Chito-oligosaccharides as an Alternative to Antimicrobials in Improving Performance, Digestibility and Microbial Ecology of the Gut in Weanling Pigs

A total of 126 crossbred weanling pigs (average body weight of $6.3{\pm}0.3$ kg) were used to investigate the effect of chito-oligosaccharide (COS) on growth performance, nutrient digestibility, pH of gastro-intestinal tract (GI), intestinal and fecal microflora of young piglets. Pigs were allocated to three dietary treatments based on body weight and gender in a single factorial arrangement. Treatments were control (No COS), T1 (0.2% COS during starter (6-13 kg) and 0.1% COS during grower (13-30 kg) phases, and T2 (0.4% COS during starter (6-13 kg) and 0.3% COS during grower (13-30 kg) phases, respectively. Each treatment had 3 replicates and 14 pigs were raised in each pen. COS is a low molecular weight water-soluble chitosan that can be obtained from chitin of the crab shell after deacetylation with concentrated sodium hydroxide at high temperature and then further decomposition by chitosanase enzyme in the presence of ascorbic acid. For the starter and grower periods, there were no significant differences (p>0.05) in average daily gain (ADG) and feed to gain ratio among treatments. However, during the overall period (6-30 kg), T2 showed better (p<0.05) feed to gain ratio than other treatments. A digestibility study was conducted at the end of grower phase which showed improvement (p<0.05) in DM and crude fat digestibility in T2 over the control. At 25 kg body weight, 6 pigs per treatment (2 per replicate) were sacrificed to determine the effect of diets on pH and microbial count at different sections of the GI tract. The pH of the cecal contents in pigs fed 0.1% COS was higher (p<0.05) than in the other treatments. Total anaerobic bacterial number increased from cecum to rectum in all treatments. The weekly total bacterial counts showed higher (p<0.05) in feces of pigs fed COS than that of untreated pigs at the $8^{th}$ week. The number of fecal E. coli in untreated pigs at $4^{th}$ wk was 7.35 log CFU/g compared to 6.71 and 6.54 log CFU/g in 0.1 and 0.3% COS-treated pigs, respectively. Similarly, at $8^{th}$ wk, fecal clostridium spp. were lower in pigs fed 0.3% COS (5.43 log CFU/g) than in untreated pigs (6.26 log CFU/g). In conclusion, these results indicated that chito-oligosaccharide could improve feed efficiency in young pigs and inhibited the growth of harmful bacteria.