Abstract
Background:
Providing a balanced diet is essential to meet the nutritional requirements of animals for optimal health and production. Due to the high cost and limited availability of conventional protein sources, the efficient utilization of available protein resources is necessary. Essential amino acids such as lysine and methionine are key precursors of amino acids used in protein synthesis, growth performance, immune function, and overall metabolic activity in ruminants, resulting in significant nutritional value from increasing their bioavailability with rumen protection modalities.

Aim:
To examine the effects of protected amino acids on rumen metabolites and nutrient digestibility in Awassi lambs.

Methods:
The study was conducted at the Department of Animal Production, College of Agriculture, Tikrit University, Iraq, from September 12, 2023, to January 11, 2024. Twelve Awassi lambs with an average weight of 21.79± 0.470 kg and age between 5 and 7 months age was used in this study. The lambs were randomly divided into three treatment groups of (4 animals per group).

Results:
Protected amino acids have a significant effect (p≤0.05) on rumen metabolites. The use of protected amino acids contributed to the reduction of rumen pH after feeding. However, there were no significant differences in NH3-N concentration. However, NH3-N concentration increment was slight. Similarly, protected amino acids had no significant impact (p > 0.05) on the total rumen bacteria count. However, there was a non-significant difference (p > 0.05) in the total number of rumen protozoa. The protected amino acids had a significant effect (p ≤ 0.05) on the digestion coefficient of crude proteins.

Conclusion:
Protected amino acids contributed to enhancing the rumen environment and crude protein coefficient digestion.

Key words: Growing lambs; Lysine; Methionine; Rumen Fluid.