نوع مقاله : مقاله پژوهشی
عنوان مقاله English
نویسندگان English
Introduction: In recent years, the emphasis on improving growth traits and increasing body weight in broiler lines has led to a significant decline in reproductive performance in broiler breeder flocks (Blesbas et al., 2004). Reduced fertility has become a major challenge in broiler breeder management. Although roosters account for only 10% of the flock population, their role in fertility is estimated to be as high as 50% (Cerolini et al., 2006; Akhlaghi et al., 2014). Among the main factors contributing to declining fertility, age and nutrition are of particular importance. Fertility reduction is often attributed to obesity, lower semen quality, decreased libido, and reduced mating efficiency (Romero et al., 2008). Peak reproductive performance in male chickens and turkeys is observed between 30 and 40 weeks of age and gradually declines, nearly ceasing by 75 weeks (Noiraud and Brillard, 1999). Sperm count and fertilizing capacity increase from 24 weeks to a peak at 39 weeks, then decline by 72 weeks of age (Kelso et al., 1997). Enhancing the reproductive potential of aging broiler breeder males is therefore essential (Fouad et al., 2020). Serine, a traditionally non-essential amino acid, plays critical roles in protein synthesis and cellular signaling (Metcalf et al., 2008; Hunter, 2012). Choline is an essential nutrient with key metabolic functions, including as a membrane phospholipid component, in hepatic lipid metabolism, and as a precursor of acetylcholine (Dudley, 1929). Choline is a methyl donor involved in methionine synthesis and indirectly functions in protein synthesis. In addition, it constitutes about 39% of the phospholipids in the plasma membrane and plays a role in cell maintenance and repair by synthesizing very low-density lipoproteins and providing phosphatidylcholine (Del Vesco et al, 2013). Despite numerous studies on the effects of unsaturated fatty acids, antioxidants, and some amino acids on sperm quality, no comprehensive study has been conducted on the interaction effects of the amino acid L-serine and choline supplementation in the nutrition of older broiler breeder roosters. This study investigated the effects of the amino acid serine and choline supplementation on sperm quality of older broiler roosters.
Materials and Methods: This experiment was conducted using 36 Ross 308 broiler breeder roosters at 45 weeks of age. Birds were randomly assigned to six groups of six individuals each and housed under controlled environmental conditions in a standard poultry house. The study was designed as a factorial arrangement in a completely randomized design with three levels of L-serine and two levels of choline. Birds were adapted to semen collection through abdominal massage for two weeks before the experiment. Semen volume was measured using a graduated collection tube (Zamiri et al., 2010). Sperm concentration was determined using modified Blaise-Tweel extender with a pH of 7.4 and osmolality of 310 mOsm/kg (Amini et al., 2015). Forward progressive motility was assessed by diluting semen samples in NaCl (1:20), placing a drop on a slide, covering it with a coverslip, and examining under a light microscope at 400× magnification (Akhlaghi et al., 2014). Plasma membrane functionality and integrity were assessed using the hypo-osmotic swelling test, while sperm viability and morphological abnormalities were determined by eosin-nigrosine staining (Tapeh et al., 2017).
Results and Discussion: Results showed that sperm concentration was significantly affected by different levels of serine and choline (P ≤ 0.05). In the interaction of experimental groups, the highest sperm concentration was observed in the group receiving 0.3% serine and 470 mg choline, indicating a positive effect of these compounds on spermatogenesis and increased sperm production. The highest sperm concentration (4.08) occurred in the group containing 0.3% serine, while the control group had the lowest concentration (3.46). Consistent with this finding, Ansari et al. (2016) reported that oral supplementation of the non-essential amino acid aspartate in the diets of aging broiler breeder roosters significantly increased sperm concentration with rising intake levels. The combined effect of L-serine and choline supplementation also increased the percentage of progressive sperm motility during the trial weeks; this synergistic effect was significant in weeks 4, 5, 8, and 9 (P ≤ 0.05). The highest progressive motility (50.75%) was recorded in week 8, whereas the lowest value (35.00%) was observed in the control group. In agreement with these results, adding serine to rooster semen as a diluent has been shown to improve sperm quality and fertility (Chankitisakul et al., 2022). The interaction of serine and choline significantly enhanced total sperm motility from week 5 to week 9. The highest total motility (88.75%) was obtained in the group with 0.15% serine and 470 mg kg⁻¹ choline in weeks 8 and 9, whereas the control diet yielded the lowest motility (70.00%), showing a significant difference from the combined group (P ≤ 0.05). Analysis of sperm viability indicated that diets containing L-serine and choline had a significant effect on this trait (P ≤ 0.05). The best viability was observed in the group receiving 0.3% serine with 470 mg kg⁻¹ choline, reaching 88.75% in weeks 8 and 9, which was significantly higher than the group lacking serine and choline (P ≤ 0.05). The lowest sperm viability (68.25%) occurred in the control group. L-serine, through its antioxidant properties and the regulation of genes involved in glutathione synthesis, increases glutathione concentration and reduces oxidative reactions (Zhou et al., 2018; Sim et al., 2015).The combined use of serine and choline significantly improved sperm membrane integrity and health compared with the control, with this increase becoming significant from week 6 to week 9 (P ≤ 0.05). The highest membrane integrity (88.00%) was observed in week 9 with 0.3% serine, while the lowest value (68.75%) belonged to the group without serine and choline. Evaluation of sperm abnormalities revealed that dietary supplementation with serine significantly affected this parameter (P ≤ 0.05). Supplementation with L-serine at 0.15% and 0.3% reduced abnormal sperm percentages, with significant decreases observed in weeks 5 and 7. The lowest percentage of abnormal sperm (13.62%) occurred in the 0.3% serine group, which differed significantly from the diet lacking serine (P ≤ 0.05). The effect of choline supplementation and the combined effect of serine and choline on abnormal sperm percentage were not significant (P > 0.05). These results agree with the findings of Long and Conn (2012), who reported that adding choline phosphate to duck semen extenders reduced acrosome head abnormalities.
Conclusion: The results of this study demonstrated that dietary supplementation with L‑serine and choline significantly increased sperm concentration, sperm membrane integrity, total sperm motility, sperm viability, and progressive sperm motility, while reducing the percentage of sperm abnormalities during most weeks of the experimental period, indicating a synergistic effect of these two compounds on sperm quality in older broiler breeder roosters. Consequently, the combined supplementation of L‑serine and choline may contribute to improved fertility potential and reproductive efficiency of older broiler breeder roosters under commercial poultry production conditions.
کلیدواژهها English
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