عنوان مقاله [English]
Introduction Reproductive performance of domestic animals has a great impact on the profitability of the farms. It has been shown that several factors such as breed, age, season and nutritional management affect the quality of the produced semen and consequently fertility of rams. Among various nutritional factors influencing semen quality, fat has a great impact on both quantity and quality of produced spermatozoa so that its value is correlated with cell membrane fluidity, potent intracellular signal transduction molecules, and susceptibility to oxidative damage. It has been postulated that by participating in sperm plasma membrane fatty acids (FA), the ingested fat can change the ratio of polyunsaturated to saturated fatty acids (PUFA: SFA) and thereby improve several aspects of sperm quality. Also, lipids comprise a wide-range class of molecules that not only is served as a source of energy but also play a crucial role in the structure and function of spermatozoa. Dietary n‑3 PUFA supplementation has also shown to improve semen quality parameters in rams. Flaxseed oil contains up to 90% PUFAs, of which about 50% is α-linolenic acid. Several studies conducted during past decades indicate that dietary flaxseed supplementation improves sperm parameters of different species such as bovine, goat and rabbit.
Materials and Methods Fifteen mature 3-5 years old Kurdish ram weighing 65±2.5 kg (mean ±SE) were randomly allocated into three groups during 12 weeks of the experimental period. Animals were individually fed a standard basal diet supplemented with different levels of flaxseed. Treatment included FLS-0 (basal diet; control), FLS-5 (basal diet containing 5% flaxseed) and FLS-10 (basal diet containing 10% flaxseed. Blood and fresh semen samples were collected at weeks 1 and 12 of the experiment. The collected samples were examined for sperm concentrations, sperm motility, viability, acrosome integrity, host test and fatty acids profiles. The testis circumference was measured with flexible cloth tape. The largest circumference of the testes and both scrotum was measured after pushing the testes firmly into the scrotum. To measure plasma concentrations of glutathione peroxidase and testosterone, blood samples were collected from the jugular vein of all the rams at the beginning and after 1 and 12 weeks of feeding experimental diet.
Results and Discussion Flaxseed supplementation did not affect testicles circumference, however, supplementation of flaxseed increased plasma concentrations of testosterone in (10% flaxseed) FLS-10 group compared to (5% flaxseed) FLS-0 (P<0.05). Treatment, time and their interaction did not affect glutathione peroxidase (GPX) activity. Semen concentration, proportion of live sperm, total motility and plasma membrane functionality was higher in FLS-10 compared to FLS-5 and FLS-0 groups (P<0.05). Flaxseed supplementation tended to increase percentage of sperm with normal acrosome (P<0. 01); however, percentage of abnormal was decreased in FLS-10 compared to the other corresponding groups (P<0.05). Treatment, time and interaction effect of treatment × time did not affect LIN, STR, ALH and VCL (P>0.05). However, BCF and VSL were improved in FLS-10 group as compared to the FLS-5 and FLS-0 group (P<0.05). A significant interactive effect of treatment × time was noted for VAP, where flaxseed supplementation did not affect VAP at first week of the experiment but higher VAP was recorded in FLS-10 compared to FLS-0 and FLS-0 groups after 12 weeks of flaxseed feeding (P<0.05). Flaxseed supplementation did not affect percentage of myristic, palmitic, stearic, oleic, linoleic, EPA and DPA, but the proportion of DHA, and the ratio of n-3:n-6 PUFA and SFA:PUFA was affected by the treatments (P<0.05). Dietary inclusion of flaxseed increased proportion of DHA and n-3: n-6 PUFA ratio and decreased SFA: PUFA ratio in FLS-10 compared to FLS-5 and FLS-0 (P<0.05). The interactive effect of treatment × time on DHA, n-3: n-6 and SFA: PUFA ratio revealed that there was no significant effect between treatment after first week of the experiment; however, proportion of DHA and n-3: n-6 PUFA ratio was higher and SFA: PUFA ratio was lower in FLS-10 compared to FLS-5 and FLS-0 (P<0.05). the significant correlations between addition of 10% flaxseed and most of the evaluated semen characteristics including live sperm, total motility, plasma membrane functionality, and acrosome status following 12 weeks of treatment feeding was in agreement with previous findings in male goat and rabbit. Other fatty acids concentrations, such as, linoleic acid, and docosahexaenoic acid (DHA) was improved by dietary flaxseed supplementation.
Conclusion It can be concluded that adding 10% flaxseed to the Kurdish ram diet out of the breeding season can improve sperm quality. Sperm fatty acid composition can also be affected by dietary fat. But more research is needed to look at the effects of other flaxseed products, such as oil and powder. It is recommended that similar studies be conducted during the breeding season and with other amounts of flaxseed.
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