Effect of Supplementation with Two Combinations of Alternative to Antimicrobials by Stages on Cecal Fermentation in Rabbits

Antimicrobials inhibit cecal fermentation when preventing rabbit from infection. This study aimed to evaluate the effect of supplementation with two combinations of alternative to antimicrobial (combination I: 1 x 10(9) cfu/kg Bacillus subtilis + 2 g/kg fructooligosaccharide; combination II: 2 g/kg acidifier and 0.6 g/kg essential oil) by stages on rabbit's growth performance and cecal fermentation. Two hundred and forty 15-day-old male kits with similar body weight were distributed randomly to five groups, which were control (basal diet), ZnB (addition of 0.1 g/kg bacitracin zinc in basal diet), II (addition of combination II), I-II (addition of combination I during days 15-35, addition of combination II during days 36-77), and I-II-I (supplemented with combination I during days 15-35 and 57-77, supplemented with combination II during days 36-56). Each group had 6 replicates. One healthy rabbit from each replicate was slaughtered at day 35 and day 77. The results showed: (1) at day 35, the two combinations and bacitracin zinc all inhibited ileal Escherichia coli (P < 0.05), decreased cecal pH, and increased total volatile fatty acid concentration (P < 0.05). Combination. decreased duodenal crypt depth and increased duodenal villi height to crypt depth ratio (VCR) (P < 0.05); (2) at day 77, I-II-I group had more cecal total bacteria than control (P < 0.05). Mode I-II or I-II-I increased cecal Bacteroides-Prevotella (P < 0.05) compared with ZnB. Mode I-II-I shortened duodenal crypt depth and increased VCR compared with control or ZnB (P < 0.05); (3) after weaning, modes I-II-I and I-II had better or similar effect on decreasing diarrhoea and mortality rate compared with ZnB. In conclusion, both modes had better or similar effect on decreasing diarrhoea and mortality rate compared with inclusion of antimicrobial or combination II alone during the whole trial, and mode I-II-I showed better effect than mode I-II.