Desempenho e parâmetros sanguíneos de bezerros leiteiros que receberam sucedâneo lácteo ou silagem de colostro / Performance and plasma metabolites of dairy calves fed a milk replacer or colostrum silage

O objetivo deste estudo foi avaliar o desempenho e os parâmetros sanguíneos de bezerros que consumiram colostro bovino fermentado sob condições anaeróbias. Após o nascimento, 18 bezerros da raça Holandês foram alojados em abrigos individuais e passaram a receber 4L da dieta líquida, sucedâneo lácteo ou silagem de colostro, divididos em duas refeições. O consumo de concentrado inicial e o escore fecal foram registrados diariamente, enquanto a pesagem e as colheitas de amostras de sangue para a determinação das concentrações plasmáticas de glicose, nitrogênio ureico, ácidos graxos livres, β-hidroxibutirato e proteínas totais séricas foram realizadas semanalmente. Os animais alimentados com silagem de colostro apresentaram menores consumo de concentrado, ganho de peso diário e peso vivo. Todos os parâmetros sanguíneos avaliados foram afetados pelos tratamentos, exceto a concentração plasmática de proteínas totais. O escore fecal foi afetado pelos tratamentos durante a segunda semana de vida, com animais alimentados com silagem de colostro apresentando fezes anormais e secas. O fornecimento de silagem de colostro como dieta líquida exclusiva não resultou em desempenho animal adequado, não sendo uma boa alternativa de substituto de leite.

The aim of this study was to evaluate the performance and plasma metabolites of calves fed colostrum fermented under anaerobic conditions as an exclusive liquid feed during the whole milk-feeding period. After birth, eighteen Holstein male calves were housed in individual hutches and fed four liters of liquid diet, milk replacer or colostrum silage, divided into two meals. The starter feed intake and fecal scores were recorded daily, and body weight and blood samples for the determination of plasma glucose, urea nitrogen, free fatty acids, β-hydroxybutyrate and serum total protein were taken weekly. Animals fed colostrum silage had lower intake of starter feed during the experimental period. Significant effects were also observed for average daily gain and body weight. All blood parameters measured were affected by the treatments, except the total protein plasma concentration. The fecal score was affected by treatments during the second week of life, with animals fed colostrum silage presenting abnormal and very dry feces. Feeding colostrum silage as exclusive liquid diet during the whole milk-feeding period resulted in inadequate animal performance, being considered a bad alternative as milk replacer.

Acute and chronic stress exert opposing effects on antibody responses associated with changes in stress hormone regulation of T-lymphocyte reactivity.

Here we show that stress exerts a differential effect on T-cell-dependent antibody production. IgG production is augmented after acute stress and impaired in a chronic situation. We found catecholamines and corticosterone levels were increased in acute situations although they were not modified after prolonged stress conditions. However, lymphocyte sensitivity to corticosterone and catecholamines was altered under stress conditions. These results point out the role of the adrenal's hormones as mediators of the differential effects of stress on the immune response providing the basis for a functional significance of stress hormone receptors on lymphocytes.

Subset-specific reductions in lung lymphocyte accumulation following intratracheal antigen challenge in endothelial selectin-deficient mice.

We previously demonstrated induction and expression of CD62E and CD62P in the lungs of mice primed and then challenged with intratracheal (i.t.) SRBC. The current study examined accumulation of endogenous lymphocytes in the lungs of endothelial E- and P-selectin-deficient (E(-)P(-)) mice after i.t. SRBC challenge. Compared with syngeneic wild-type (wt) mice, E(-)P(-) mice showed an 85-95% decrease in CD8(+) T cells and B cells in the lungs at both early and late time points. In contrast, CD4(+) T cell accumulation was reduced by approximately 60% early, but equivalent to wt levels later. Surprisingly, many gammadelta T cells were found in lungs and blood of E(-)P(-) mice but were undetectable in the lungs and blood of wt mice. Absolute numbers of peripheral blood CD4, CD8, and B lymphocytes in E(-)P(-) mice equaled or exceeded the levels in wt mice, particularly after challenge. Trafficking studies using alphabeta T lymphoblasts confirmed that the recruitment of circulating cells after challenge was markedly reduced in E(-)P(-) mice. Furthermore, Ag priming occurred normally in both the selectin-deficient and wt mice, because primed lymphocytes from both groups transferred Ag sensitivity into naive wt mice. Lung production of mRNA for six CC and two CXC chemokines after challenge was equivalent by RT-PCR analysis in wt and E(-)P(-) mice. Therefore, reduced lung accumulation of alphabeta T cells and B cells in E(-)P(-) mice did not result from reduced delivery of circulating lymphocytes to the lungs, unsuccessful Ag priming, or defective pulmonary chemokine production. Selectin-dependent lymphocyte recruitment into the lungs following i.t.-SRBC challenge is subset specific and time dependent.

Somatic hypermutation of an artificial test substrate within an Ig kappa transgene.

We have characterized a novel substrate for somatic hypermutation, confirming that non-Ig sequences can be targeted for mutation and demonstrating that this substrate allows for the rapid assay for mutations. An artificial sequence containing alternating EcoRV and PvuII sites (EPS) was inserted into the Vkappa167 transgene, which is known to be a target for mutation. To assay for somatic hypermutation, the EPS is amplified using flanking transgene primers, and the PCR product is subsequently digested with either EcoRV or PvuII. A mutation is seen as the appearance of a larger fragment, indicating a base change in a restriction enzyme site. The original transgene, Vkappa167/EPS, showed evidence of a low level of mutation in both splenic hybridomas and Peyer's patch-derived or immunized splenic B220+ cells with high peanut agglutinin levels. Two derivative lines of Vkappa167/EPS were made, Vkappa167/POX and Vkappa167/PEPS. While none of the Vkappa167/POX transgenic lines demonstrated mutation, the Vkappa167/PEPS transgene was highly mutated in B220+ splenic B cells with high peanut agglutinin levels at a frequency similar to that of endogenous Ig genes. An analysis of splenic RNA from the unimmunized transgenic mice indicated that the levels of stable message in splenic B cells could not be correlated with the mutation seen in GC B cells. The mutable Vkappa167/PEPS transgenic line is a unique tool to study somatic hypermutation in vivo.