Stimulation of development of rabbit offspring by probiotic bacteria of the mother’s soft faeces

Abstract

The study of mother‐offspring interactions at various stages of ontogeny is important for understanding physiological characteristics, both species- and individual-specific, and the formation of adult behavior [1]. These processes during the lactation period have been studied well in rodents and lagomorphs. The prepubertal period is less investigated. In lactating female Rattus norvegicus and Acomys cahirinus (rats and spiny mice, respectively), a maternal pheromone is synthesized in the caecum and released in faeces to serve as an attractant for the young [2‐4]. The pheromone appears in females when the purely milk diet of their young is replaced by mixed food; the pheromone synthesis ceases by the moment of weaning. Eating the mother’s excrements containing the pheromone is assumed to prevent necrotic enterocolitis in the young [5]. The active pheromone fraction includes deoxycholic acid formed via cholic acid dehydroxylation and deconjugation by the intestinal bacteria Lactobacillus spp. and Bifidobacterium spp. The presence of the mother stimulates the development of weanlings [6, 7]. When kept together with the mother until the age of three months, young dwarf rabbits gain weight more rapidly than control young rabbits (in the absence of the mother) [8]. However, the mechanisms of the mother’s influence on the offspring growth remain unclear. We assumed that the mother’s soft faeces containing useful microsymbionts that are transferred to the offspring’s gastrointestinal tract have a stimulating effect. Adult rabbits eat their own soft faeces containing intestinal bacterial biomass, proteins, and organic acids [9‐11]. Deprivation of coprophagy has proved to have a negative effect on their physiological state [12]. We studied the maternal influence on the growth and development of prepubertal rabbits, including the possibility that bacteria of the mother’s soft faeces are transferred to the offspring’s body. Symbiont microorganisms were isolated from soft faeces of the lactating female rabbits, and their influence on the growth of young rabbits was studied. Dwarf colored rabbits were used in our experiments. Young rabbits were kept in standard cages (50 × 50 × 40 cm 3 ), three individuals matched for the body weight per cage. They received the standard diet. The following food composition was used: hay (mostly cereal), fodder grain (oats), flakes (rolled oats), vegetables (carrots, cabbage, apples, etc.), bread, and mineral additives (calcium phosphate and sodium chloride). Two groups of two-month-old rabbits were observed continuously for 24 h. A ceramic plate with fresh soft faeces of a lactating female (5 g) was placed before the experiment into each cage. All contacts of the young rabbits with the soft faeces were recorded during the observation. A pure culture of enterococcus was obtained from freshly collected soft faeces of a lactating female. The morphological, cultural, physiological, and biochemical characteristics of the microorganism were studied by the standard methods of general bacteriology [13]. Phylogenetic analysis based on sequencing 16S rRNA was used to identify the microorganism. The probiotic properties of the strain were assessed by estimating its ability to grow in the presence of 4% NaCl, 40% bile, alkaline pH, and 40% trypsin. The influence of the isolated microorganism added to the diet on the rabbit growth and development was studied using an original technique. Two-day-old bacterial culture in 0.5% milk was sprayed over the surface of Hercules oat flakes (GOST 21149‐93; 100‐200 ml of the culture per 1000 g of flakes), and the mixture was carefully dried. The cells remained viable for 15 days; therefore, a fresh preparation was obtained every two weeks. The resultant “bioflakes” was added to the diet of the young rabbits. The experimental group ( n = 6) included young rabbits under one month of age and their mother; afterwards, the same young rabbits were