Competency of blood coagulation in the newborn calf

DINÂMICAS PRÉ E PÓS-COLOSTRAL DO ERITROLEUCOGRAMA, DA PROTEÍNA PLASMÁTICA TOTAL E DO FIBRINOGÊNIO DE CORDEIROS

Resumo O objetivo deste estudo foi caracterizar a dinâmica de alguns parâmetros hematológicos em cordeiros recém-nascidos sadios, antes e após a ingestão de colostro. Foram coletadas amostras sanguíneas de 28 cordeiros recém-nascidos, determinando-se o eritroleucograma, as concentrações de proteína plasmática total (PPT) e de fibrinogênio nos momentos pré e pós-colostro. Os dados foram analisados comparando-se a variabilidade dos parâmetros entre os dois momentos. O hematócrito (P<0,001), a concentração de hemoglobina (P<0,05) e o volume globular médio (VGM) (P<0,05) diminuíram após a ingestão de colostro, enquanto a concentração de hemoglobina globular média (CHGM) aumentou (P<0,01) no momento pós-colostro. Houve aumento no número de leucócitos totais (P<0,001) e nas contagens absolutas de neutrófilos segmentados (P<0,05) e de linfócitos (P<0,01) após a ingestão de colostro. As concentrações de PPT e de fibrinogênio também aumentaram no momento pós-colostro (P<0,001 e P<0,01, respectivamente). O eritroleucograma, as concentrações de PPT e de fibrinogênio variam consideravelmente antes e após a ingestão de colostro, sendo modificados em função da própria ingestão do colostro e/ou da adaptação dos processos fisiológicos do animal à vida extrauterina. Portanto, recomenda-se que a interpretação de hemogramas realizados em cordeiros recém-nascidos seja feita com base em intervalos de referência específicos para o período neonatal.

Coagulology, biochemical profile and muscle pathology in calves diagnosed with nutritional muscular dystrophy

The aim of this study was to explain the correlations between selenium deficiency, hemostatic and biochemical disorders, and the progression of pathological changes in calves diagnosed with nutritional muscular dystrophy (NMD). The study was performed on 20 calves with supplementation of 8 ml selenium and vitamin E preparation and 20 calves with symptoms of NMD. Blood was sampled from calves aged 5, 12 and 19 days. On day 19, samples of the biceps femoris muscle were collected from 6 animals in each group for histopathological analysis. The following blood parameters were determined: PLT, PT, TT, APTT, fibrinogen and D-dimer concentrations, antithrombin III activity, glucose, selenium and vitamin E concentrations, activity of CK, LDH and GSH-Px. Muscle sections were stained with H&E and HBFP. Platelet counts were significantly lower in calves with symptoms of NMD. No significant differences in coagulation parameters were observed between the groups. Sick calves were diagnosed with hyperglycemia and elevation of CK and LDH activity. Selenium and vitamin E concentrations in the blood serum were significantly lower in the experimental group together with significant drop in GSH-Px activity. Changes characteristic of Zenker's necrosis were observed in a muscle of the sick animals. To our best knowledge this is the first study in which the attempt was made to explain the relationship between selenium deficiency and changes in the coagulation system in ruminants.

Thromboelastometric assessment of hemostasis in newborn Piemontese calves

We investigated possible age-related differences in coagulation profiles in bovine species by means of rotational thromboelastometric (ROTEM) analysis. We evaluated hemostasis by ROTEM in newborn Piemontese calves at birth (T0), 8 d (T8), and 15 d (T15) of age and compared the ROTEM results obtained in 16 newborn calves with 28 adult Piemontese cattle. Hemostasis was evaluated using standard coagulation tests and ROTEM analysis, obtaining in-TEM, ex-TEM, and fib-TEM profiles. Statistically significant differences in the ROTEM profiles of newborn calves were found between T0 and T8 and between T0 and T15 ( p < 0.05) but not between T8 and T15. Differences between ROTEM profiles of calves and adults were statistically significant at T0 ( p < 0.05) but no differences were found at T15 ( p < 0.05). Hence, ROTEM reference intervals for adult cattle can be used to evaluate profiles in Piemontese calves ≥8 d of age.

A genetic predisposition for bovine neonatal pancytopenia is not due to mutations in coagulation factor XI

Bovine neonatal pancytopenia (BNP) is a newly emerging disease in many European countries that causes haemorrhagic diathesis and mortality in neonatal calves. This study tested the hypothesis that genetic factors might be involved in BNP, since genetic defects resulting in coagulation disorders have been described in many species, including cattle. A familial pattern of occurrence of BNP cases was observed in an experimental population of cattle in Germany and BNP was diagnosed in nine calves on an experimental dairy herd from May 2007 to December 2009. All affected calves were descendents of a single F(1) sire in a specific F(2) resource population generated from Charolais and German Holstein bloodlines. Sequence analysis of the bovine coagulation factor XI (F11) gene as a functional candidate gene for BNP revealed an unusually high number of non-synonymous mutations within the gene compared to a whole genome mutation screen in cattle targetting random sequences. However, none of the mutations in the F11 gene were concordant with BNP status. Although these data and further pedigree analysis excluded a simple mode of inheritance of the BNP phenotype, there was a statistically significant (P=0.0001) accumulation of BNP cases in the specific pedigree examined, suggesting that a genetic component is involved in the development of BNP.

Comparative aspects of blood coagulation

Blood coagulation is a basic physiological defense mechanism that occurs in all vertebrates to prevent blood loss following vascular injury. In all species the basic mechanism of clot formation is similar; when endothelium is damaged a complex sequence of enzymatic reactions occurs that is localized to the site of trauma and involves both activated cells and plasma proteins. The reaction sequence is initiated by the expression of tissue factor on the surface of activated cells and results in the generation of thrombin, the most important enzyme in blood clot formation. Thrombin converts soluble fibrinogen, via soluble fibrin monomers, into the insoluble fibrin that forms the matrix of a blood clot as well as exerting positive-feedback regulation that effectively promotes additional thrombin generation that facilitates the rapid development of a thrombus. Both spontaneous and trauma-induced haemorrhagic episodes can develop in all mammals with inherited or acquired abnormalities in one or more of the coagulant proteins. Experimental studies with plasma from a wide range of species have led to the conclusion that there are extensive differences in the rates of thrombin generation and fibrin formation among species. However, current evidence suggests that at least some of these quantitative differences are likely due to the use of non-species specific laboratory reagents. Although the individual proteins involved in the procoagulant pathways exhibit similar functions in all animals, differences in amino acid sequence cause incomplete homology and varying degrees of immunological cross-reactivity for the same protein across species.