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Transferência de imunidade passiva em equinos
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Resumo(s)
Na espécie equina a placenta é do tipo epiteliocorial, o que impossibilita a passagem de
anticorpos para o feto durante a gestação. A transferência de imunidade depende
integralmente da ingestão e absorção intestinal das imunoglobulinas (Ig) maternas
veiculadas pelo colostro, nas primeiras 24 horas de vida. As infecções neonatais devem-se,
principalmente, à falha na transferência passiva de imunidade (FTPI), que tem como
principais causas a lactação prematura, a produção de colostro de fraca qualidade ou em
reduzida quantidade e a incapacidade de ingestão de colostro ou falha/anomalia na
absorção intestinal de Ig.
O principal objectivo deste trabalho consistiu na avaliação de factores que influenciam a
transferência passiva de imunidade (TPI), através da determinação das concentrações de
IgG e Proteína Total (PT) no soro de éguas, no dos respectivos poldros e no colostro (antes
e após a sua ingestão). Foi determinada a densidade do colostro com o auxílio de um
colostrómetro, a concentração de PT pelo método de Bradford e o teor de IgG por
cromatografia por afinidade (High Performance Liquid Chromatography). Paralelamente, no
pós-parto foram avaliados os parâmetros vitais do poldro com vista à determinação da sua
categoria de risco, tendo-se verificado posteriormente a sua correlação positiva com o seu
nível sérico de IgG. Nas amostras de colostro recolhidas após ingestão, e considerando a
variável tempo decorrido desde o parto, verificou-se um decréscimo significativo do rácio
IgG:PT. Não se verificou a existência de correlação entre o nível sérico de IgG na égua e no
respectivo colostro, assim como entre o colostro e os níveis séricos nos poldros em que se
verificou prévia ingestão. Contudo, o nível sérico de IgG na égua parece influenciar
positivamente o respectivo nível sérico nos poldros que ingeriram colostro. Foram
encontrados níveis séricos de IgG mais elevados em poldros que ingeriram colostro
relativamente aos que não ingeriram, o que confirma o importante papel do colostro na TPI.
Com a realização do presente trabalho, concluiu-se que os níveis de PT no poldro podem
ser falíveis para a avaliação da TPI.
ABSTRACT - In the equine species the placenta is epitheliochorial, which does not allow the transfer of antibodies to the fetus during the pregnancy. Therefore, the transfer of immunity from the mare to the foal entirely depends on the ingestion and intestinal absorption of maternal immunoglobulins (Ig) from the colostrum in the first 24 hours of life. The neonatal infections are mainly due to the failure of passive transfer of immunity (FTPI) that has as main causes premature lactation, production of low quality colostrum or in reduced quantity and incapacity to suckle or failure to absorb the Ig. The main aim of this work consisted of the evaluation of factors that influence the transfer of passive immunity (TPI) through the determination of IgG and Total Protein in mares’ serum, their respective foals’ serum and colostrum (pre and post suckling). The determination of the colostrum density by a colostrometer, total protein content with the Bradford Protein Assay and the content of IgG by High Performance Liquid Chromatography were performed. Evaluation of the vital parameters of the foal in the post-partum period was carried out, as well as the determination of their risk category and it has been observed a relationship between the risk category and the IgG level in the foals’ serum. In the colostrum samples collected after suckling and considering the time elapsed since parturition, it was observed a significant decrease of the IgG:PT ratio. A correlation between mare’s serum IgG and colostrum could not be reached, as well as between the colostrum and the foals after suckling. However, mare’s serum IgG seem to positively influence the foals’ serum IgG level in the foals that had suckled. It could be observed an increased serum IgG levels in foals that had suckled comparing with the ones that did not, fact that confirms the important role of colostrum in TPI. With the completion of this work, a conclusion was reached that total protein levels in the foal can be considered an unreliable parameter to evaluate the TPI.
ABSTRACT - In the equine species the placenta is epitheliochorial, which does not allow the transfer of antibodies to the fetus during the pregnancy. Therefore, the transfer of immunity from the mare to the foal entirely depends on the ingestion and intestinal absorption of maternal immunoglobulins (Ig) from the colostrum in the first 24 hours of life. The neonatal infections are mainly due to the failure of passive transfer of immunity (FTPI) that has as main causes premature lactation, production of low quality colostrum or in reduced quantity and incapacity to suckle or failure to absorb the Ig. The main aim of this work consisted of the evaluation of factors that influence the transfer of passive immunity (TPI) through the determination of IgG and Total Protein in mares’ serum, their respective foals’ serum and colostrum (pre and post suckling). The determination of the colostrum density by a colostrometer, total protein content with the Bradford Protein Assay and the content of IgG by High Performance Liquid Chromatography were performed. Evaluation of the vital parameters of the foal in the post-partum period was carried out, as well as the determination of their risk category and it has been observed a relationship between the risk category and the IgG level in the foals’ serum. In the colostrum samples collected after suckling and considering the time elapsed since parturition, it was observed a significant decrease of the IgG:PT ratio. A correlation between mare’s serum IgG and colostrum could not be reached, as well as between the colostrum and the foals after suckling. However, mare’s serum IgG seem to positively influence the foals’ serum IgG level in the foals that had suckled. It could be observed an increased serum IgG levels in foals that had suckled comparing with the ones that did not, fact that confirms the important role of colostrum in TPI. With the completion of this work, a conclusion was reached that total protein levels in the foal can be considered an unreliable parameter to evaluate the TPI.
Descrição
Dissertação de Mestrado Integrado em Medicina Veterinária
Palavras-chave
colostro FTPI imunidade passiva imunoglobulinas neonato poldro colostrum foal immunoglobulins neonate passive immunity
Contexto Educativo
Citação
Alves, I.R. (2015). Transferência de imunidade passiva em equinos. Dissertação de mestrado. Universidade de Lisboa, Faculdade de Medicina Veterinária, Lisboa.
Editora
Universidade de Lisboa. Faculdade de Medicina Veterinária