The Increase of Lactobacillus Species in the Gut Flora of Newborn Broiler Chicks and Ducks Is Associated with Weight Gain

BACKGROUND: A bacterial role in the obesity pandemic has been suspected based on the ingestion of probiotics that can modify the gut flora. The objective of our study was to determine if increased Lactobacillus sp. in the gut flora of newborn broiler chicks and ducks could result in weight gain increase. METHODOLOGY: Female broiler chicks (Gallus gallus domesticus) and ducks (Anas platyrhynchos domestica) were separated into one control and two experimental groups, and inoculated once or twice with 4×10(10) Lactobacillus spp. per animal in PBS, or with PBS alone. Fecal samples were collected before and at 24 hours, 2, 4, 8, 16 and 30 days after the inoculation. DNA was extracted from the stools, and qPCR assays were performed on a MX3000™ system for the detection and quantification of Lactobacillus sp., Bacteroidetes and Firmicutes, using a quantification plasmid. Animals were measured and sacrificed 60 days after the beginning of the experiment, and livers were collected and measured. PRINCIPAL FINDINGS: Chicks inoculated once and twice with Lactobacillus weighed 10.2% (p = 0.0162) and 13.5% (p = 0.0064) more than the control group animals, respectively. Similarly, ducks inoculated once and twice weighed 7.7% (p = 0.05) and 14% (p = 0.035) more than those in the control group, respectively. Liver mass was also significantly higher in inoculated animals compared to the control group. Inoculation with Lactobacillus sp. increased the DNA copies of Lactobacillus spp. and Firmicutes in the stools. Bacteroidetes remained stable, and only the second Lactobacillus sp. inoculation significantly decreased its population in chicks. The ratio of DNA copies of Firmicutes to those of Bacteroidetes increased to as much as 6,4 in chicks and 8,3 in ducks. CONCLUSIONS: Differences in the intestinal microbiota may precede weight increase, as we found that an increase of Lactobacillus sp. in newborn ducks and chicks preceded the development of weight gain.