نوع مقاله : مقاله پژوهشی
1 گروه علوم دام و طیور، دانشکده فناوری کشاورزی، دانشکدگان کشاورزی و منابع طبیعی، دانشگاه تهران، تهران، ایران
2 گروه علوم دام و طیور، دانشکده فناوری کشاورزی، دانشکدگان کشاورزی و منابع طبیعی ، دانشگاه تهران، تهران، ایران
3 گروه علوم طیور، دانشکده کشاورزی، دانشگاه تربیت مدرس، تهران، ایران.
عنوان مقاله [English]
Introduction Rooster’s reproductive performance is an indispensable component of breeder production because it plays a vital role in the maximum production of fertilized eggs. Existence feed supplement in the poultry industry, intermediary metabolites have been including in the diet to improve fertility and reproductive outcomes. Carnitine (β-hydroxy-γ-trimethylaminobutyrate), vitamin-like-amino acid, is a quaternary ammonium compound, that has multifunctional roles in reproduction. High concentrations of L-carnitine (LC) are present in epididymal lumen, where it participates in sperm energy balance and the maturation of spermatozoa. In light of previously reported breeder birds supplemented with dietary LC have shown improvements in semen traits and fertility parameters. The present study is an attempt to investigate the effects of several levels of dietary LC supplementation on semen quality parameters and gonadosomatic and hepatosomatic indexes at maturity and production peak.
Materials and Methods For the present experiment, thirty-six Ross (12-week-old) breeder broilers were used for 22 weeks in a completely randomized design with three treatments (0, 250 and 500 mg L-carnitine in kg of diet) and twelve replications. All roosters were fed standard isocaloric (2754 kcal/kg) and isonitrogenous diet (12 % protein). The birds for 22 weeks in a completely randomized design with three treatments (0, 250 and 500 mg / kg of LC in the diet) and six replications were used. During the adaptation period (21-24 weeks of age), the roosters were trained by abdominal massage for semen collection. After the experimental period was commenced (24 weeks of age), semen samples were collected and evaluated for seminal attributes every two weeks (from week 24 to week 34). The following parameters were determined immediately after the semen collection; to measure the semen samples were collected weekly to evaluate semen volume, total motility, membrane functionality, mitochondria activity parameters. Also, to determine gonadosomatic and hepatosomatic indexes at 24 and 34 weeks of age, six birds in each treatment weighing then were slaughtered and immediately the testes and liver were removed and weighed.
Results and Discussion The highest sperm motility (96.60%) was observed in birds fed 250 mg LC (P <0.04). By increasing the level of LC in the diet, sperm membrane functionality improved linearly (6.8% increase compared to control) (P <0.04). A linear trend (P = 0.06) was observed in mitochondrial activity with increasing levels of LC in the diet (69.31, 72.00 and 76.25). LC plays an essential role in energy metabolism by carrying over fatty acids in the mitochondria matrix for β-oxidation producing energy. Therefore, it provides a better supply of energy for spermatogenesis and normal physiology of sperm, are presumably improved by an optimum level of LC, as a result, sperm concentration and live. These data provide evidence that LC can be effectively used in diets up to 500 mg/kg of diet or 30 mg/kg of body weight /day for semen improvements of rooster’s breeder. At 24 weeks of age, the changes in gonadosomatic index (0.55, 0.68 and 0.64) were affected by different levels of LC (P <0.01). During testis development in the chicken (from 2 to 15 weeks of age), there is no significant increase in testicular weight, however, the early stage is the most important period for testicular development. The mature testis has seminiferous tubules with a multilayered epithelium representing the different stages of spermatogenesis. Sexual maturity is associated with the highest testes weight and consequently with the highest plasma concentration of reproductive hormones. Gonads of the mature male broiler breeder are organized into separate, comfortably discernible cellular correlations and functional compartments. It has been accepted that steroid hormones biosynthesis and generation of spermatozoa are two major actions that the testicles fundamentally carry out. The improvements in gonadosomatic Index of roosters observed in this study in response to dietary LC may be attributed, at least partly, due to improved utilization of dietary nitrogen, achieved through more efficient fat oxidation by LC. Testicles contain the seminiferous tubules and the interstitial space. Seminiferous tubules are the functional elements of the testis and sertoli cells are the principal structural basis of the seminiferous epithelium, inhabiting on the substratum membrane.
Conclusion The addition of 250 and 500 mg of L-carnitine to the diet due to the increase in gonad index led to an improvement in sperm quality parameters at the beginning of the production period (puberty).
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