Document Type : Research Articles
Authors
1
1Ph. D student in Poultry Nutrition, Department of Animal Science, Faculty of Animal Science and Food Technology, Agricultural Sciences and Natural Resources University of Khuzestan
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Assistant Professor of Khuzestan University of Agriculture and Natural Resources
3
Associate Professor, Department of Animal Science, Faculty of Animal science and Food Technology, Agricultural Sciences and Natural Resources University of Khuzestan, Mollasani, Iran
10.22067/ijasr.2025.94457.1260
Abstract
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 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). Moreover, significant changes occur in the sperm phospholipid composition, with phosphatidylcholine increasing while phosphatidylserine and phosphatidylserine decrease near the end of the reproductive cycle, affecting sperm function and fertility (Cerolini 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). Despite several studies investigating the effects of unsaturated fatty acids and antioxidants on sperm quality, little research has explored the combined effects of L-serine and choline supplementation in aged broiler breeder roosters. This study aimed to evaluate the impact of dietary L-serine and choline on semen quality and fertility performance in aged male broiler breeders.
Materials and Methods: This experiment was conducted on 36 aged Ross 308 broiler breeder roosters aged 45 to 50 weeks. 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: Statistical analysis showed that sperm concentration was significantly affected by L-serine and choline levels. L-serine supplementation increased sperm concentration considerably from week 3 to week 9 compared to the control group. Diets supplemented with L-serine and choline showed significantly higher forward progressive motility than the unsupplemented group. These results align with previous findings indicating that L-serine enhances sperm quality and fertility (Chankitisakul et al., 2022). Both L-serine and choline significantly increased total motility (P ≤ 0.05). Sperm viability was also improved considerably in the L-serine and choline-supplemented groups (P ≤ 0.05). Similar findings were reported by Tananurak et al. (2020), where serine enhanced frozen-thawed semen quality. The antioxidant role of L-serine contributes to increased glutathione levels and reduced oxidative stress by regulating glutathione synthesis gene expression (Zhou et al., 2018; Sim et al., 2015), reducing malondialdehyde, and increasing superoxide dismutase and catalase activities. These changes lead to increased glutathione peroxidase and enhanced spermatogenesis and fertility (Wang et al., 2016). Treatments containing 0.15% and 0.3% serine from the fourth week significantly improved sperm membrane integrity. Sperm membrane integrity is critical for avian sperm fertility due to the high surface-to-volume ratio of their elongated morphology (Steele et al., 1994). Furthermore, L-serine supplementation at both levels significantly reduced sperm abnormalities in weeks 5 and 7.
Conclusion: The results of this study demonstrated that supplementation with 0.3% L-serine and 1400 mg/kg choline significantly improved semen concentration, membrane integrity, total motility, progressive motility, sperm viability, and reduced morphological abnormalities in aged broiler breeder roosters. Additionally, the interaction between serine and choline had significant synergistic effects on most parameters. These findings suggest that dietary L-serine and choline supplementation could enhance fertility performance and productivity of aging male breeders in the poultry industry.
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