Abstract
Background:
Gaok chicken spermatozoa that is diluted and stored at freezing temperatures will reduce spermatozoa motility. The specific target to be achieved by this research is to increase the population by improving the quality of frozen semen with the addition of green tea extract (GTE) to egg yolk–milk diluent. Epigallocatechin-3-gallate contained in GTE acts as an antioxidant in the cooling and freezing process of chicken semen.

Aim:
This study examined the addition of GTE to fructose egg yolk–milk diluent to improve chicken spermatozoa quality before and after freezing, with the goal of enhancing the efficacy of artificial insemination programs to increase the Gaok chicken population.

Methods:
This study consisted of four groups: T0, the control group: fructose egg yolk–milk diluent without GTE + semen; TI: fructose egg yolk–milk diluent + GTE dose 0.05 mg/100 ml diluent + semen; T2: fructose egg yolk–milk diluent + GTE dose 0.10 mg/100 ml diluent + semen; and T3: fructose egg yolk–milk diluent + extract green tea dose 0.15 mg/100 ml diluent + semen.

Results:
Analysis of variance (p < 0.05) showed no significant effects at T0, T1, and T3, indicating that T2, the treatment group supplemented with extract green tea (Camellia sinensis), produced the most notable results. This group is maintained better than another group on parameters sperm motility, viability, plasma membrane integrity, and minimized necrosis, alongside increased catalase enzyme and superoxide dismutase activity.

Conclusion:
The addition of green tea leaf extract reduced the malondialdehyde level. The addition of GTE at a dose of 0.10 mg/100 ml of egg yolk–milk diluent can act as an antioxidant in maintaining the quality of post-thawing Gaok chicken spermatozoa.

Key words: Antioxidant levels; Conservation; Freezing; Gao chicken; Semen quality