الفهرس 
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Abstract
Subacute ruminal acidosis is one of the main metabolic diseases in the modern dairy industry since it lead to drastic reduction in the production capacity of the dairy cattle all over the world, which result from ingestion of large quantities of highly fermentable CHO and in adequate amount of fiber in cows in early –lactation and in cows in mid-lactation , due to their high feed intake and are particularly sensitive to sudden change in feed composition lead to eventually to production of large quantities of lactate resulting in low rumen pH and consequently the secondary signs associated with such problem including, laminitis, decrease body condition, liver abscesses, decrease milk production and decrease feed intake .The present study was conducted on a farm in Salhia area with Holstein dairy cattle and the investigated animals were a total of sixty-three dairy cows (twenty-one in each stage of lactation).
Accordingly, the main goals of this study are:
1- Determination the prevalence of SARA in early, mid and late lactation period where the percentage of SARA affected dairy cows was 25% depending on ruminal pH where we classified investigated animals into two groups (SARA affected dairy cows (≤5.5) and control dairy cows (>5.5) of total percent of investigated dairy cows and the percentage of SARA affected dairy cows in early and mid lactation periods was equal which was more than the percentage of SARA affected dairy cows in late lactation period.