Transfer of maternal colostral leukocytes promotes development of the neonatal immune system I. Effects on monocyte lineage cells

Although it has been established that maternal leukocytes traffic from colostrum into the neonatal circulation, the effects of these cells on neonatal immunity are only beginning to be understood. This study examined the effects of maternal colostral leukocytes on development and maturation of neonatal antigen presenting cells. At birth, groups of neonatal calves received whole or cell-free colostrum (CFC) from their respective dams. Peripheral blood samples were obtained over the first 4 weeks of life, and expression of surface markers associated with cellular activation and physiological stress were monitored on monocyte lineage cells. Calves receiving cell-free colostrum at birth expressed elevated levels of CD11a, CD11c, and CD14, compared to calves receiving whole colostrum (C). Calves receiving cell-free colostrum had an elevated number of monocytes in the peripheral blood during the first 2 weeks of life, however, these cells expressed lower levels of expression of CD25 and MHC class I compared to calves receiving whole colostrum. The most significant differences in marker expression occurred within the first 7 days of life.     

Effects of the ingestion of whole colostrum or cell-free colostrum on the capacity of leukocytes in newborn calves to stimulate or respond in one-way mixed leukocyte cultures

OBJECTIVE: To evaluate effects of colostral cells on the ability of neonatal leukocytes to respond in a mixed leukocyte response (MLR) as a means of evaluating specific immune responsiveness. ANIMALS: 10 Holstein calves, their respective dams, and 10 unrelated adult Holstein cows. PROCEDURE: Soon after birth, their calves were fed maternal whole colostrum or colostrum after cells were removed by centrifugation. Responses for leukocytes obtained from calves during the first 5 weeks after birth, their dams, and unrelated cows were measured by use of 1-way MLR as an indicator of immune development. An internal control treatment, proliferation of lymphocytes stimulated with Staphylococcus enterotoxin B (SEB), was also measured. RESULTS: Transfer of colostral leukocytes had a significant effect on the MLR and SEB-induced response in calves. Calves receiving whole colostrum had enhanced responses to maternal and unrelated leukocytes 24 hours after ingestion of colostrum. These responses decreased quickly, indicating direct modulation of the neonatal immune response. Calves receiving whole colostrum effectively stimulated the MLR by 24 hours after ingestion of colostrum. In contrast, calves receiving acellular colostrum did not effectively stimulate the MLR until 2 to 3 weeks after birth. CONCLUSIONS AND CLINICAL RELEVANCE: Ingestion of maternal colostral leukocytes immediately after birth stimulates development of the neonatal immune system. These maternal leukocytes enhance development of antigen-presenting capacity as indicated by their ability to stimulate the MLR and SEB response. The influence of ingested maternal cells on neonatal immunity was also indicated by a reduction in reactivity of neonatal cells to maternal alloantigens.     

Effect of maternal cells transferred with colostrum on cellular responses to pathogen antigens in neonatal calves

OBJECTIVE: To assess the effect of maternal cells or cellular components on neonatal immune responses to intracellular pathogens in calves. ANIMALS: 15 Holstein calves. PROCEDURES: Calves were fed whole colostrum, frozen colostrum, or cell-free colostrum within 4 hours after birth. Leukocytes were obtained from calves before feeding colostrum and 1, 2, 7, 14, 21, and 28 days after ingestion. Proliferative responses against bovine viral diarrhea virus (BVDV) and mycobacterial purified protein derivatives were evaluated. Dams received a vaccine containing inactivated BVDV, but were not vaccinated against mycobacterial antigens. RESULTS: All calves had essentially no IgG in circulation at birth, but comparable and substantial concentrations by day 1. Calves that received whole colostrum had enhanced responses to BVDV antigen 1 and 2 days after ingestion of colostrum. In contrast, calves that received frozen colostrum or cell-free colostrum did not respond to BVDV. No differences were identified among the 3 groups in response to mycobacterial antigens. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that transfer of live maternal cells from colostrum to neonatal calves enhanced responses to antigens against which the dams had previously responded (BVDV), but not to antigens to which the dams were na?ve (mycobacterial purified protein derivatives). Results suggested that cell-mediated immune transfer to neonates can be enhanced by maternal vaccination.     

The influence of colostral leukocytes on the immune system of the neonatal calf. II. Effects on passive and active immunization

The influence of colostral leukocytes on the concentration of immunoglobulins and antibodies against an enterotoxigenic strain of E. coli in the sera of newborn calves was investigated for four weeks using four experimental groups. The calves received either complete colostrum (COL-, n = 16), cell-supplemented milk substitute (MS+, n = 7) or pure milk substitute (MS-, n = 6) during the first three days of life. The cows were not specifically immunized. The sera of the COL+ calves had significantly higher concentrations of antibodies against E. coli mainly of IgG1 specificity on the second day of life as compared to those of the COL-. The sera of the COL+ calves contained significantly more IgM on days 2 and 5 and slightly more IgA during the first week. Both COL groups had equal concentrations of serum IgG. It appears that colostral leukocytes which are an integral part of the colostrum enhance the passive immunity of the neonatal calf, especially in regard of antibodies and immunoglobulin classes which are essential for intestinal immunity. The concentration of IgM in the sera of the MS+ calves was reduced, that of IgG did not rise to appreciable amounts; the IgA synthesis started one week later as compared to the MS- group. The administration of isolated colostral cells led to an impairment of the natural active immunization.     

Passive transfer of antibodies to Shiga toxin-producing Escherichia coli O26, O111 and O157 antigens in neonatal calves by feeding colostrum

To study whether or not passive immunity of neonatal calves against Shiga toxin-producing Escherichia coli (STEC) O26, O111, and O157 was obtained by colostrum administration, serum antibodies in calves after the feeding were determined by enzyme-linked immunosorbent assay (ELISA) in comparison with antibodies in colostrum and sera from donor dams. The highest antibody titers to STEC in colostrum from dams were detected soon after parturition. The antibody titers were found to be elevated in sera of neonatal calves (4-9 hr after birth) orally administered with colostrum with high antibody titers, suggesting that passive immunity of neonatal calves to STEC infection may be obtained by feeding colostrum. These results suggest that colostrum administration to neonatal calves may play an important role in elevating serum antibodies against STEC in neonatal calves.     

The influence of colostral leukocytes on the immune system of the neonatal calf. I. Effects on lymphocyte responses

The influence of colostral leukocytes on lymphocyte counts in the blood of calves and on lymphocyte responses, in particular the Concanavalin A-induced blastogenic response in vitro and the formation of antibodies against sheep erythrocytes, was investigated for four weeks postnatum using four experimental groups. The calves received either complete colostrum (COL+, n = 16), cell-depleted colostrum (COL-, n = 16), colostral cell-supplemented milk substitute (MS+, n = 7) or pure milk substitute (MS-, n = 6) during their first three days of life. In contrast to the calves fed with cell-depleted colostrum (COL-) the calves fed with complete colostrum (COL+) showed no decrease of lymphocyte numbers in the blood on the second day of life, uniform blastogenic responses to two different Concanavalin A concentrations, slightly enhanced antibody formation against sheep erythrocytes and a high spontaneous proliferation of mononuclear cells during the first week of life. In the calves fed with milk-substitute supplemented with colostral cells (MS+) a higher blastogenic response to Concanavalin A and an intensified formation of antibodies against sheep erythrocytes was observed as compared to the MS- calves. A passage of vital colostral lymphocytes through the intestinal wall is postulated. They seem to stimulate and regulate the blastogenic response and enhance the T-helper cell-dependent formation of antibodies against sheep erythrocytes in calves.     

Colostrum induced phenotypic and trafficking changes in maternal mononuclear cells in a peripheral blood leukocyte model for study of leukocyte transfer to the neonatal calf

The relationship between the colostral environment and the function of leukocytes in colostrum is not clearly defined. This study examined the effects of defatted, acellular colostrum (AC) on the phenotype of peripheral blood mononuclear cells (PBMC) and their capacity to enter the circulation of neonatal calves after ingestion as a model of this relationship. Maternal PBMC were exposed to medium alone or medium supplemented with 25% AC. Expression of CD11a, CD11b, CD11c, CD43, CD49d, CD49e, and CD62L was assessed on freshly isolated and treated PBMC. Exposure to AC increased the percentage of cells expressing CD11a, CD11c and CD43, but decreased the percentage of cells expressing CD62L relative to freshly isolated PBMC. The density of expression of CD11b and CD11c was reduced, but increased for CD43 after exposure to AC relative to freshly isolated PBMC. Density of CD62L expression and percentage of cells expressing CD11a and CD43 were significantly different for cells treated with AC relative to medium alone. Further, these changes could not be attributed to occult bacterial contamination of the AC, as treatment of PBMC with LPS in the same medium yielded none of the observed changes. Maternal PBMC (treated as described) were labeled with the fluorescent tracer, PKH26-GL, and fed to neonatal calves within 6 h of birth. The circulation of these cells in the neonate was monitored by flow cytometry. We observed that: (1) cells exposed to AC, but not medium alone, entered the circulation; (2) peak trafficking occurred 12-24 h after ingestion; (3) a large fraction of labeled cells appeared in the neonatal circulation; and (4) labeled cells disappeared from circulation by 36 h after ingestion. This study indicates that exposure to the colostral environment induced phenotypic changes facilitating trafficking of colostral cells into the neonate.     

The influence of colostral leukocytes on the immune system of the neonatal calf. IV. Effects on bactericidity, complement and interferon; synopsis.

The influence of colostral leukocytes on the bactericidity of whole blood of calves against a strain of E. coli and on the activities of haemolytic complement and interferon-alpha (the antiviral activity of sera resisting an acidic treatment at pH 2 for 6 h) in the serum was investigated during a period of 4 weeks using 4 experimental groups. The calves received either complete colostrum (COL+, n = 16), cell-depleted colostrum (COL-, n = 16), cell-supplemented milk substitute (MS+, n = 7) or pure milk substitute (MS-, n = 6) during their first three days of life. The bactericidity of whole blood of the COL+ group was significantly higher on the second and third days of life while the activity of haemolytic complement was lower after the first week as compared to the COL- group. No interferon-alpha was detectable in the sera of both COL groups. The bactericidity of the MS groups was significantly lower than that of the COL groups after the first day of life. It was significantly lower in the MS+ group after one week of life while the activity of haemolytic complement was higher than that of the MS- group. Three out of 5 MS- and only one out of 7 MS+ calves had low titres of interferon-alpha in their sera on the third day. Three out of 6 MS- calves died and 5 out of 7 MS+ animals. The mean day of death was 4.0 in the MS- and 8.4 in the MS+ group. Based on the in vitro results of this and the previous three communications it can be concluded that leukocytes which are an integral part of normal bovine colostrum, influence immunological reactions of the calf and that they may enhance its defence against infection. Colostral leukocytes in the absence of humoral components of the colostrum are not able to prevent fatal losses in the calves due to natural infection, although their influence on immune responses of the calves was detectable in vitro.     

Comparison of levels and duration of detection of antibodies to bovine viral diarrhea virus 1, bovine viral diarrhea virus 2, bovine respiratory syncytial virus,bovine herpesvirus 1, and bovine parainfluenza virus 3 in calves fed maternal colostrum or a colostrum-replacement product

Colostrum-replacement products are an alternative to provide passive immunity to neonatal calves; however, their ability to provide adequate levels of antibodies recognizing respiratory viruses has not been described. The objective of this study was to compare the serum levels of IgG at 2 d of age and the duration of detection of antibodies to bovine viral diarrhea virus 1 (BVDV-1), bovine viral diarrhea virus 2 (BVDV-2), bovine respiratory syncytial virus (BRSV), bovine herpesvirus 1 (BHV-1), and bovine parainfluenza virus 3 (BPIV-3) in calves fed maternal colostrum (MC) or a colostrum replacement (CR) at birth. Forty newborn male Holstein calves were assigned to the CR or the MC group. Group CR (n = 20) received 2 packets of colostrum replacement (100 g of IgG per 470-g packet), while group MC (n = 20) received 3.8 L of maternal colostrum. Blood samples for detection of IgG and virus antibodies were collected from each calf at birth, at 2 and 7 d, and monthly until the calves became seronegative. Calves in the MC group had greater IgG concentrations at 2 d of age. The apparent efficiency of absorption of IgG was greater in the MC group than in the CR group, although the difference was not significant. Calves in the CR group had greater concentrations of BVDV neutralizing antibodies during the first 4 mo of life. The levels of antibodies to BRSV, BHV-1, and BPIV-3 were similar in the 2 groups. The mean time to seronegativity was similar for each virus in the 2 groups; however, greater variation was observed in the antibody levels and in the duration of detection of immunity in the MC group than in the CR group. Thus, the CR product provided calves with more uniform levels and duration of antibodies to common bovine respiratory viruses.     

Bovine neonatal immunology.

The majority of early, in utero immune development occurs independent of antigen exposure. Only later during development can a fetus respond to antigens, and even then the response depends on the stage of fetal development and the nature of the antigen. At birth, the neonate is rapidly exposed to large numbers of potential pathogens. Although immunocompetent, the neonate is immunonaive and dependent on passively acquired maternal immunoglobulins, immune cells, and other substances from colostrum for protection. Neonates that suffer failure of passive transfer of maternal immunoglobulins may be at increased risk for disease; however, many other factors interact in conjunction with the level of passively acquired immunoglobulin to determine the occurrence of disease. These include, but are not limited to, management, environment, hygiene, infection pressure, virulence of organisms, and antibody specificity. In addition to immunoglobulins, colostrum contains large numbers of immune cells and cytokines. It is thought that the primary role for the cellular component of colostrum is to interact with the development of local immunity and to modulate active immunization of the neonatal intestine. In particular, T lymphocytes are thought to transfer immune functions and secrete cytokines. Although most of the major cytokines have been identified in colostrum and milk, their biologic effects on the neonate have yet to be determined.     

The influence of colostral leukocytes on the immune system of the neonatal calf. III. Effects on phagocytosis

The influence of colostral leukocytes on the activity of phagocytic cells from the blood of calves, in particular the concentration of neutrophils (PMN) in blood, ingestion of Streptococcus agalactiae, reduction of NBT-dye and activity of lysozyme, was investigated for four weeks using four groups. The calves received either complete colostrum (COL+, n = 16), cell depleted colostrum (COL-, n = 16), cell-supplemented milk-substitute (MS+, n = 7) or pure milk-substitute (MS-, n = 6). Calves of the COL+ group had a significantly lower PMN concentration in their blood on day 2 and a significantly higher activity of lysozyme during their first three weeks of life as compared to the COL- animals. A postnatal increase in number of ingested Streptococcus agalactiae test bacteria per 100 phagocytic cells occurred later in the COL+ calves than in the COL-. No difference between both COL groups in NBT-reduction was observed. The calves of the MS+ group showed higher lysozyme activity and a retarded increase in the ingestion of test bacteria during the first week of life as compared to the MS-. The MS+ group had a transient neutrophilia on the second day of life while the concentration of PMN was not altered in the MS- from the first to the second day.     

Modulation by colostrum-acquired maternal antibodies of systemic and mucosal antibody responses to rotavirus in calves experimentally challenged with bovine rotavirus

The effect of colostral maternal antibodies (Abs), acquired via colostrum, on passive protection and development of systemic and mucosal immune responses against rotavirus was evaluated in neonatal calves. Colostrum-deprived (CD) calves, or calves receiving one dose of pooled control colostrum (CC) or immune colostrum (IC), containing an IgG1 titer to bovine rotavirus (BRV) of 1:16,384 or 1:262,144, respectively, were orally inoculated with 105.5 FFU of IND (P[5]G6) BRV at 2 days of age. Calves were monitored daily for diarrhea, virus shedding and anti-BRV Abs in feces by ELISA. Anti-rotavirus Ab titers in serum were evaluated weekly by isotype-specific ELISA and virus neutralization (VN). At 21 days post-inoculation (dpi), all animals were euthanized and the number of anti-BRV antibody secreting cells (ASC) in intestinal and systemic lymphoid tissues were evaluated by ELISPOT. After colostrum intake, IC calves had significantly higher IgG1 serum titers (GMT=28,526) than CC (GMT=1195) or CD calves (GMT<4). After BRV inoculation, all animals became infected with a mean duration of virus shedding between 6 and 10 days. However, IC calves had significantly fewer days of diarrhea (0.8 days) compared to CD and CC calves (11 and 7 days, respectively). In both groups receiving colostrum there was a delay in the onset of diarrhea and virus shedding associated with IgG1 in feces. In serum and feces, CD and CC calves had peak anti-BRV IgM titers at 7 dpi, but IgA and IgG1 responses were significantly lower in CC calves. Antibody titers detected in serum and feces were associated with circulation of ASC of the same isotype in blood. The IC calves had only an IgM response in feces. At 21 dpi, anti-BRV ASC responses were observed in all analyzed tissues of the three groups, except bone marrow. The intestine was the main site of ASC response against BRV and highest IgA ASC numbers. There was an inverse relationship between passive IgG1 titers and magnitude of ASC responses, with fewer IgG1 ASC in CC calves and significantly lower ASC numbers of all isotypes in IC calves. Thus, passive anti-BRV IgG1 negatively affects active immune responses in a dose-dependent manner. In ileal Peyer's patches, IgM ASC predominated in calves receiving colostrum; IgG1 ASC predominated in CD calves. The presence in IC calves of IgG1 in feces in the absence of an IgG1 ASC response is consistent with the transfer of serum IgG1 back into the gut contributing to the protection of the intestinal mucosa.     

Phenotypical characterization of peripheral blood leucocytes in the newborn calf

The present study was undertaken to establish reference values for the composition of blood leucocyte populations in neonatal calves by differential leucocyte counts and immunophenotyping. Neonatal calves 1 h post partum (p.p.) were found to have a very high absolute number of granulocytes while the number of peripheral blood mononuclear cells was lower than in calves aged 3-9 weeks. The relative numbers of T cell subpopulations were similar in newborn and older calves, but newborn calves had lower percentages of B cells and MHC class II positive cells. Within the first 4 h of life the relative numbers of CD2+, CD6+, and CD8+ T cells declined in colostrum-fed as well as in colostrum-deprived calves. In contrast, the percentage of MHC class II positive cells and monocytes increased from 1 h to 4 h p.p. particularly in colostrum-fed calves. Although there is some evidence for immaturity of lymphocytes in neonatal calves, the immune system of these animals seems to be fully present at birth.     

Colostral and milk insulin-like growth factors and related substances: mammary gland and neonatal (intestinal and systemic) targets

The identification of hormones and regulatory factors in colostrum and milk has led to intensive investigations on their roles in the development and maintenance of the mammary and neonatal tissues. Insulin-like growth factors (IGFs) and IGF binding proteins (IGFBPs) in transgenic mice influence mammary biology gland towards the end of lactation. In the bovine, IGFBP-3 is the major IGFBP in mammary secretions. In addition to binding IGFs, IGFBP-3 also binds to lactoferrin (Lf). Secreted IGFBP-3 re-enters mammary epithelial cells and with the presence of a nuclear localization sequence, IGFBP-3 and Lf enter the nucleus. Nuclear IGFBP-3 affects apoptotic signaling through the retinoic-x-receptors, while Lf affects apoptotic events through unknown mechanisms. Such interactions likely influence mammary development and involution. Furthermore, ingested colostral bioactive factors can exert regulatory functions in neonates. Intestinal receptors for IGFs and insulin are modified by age and/or diet. Feeding IGF-I had no effect, but colostrum extracts had small intestinal effects (stimulation of proliferation and villus size), suggesting that several factors, rather than one single bioactive factor were responsible. Systemic changes of metabolic and endocrine profiles in neonates depend on composition, amounts, time and duration of feeding colostrum. Early postnatal colostrum intake is not only important for the provision and absorption of immunoglobulins. Thus, in neonatal calves the lack of colostrum intake during the first 24h after birth results in a low immunoglobulin G, beta-carotene and Vitamin A status that persists for weeks and plasma patterns of fatty acids, essential amino acids and the glutamine/glutamate ratios are affected. In calves oral administration of IGF-I had no and feeding of colostrum whey extracts had only minor effects on metabolic and endocrine traits. Thus, mammary secretions influence regulatory functions of mammary and neonatal tissues.     

Postnatal development of leukocyte subset composition and activity in dogs

The aim of the presentation is to summarise our data on the counts and activity of circulating canine leukocytes at birth and on their changes in the first 3 months of life. On day 1, neutrophil counts were almost three times higher than lymphocyte counts. During the first week of life, a decrease of neutrophil and an increase of lymphocyte counts, resulting in a predominance of lymphocytes, were observed. Neutrophil counts reached values comparable with those in adults in 1 month. Lymphocyte counts were higher than those in adults during the first 3 months. From birth to the age of 3 months, the phagocytic activity of neutrophils was nonsignificantly higher than in young adults. When compared with adults, the peripheral blood of new-born pups contained a lower proportion of T lymphocytes (detected by CD3 and CD5 markers), with a very low percentage of CD8(+) cells and a higher proportion of CD21(+) B lymphocytes. The counts of individual subsets levelled out during the first 3 months of life, although the proportion of CD21(+) B cells remained higher all the time. Lymphocytes of new-born pups were able to respond to nonspecific mitogen stimulation. Spontaneous proliferation in vitro was higher during the first week of life. Although in vitro stimulation of lymphocytes with Concanavalin A in some pups was comparable with that of adult dogs, mean activity was weaker. Pups with zero or very low levels of maternal antibodies were able to develop specific immune responses to a parvovirus antigen as early as at 2 weeks of age. On the basis of these data, we assume that pups are born with an immune system that can respond to external stimuli. Nevertheless its development continues in the postnatal period and some parameters differ from adult values for at least 3 months after birth.     

Colostral transfer of bovine immunoglobulin E and dynamics of serum IgE in calves

The role of IgE in protective immunity is becoming understood, therefore the colostral transfer of IgE and the age-dependent changes of IgE levels may be important for neonatal immunity. To investigate this question, serum samples were collected from range-fed Hereford cows and their calves from birth through 9 months of age. The sera were assayed for total IgE by enzyme-linked immunosorbent assay (ELISA). Calves were found to have significant levels of IgE during the first week postpartum, indicating colostral transfer of IgE. Thereafter, serum levels declined rapidly within 3 weeks from birth. The IgE levels began to increase after 12 weeks of age, and in some cases reached adult levels. The passive transfer of maternal IgE through colostrum may be important in providing early protection from disease, especially against intestinal parasites.     

Changes in the plasma levels of several bone markers in newborn calves during the first two days of life

The fluctuations in the plasma levels of several bone markers were investigated in newborn calves. Experiment 1 monitored the postnatal changes in the plasma levels of tartrate-resistant acid phosphatase isoform 5b (TRAP5b), total alkaline phosphatase (t-ALP) and bone-specific alkaline phosphatase (BAP) in four calves. These markers increased significantly from 9−20 hr after the first colostrum-suckling compared with the values immediately after birth. Experiment 2 evaluated changes in the plasma TRAP5b, t-ALP, BAP and type I collagen cross-linked N-telopeptide (NTx) levels within 2 days post-birth in five calves with successful passive immunization via colostrum (non-deficient group) and five others with poor colostrum intake (deficient group). The non-deficient group had significantly higher plasma levels of the four parameters around 12 hr of life compared with the deficient group. The results suggest that the increase in plasma bone markers in calves in the first day of life is related to the colostrum intake.     

Evaluation of colostrum and whey-derived gamma globulins for prevention of cryptosporidiosis in artificially infected neonatal calves

Thirty colostrum-deprived Friesian male calves were used to study the effect of colostrum and whey-derived gammaglobulins on the clinical events and oocyst-excretion pattern following artificial infection with a fresh, field-sourced strain of Cryptosporidium parvum. The calves were raised naive and free from contact with C. parvum from birth until infection at either 10 or 17 days of age. The two age groups comprised three sub-groups that were each given a single treatment of colostrum, whey-derived gammaglobulins or whole milk (controls) at 5 hours after birth. Blood samples taken both before and 48 hours after this dosing showed the mean serum gamma globulin concentrations changed from almost zero in all calves to 462,279 and 29 mg/dl for the colostrum, whey-derived gammaglobulin and whole milk sub-groups respectively. The results showed that a majority of calves shed Cryptosporidium oocysts within 7 days of oral infection but that no diarrhoea or other clinical signs were associated with this. However, when the level of C. parvum faecal shedding was graded, the results showed a trend towards a higher level of oocyst shedding and over a longer period of time in the control calves deprived of any passive immunity than in the two groups given either colostrum or whey-derived gammaglobulins.     

Postnatal changes in lymphocyte function of dairy calves

Lymphocyte blastogenic response, B-lymphocyte population and antibody-producing activity of lymphocytes were determined to evaluate the lymphocyte function in neonatal calves during the first 4 weeks of life. The mean percentage of B-lymphocytes ranged from 10.2 to 12.5% during the first 14 days of life and from 15.3 to 17.5% in calves from the day 21 to day 28 after birth. The absolute number of B-lymphocytes increased significantly (P less than 0.05) from 370/microliters at birth to 736/microliters on day 28 after birth. The mean stimulation index of blastogenic response, measured by fluorometric assay, ranged from 5.75 to 6.61 with Con A, from 5.29 to 5.98 with PHA and from 1.89 to 2.50 with PWM. The mean (+/- S.D.) number of plaque forming cells ranged from 22.0 (+/- 12.0) to 24.7 (+/- 9.2) in cultured lymphocytes from 5 calves at birth to 14 days after birth and their levels increased markedly from 137.8 (+/- 88.3) to 162.0 (+/- 57.8) in lymphocytes from 20 days to 28 days after birth. The present study showed that antibody-producing activity of lymphocytes is lower in calves within 3 weeks after birth compared to that of calves 3 weeks after birth, indicating that neonatal calf lymphocytes have a low antibody-producing activity at least up to 1 month after birth.     

Reproducibility of bovine neonatal pancytopenia (BNP) via the application of colostrum

A haemorrhagic diathesis has been observed in young calves since 2007 which is described as bovine neonatal pancytopenia (BNP) and presents a completely new disease. The objectives of our investigation were to test if BNP could be reproduced using colostrum of cows with a BNP history and pre-colostral calves from farms where BNP has not been observed. In the present experiment, 22 German Holstein calves from BNP-free farms were fed four to six hours after birth 2.5 l colostrum from cows which had been reported to have had at least one calf with BNP in the last lactation. We distinguished three different experimental groups according to the composition of the colostrum. In experimental group I, each of the six calves received colostrum of a single cow, in experimental group II all six calves received colostrum from the same cow and in experimental group III each of the ten calves received a colostrum mix from ten different cows. Clinical signs of BNP were observed in 50% of the calves in experimental group I, 67% of the calves in experimental group II and all calves in experimental group III. The lethality in the three experimental groups was significantly different with rates of 16.7%, 66.7% and 80%, respectively. Calves fed with a colostrum-mix in experimental group III had the highest lethality. Neither the farm nor the amount of the colostrum fed had a significant effect on the occurrence and course of BNP. The profiles for thrombocytes, leucocytes and erythrocytes significantly differed in dependence of the severity of BNP signs. Calves with non-lethal BNP showed thrombocytopenia with values below 100 G/l on the 1th to 3rd and the 7th to 11th day of life. In calves with lethal BNP, thrombocytes decreased under 50 G/l from day 5. In calves with non-lethal BNP, a decrease of the leucocytes under the threshold was present only for a short period of time. In calves with lethal BNP, leucocytes decreased in the first 5 days after birth continuously and increased on the 6th to the 8th day to normal values and then a rapid decrease occurred. Erythrocytes decreased under the normal threshold just in the last two days before the calves died or were euthanized. Thus, the present experiments showed that colostrum of cows with a BNP-history and vaccination with PregSure BVD from Pfizer caused lethal BNP. We can assume that the different reactions of the calves are due to immunogenetic reactions to colostral alloreactive antibodies. The reaction spectrum of calves depends on the presence of antigens which can react with these colostral antibodies. The experimental results can explain the different incidences of BNP within and among farms as well as between breeds.