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The aim of this study was to evaluate the capacity of cells from colostrum to modulate the intestinal microbial colonization, the activity of the inflammatory response, and for their influence on the development of diarrheal disease in calves. Twenty calves were distributed into two groups: COL+ (n = 10) receiving fresh whole colostrum; COL- (n = 10) receiving pooled frozen colostrum, containing no viable cells. All assessments were made before colostrum intake (D0), the next day (D2), and weekly on the 7th (D7), 14th (D14), 21st (D21) and 28th (D28) day of age. Diarrhea was assessed using a fecal score, and the systemic inflammatory status was assessed using a combination of temperature, anemia, total serum iron level, total haptoglobin concentration and the need for systemic antimicrobial treatment. The number of indicator bacteria present in the fecal population was estimated using qPCR. However, COL- calves presented more frequent signs of systemic inflammatory response including, fever at D7 (P = 0.011); indicator haptoglobin levels on D7 and D14, and lower levels of iron on D7, D14. Anemia was detected more often in the COL- calves on D21 (P = 0.043) and D28 (P = 0.016). COL- calves had a 1.66 greater chance of having elevated haptoglobin and a 1.8 greater chance of needing treatment with antimicrobials than COL+. A lower number of DNA copies of Clostridium perfringens were detected in COL+ calves on D2 (P = 0.088) and D7 (P = 0.040). Similarly, a low number of DNA copies was observed for Escherichia coli and Lactobacillus spp. (P = 0.012) in the fecal samples of COL+ calves on D7.

RESUMO Objetivou-se avaliar o efeito dos anticorpos (ACs) maternos sobre resposta imune humoral induzida pela vacinação em bezerros Holandeses. Bezerros foram distribuídos aleatoriamente em quatro grupos: G1 - vacinados no D14 e D44 (n=6); G2 - vacinados no D90 e D120 (n=5); G3 - vacinados no D180 e D210 (n=8); controle: não vacinado (n=5). Utilizaram-se 5mL de vacina comercial (Cattle Master Gold FP5+L5® - Zoetis, Brasil), por via subcutânea. Foi realizada vírus neutralização (VN) no momento da vacinação, booster e 30 dias após a revacinação. Não foram observadas diferenças entre controle e G1 ou G2 para a frequência de soropositivos ou títulos de ACs contra os vírus respiratórios (P≥0,05). G3 apresentou maior produção de ACs em relação ao controle para BoHV-1 (P

Biofilm formation is a significant virulence factor in Staphylococcus (S.) aureus strains causing subclinical mastitis in dairy cows. A role of environmental signals and communication systems in biofilm development, such as the agr system in S. aureus, is suggested. In the context of multispecies biofilm communities, the presence of non-aureus staphylococci (NAS) might influence S. aureus colonization of the bovine mammary gland, yet, such interspecies interactions have been poorly studied. We determined whether 34 S. chromogenes, 11 S. epidermidis, and 14 S. simulans isolates originating from bovine milk samples and teat apices (TA) were able to affect biofilm formation and dispersion of S. aureus, and if so, how isolate traits such as the capacity to regulate the S. aureus agr quorum sensing system are determinants in this process. The capacity of an agr-positive S. aureus strain to form biofilm was increased more in the presence of S. chromogenes than in the presence of S. simulans and S. epidermidis isolates and in the presence of NAS isolates that do not harbor biofilm related genes. On the other hand, biofilm dispersion of this particular S. aureus strain was suppressed by NAS as a group, an effect that was more pronounced by isolates from TA. Furthermore, the observed effects on biofilm formation and dispersion of the agr-positive S. aureus strain as well as of an agr-negative S. aureus strain did not depend on the capacity of NAS to repress the agr system.

Communications via quorum sensing (QS) between non-aureus staphylococci (NAS) and Staphylococcus (S.) aureus in the bovine mammary gland remains largely unexplored. We determined whether 34 S. chromogenes, 11 S. epidermidis, and 14 S. simulans isolates originating from bovine milk samples and teat apices were able to regulate the QS of S. aureus, and if so, how in vitro growth inhibition of S. aureus by NAS, or NAS metabolites, or NAS cells themselves play a role in this process. In co-culture with S. aureus we observed that these 3 NAS species in general downregulated the expression of rnaIII, the effector molecule of the QS system, but this effect was more pronounced in S. chromogenes and S. simulans isolates than in S. epidermidis isolates. In vitro growth inhibition of S. aureus by NAS resulted in a small underestimation of the downregulating effect of NAS on rnaIII expression of S. aureus. Additionally, the culture supernatant of these NAS isolates and supernatant treated with proteinase K expressed greater regulatory activity over S. aureus virulence genes rnaIII, hla, and spa than washed NAS cells suspended in sterile water. These microbial interactions may influence S. aureus virulence and pathogenesis within the host. Isolation and identification of NAS metabolites affecting the QS system of S. aureus might help to develop alternative strategies for treatment and control of S. aureus mastitis.

Background: Newborn calves are born immunosuppressed, hypogammaglobulinemic, immunologically immature, and therefore more vulnerable to many infectious diseases. During pregnancy, the fetal-placental environment is regulated by Th2-type cytokines that neutralize Th1 responses, an important factor for immune defense against viral agents. The ingestion and absorption of colostral immunoglobulins enhance the immunity of the neonate. However, the presence of maternal antibodies might negatively affect the success of parental vaccination in the first two months of life. This study aimed to evaluate the effecacy of parenteral vaccination in newborn calves with high titers of maternal antibodies against respiratory viruses. Materials, Methods & Results: Twenty-eight Holstein calves were allocated to the vaccinated group (VAC, n = 18) or an unvaccinated control group (NVAC, n = 10). The initial vaccination with 5 mL of a commercial vaccine occurred around the 14th day of life (D14) and the booster at D35. Respiratory and diarrhea symptoms were evaluated at D12, D14, D16, D20, D31, D36, D45, D53, and D60. Blood samples were taken for leukogram, haptoglobin, and seroneutralization of BVDV, BoHV-1, BRSV, and BPI3V, at the time of vaccination at D14 (T1), at booster (D35, T2), and 21 days after the booster (D56, T3). Despite the increased prevalence of BRD during the period of the study, no calves from either group exhibited respiratory disease at D12 or D14. In subsequent assessments, the frequency of BRD increased over time in the VAC group until it reached a maximum prevalence of 38.9% (7/18) at D31. In the NVAC group, the maximum prevalence observed was 40% at D45 and D60. A comparison of the frequencies for BRD cases showed a statistical trend at D36 (P = 0.07), with a higher prevalence for the NVAC group (30%) in relation to the VAC group (5.6%). For the NVAC group, a greater number of total leukocytes was observed at T3 (P = 0.038) and granulocytes (trend) at T2 (P = 0.066). Time analysis demonstrated a decrease in haptoglobin concentration in both groups (NVAC, P = 0.005 and VAC, P = 0.006), with a reduction in the values at T1 and T3 (NVAC = 0.005 and VAC = 0.024). Antibody titers were similar between groups for BVDV, BoHV-1, and BRSV. Higher titers for BPI3V were observed for the VAC group at D56 (P = 0.045). Discussion: The early-onset BRD was present in both groups between 30 and 60 days of age, based on the higher prevalence observed. These data reinforce the importance of early immunization programmes before infection. Factors such as management practices and facilities may have also contributed to the higher prevalence of BRD. The increased number of leukocytes and neutrophils at T2 (D35) and T3 (D56) in the NVAC group points to a stronger inflammatory response to various types of potential challenges. The inflammatory leukocyte profile explains the higher haptoglobin values observed in the NVAC group at T2 (D35). The similarity of titers of antibodies against BVDV, BoHV-1, and BRSV between groups may indicate that vaccinating the calves at 14 days of age did not induce a humoral immune response to these viruses, likely due to interference from the maternal antibodies. Early vaccination prevented a drop in specific viral antibodies and promoted partial protection for vaccinated calves around 14 days of age, with a decrease in the intensity of the inflammatory response at the peak of the disease and a higher concentration of antibodies against BPI3V after the booster. Fil: Gomes, Viviani. Universidade de Sao Paulo; Brasil Fil: Gonzalez, Diego Daniel. Instituto Nacional de Tecnologia Agropecuaria. Centro de Investigacion En Ciencias Veterinarias y Agronomicas. Instituto de Virologia E Innovaciones Tecnologicas. - Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Pque. Centenario. Instituto de Virologia E Innovaciones Tecnologicas.; Argentina Fil: Medici Madureira, Karina. Universidade Federal da Bahia; Brasil Fil: Mozgovoj, Marina Valeria. Instituto Nacional de Tecnologia Agropecuaria. Centro de Investigacion En Ciencias Veterinarias y Agronomicas. Instituto de Virologia E Innovaciones Tecnologicas. - Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Pque. Centenario. Instituto de Virologia E Innovaciones Tecnologicas.; Argentina Fil: Costa Baccili, Camila. Universidade de Sao Paulo; Brasil Fil: Toledo Silva, Bruno. Universidade de Sao Paulo; Brasil Fil: Silva Ramos, Jean. Universidade de Sao Paulo; Brasil Fil: Nascimento Silva, Karen. Universidade de Sao Paulo; Brasil Fil: Maristella Pituco, Edviges. Instituto Biológico; Brasil

The objective of this research was to evaluate the influence of cells from colostrum on the health of neonate calves. Animals were distributed in 2 groups: COL + (n = 9) which received fresh colostrum from their own damns; and COL − (n = 10) which received frozen colostrums from donors. Heifers were assessed before colostrum intake – D0; D2; D7; D14; D21 and D28. Heifers were monitored by clinical examination, hematological profile and serum iron. COL − had a higher diarrhea intensity score (typically 3) on D7. Moreover, a single case each of bronchopneumonia and navel inflammation were observed in COL − calves. COL − had fewer red blood cells (RBC) (6.5 ± 0.8 × 106/μL) and less hemoglobin (Hgb) (8.3 ± 1.4 g/dL) than COL + (RBC = 7.2 ± 0.8 × 106/μL; Hgb = 9.6 ± 1.3 g/dL) at D14 (P ≤ 0.05). COL − had more anemia on D21 (P = 0.03) and on D28 (P = 0.02). Iron was lower in COL − (5.6 ± 2.7 μM/L) than COL + (10.7 ± 6.2 μM/L) (P = 0.03) on D7. Lymphocytes was lower in COL − than COL + on D7 (3.8 ± 1.0 × 103/μL COL + and 5.4 ± 2.2 × 103/μL COL −, P = 0.02). COL − calves had more anemia and lower serum iron concomitant with diarrhea on D7. The number of leukocytes was relatively consistent in the COL + calves, while COL − calves showed an increasing number of of lymphocytes starting on D7., Highlights • Calves fed with frozen colostrum (COL −) had high intensity of disease. • COL − had anemia and low serum iron. • COL − had higher number of lymphocytes (D7) due to natural exposure to pathogens.

O objetivo deste estudo foi a comparação das metodo-logias mais comuns empregadas em diferentes fazendas para a avaliação da qualidade do colostro e identificação de falha na transferência de imunidade passiva (FTIP) em bezerras Holandesas. Sessenta e oito bezerras Holandesas recém-nascidas foram distribuídas em dois grupos: G1 - provenientes de propriedade com manejo de colostro adequado; G2 - oriundas de propriedade com falhas no manejo do colostro. Foram colhidas amostras de colostro fornecido para cada bezerra de cada grupo (250 ml) para a avaliação de IgG, sólidos totais, PT e albumina. Amostras sanguíneas foram obtidas às 48 horas de vida para a determinação de PT e de globulina e para a estimativa indireta de IgG por meio dos testes de turvação pelo sulfato de zinco, precipitação pelo sulfito de sódio e coagulação do glutaraldeído. Os teores de IgG observados no colostro pelo colostrômetro (G1: 98,63 ±1 5,58 mg/ml; G2: 85,66 ± 29,81 mg/ml; p = 0,09), índice Brix (G1: 27,61 ± 2,96%; G2: 22,40 ± 4,58%; p = 0,00), PT (G1: 10,42 ± 2,29g/dL; G2: 9,04 ±2 ,29g/dL; p = 0,06) e albumina (G1: 1,25 ± 0,37g/dL; G2: 0,91 ± 0,38g/dL; p = 0,00) foram superiores no G1 quando comparados ao G2. A determinação de PT no soro das bezerras foi realizada por um analisador bioquímico automático, revelando taxas de FTIP (< 5,2 g/dL) somente no G2 (46,67%). Os resultados dos testes qualitativos (turvação pelo sulfato de zinco, precipitação pelo sulfito de sódio e coagulação do glutaraldeído) foram diferentes dos resultados de PT (p = 0,00) e não se mostraram eficientes para a detecção da FTIP. Esta pesquisa demonstrou que além do uso do colostrômetro para a avaliação da qualidade do colostro, a utilização do refratrômetro Brix e níveis de PT do colostro devem ser consideradas. A identificação de FTIP no rebanho pode ser realizada seguramente por meio dos níveis séricos de PT e globulina.

O tetano e uma doenca infecciosa grave e altamente fatal, causada pela toxina Clostridium tetani, uma bacteria Gram-positiva formadora de esporos anaerobicos. A doenca e caracterizada por rigidez muscular (tetania) e pode levar a morte por parada respiratoria ou convulsoes. O presente trabalho relata um caso de tetano em um potro Quarto de Milha de 6 dias de idade. O animal apresentava apatia, decubito lateral, espessamento umbilical, protrusao da terceira palpebra e convulsoes em resposta a estimulos externos, como som, luz e toque. Foi tratado com 110.000 IU / kg de penicilina potassica; com imunoglobulina anti-toxina tetânica homologa, numa dose de 25000 UI, 20.000 UI e 20000 UI por via intravenosa, intramuscular e intratecal, respectivamente; com cloridrato de acepromazina (0,05 mg / kg); fluidoterapia a base de Ringer com lactato e curativo no cordao umbilical. Decorridas 48 horas de tratamento, o animal demonstrou sintomas hiperagudos e veio a obito, mostrando insucesso no tratamento. Possivelmente, a infeccao foi causada pela limpeza inadequada do cordao umbilical.

RESUMO Esta pesquisa avaliou a TIP e a dinâmica de anticorpos (ACs) específicos em bezerros naturalmente expostos aos agentes causadores da doença respiratória bovina (DRB). Foram selecionados 19 bezerros Holandeses alimentados com colostro proveniente de doadoras vacinadas para DRB. Amostras de soro foram obtidas antes e após a ingestão do colostro (48h) para a soroneutralização (SN). Os valores médios (log2) detectados após colostragem foram de 11,5±1,6 (BVDV), 8,8±1,3 (BoHV-1), 5,5±1,6 (BRSV) e 8,4±1,5 (BPIV-3). Cinco bezerros foram criados do nascimento aos 240 dias de vida, observando-se decréscimo nos títulos de ACs para BVDV, BoHV-1 e BPIV-3 ao longo do tempo (P≤0,001). As taxas de infecções detectadas entre o D14 e o D240 foram de 40% (2/5), 20% (1/5), 80% (4/5), e 60% (3/5), respectivamente, para BVDV, BoHV-1, BRSV e BPIV-3. A maioria dos bezerros manifestou broncopneumonia após as infecções virais. Os bezerros apresentaram ACs para todas as viroses às 48 horas de vida, porém os títulos adquiridos para o BRSV foram baixos. A susceptibilidade para as infecções variou de acordo com os níveis e a duração dos títulos de ACs maternos. ABSTRACT This research evaluated the PIT and the dynamics of specific antibody (Ab) for calves naturally exposed to the viral agents involved in Bovine Respiratory Disease (BRD). Nineteen Holstein calves fed colostrum from vaccinated donors for DRB. Serum samples were obtained before and after colostrum intake (48h) for serum neutralization (SN). Mean values (log2) detected after colostrum feeding were 11.5±1.6 (BVDV), 8.8 ±1.3 (BoHV-1) 5.5±1.6 (BRSV) and 8.4±1.5 (BPIV-3). Five calves were raised from birth to 240 days of life and presented a decrease in Ab titers for BVDV, BoHV-1 and BPIV-3 over time (P≤ 0.001). Infection rates from D14 to D240 were of 40% (2/5), 20% (1/5), 80% (4/5) and 60% (3/5), respectively for BVDV, BoHV-1, BRSV and BPIV-3. Most of the calves presented bronchopneumonia after seroconversion to the virus. Calves presented Ab for all viruses at 48 hours of life, however BRSV Ab titer were low. Levels and persistence of maternal antibody titers determined the susceptibility to viral infections.

Changes in the composition of colostrum in the peripartum period focused on the neonate’s immunity can minimize the response of the mammary gland before natural exposure to mastitis pathogens. This research evaluated the oxidative activity of mononuclear and polymorphonuclear phagocytes of bovine colostrum. Bacteriologically negative (n = 171) bovine colostrum samples of first and second milking postpartum were evaluated. The oxidative activity was assessed by the production of hydrogen peroxide (H2O2) released either spontaneously or upon stimulation by enterotoxigenic Escherichia coli (ETEC). For this, three treatments were used: control (C) – only cells; non-opsonized (NO) - cells and ETEC non-opsonized; and opsonized (O) – cells and ETEC opsonized. Median values of concentrations (nmol/106) of H2O2 produced by cells obtained from the first and second milking treatments C, NO and O were 149.1 and 39.9 (P = 0.0007); 125.5 and 49.1 (P = 0.0007); 102.4 and 54.4 (P = 0.008), respectively. No differences were observed between the treatments at each milking. The amount of H2O2 produced at first milking exceeded the values found thereafter. Furthermore, the presence of bacteria did not determine the increased amount of H2O2 released by phagocytes. Thus, we concluded that the mammary gland’s events during the peripartum period have an effect on the proportion and activity of phagocytes, which can cause injuries to the breast parenchyma by the large amount of free radicals produced. The high frequency of bovine mastitis during this period indicates the need for studies of the immunity of the mammary gland and research of susceptibility factors for bacterial infections.

Consumers increasingly demand natural food and absent of toxic waste and medicated. The aim of this study was to evaluate the aqueous extract of dried and in natura stem from pomegranate on the larval inhibition of Haemonchus spp. and Cooperia spp. obtained from cattle. Dried and in natura aqueous extract from pomegranate stem (AEPS), negative control (autoclaved distilled water) and positive control (levamisole hydrochloride 0.05 mg / mL) were evaluated. Four mL of each treatment were used, and the results were evaluated in triplicate by egg counts per gram of feces (EPG), faecal culture and counting of the larvae. The mean of the larvae that developed per gram of feces was submitted to logarithimic transformation log. (X + 10). The EPG had an average value of 3.620 eggs, identified in faecal cultures of larvae from Haemonchus spp. and Cooperia spp. Dried AEPS presented, by the reduction of larvae, effectiveness of 92.29% for Haemonchus spp. and 96.97% for Cooperia spp. In natura, this extract showed 80% of efficacy against Cooperia larvae, being considered moderately effective; however, for Haemonchus spp. this extract was not effective. These results are specially important for organic and agroecological systems of production, that not allow the use of chemical parasiticides. In conclusion, the use of dried AEPS showed potential anthelmintic and may represent important natural therapeutic option.

Background: Newborn calves are agammaglobulinemic, immunosuppressed and immunologically immature at birth. The passive immune transfer is fundamental to protect calves against pathogens. The decay of maternal antibodies precedes the immune maturation at puberty enhancing the susceptibility of calves to infections caused by BVDV. Then, the objective of this research was to evaluate the interface between passive and active immunity for Bovine Viral Diarrhea Virus (BVDV) in Holstein dairy heifers in the first 13 months of age to detect susceptibility periods and establish prophylactic measures on prevention of Bovine Viral Diarrhea.Materials, Methods & Results: Sera were analyzed from 585 heifers by serum neutralization (SN) and enzyme linked immunosorbent assay (ELISA) for the p80 protein of BVDV. Heifers were categorized according to their age by the month of life. Heifers were seropositive (100%) from 1st to 13th. Median of neutralizing antibodies (Ab) titers obtained from 1st up to 13th month were 316.2; 125.9; 63.1; 50.1; 50.1; 39.8; 63.1; 63.1; 39.8; 79.4, 100.0; 74.4; and 79.4, respectively. The neutralizing Ab titers obtained in 1st month were different of the values observed from 2nd until 13th (P < 0.001), furthermore the Ab titers from 2nd month was statistical different of 4th (P = 0.01) and 6th (P = 0.05). The frequencies (%) of positive heifers for p80 from 1st up to 13th were 24.7; 18.2; 10.4; 11.8; 73.3; 73.8; 72.4; 58.1; 45.9; 48.4; 46.2; 43.8 and 61.5, respectively. The correlation observed for neutralizing Ab titers and age was negative and weak (ρ= -0.299; P < 0.001). On the other hand, the correlation between positive heifers for p80 and age was positive and moderate (ρ= 0.319; P < 0.001).Discussion: The newborn calves had higher titers of neutralizing antibodies than other age groups and some calves were seropositive for the p80 protein. This profile points to the transfer of maternal antibodies produced by vaccination and/or natural exposure to BVDV. The exposure of the cows to the inactivated and live virus stimulates the production of neutralizing antibodies to the structural proteins of the virus, particularly the glycoprotein E2, detected by the serum neutralization test. The titers of serum neutralizing antibodies and the frequencies of seropositive for p80 protein decreased gradually from the first to the 4-6th month of life due to the metabolization of maternal immunoglobulins acquired by ingestion of colostrum. Frequencies of seropositive animals for protein p80 increased from the fifth month of life, which is the same moment that was observed declined of neutralizing maternal antibody titers. The phase of higher frequency of p80 positive animals coincides with greater rates of Babesiosis and Anaplasmosis. This history could justify the importance of the BVDV immunodepression as a risk factor for concomitant diseases. In general, the neutralizing antibody titers increased after the peaks of positive reactions to the p80 protein, but this moment coincides with the primo-vaccination in calves. Therefore, it is not possible to state the origin of these antibodies. Correlations between ages and serologic tests are consistent with previous data reporting the decrease in antibody titers and increase of seropositive animals for p80 protein, from the first month of life to puberty. In conclusion, maternal neutralizing Ab titers had gradual decreased whereas the frequency of positive heifers for p80 had increased values. The inversion observed between the maternal antibody titers and the increase in antibody for p80 indicates the moment of greatest risk for natural infections caused by BVDV.

O objetivo geral desta pesquisa foi avaliar a transferência de imunidade passiva e a sua influência na resposta vacinal para as viroses envolvidas na Doença Respiratória Bovina (DRB). Os dados obtidos nesta pesquisa estão apresentados em dois capítulos. Capítulo 1 - Objetivou-se avaliar a dinâmica de anticorpos (Acs) específicos para as viroses respiratórias e subpopulações de linfócitos em bezerros do nascimento aos 240 dias (d) de vida. Para tanto, acompanhou-se a transferência de imunidade passiva de Acs específicos para as viroses respiratórias em 19 bezerros, destes cinco foram selecionados para acompanhamento da dinâmica de Acs neutralizantes e subpopulações de linfócitos dos 14 aos 240d. O colostro fornecido era proveniente de vacas doadoras vacinadas. A análise da qualidade individual do colostro revelou índice Brix ≥21%, observando-se forte correlação desses valores com proteína total (r= 0,942 e P= 0,001). Após 48 horas da ingestão do colostro, pôde-se observar soroconversão dos 19 animais (100%) para os agentes virais envolvidos na DBR. As medianas (Log2) encontradas foram de 12,3, 9,0, 5,0 e 8,5 para BVDV, BoHV-1, BRSV e BPIV-3. Dos 14 aos 240d os 5 bezerros avaliados, demonstraram declínio gradual dos títulos de Acs (Log2) para BVDV (12,8-3,3), BoHV-1 (10,0-3,3) e BPIV-3 (10,0-2,0), embora o BVDV não tenha apresentado soronegatividade até os 240d. Manifestações clínicas de broncopneumonia foram observadas em 4/5 (80%) bezerros dos 80 aos 135 d. BRSV (11,3-2,0) apresentou perfil diferenciado na dinâmica de anticorpos em relação às demais viroses. Não foram detectadas diferenças estatísticas entre os momentos para as viroses apesar das variações detectadas (P>0,05). A meia-vida e tempo para soronegatividade foram de 36,2±6,1 e 367,01±68,7d para BVDV, 50,7±18,0 e 239,67±66,88d para BoHV-1 e, 46,8±21,1 e 303,36±60,15d para BPIV- 3. BRSV não respeitou modelo de regressão para cálculos de meia-vida e soronegatividade. Valores absolutos e relativos das populações de linfócitos não revelaram diferenças estatísticas entre os momentos (P>0,05). Contudo, a dinâmica das subpopulações de linfócitos revelou aumento de células B CD21+ até 150d; aumento nos valores relativos das subpopulações CD4+, CD8+ e CD3+CD4-CD8- principalmente aos 74-90d. Assim, pôde-se determinar uma janela de susceptibilidade a partir dos 74d especialmente ao BRSV e BoHV-1, momento que precede o aumento dos títulos de Acs após exposição natural. Capítulo 2 Objetivou-se avaliar a influência dos Acs maternos na resposta imune para DRB induzida pela vacinação. Foram selecionados 23 bezerros recém-nascidos, distribuídos aleatoriamente entre 4 grupos experimentais: G1 vacinado aos 14d e booster aos 44d; G2 aos 90d e aos 120d; G3 aos 180d e aos 210d. Além disso manteve-se um grupo controle não vacinado CG1, CG2 e CG3. Os bezerros foram vacinados com a mesma vacina comercial empregada para vacinação das doadoras de colostro. Observou-se: (1) a vacina com BVDV inativado não promoveu aumento dos títulos de Acs para nenhum dos grupos avaliados; (2) G1 não demonstrou soroconversão para nenhuma das viroses, enquanto controle CG1 exibiu decréscimo dos títulos para BVDV, BoHV-1 e BPIV-3; (3) o BRSV apresentou baixa soroconversão no G2, enquanto o controle demonstrou altos títulos dos 44-120d; (4) não foi possível distinguir entre quais tempos ocorreram diferenças entre títulos (P>0,0167); (5) linfócitos B (CD21+) aumentaram do T0-T2 para G1, diminuíram para G2, e aumentaram no G3; (6) linfócitos T CD3+ diminuíram ao longo do tempo para todos os grupos, exceto CG3; (7) apesar de oscilações, linfócitos T CD4+, CD8+ e WC1+ se mantiveram praticamente constantes até 240d, exibindo maiores proporções nos grupos vacinados; (8) a expressão do marcador CD25+foi mantida pelo grupo G1 até o T2, mas apresentou aumento no G2 e G3; (9) manifestações de broncopneumonias foram identificadas nos bezerros do grupo controle (4/5 - 80%) e podem ter exercido influência nas diferenças encontradas para as células entre os grupos. Em geral, a vacinação dos bezerros aos 90 (G2) e 180d (G3) manteve ou estimulou a produção de Acs para o BoHV-1, BRSV e BPIV-3, e a ativação das células T expressas pelo marcador CD25+ pode ter sido responsável pela proteção dos bezerros frente à DRB. Assim, com base nos resultados, concluiu-se que a intensidade da imunidade dos bezerros induzida pela vacinação aumentou de acordo com o desenvolvimento etário e diminuição dos títulos de Acs maternos. A conclusão geral desta dissertação aponta para a necessidade precoce de imunização dos bezerros, especialmente pela susceptibilidade observada para BRSV e BPIV-3 aos 74-90d de vida. Entretanto, esta pesquisa não encontrou resposta humoral induzida pela vacinação no grupo de bezerros vacinados aos 14 e 44 dias, apesar dos indícios de resposta imune celular. Assim, estudos futuros devem ser elaborados considerando estratégias para amplificar a resposta imune precoce dos bezerros para os agentes virais envolvidos na DRB The main purpose of this research was to evaluate the transfer of passive immunity and its influence on vaccine response to the viruses involved in bovine respiratory disease (BRD). The data obtained in this study are presented in two chapters. Chapter 1 - The objective was to evaluate the dynamics of specific antibodies to the respiratory viruses and lymphocyte subpopulations in the calves from birth to 240 days (d) of life. Thus, the transfer of passive immunity of specific antibodies to the respiratory viruses were assessed in 19 calves; from these, five were selected for monitoring the dynamic of neutralizing Abs and lymphocytes subpopulations from 14 to 240d. The colostrum was provided from donor vaccinated cows. The analysis of individual quality of the colostrum revealed Brix ≥21%, observing strong correlation of these values with total protein (r = 0.942 and P = 0.001). After 48 hours of colostrum intake, was observed seroconversion of the 19 animals (100%) for the viral agents involved in the DBR. The median (Log2) ratio found was 12.3, 9.0, 5.0 and 8.5 for BVDV, BoHV-1, BRSV and BPIV-3. The 5 calves followed from 14 to 240d showed gradual decline in antibody titers (Log2) to BVDV (12.8 to 3.3), BoHV-1 (10.0 to 3.3) and BPIV-3 (10, 0-2.0), although could not be detected seronegative calves for BVDV up to eight months of age. Clinical manifestations of bronchopneumonia were observed in 4/5 (80%) calves from 80 to 135 days of life. BRSV (11.3 to 2.0) showed a distinct profile in the dynamics of antibodies compared to other viruses. There were no statistical differences between times for viruses despite variations detected (P> 0.05). The half-life and time to become seronegative were 36.2±6.1 and 367.01±68.7d for BVDV, 50.7±18.0 and 239.67± 66.88d for BoHV-1 and, 46.8±21.1 and 303.36±60.15d for BPIV-3. BRSV did not respect regression model to perform half-life and seronegative calculations. Absolute and relative values of lymphocyte populations revealed no statistical differences between times (P> 0.05). However, the dynamics of lymphocyte subpopulations showed increase in B cells CD21+ up to 150d; increase in the relative values of CD4+, CD8+ and CD3+CD4-CD8- subpopulations, mainly to 74-90d. Thus, it was possible to determine a window of susceptibility since 74d especially for BRSV and BoHV-1, moment that precede the increase in antibody titers after natural exposure. Chapter 2 - The objective was to evaluate the influence of maternal antibodies in the immune response to respiratory viruses induced by vaccination. Was selected 23 newborn calves that were randomly distributed in four groups: G1 - vaccinated at 14d and booster at 44d; G2 - vaccinated at 90d and booster at 120d; G3 - vaccinated at 180d and booster at 210d. Furthermore were kept a non-vaccinated control group - CG1, CG2 and CG3. Calves were vaccinated with the same commercial vaccine in the colostrum donors. From these, could be observed: (1) the vaccine with inactivated BVDV did not promote increase of antibodies titers in any of the assessed groups; (2) G1 did not demonstrated seroconversion for any of the viruses while CG1 control exhibited decrease in the titers for BVDV, BoHV-1 and BPIV-3; (3) BRSV had low seroconversion in G2, while the control showed high titers from 44 to 120d; (4) where the differences between times occurred could not be distinguished (P