Clinic of 1 Obstetrics and A.I. and 5 Productive Animal Medicine, School of Veterinary Medicine, Aristotle University of Thessaloniki, Thessaloniki, Macedonia, Greece; 2 Laboratory of Prevention and Control of Livestock Diseases, School of Agriculture Animal Production and Hydatic Environment, University of Thessaly, Volos, Greece; 3 Clinic of Medicine, School of Veterinary Medicine, University of Thessaly, Karditsa, Greece and 4 Medical Microbiologist, Kazazi, Kalamaria, Greece Field evaluation of the efficacy of a probiotic containing Bacillus licheniformis and Bacillus subtilis spores, on the health status and performance of sows and their litters By C. Alexopoulos 1 , I. E. Georgoulakis 2 , A. Tzivara 3 , S. K. Kritas 3 , A. Siochu 4 and S. C. Kyriakis 5 Summary The aim of this study was to assess the efficacy of BioPlus 2B, a probiotic containing Bacillus licheniformis and Bacillus subtilis spores, on the health status and productivity of sows and their litters. A total of 109 gilts and sows were allocated into two experimental groups, as follows: untreated controls (UC) and BioPlus 2B (same feeding as the UC group plus BioPlus 2B) at a dose of 400 g/ton of feed (equal to 1.28 · 10 6 viable spores/g of feed). Treatment started from the day of allocation (14 days prior to the expected farrowing) up to the weaning day. Homogeneity of the groups was satisfied with regard to the parity. From the results it was evident that BioPlus 2B supplementation of the feed improved gilt/ sow performance as shown by: (i) the increase of sow feed consumption during the first 14 days postpartum and (ii) the decrease of sow weight loss during the suckling period. Certain blood and milk parameters were significantly improved, as shown by higher serum cholesterol and total lipids concentrations and higher milk fat and protein content at mid- suckling period. As a consequence, a positive effect was also noticed as regard litter health and performance characteristics in terms of: (i) decrease in piglet diarrhoea score, (ii) decrease in pre-weaning mortality thus leading to increase in the number of weaned piglets per litter and (iii) increase in piglet body weight at weaning. Moreover, BioPlus 2B tended to improve the health status and fertility of sows demonstrating: (i) tendency to a lower proportion of sows with Mastitis-Metritus-Agalactia (MMA) problems and (ii) lower proportion of sows returning to oestrus. Introduction Gastrointestinal microflora of the clinically healthy animal consists of hundreds of different types of micro-organisms, which are biologically important for optimum digestion (Walket and Duffy, 1998). The balance among populations of these micro- organisms in the intestinal tract promotes digestion and absorption of nutrients and increases the body resistance to infectious diseases (Tannock, 1988). The term probiotics has been used to describe live microbial feed supplements, which beneficially affect the host animal by improving its intestinal balance (Fuller, 1992; Tournout, 1994). Administration of probiotics to re-establish the ideal balance between beneficial and J. Anim. Physiol. a. Anim. Nutr. 88 (2004), 381–392 Ó 2004 Blackwell Verlag, Berlin ISSN 0931-2439 Receipt of Ms.: 17. 11. 2003 Accepted: 27. 01. 2004 U. S. Copyright Clearance Center Code Statement: 0931-2439/2004/8811–0381 $15.00/0 www.blackwell-synergy.com