The present study was designed to investigate the effects of different levels of l-carnitine (LC) on sperm quality factor (SQF), alterations in testis fatty acid profiles, testicular histology and reproductive hormones in young roosters. Eighteen broiler breeders (Ross 308) weighed at 3 months of age. They were randomly classified while each group had six birds. There were three experimental groups based on the LC concentrations (i.e. LC-0, LC-250, LC-500 mg per kg of diet). After two weeks of adaptation, semen samples were collected and evaluated for seminal attributes every two weeks (from week 24 to week 34). At the end of the experiments, four roosters from each treatment group were sacrificed in order to analyze testicular histology, testis fatty acid profiles and reproductive hormones. Supplementing the diet with two of the LC levels for 22 weeks caused significant rise in sperm concentration, viability and SQF compared to that of the control group (P < 0.05). Quadratic analysis in terms of number of seminiferous tubules and spermatogenesis index were significant (P<0.05). Tubular differentiation index improved linearly by the increasing levels of LC supplementation (P<0.01). The analysis of fatty acid profiles showed that LC significantly (P < 0.05) reduced the percentages of C14:0, C21:0, total saturated fatty acids, total odd-chain fatty acids and n-6/n-3 ratio. Moreover, LC significantly increased the percentage of C20:5n-3 (Eicosapentaenoic acid; EPA) (P < 0.05). Analysis of the correlation coefficient revealed that the SQF is in consistency with EPA (r = 0.98; P < 0.04). In contrast, SQF negatively and significantly correlates with odd-chain fatty acids (r = - 0.99; P < 0.001). The desaturation index for C16 fatty acids (16:1cis/C16:0) negligibly increased linearly as LC was added to the diet (P < 0.05). Furthermore, LC caused the roosters to have significant (P < 0.05) high levels of total testosterone and FSH concentrations. The concentration of LH in different treatment groups, however, turned out to be similar in response to the different levels of LC. In conclusion, long-term supplementation of rooster diet with LC can have beneficial effects on SQF and testis histology. The benefits include alterations in testicular histology, reproductive hormones and testicular fatty acid profiles.

中文翻译：

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左旋肉碱对公鸡睾丸中脂肪酸谱的调控、性激素的改变、睾丸组织学特征的改善和精子质量因子的提高

本研究旨在调查不同水平的左旋肉碱 (LC) 对精子质量因子 (SQF)、睾丸脂肪酸谱的改变、睾丸组织学和年轻公鸡的生殖激素的影响。18 只肉种鸡 (Ross 308) 在 3 个月大时称重。他们被随机分类，而每组有六只鸟。根据 LC 浓度（即 LC-0、LC-250、LC-500 mg/kg 饮食），有三个实验组。经过两周的适应，每两周（从第 24 周到第 34 周）收集精液样本并评估精液属性。在实验结束时，每个治疗组的四只公鸡被处死，以分析睾丸组织学、睾丸脂肪酸谱和生殖激素。与对照组相比，在饮食中添加两种 LC 水平 22 周后，精子浓度、活力和 SQF 显着增加（P < 0.05）。生精小管数和生精指数的二次分析有显着性差异（P<0.05）。随着LC补充水平的增加，肾小管分化指数线性提高（P<0.01）。脂肪酸谱分析表明，LC显着(P < 0.05)降低了C14:0、C21:0、总饱和脂肪酸、总奇数链脂肪酸和n-6/n-3比率的百分比。此外，LC显着增加了C20:5n-3（二十碳五烯酸；EPA）的百分比（P < 0.05）。相关系数分析表明，SQF 与 EPA 一致（r = 0.98；P < 0.04）。相比之下，SQF 与奇数链脂肪酸呈负相关且显着相关（r = - 0.99；P < 0.001）。C16 脂肪酸（16:1 顺式/C16:0）的去饱和指数随着 LC 的添加而线性增加（P < 0.05），可忽略不计。此外，LC 导致公鸡具有显着（P < 0.05）高水平的总睾酮和 FSH 浓度。然而，不同治疗组中的 LH 浓度在响应不同水平的 LC 时结果是相似的。总之，长期在公鸡饮食中补充 LC 可以对 SQF 和睾丸组织学产生有益影响。好处包括睾丸组织学、生殖激素和睾丸脂肪酸谱的改变。1cis/C16:0) 随着 LC 添加到饮食中，线性增加可忽略不计（P < 0.05）。此外，LC 导致公鸡具有显着（P < 0.05）高水平的总睾酮和 FSH 浓度。然而，不同治疗组中的 LH 浓度在响应不同水平的 LC 时结果是相似的。总之，长期在公鸡饮食中补充 LC 可以对 SQF 和睾丸组织学产生有益影响。好处包括睾丸组织学、生殖激素和睾丸脂肪酸谱的改变。1cis/C16:0) 随着 LC 添加到饮食中，线性增加可忽略不计（P < 0.05）。此外，LC 导致公鸡具有显着（P < 0.05）高水平的总睾酮和 FSH 浓度。然而，不同治疗组中的 LH 浓度在响应不同水平的 LC 时结果是相似的。总之，长期在公鸡饮食中补充 LC 可以对 SQF 和睾丸组织学产生有益影响。好处包括睾丸组织学、生殖激素和睾丸脂肪酸谱的改变。结果证明在响应不同级别的 LC 时是相似的。总之，长期在公鸡饮食中补充 LC 可以对 SQF 和睾丸组织学产生有益影响。好处包括睾丸组织学、生殖激素和睾丸脂肪酸谱的改变。结果证明在响应不同级别的 LC 时是相似的。总之，长期在公鸡饮食中补充 LC 可以对 SQF 和睾丸组织学产生有益影响。好处包括睾丸组织学、生殖激素和睾丸脂肪酸谱的改变。