Abstract
BACKGROUND: Heat stress negatively affects the physiology and reproductive functions of rabbits. In order to mitigate these effects, palm date seeds were fermented with Bacillus (B.) subtilis and/or Saccharomyces (S.) cerevisiae to generate microbial-derived active metabolites, postbiotics, which were subsequently characterized using GC-MS. Notably, the postbiotic generated by the combined microbial fermentation (BYP) exhibited the highest concentration of secondary active metabolites. This postbiotic was then incorporated into rabbit diets in either free (BYP) or nano-encapsulated (NBYP) formulations. METHODS: Forty-five nulliparous rabbit does were randomly assigned to one of three groups and received dietary supplementation with either 0.9 g/kg BYP, 0.9 g/kg NBYP, or no supplementation (C) over 30 days spanning mating and the first and second semesters of pregnancy. RESULTS: Supplementation with BYP and NBYP significantly increased feed intake compared to the C group, while concurrently reducing rectal temperatures and respiratory rates. Both treatments markedly enhanced hematological, immunological, and redox parameters, as well as progesterone levels during pregnancy. The NBYP demonstrated superior effects for most variables, particularly during pregnancy. Additionally, the kindling rate and litter size and litter weight at birth were significantly higher in the BYN and NBPY groups compared to the C group. CONCLUSIONS: The incorporation of NBYP is recommended as an innovative natural microbial-derived supplement to enhance the health status, heat tolerance, and reproductive efficiency of rabbit does maintained under natural thermal stress conditions.