Bulletin USAMV serie……………………69(1-2)/2012 Print ISSN 1843-5262; Electronic ISSN 1843-536X Does the aridity of Algerian Steppe affect the Ewe’s raw milk quality? Benalia YABRIR*, Ahcène HAKEM (ex. AKAM)*, Abbes LAOUN*, Moussa LABIAD*, Nazek EL-GALLAS**, Attia HAMADI***, Abderrahmane MATI**** * Laboratoire d’Exploration et Valorisation des Ecosystèmes Steppiques, Université. Djelfa, B.P.3117, Djelfa 17000, Algérie; byabrir@yahoo.fr ** Lab. Contrôle des Eaux et Denrées Alimentaires, Institut Pasteur de Tunis, Tunis, Tunisie *** Lab. Analyses alimentaires, Ecole Nationale d’Ingénieur, Sfax, Tunisie *** Lab. Biochimie Analytique et Biotechnologies, Université M. Mammeri Tizi-Ouzou, Algérie Abstract. The microbiological and physico-chemical quality of milks varies from bioclimatic stage to another. The latest has significant effect on Total Bacterial Count (TBC), Total and Fecal Coliforms (TC and CT) and reduction time (P<0.001). The effect is highly significant for TBC, faecal Streptococci (P< 0.01) and significant only for Yeasts (P<0.05). No effect was observed for other microbiological variables. The variability of the chemical composition is significant for density and protein (P<0.05), highly for pH, Dornic acidity, freezing point and solids-non-fat (P<0.01). Lactose, fat and total solids are independent. The semi-arid zone contains milks with a high density, weak freezing point and less loaded on TBC, TC, FC and Moulds. They are rich in protein, fat and total solids. They differ from those other zones by the highest frequency of faecal Streptococci and absence of Staphylococcus aureus. The inferior-arid includes the poorest in protein, fat, total solids, solids- non-fat and lactose. It contains the most acidic milks (lowest pH and highest acidity), the less density milks and having the highest freezing point and it had the most loaded on TBC, TC, FC and Moulds. However, there are less milk loaded in Yeast and distinguished by the absence of faecal Streptococci and Brucella. The middle and superior arid reassemble milks with same characteristics and intermediate between the two stages. It seems that the milks which come from superior arid are richer in fat. These two zones are differentiated by the level of presence of E. coli, S. aureus and Brucella. The superior-arid combines milks with the highest count of Yeast and mostly contaminated with anaerobic sulfito-reducing. Keywords: raw milk, sheep steppe, bioclimatic stages, microbiological and physico-chemical and quality, Algeria INTRODUCTION In Algeria, the steppe covers over 20 million hectares and supports a sheep estimated at over 21 million heads (ONS, 2009). In the middle of central steppe, the province of Djelfa, extending over an area of 32.362 km 2 and contains four climatic stages: Semi-arid (SA), Superior-Arid (SsA), Midlle-Arid (MA) and Inferior-Arid (IA) (Claudin et al., 1979). Each stage is characterized by different vegetal formations (forest, steppe, cultures) and classes of rangelands (Pouget, 1977). In this area, the ruminant livestock were mostly represented by sheep. Its milk production is estimated at more than 32 million litters per year (DSA, 2010). This milk is generally used for breast lambs in the first place, then it is consumed by the farmers in the region as well as or transformed often on 'smen' (traditional butter) on ' l’ben' (fermented milk) or in ' djeben' (fresh cheese). Milk is undoubtedly the most widely consumed such as it is or processed. The raw milk quality interested all actors of the sector. From a microbiological point of view, the hygienic quality preoccupies the consumer that is becoming more demanding. Raw milk and