ABSTRACT This experiment aimed to discover the effect of reducing dietary protein supplemented with lysine, methionine, and threonine on growth performance, volatile fatty acid profile, and intestinal villus height and crypt depth of broilers, as well as the microflora counts isolated from broiler chicken faeces. A total of 288-day-old broilers were allocated to eight treatments with six replicates consisting of 36 birds per treatment. The diets contained dietary protein from 21 to 18% in starter diet and 18 to 16% in finisher diet supplemented with L-lysine, DL-methionine, and L-threonine at the same ratio for all dietary treatments. Body weight and feed intake were determined, and feed conversion ratio was calculated. Blood, intestine, and digesta samples were collected at 21 and 42 days for further analysis. Dietary protein supplemented with amino acids improved growth performance, reduced pathogenic bacteria, and increased beneficial bacteria counts, small intestine villi height and crypt depth, and ileal-digesta volatile fatty acid concentrations of broiler chickens. However, reducing 2% of dietary protein supplemented with lysine, methionine, and threonine showed the best results, especially in growth performance, feed conversion ratio, microflora count, duodenal and jejunal villi height, and ileal-digesta volatile fatty acid concentrations, such as butyric and valeric acids. It is believed that by reducing the level of dietary protein in broiler diet while supplementing with synthetic amino acid may enhance the intestinal morphology, nutrient digestibility, and absorption in broiler chickens and will simultaneously result in better performance.

ABSTRACT An in vitro study was carried out to identify the effects of different inclusion levels of postbiotics from Lactobacillus plantarum RG14 on rumen fermentation profiles, gas production kinetics, and microbial population in rumen fluid collected from goats. Postbiotics were added at different levels (0, 0.3, 0.6, 0.9, and 1.2%) and incubated for 72 h with 200 mg dry matter (DM) of a substrate containing 60% Guinea grass and 40% commercial concentrate. The experiment was conducted in triplicate on different days with four replications per treatment. Rumen fermentation kinetics, pH, organic matter digestibility (OMD), volatile fatty acids (VFA), and microbial populations were investigated. Net gas production and gas production from the immediate soluble fraction (a) increased linearly, and the volume of gas produced from the insoluble fraction (b) and potential gas production (a + b) quadratically increased with the increasing levels of postbiotics. A significant linear increase in OMD was observed for increasing postbiotic levels. Total and individual molarity of ruminal VFA and acetic acid to propionic ratio were also significantly increased by postbiotic inclusion. Populations of total bacteria, cellulolytic bacteria ( Fibrobacter succinogenes , Ruminococcus albus , Ruminococcus flavefaciens ), and total protozoa were significantly increased in the postbiotic treatment. Postbiotics in the ruminal fluid in vitro enhance rumen fermentation and improve digestibility and VFA production without any adverse effects on pH.