نوع مقاله : مقاله پژوهشی
نویسندگان
گروه علوم دامی دانشکده کشاورزی، دانشگاه تبریز، تبریز، ایران
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Introduction: Selenium has a special place in the natural antioxidants and prevents the oxidation of cell structures. Se supplementation may also improve the efficiency of the antioxidant system; enhance the disease resistance and nutritional quality of the livestock product. Selenium is recognized as an essential trace element for domestic animals. It is a powerful catalytic element constituting the active centre of about 20 selenoproteins. As a component of these selenoproteins, Selenium displays metabolic function related to maintenance of integrity and defenses of the organism. Se supplementation may be required to improve the performance and health of dairy cow. Furthermore, Se supplementation may enhance the nutritional quality of the milk product. Two principle forms of Se, inorganic Se (sodium selenite or selenate) and organic Se (selenium-yeast [SY]), can be supplemented to cattle diets. Most studies reported that organic Se is less toxic than inorganic Se. Bioavailability of selenium-yeast has been found to be higher than that of inorganic Se sources. Most trials in dairy cattle have demonstrated that selenium-yeast leads to higher Se content in milk and in blood but also show higher Se blood levels in beef cattle. Results of selenium-yeast on milk yields and milk components from literature are inconclusive. Several studies observed that Se source and dietary Se concentration had no effect on milk yields and milk components. In contrast, other studies found that selenium may exert an effect on milk fat. These contrasting results could be due to differences in the composition of the diet and/or to the dose of selenium-yeast and lactation period of dairy cow.
This experiment was conducted in order to investigate the effects of selenium and whole cottonseed on milk yield, milk composition and blood parameters in lactating Holstein dairy cows.
Materials and Methods: In order to study effect of adding selenium source to the diets containing height levels of whole cottonseed 12 lactating Holstein dairy cows with average milk production of 25±4kg were used in complete randomized design with 2 treatments and 6 repeat for each treat. The experiment was conducted in a periods of 28 days including 21 day adaptation and 7 day sampling. Two treatments including; 1) basal diet containing 10% cottonseed, without selenium supplement and 2) basal diet + 0.3 ppm organic selenium. The cows were fed three times a day (morning, noon, and noon) with a diet that was completely mixed with appetite. Fresh water was freely available during the experimental period. The milk produced per day was recorded per meal. Production of milk for experimental animals at the beginning of the experiment and measured for seven days at the end of each experimental period. On the last day of the course, 2 hours after the morning feeding, blood samples were collected from each vetiver vein of the cow. After the clot, it was centrifuged to separate the serum. Milk production and composition were measure In the first and the last days of each period and hematologic parameters were measured at the last day of experimental period. Protein, fat, lactose and milk solids-non-fat are measured with the milkoscan machine. All statistical analyses were performed using PROC MIXED of SAS.
Results and Discussion: Statistical analysis showed that there were significantly effect of treatments on milk yield and 4%FCM (P<0.05). Milk yield of cows fed diets 1, 2 was 30.19, 33.98 kg/d respectively, and FCM4% were 27.70, 29.83 respectively for 2 experimental treatments. Adding selenium source to the basal diet has not any significant effects on milk composition. However selenium supplement numerically decreased the somatic cell counts (SCC) in treatments (P>0.05). The obtained data showed that selenium supplementation to diet did not have significant effect on the concentrations of serum glucose, urea-N, cratenin, Triglyceride, Cholesterol, High density lipoprotein (HDL) and Low density lipoprotein (LDL) of dairy cows, but in contrast adding of selenium to the diet significantly increased the concentration of blood glutathione peroxidase activity (P<0.05).
CONCLUSIONS: Finally the results indicate that supplement organic selenium to diets with high level of cottonseed Increase milk production protection effects on milk secretion cells with against oxidants and free radicals of dairy cattle. present study showed that selenium supplementation increased antioxidant capacity of serum which is reflected in improved milk production of the cows.
کلیدواژهها [English]
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