity. Strong proliferative responses and gamma-interferon production were detected in lymph node cells from calves vaccinated with the live vaccine and from infected calves, especially in response to stimulation with an outer membrane protein preparation from P. haemolytica. Greater proliferative responses and gamma-interferon production were associated with the lymph node nearer the site of bacterin administration (superficial cervical lymph node) or the site of infection (mediastinal lymph node), whereas greater proliferative responses and gamma-interferon production were associated with the more distant lymph node (mediastinal lymph node) in calves vaccinated with the live vaccine. Neither proliferative responses nor gamma-interferon production were detected in peripheral blood mononuclear cells from calves that were vaccinated for or infected with P. haemolytica. Antileukotoxin antibody titers were determined by a serum neutralization assay, and protection against pneumonic lesions was more closely correlated with antileukotoxin antibody responses than with lymphocyte proliferation or gamma-interferon responses.     

Immunologic reactions of pigs regrouped at or near weaning

Using 64 pigs, 2 experiments (32 pigs each) were conducted to evaluate the effects of regrouping nonlittermate pigs at weaning or 2 weeks after weaning on mitogen-induced lymphocyte blastogenesis, intradermal reactions to phytohemagglutinin, and primary antibody responses to sheep erythrocytes. Plasma cortisol concentrations were determined in all pigs and behavior of regrouped pigs was monitored. Compared with control values, plasma cortisol concentrations were higher in nonlittermate pigs regrouped at weaning (P less than 0.001) or 2 weeks after weaning (P less than 0.01). However, regrouping pigs at weaning or 2 weeks after weaning did not influence lymphocyte blastogenesis, phytohemagglutinin skin-test responses, or antibody titers to sheep erythrocytes. Plasma cortisol concentrations were not related to agonistic behavior in regrouped pigs or to lymphocyte blastogenic or phytohemagglutinin skin-test responses; however, higher plasma cortisol concentrations were related (P less than 0.05) to lower sheep erythrocyte antibody titers. These data indicate that regrouping nonlittermate pigs at weaning or 2 weeks after weaning is an acute stressor that does not detrimentally affect mitogen-induced lymphocyte blastogenesis, intradermal reactions to phytohemagglutinin, or primary antibody responses to sheep erythrocytes.     

Estimation of immunity in the developing calf: cellular and humoral responses to keyhole limpet haemocyanin

The efficacy of keyhole limpet haemocyanin (KLH) as a test antigen was determined in calves. Humoral and cellular (in vivo and in vitro) responses were compared. Calves were immunized with KLH at either 3 weeks or up to 5 months of age and immune responses were subsequently tested. Class and subclass antibody responses were detected by ELISA, lymphocyte blastogenesis was measured using a whole blood culture technique (LTT) and skin sensitivity responses were measured as an increase in skin thickness following intradermal injection. In young calves, skin test responses were maximal at 24 h and were found to correlate with IgG1 and IgG2 responses (P less than 0.01), with IgA (P less than 0.05) but not with IgM or LTT. Histological examination of skin swellings found a sequence of cellular events, with polymorphonuclear cells dominating until 48 h after intradermal injection, when mononuclear cells became involved. However, in older calves, skin test responses correlated not only with IgG1 and IgA responses but also with lymphocyte transformation (P less than 0.05). These findings suggest that, while immune responses to KLH may be a useful indicator of immune competence in calves, interpretation should be made with caution particularly in young calves.     

Suppressed lymphocyte blastogenic responses and enhanced in vitro growth of infectious bovine rhinotracheitis virus in stressed feeder calves

Hereford steers were stressed on a large-animal treadmill operating at speeds of 1.8 to 2.2 m/s. Blood samples were collected from indwelling jugular catheters before, during, and after exercise. Peripheral blood lymphocytes from stressed calves at 5 and 30 minutes after exercise had less (P less than 0.01) mitogen-induced blastogenic responses when compared to pre- or 60-minute postexercise values. Serum from stressed calves incorporated into lymphocyte cultures from nonstressed steers resulted in less (P less than 0.01) lymphocyte blastogenic responses. Infectious bovine rhinotracheitis viral growth in bovine kidney cell cultures was enhanced 4-fold when cultured with serum from stressed calves. These data indicate that acute physical exertion may cause physiologic alterations in calves that modulate cellular immunity and viral replication.     

Immunologic profiles of cats with persistent, naturally acquired feline leukemia virus infection

Several immunologic responses were measured in 13 healthy cats with naturally acquired, persistent feline leukemia virus (FeLV) viremia from 4 multiple-cat households and were compared with responses from 28 of their healthy, non-FeLV-viremic housemates. Significant differences (P = less than 0.05) were not observed between results of FeLV-viremic and nonviremic cats for peripheral blood leukocyte or lymphocyte count, percentage of peripheral blood mononuclear cells able to form rosettes with guinea pig RBC or with antibody- and complement-coated sheep RBC, lymphocyte proliferative response to concanavalin A or pokeweed mitogen, or serum immunoglobulin G concentration. Seemingly, persistent FeLV viremia, when naturally acquired, may exist for some time without lymphopenia or a marked loss of mitogen-induced lymphocyte proliferation.     

Immunosuppression of lymphocyte blastogenesis in cattle infected with Ostertagia ostertagi and/or Trichostrongylus axei

Twenty 4-month-old calves were infected with O ostertagi and/or T axei and the responses to phytolectins were evaluated. Whole blood cultures were incubated with phytohemagglutinin (PHA), concanavalin A (Con A) and pokeweed mitogen (PWM). The blastogenic response was determined by tritiated thymidine uptake with results presented as counts per minute (cpm), stimulation indices (SI) and a mononuclear cell responsive index determined by dividing the phytomitogen induced cpm by the absolute mononuclear cell number per ul. The control group results were adjusted to 100 percent and changes in the percentage difference by the parasitized calves was determined. There was a decline in lymphocyte responsiveness to PHA beginning at the time of infection. Significant depression of responses to PHA was observed in all parasitized calves 8 weeks after infection although clinical signs of parasitism did not occur. Lymphocyte responses to PW, were not different in infected calves from the control, although the O ostertagi group had significantly higher PWM mean upon than the calves infected with T. axei. A slight depression in response to Con A was also observed at 8 weeks after infection followed by a significant increase after 10 weeks. The immunosuppression appeared to be a feature of gastrointestinal parasitism and related to infections with O. ostertagi and/or T. axei.     

Suppression of bovine lymphocyte responses to mitogens following in vivo and in vitro treatment with dexamethasone.

Gnotobiotic calves given intramuscular injections of dexamethasone (DM, 0.5 mg kg-1 day-1) showed marked changes in haematological parameters including a neutrophilia and a lymphopaenia. Not only was there a reduction in the numbers of circulating mononuclear cells, but there was also a significant (P less than 0.01) decrease in the in vitro responsiveness of the remaining circulating peripheral blood lymphocytes to the mitogens, phytohaemagglutinin (PHA), concanavalin A (ConA) and pokeweed mitogen (PWM). Responses to all three mitogens were suppressed to a similar degree. Analysis of the circulating mononuclear cell sub-populations before and during DM treatment demonstrated a selective depletion of B cells; the T lymphocyte sub-population that expresses the gamma/delta form of T cell receptor, are CD2-, CD5+, CD8-, CD4- and constitute a major population in peripheral blood of calves. In vitro studies in gnotobiotic and conventional calves confirmed that DM was highly inhibitory for PHA responses but, in contrast to the in vivo findings, showed little effect of DM on ConA responses. Expression of surface antigens after 72 h in vitro culture in the presence of DM were little affected with the exception of BoCD8 and MHC II, which showed increased and decreased expression, respectively. These observations would suggest that distinct mechanisms are involved in glucocorticosteroid suppression of the responses to these two mitogens.     

Effect of estradiol-17 beta treatment of gilts on blood mononuclear cell functions in vitro.

Porcine blood mononuclear cells (BMC) were exposed to prepartum concentration of estrogen in gilts before acquisition (in vivo), and their subsequent reactivity (in vitro) was explored. In a cross-over experimental designed study, 6 ovariectomized gilts were injected once with 3.75 mg of estradiol-17 beta benzoate in arachidic oil or with arachidic oil only during 2 experiments. The ability of their BMC to proliferate in response to stimulation with phytohemagglutinin, concanavalin A, and pokeweed mitrogen was assayed in cultures of blood and in cultures of purified BMC. After 2 days of mitogen stimulation, activity of accessible interleukin 2 was quantified in supernatants obtained from cultures of purified BMC and supernatants of blood cultures stimulated with pokeweed mitogen. Also, production of immunoglobulins by purified BMC in response to polyclonal stimuli was measured. Three days after treatment with estradiol, the proliferative response was suppressed in blood cultures stimulated with concanavalin A (P less than 0.05) and phytohemagglutinin (P less than 0.07). Effects of estradiol treatment were not found in any of the assays performed with purified BMC. We, therefore, assumed that in vivo exposure to estradiol can affect the function of porcine BMC; however, this was only evident when the in vitro assays were performed on blood cultures.     

Adverse immune reactions and the pathogenesis of Ostertagia ostertagi infections in calves

The possible development of type-1 hypersensitivity reactions in the abomasal mucosa caused by soluble L3 products of Ostertagia ostertagi was studied in 4-month-old calves sensitized by repeated exposure to L3 over a 50-day period followed by anthelmintic treatment. Four groups each of 4 calves were used. Group 1 served as nonsensitized controls and group 2 as sensitized controls, group 3 was challenge exposed at 2-week intervals beginning at week 10 with a soluble L3 product (OAG), and group 4 was challenge exposed at 2-week intervals with an oral dose of L3, followed by anthelmintic treatment 3 days later. All calves infected with L3 became sensitized, as indicated by a positive reaction to an intradermal skin test. However, a passive cutaneous anaphylaxis was only partly effective in indicating the presence of homocytotropic antibody in the infected calves. Sensitized calves had significantly (P less than 0.05) higher eosinophil counts and plasma pepsinogen values for the entire 14 weeks than uninfected controls. Globule leukocyte and mast cell counts from the abomasal mucosa were also significantly (P less than 0.05) higher. Studies for possible immunomodulation revealed that lymphocyte counts decreased between every 2-week challenge-exposure period for groups-3 and -4 calves. A transient depression of blood lymphocyte (BL) responses to phytohemagglutinin (PHA), a T-cell mitogen, was observed over the first 8 weeks in the infected calves. Increases in BL responses to OAG were also observed. Differences were not observed in BL responses to pokeweed mitogen, a T- and B-cell mitogen. Blood lymphocyte responses to PHA in group-3 calves were low following the initial challenge exposure with OAG.(ABSTRACT TRUNCATED AT 250 WORDS)     

Isoprinosine and levamisole immunomodulation in artificially reared neonatal pigs

An experiment was conducted to determine the capability of isoprinosine (ISO) and levamisole (LEV) to augment delayed-type hypersensitivity and lymphocyte blastogenic reactions in artificially reared pigs. Sow-reared pigs (n = 15) were kept with their dams; artificially reared pigs (n = 15) were removed from sows within 2 days after parturition and reared artificially for 21 days. Isoprinosine was administered orally (75 mg/kg/day) from days 0 to 10. Levamisole (2 mg) was injected subcutaneously on days 5 and 10. Control pigs were given distilled water orally from days 0 to 10 and injected subcutaneously with 0.15M NaCl on days 5 and 10. Lymphocyte proliferative responses to phytohemagglutinin, concanavalin A, and pokeweed mitogen were evaluated at week 2. The phytohemagglutinin skin-test responses were evaluated in all pigs at weeks 1 and 3 of the trial. Hematologic values, body weight, and mortality were evaluated each week. The skin-test responses and mitogen-induced lymphocyte proliferative responses were lower (P less than 0.05) in artificially reared controls when compared with responses in sow-reared pigs. However, ISO and LEV enhanced (P less than 0.05) the responses in the artificially reared pigs to values comparable with those of the sow-reared controls. Body weight was greater (P less than 0.01) in sow-reared pigs than in artificially reared pigs; drug treatment did not influence weight gain. These data indicated that immunopotentiation of the cellular immune responsiveness of artificially reared pigs may be possible with ISO or LEV.     

Dietary lutein stimulates immune response in the canine

The possible immuno-modulatory action of dietary lutein in dogs is not known. Female Beagle dogs (17-18-month old; 11.4+/-0.4kg body weight) were supplemented daily with 0, 5, 10 or 20mg lutein for 12 weeks. Delayed-type hypersensitivity (DTH) response to saline, phytohemagglutinin (PHA) and a polyvalent vaccine was assessed on Weeks 0, 6 and 12. Blood was sampled on Weeks 0, 2, 4, 8 and 12 to assess (1) lymphocyte proliferative response to PHA, concanavalin A (Con A), and pokeweed mitogen (PWM), (2) changes in peripheral blood mononuclear cell (PBMC) populations, (3) interleukin-2 (IL-2) production and (4) IgG and IgM production. After the completion of 12-week study, we continued to collect the blood weekly up to 17 weeks to evaluate the changes in immunoglobulin production upon first and second antigenic challenges on Weeks 13 and 15. Plasma lutein+zeaxanthin was undetectable in unsupplemented dogs but concentrations increased (P<0.05) rapidly on Week 2 in lutein-supplemented dogs. Thereafter, concentrations generally continued to increase in dose-dependent manner, albeit at a much slower rate. Dogs fed lutein had heightened DTH response to PHA and vaccine by Week 6. Dietary lutein increased (P<0.05) lymphocyte proliferative response to all three mitogens and increased the percentages of cells expressing CD5, CD4, CD8 and major histocompatibility complex class II (MHC II) molecules. The production of IgG increased (P<0.05) in lutein-fed dogs after the second antigenic challenge. Lutein did not influence the expression of CD21 lymphocyte marker, plasma IgM or IL-2 production. Therefore, dietary lutein stimulated both cell-mediated and humoral immune responses in the domestic canine.     

Effects of alpha-ketoisocaproate on adrenocorticotropin-induced suppression of lymphocyte function in sheep.

Previous studies of the amino acid analogue, alpha-ketoisocaproate (KIC), indicate that it can stimulate lymphocyte blastogenesis and antibody responses of sheep. To determine whether KIC could overcome the effects of adrenocorticotropic hormone (ACTH)-induced lymphocyte suppression, 24 lambs were fed a control diet, a diet supplemented with 0.05% KIC, or a diet supplemented with 0.05% of the parent amino acid leucine. Immune status was monitored by determining lymphocyte blastogenic responsiveness to phytohemagglutinin-P (PHA), concanavalin A (conA), and pokeweed mitogen (PWM) and percentages of T-cell subsets in the blood, using monoclonal antibodies and a flow cytometer. Serum cortisol, insulin, and glucagon concentrations also were determined. After 60 days of consuming the respective diet, lambs were administered either saline solution or ACTH (100 IU) twice daily for 3 consecutive days. Administration of ACTH increased serum cortisol and insulin concentrations; however, no effects were seen for serum glucagon concentration. Compared with saline administration, ACTH administration significantly (P less than 0.05) suppressed mitogen-stimulated lymphocyte blastogenesis by approximately 50%, regardless of the mitogen used, and significantly (P less than 0.01) decreased the percentage of circulating T lymphocytes and decreased (P less than 0.01) the ratio of T4 to T8 cells. Lambs fed KIC had greater PHA- and conA-stimulated blastogenic responses and significantly (P less than 0.05) increased ratio of T4 to T8 cells in the blood, compared with lambs fed the leucine-supplemented diet or the control diet and given corresponding injections. These data indicate that ACTH decreased in vitro lymphocyte blastogenesis and altered the subset ratios of blood lymphocytes in sheep. These changes were partially prevented by feeding KIC.     

断奶应激对奶水牛犊牛血液生理生化指标和免疫功能的影响

为研究断奶应激对奶水牛犊牛的影响,选用5头健康犊牛,分别于断奶前1 d、断奶后1、14和21 d进行采血,测定犊牛的血常规、血清生化指标和免疫指标。结果显示,奶水牛犊牛的白细胞数、淋巴细胞数、红细胞数、单核细胞数、红细胞压积、天冬氨酸转氨酶活性、血糖含量、皮质醇含量、免疫球蛋白G含量在断奶前后无显著变化（P > 0.05）;中性粒细胞数在断奶后21 d显著低于断奶前1 d（P < 0.05）;血清乳酸脱氢酶、丙氨酸转氨酶活性在断奶后显著高于断奶前（P < 0.05）;血清尿素氮含量在断奶后21 d显著高于断奶前1 d（P < 0.05）;血红蛋白含量在断奶21 d显著低于断奶前1 d（P < 0.05）。结果表明断奶应激不仅影响了奶水牛犊牛的生理机能,而且降低了其免疫力和抵抗力。     

Effect of Weaning Stress on Blood Physiology and Biochemistry Indexes and Immune Function in Dairy Buffalo Calves

To study the effect of weaning stress on dairy buffalo calves,5 healthy calves were chosen and weaned,and the blood samples were collected at 1 day before weaning,and 1,14 and 21 days after weaning to analysis blood physiology and biochemistry indexes and immune function.The results showed that the count of white blood cell,lymphocyte,erythrocyte,monocytes and hematocrit,aspartate aminotransferase activity,blood glucose,cortisol and immunoglobulin G contents of dairy buffalo calves were no significant difference between before and after weaning treatments (P > 0.05).The count of neutrophils at 21 d after weaning were significantly lower than that of 1 d before weaning of dairy buffalo calves (P < 0.05).However,lactate dehydrogenase and alanine aminotransferase activity in weaned treatments were significantly higher than those of animals in the treatment before weaning (P < 0.05).The serum urea nitrogen of dairy buffalo calves at 21 d after weaning was significantly higher than that of 1 d before weaning (P < 0.05) and hemoglobin content at 21 d after weaning was significantly lower than that at 1 day before weaning (P < 0.05).It indicated that the physiological and immunity function of dairy buffalo calves were challenged under weaning stress.     

The effect of abrupt weaning of suckler calves on the plasma concentrations of cortisol, catecholamines, leukocytes, acute-phase proteins and in vitro interferon-gamma production

The objective of this study was to examine the effect of abrupt weaning (inclusive of social group disruption and maternal separation) on the physiological mediators of stress and measures of immune function. Thirty-six male and 36 female calves (Limousin and Charolais crosses), habituated to handling, were blocked by sex, weight, and breed of dam and randomly assigned, within block, to either a control or abruptly weaned group. Animals were separated into the respective treatment groups at 0 h. Calves were bled at -168, 6 (males only), 24, 48, and 168 h after weaning, and the behavioral reaction of calves to handling was scored. Cortisol, catecholamine (not sampled at -168 h), acute-phase protein concentrations, and in vitro interferon-gamma production and neutrophil:lymphocyte ratio were measured. The effects of weaning, calf sex, time, and their respective interactions were described. Disruption of the established social group at 0 h increased (P < 0.001) the plasma cortisol concentration and neutrophil:lymphocyte ratio and decreased the leukocyte concentration (P < 0.001) and the in vitro interferon-gamma response to the mitogen concanavalin-A (P < 0.001) and keyhole limpet hemocyanin (P < 0.001) for weaned and control animals compared with -168 h. There was no effect of weaning or sex on the behavioral reaction of calves to handling. Plasma cortisol and adrenaline concentrations were not affected by weaning or sex. Plasma noradrenaline concentration was influenced by weaning x sex (P < 0.05) and time x sex (P < 0.05). The response increased for male calves with weaning and increased with each sampling time after weaning. For heifers, the response was not affected by weaning and plasma concentrations decreased at 168 h after weaning. There was no effect of weaning or sex on leukocyte concentration. The neutrophil:lymphocyte ratio increased after weaning (P < 0.01) and was affected by sex (P < 0.05). Weaning decreased (P < 0.05) the in vitro interferon-gamma response to the antigen keyhole limpet hemocyanin. There was a time x weaning x sex (P < 0.05) interaction for fibrinogen concentration but no effect of treatment on haptoglobin concentration. Abrupt weaning increased plasma cortisol and noradrenaline concentrations that were accompanied by attenuation of in vitro interferon-gamma production to novel mitogen and antigen complexes up to 7 d after weaning.