Tannins are a diverse group of plant phenolic compounds. Condensed tannins (CTs) represent a major subgroup of tannins and were extracted from tilia (Tilia L.) flowers and black locust (Robinia pseudoacacia) leaves. These extracts were examined for their effects on the metabolic profile of chicken caeca. By using in vitro, a nuclear magnetic resonance (1H-NMR), which was combined with multivariate statistics, the current study was applied for the first time to investigate how three different CT compositions, procyanidins (PC) and/or prodelphinidins (PD) units influenced the metabolic end-products in caecal contents of chickens. In the presence of tannins, glutamate, leucine, lysine, pyroglutamate, phenylalanine, proline, and sarcosine were significantly decreased. CT extracts significantly influenced the fermentation, increasing the concentrations of some fatty acids such as acetate, butyrate, and propionate whereas. In contrast, lactate decreased between the treatments. This study identified the key structural features of CTs that contain either high molar proportions of PD or PC, which might be useful to improve the efficiency of feed utilization in chickens.

To investigate premium palm kernel cake (PKC) based diet’s effect on amino acid digestibility, this study conducted a feeding trial. Four groups of 150 day-old broiler chickens in every group were given four isocaloric diets using these formulation: Diet 1 - commercial feed for both starter and grower phase Diet 2 - broiler feed that contains 30% PKC for starter phase + commercial grower, Diet 3 - commercial starter + broiler feed that contains 45% PKC for grower phase (and Diet 4 - broiler feed that contains 30% PKC for starter phase + broiler feed that contains 45 % premium PKC for grower phase. During the experiment’s day 31, bird faeces’ samples were collected based on group diets in order to estimate the availability of amino acid as well as the digestibility of amino acids using balance experiment. Ultra-Performance Liquid Chromatography with photo-diode array detector was used to analyse amino acid. The findings showed no significant difference in digestibility of amino acids with p<0.05 in the feed broiler chickens’ comparison with commercial feed in terms of different levels of PKC based diet. This study shows that by including 30-45% premium PKC in poultry diet, it could contribute as protein source in broiler feed production with suitable supplementation of essential amino acid. Further studies are encouraged to combine the analysis of excreta, ileal digesta and growth performance in order to achieve more concrete findings.