The ultrasonographic appearance and size of the liver and kidneys of a litter of five pups was examined from birth until six months of age, and compared with a group of five adults of the same breed. Increased renal cortical echogenicity was evident for the first two weeks of life. Up to 12 weeks of age renal size was relatively large in comparison with body size parameters. After 12 weeks measures of renal size were proportionate with body size and were not significantly different from adult dogs. The neonatal liver had a similar ultrasonographic appearance to the adult, although in the first eight weeks parenchymal echogenic stippling was less coarse and portal veins were less well delineated. Measures of hepatic length were inaccurate during the first four weeks after birth due to changes in body conformation. From eight weeks to six months of age these measures were proportionate with body size, although the ratios differed from adult dogs.

29 per cent) classified as class A had seroprevalence rates of 54 per cent with a predominance of serovar hardjo, followed by bratislava. Serovar pomona was least important on these farms. Eleven farms were classified as class B, with 73 per cent of reactive cows, and four properties were considered as class C, and presented higher levels of reactivity (80 per cent).The relatively great importance of serovar hardjo on farms classified as class A is probably due to the role of cattle as host of this strain, that is, the more intensive the stocking rate, the easier transmission occurs (Ellis and others 1981).The rates observed in this study are very similar to those found in other studies carried out on clinically suspect animals (Carter and others 1982 [73 per cent], Ellis and others 1982 [63 per cent], Salas 1986 [76 per cent]). The most frequent serovar was hardjo, which agrees with the majority of the authors.Acknowledgements. -The authors would like to thank CNPq, Brazil and its research committee for support.