LACTITOL ENHANCES SHORT-CHAIN FATTY-ACID AND GAS-PRODUCTION BY SWINE CECAL MICROFLORA TO A GREATER EXTENT WHEN FERMENTING LOW RATHER THAN HIGH-FIBER DIETS

The study was conducted to determine if the response of swine cecal mi croflora to lactitol (beta-D galactopyranosyl-(1 --> 4)-D-sorbitol; 3 mmol/L) varies when fermenting low (LF) or high fiber (HF) predigested diets. The inoculum was collected from four sows fitted with cecal ca nnulas, pooled, buffered and dispensed in 27 vessels under anaerobic c onditions. The LF or HF predigested diets were used as substrate in tw o separate experiments. In each trial nine vessels were used as contro ls (C) without feed addition, nine received predigested feed (LF or HF ) and the remaining nine vessels received the same amount of feed with the supplementation of lactitol (LF + L or HF + L). Lactitol (L) sign ificantly lowered pH and the acetic to propionic acid ratio in the fir st 8 h of fermentation in both experiments (P < 0.05). At 4 and 8 h, t he addition of lactitol reduced ammonia by 100 and 84% in LF + L and b y 56 and 38% in HF + L (P < 0.05). In addition, LF + L and HF + L diet s gave higher short-chain fatty acid energy yields by 70 and 40% than LF and HF, respectively (P < 0.05). Two bacterial growth models (logis tic and Gompertz) were tested to fit gas production data. The Gompertz equation provided a better fit than the logistic model to gas product ion data for both LF and HF experiments. Lactitol reduced culture lag time in both experiments by approximately 50%, but it increased gas pr oduction rate and maximum gas production by approximately 60% only whe n the microflora was fermenting the LF predigested diet (P < 0.05). No difference in the duration of the exponential phase due to lactitol w as observed in either experiment. Our results indicate that lactitol m ay be an interesting additive to animal feeding. It controlled harmful fermentation processes and stimulated short-chain fatty acid producti on to a greater extent in low than in high fiber diets, suggesting an improved fermentation of low fiber feed carbohydrates and eventually a n increased availability of short-chain fatty acids for the host.