Impact of Dietary Lactobacillus plantarum Postbiotics on Performance of Layer Hens under Heat Stress Conditions

Abstract

It has been reported that probiotic bacteria may acquire and transfer antibiotic resistance genes between organisms. Subsequently, postbiotics, which are metabolites of probiotics, have been used as feed additives as a potential replacement for antibiotics and probiotics. For this purpose, this experiment was conducted to determine the performance of heat-stressed layers fed a diet containing the probiotic Lactobacillus plantarum RS5 or its products of fermentation. A total of 192 twenty-week-old pullets of an Isa White strain, were equally subdivided into six treatments of 32 birds individually caged. Half of the birds were reared under regular temperature conditions, while the other half was subjected to cyclic daily heat stress gradually reaching about 30°C. Layers were offered one of three different diets: 1) Control, or 2) Control + Lactobacillus plantarum RS5 probiotic, or 3) Control + Lactobacillus plantarum RS5 postbiotic products. The liquid probiotics (RS5 in MRS broth) and postbiotics (CFS in MRS broth) were mixed with 100 kg of the feed at a concentration of 200 ml and 300 ml of solution respectively. The birds were tested for performance parameters and visceral organ development and the feeding trial lasted for 5 months. The study demonstrated that heat stress negatively affected the birds feed intake especially during the first month (79.1g vs 84.2g for the control; p<0.05) resulting in a numerical decrease in egg production, however the birds quickly adapted to the elevated temperature. Furthermore, high cyclic temperature showed a negative impact (p<0.05) on the egg weight, percent shell weight, Haugh unit, shell thickness, and yolk color in addition to the birds’ weight and percentage spleen weight. Postbiotic supplementation in feed showed a faster effect on percentage egg production than probiotic supplementation. Hens with dietary postbiotic showed a higher (p<0.05) egg production percentage than the control and the probiotic feed group (94.8% vs 92.6% vs 93.1%, respectively). In addition, birds under probiotic or postbiotic diet showed a significantly higher (p<0.05) feed intake. Probiotic and postbiotic treatments had a positive impact (p<0.05) on egg weight, although probiotic had a more pronounced and gradual effect. The Haugh Unit was significantly higher (p<0.05) in probiotic group due to the increase in albumen weight percentage; however, the percentage of egg white weight was significantly lower in the postbiotic group (59.3% vs 59.7% for the control; p<0.05). Specific gravity, yolk weight percentage and shell thickness didn’t show differences among dietary groups. Nevertheless, probiotic showed a significantly lower percentage shell weight (p<0.05); and both probiotic and postbiotic groups showed a significantly lower yolk color (p<0.05). The different feed treatments did not have any effect on the bird’s visceral organ weight, except for the ileum that showed a significantly lower percentage weight (p<0.05) under postbiotic supplementation and a slight decrease in ileum weight under probiotic supplementation to feed. In conclusion, both probiotics and postbiotics could be used as a potential alternative antibiotic growth promoter and might alleviate the impact of heat stress in the poultry industry.