Abstract:

The purpose of this study was to investigate the effects of lactic acid bacteria (LAB) on the growth performance, digestive function, and nutrient utilization of yellow-feathered chickens. A total of 480 male yellow-feathered broiler chickens with an initial body weight of (31.95±0.56)g were randomly divided into 3 groups, with 8 replicates per group and 20 chickens per replicate. The experiment lasted for 70 days, which was divided into an early phase (1-35 days) and a late phase (36-70 days). The broiler chickens in the control group (CON) were fed a basal diet, while the experimental groups (LAB1 and LAB2) were fed diets supplemented with 500 mg ·kg^－1 or 1 000 mg ·kg^－1 of LAB (with a live bacteria count of 1×10⁸ CFU ·g^－1), respectively. The results showed that broiler chickens in the LAB1 and LAB2 groups had higher gizzard and pancreas indices at 35 days of age, higher pancreas indices at 70 days of age, higher apparent metabolic rates of organic matter at 33-35 and 68-77 days of age and crude protein at 68-70 days of age, and lower serum urea nitrogen content at 35 days of age compared to those in CON group (P < 0.05). The broiler chickens in the LAB2 group exhibited significantly higher final body weight, average daily weight gain, average daily feed intake, and apparent metabolic rate of crude protein at 68-70 days of age than those of both the CON and LAB1 groups (P < 0.05).The LAB1 and LAB2 groups showed higher lipase activity in the pancreas at 35 days of age, higher amylase and lipase activities in the jejunal chyme at 35 days of age, higher trypsin, amylase, and lipase activities in the jejunal chyme at 70 days of age, and higher expression of Trypsin genes at 35 and 70 days as well as Amylase genes at 70 days in the pancreas compared to the CON group. The LAB1 group had higher trypsin activity in the jejunal chyme at 35 days of age than the CON and LAB2 groups, and the LAB2 group had higher trypsin activity at 70 days of age in the pancreas and higher amylase and trypsin activities in the jejunal chyme at 70 days of age compared to the CON and LAB1 groups (P < 0.05). In conclusion, dietary supplementation with LAB upregulated the expression of digestive enzyme genes, increased the activity of digestive enzymes in the pancreas and jejunal chyme, reduced serum urea nitrogen content, improved the apparent metabolic rates of organic matter and crude protein, enhanced digestive organ development, and improved the growth performance in broiler chickens. The effects were more pronounced with the 1 000 mg ·kg^－1 LAB supplementation under the condition of the current experiment.

Key words: lactic acid bacteria, yellow-feathered broiler, growth performance, nutrient apparent metabolic rate, digestive enzyme activity