Safety and efficacy of probiotic lactobacilli in promoting growth in post-weaning Swiss mice Marion Bernardeau a,b , Jean Paul Vernoux b , Micheline Gueguen b, * a Sorbial SAS, ZI Sud, Bd Lefaucheux, 72024 Le Mans Cedex, France b Laboratoire de Microbiologie Alimentaire, SC INRA, Universite ´ de Caen Basse-Normandie, Esplanade de la Paix, 14032 Caen Cedex, France Received 24 July 2001; received in revised form 10 December 2001; accepted 18 January 2002 Abstract Lactobacillus rhamnosus MA27/6B and L. acidophilus MA27/6R are strains used in feed as probiotics. Their safety profiles and growth-stimulating properties were investigated via in vivo studies on young Swiss mice. After repeated administrations of different probiotic preparations in drinking water, safety parameters determined from liver, spleen and total weight remained unchanged. The growth-stimulating properties of viable or dead lactobacilli were studied after supplementation in drinking water. The feed intake (FI), water intake and body weight gain (WG) of the animals were compared to those of control mice. The lactobacilli supplementation of a sub-optimal diet made of barley allow recording of measurable growth performance of mice. It significantly increased WG compared to control groups ( P < 0.01), by + 28.9% and + 31.7% for L. rhamnosus MA27/ 6B and L. acidophilus MA27/6R, respectively. This WG was correlated with a decrease in the consumption index. The effect of the dose ingested was also investigated: 10 8 lactobacilli CFU/mouse/day produced greater WG than 10 2 , 10 4 or 10 6 CFU/ mouse/day. No significant differences in growth performance parameters were observed between mice fed with 10 8 cells of viable or nonviable preparations. The mouse assay described could be used as a preliminary criterion when screening candidate probiotics for growth performance properties. D 2002 Elsevier Science B.V. All rights reserved. Keywords: Probiotic; Lactobacillus; Growth promoter; Toxicity; Mouse; Feed 1. Introduction Diet, stress, antibiotics and modern husbandry prac- tices have been identified as factors capable of affect- ing animal health and animal growth performance. However, antibiotics have indirect adverse side effects with implications for human health. Probiotics are alternative products for replacing those chemical sub- stances. According to Fu ¨ller (1989), probiotics are ‘‘live microbial feed supplements which beneficially affect the host animal by improving its intestinal microbial balance’’ and they are expected to prevent digestive disorders and/or to increase performance in animal husbandry (Wren, 1987; Fox, 1988). Beneficial effects on the growth of rats (Hargrove and Alford, 1978, 1980; Wong et al., 1983) and piglets (Pollmann et al., 1980; Underdahl et al., 1982; Sarra et al., 1983; Toruero et al., 1990; Rodriguez, 1994; Anonymous, 1999) have been shown for some strains of lactic acid bacteria (LAB) administered orally during the first few days of life. 0168-1605/02/$ - see front matter D 2002 Elsevier Science B.V. All rights reserved. PII:S0168-1605(02)00059-4 * Corresponding author. Tel.: +33-231-565-621; fax: +33-231- 566-179. E-mail address: gueguen@ibba.unicaen.fr (M. Gueguen). www.elsevier.com/locate/ijfoodmicro International Journal of Food Microbiology 77 (2002) 19 – 27