L-arginine supplementation minimizes aging-induced changes in the sperm chromatin of roosters

Arginine is the main amino acid that constitutes the sperm protamine of roosters, named galline, which complexes with sperm DNA, allowing high compaction of its chromatin. Arginine supplementation has positive effects on semen quality in aged roosters, but this supplementation is not known to limit the progressive worsening of sperm chromatin compaction. This work aimed to verify whether L-arginine supplementation in the feed improve or maintain sperm chromatin quality since aging in roosters is usually accompanied by worsening chromatin quality. Four groups of 52-wk-old Ross AP95 lineage roosters were used, of which 6 semen samples per group were evaluated, totaling 24 samples. Another 24 samples, 6 per group, were evaluated after 6 wk of supplementation when one group was not supplemented (control) and the other 3 were supplemented with 1.15 kg (treatment 1), 2.17 kg (treatment 2), and 3.18 kg (treatment 3) of L-arginine/ton of feed. Computer image analysis of semen smears stained with toluidine blue pH 4.0 was used for sperm chromatin evaluation. Sperm chromatin was evaluated for compaction heterogeneity and compaction intensity by percentage decompaction relative to standard heads and by integrated optical density (IOD), which was used for the first time to identify sperm chromatin changes. Sperm head morphology was also evaluated by means of area and length. The IOD proved to be more efficient in identifying changes in rooster sperm chromatin compaction than the percentual decompaction. In general, chromatin compaction was positively influenced by the supplementation with L-arginine, being better in the supplementation with the highest levels tested. This was corroborated by the smaller average of the variables referring to the size of the spermatozoa heads of the animals that received feed with a higher content of L-arginine, since better compacted heads naturally tend to be smaller. Finally, arginine supplementation was able to limit or even improve sperm chromatin decompaction during the experimental period.