Effect of adding Lactobacillus plantarum or a formic acid containing-product to fermented liquid feed on gastrointestinal ecology and growth performance of piglets

A study was carried out to investigate whether adding a starter culture or a formic acid containing-product to fermented liquid feed of suboptimal microbial quality could improve the characteristics of the mixture and the gastrointestinal ecology and growth performance of piglets. Four experimental diets were prepared: Feed and water were mixed in the ratio 1:2.5 (w/w) in four closed tanks. Diet 1) Three times daily, 50% of the mixture stored in the tank was removed and then replaced with an equal amount of fresh feed and water, (FLF), positive control; Diet 2) Three times daily, 95% of the mixture stored in the tank was removed and then replaced with an equal amount of fresh feed and water. Escherichia coli K12 (1 × 106/g) was added every morning (COLI); Diet 3) as the COLI treatment and added Lactobacillus plantarum VTT E-78076 (1 × 106/g) every morning (+PLANTARUM); and Diet 4) as the COLI treatment and added 0.26 g AIV/KemiSile 2 plus/100 g mixture three times daily (+ACID). One hundred and sixty weaners were used. On day 14, one littermate from each pen was killed and the gastrointestinal tract removed. The remaining piglets were used to measure the effect of the experimental diets on growth performance during the first six weeks post-weaning. The +ACID diet had lower numbers of lactic acid bacteria and Enterobacteriaceae, higher numbers of yeasts, and lower concentration of lactic acid and acetic acid than the COLI and +PLANTARUM diets. Feeding the +PLANTARUM and the +ACID diets increased daily weight gain during the six weeks post-weaning (P ≤ 0.02) compared to feeding the COLI diet. The +ACID group showed the highest numerical daily feed intake in all periods. The gain/feed during the six weeks post-weaning tended to be lowest in the COLI group (P < 0.10). The counts of lactic acid bacteria able to grow at 20 °C were lowest in the stomach (P ≤ 0.003) and distal small intestine (P ≤ 0.06) of the +ACID group. The counts of yeasts able to grow at 37 °C in the stomach were highest in the +ACID (P ≤ 0.01) and FLF groups (P ≤ 0.09). The number of yeasts able to grow at 20 °C in the stomach and distal small intestine was highest in the FLF fed piglets, followed by the +ACID group. This study showed that addition of L. plantarum VTT E-78076 or AIV/KemiSile 2 plus to fermented liquid feed of suboptimal microbial quality improved growth performance without affecting the gastrointestinal ecology of piglets substantially.