Der thyreoidale Status von Ziegenlämmern und deren Müttern in der peripartalen Periode
Abstract
In order to examine the data so far obtained only from sheep and cattle on the peripartal and perinatal hormone balance of the thyroid gland in goats and, for the first time, to explain the thyroidal adaptation processes in the neonatal, caprine organism, a survey conducted on the thyroid gland hormone profiles of T4, T3 and their free fractions (FT4, FT3) using chemiluminescence assay on newborn kids during the first four weeks of life and on their mothers six days ante partum up to four weeks post partum. In addition, the thyroidal quotients (T3/T4, T3/FT3, T4/FT4 and FT3/FT4 ratios) were calculated and the vital parameters recorded: heart and respiratory rates, rectal temperature, vertex-breech length and progressive weight development. During the kidding season in 1998, 28 mother goats of the breed WDE (White German goats) (n=15), Buren goats (n=7) and Toggenburg goats (N06) as well as all their 46 kids (WDEs n=26; Buren goats n=9; Toggenburg goats n=11) were included in the study. In the group of WDE kids, severe diarrhoea caused by clostridium perfringens type B occurred from the 5th day of life resulting in the death of all the kids affected (n=7) without exception. Serum samples to determine the thyroidal hormone concentrations were also obtained from this group until their death and the vital parameters documented. The evaluation of the parameters measured and calculated showed that healthy kids undergo post natum extreme stimulation of the thyroid gland compared with their mothers and, as a consequence, a hyperthyroid function condition. The profiles of the thyroid gland hormone conditions of the mother goats and their kids exhibit differences after the birth and in some cases run inversely to each other. The maternal thyroxin profiles are characterised by a significant antepartal reduction of the T4 and FT4 serum concentrations (p< 0.001) in a period of two days ante partum up until directly after birth and a subsequent stabilisation of the thyroidal function. In the group of mother goats different hormone concentrations specific to each breed were found both for T3 and FT3 and for T4 and FT4. In addition, it was evident that in all breed groups tremendous adaptation processes take place within the postnatal period of the kids in the sense of a mediumterm reduction in concentration. The neonatal adaptation could be divided into two different phases. The first adaptation phase directly post natum, which is characterised by a hyperthyroid function condition compared with the mothers, is followed by a second adaptation period up to the second week of life. This involves a general reduction in the peripherally circulating concentrations of all thyroidal hormone fractions. In a comparison of the thyroidal secretion rates of clinically healthy WDE kids and those suffering from diarrhoea, significantly lower serum concentrations of all thyroidal hormone fractions were determined in the group of sick kids even before the clinical outbreak of the illness up to the end of the study period. Moreover, the mothers of the affected kids already exhibited ante partal a trend towards lower thyroid gland hormone concentrations than the mothers of the clinically healthy kids. These differences could not, however, be substantiated statistically. The bidirectional relationship between the hypothalamus, hypophysis and thyroidal axis and the immune system is evaluated against this backdrop. Possible factors influencing both systems such as birth conditions and alimentary iodine ingestion are discussed. With these findings thyroidal basic values of caprine neonates and mother goats in the peripartal period are available for the first time and they also provide an insight into the pathophysiology of the thyroid gland system. However, in order to obtain more indepth knowledge of the relationship between the thyroid gland function and illnesses of newborn animals, it is imperative to conduct further studies which examine the complex interaction between the mediators and the cellular and humoral components of the immune system and the hypothalamus, hypophysis and thyroidal axis.
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