Mortality in neonatal calves has mostly been attributed to infectious agents that generally result in diarrhea, dehydration, and death causing huge economic losses in livestock production. Colibacillosis or white scours is the most important disease of bovine calves. The most common enteropathogen which causes diarrhea in new born calves is the Escherichia coli. Given the range of ill- effects of Escherichia coli causing diarrhea in new born calves in Pakistan there is strong need for detection of strain involved.

In the present project the relatedness by electrophoretic profile of Escherichia coil isolates involved in white scour at a dairy farm were studied, to compare the isolates of Escherichia coli from different dairy farms. The 25 samples from clinically affected calves at farms were collected, for isolation of Escherichia coil these samples were streaked onto MacConkey Agar media plates and Escherichia coil were confirmed through biochemical (IMViC) and sugar fermentation tests. These confirmed Escherichia coli isolates were subjected to sodium dodecyl sulphate polyacrylarnide gel electrophoresis (SDS-PAGE) for electrophoretic protein profiling. The banding pattern various isolates as against known molecular weight markers were recorded for interpretation of results.

SDS-PAGE of whole cell protein extracts of E. coil strains produced patterns containing about 25 discrete bands with molecular weights of 16000 to 250000 Da. The whole cell protein patterns of E. coil isolates were fairly homogenous with some

Veraibility primarily localized in the low molecular weight region estimated molecular weight. 20000 to 60000 Da. The most common peptide bands were band no. 13, 14, 15.
16, 17 and 1 8. detected almost in all strains isolated. In order to estimate relationship among E coli isolates a genetic distance was constructed with similarity matrix using Bio-Rad (Quantity one) software. A complete linkage dandrogram was constructed by Dice coefficient analysis using Quantity One Software. The dandrogram divided the isolates into four clusters based on the whole cell protein profile. The first group contained isolates 2. 4. 6, 7, 3, 5, 13 and 8 that shared 52 percent similarity. The second cluster included isolate numbered 12, 18, 9, 16 and 17 at 60 % similarity. The third cluster included isolate numbered 19, 20 and 15 with 57 percent similar band pattern. The fourth cluster included isolates 10 and 14 that shared 59% similarity.

It was concluded that protein profile is one of the useful methods for determining the relatedness or unrelated ness of bacterial strains. As immunization has been often attempted in efforts to control the calves' diarrhea, the diversity of E. coil strains and difficulties in vaccine development instruct that use of one or likely several strains of E.coli that are antigenicallv representative of the majority of the causative strains in a herd or even in herds located in the same geographical region are recommended. Decision on representative strains can be made on basis of whole cell proteins, the isolates could be characterized by their total protein profiles and use of one or likely several strains of E. coli that arc antigenically representative of the majority of the causative strains will overcome vaccine development difficulties.