A suplementação de L-arginina na ração contribui para minimizar alterações na compactação da cromatina espermática de galos (Gallus gallus)

Abstract

Arginine is the main amino acid that constitutes the sperm protamine of cockerels. This protein complexes with sperm DNA allowing high compaction of sperm chromatin. Arginine supplementation has positive effects on semen quality in aged cocks. The objective of this work was to verify whether L-arginine supplementation in the feed contributed to improve or maintain sperm chromatin quality, since aging in roosters is usually accompanied by worsening chromatin quality. Four different lots of 52-week-old Ross strain breeders were used, from which six semen samples per lot were evaluated, totaling 24 samples. Another 24 samples, six per lot, were evaluated after six weeks of supplementation, when one lot was not supplemented (control) and the other three were supplemented with 1.15 kg (treatment 1), 2.17 kg (treatment 2) and 3,18 kg (treatment 3) of L-arginine/ton of ration. Computer image analysis of semen smears stained with toluidine blue pH 4.0 was used to evaluate spermatozoa. Chromatin was evaluated for heterogeneity of compaction by means of the coefficient of variation of pixel values, and for compaction intensity by means of percent decompaction relative to standard heads and by integrated optical density (IOD), which was used for the first time to identify sperm chromatin alterations. Sperm head morphology was also evaluated by means of area, length, and the zero, one, and two harmonics of the Fourier transform. Furthermore, Pearson correlation coefficients were calculated between morphological variables and those related to chromatin compaction. The IOD proved to be more efficient in identifying changes in sperm chromatin compaction than the percentual decompaction. In general, the compaction of the chromatin was positively influenced by the supplementation with L-arginine, being better in the supplementation with higher levels of this amino acid, what was corroborated with the smaller average of the variables referring to size of the spermatozoa heads of the animals that received feed with higher levels of L-arginine. Finally, arginine supplementation was able to maintain or even improve sperm chromatin quality during the experimental period, showing better results at 3,18 kg L-arginine/ton feed.