پژوهش های علوم دامی (Sep 2021)
Investigation of different forms of selenium on digestibility of high production lactating dairy cows totally mixed ration using in vitro and in situ techniques
Abstract
Introduction: Selenium is one these trace mineral elements which is essential for health, immunity and maximum production performance of animals. Selenium is an essential trace element, and its importance for animal health and productivity has been well confirmed. Selenium has known to be involved in enzyme activity and preventing oxidative damage to body tissue. Selenium plays important roles in antioxidant defence systems, prevents cell damage and is necessary for growth, fertility, and immune system in farm animals. Recently, nano -elemental Se has attracted wide spread attention due to its high bioavailability and low toxicity, because nanometer particulates exhibit novel characteristics, such as great specific surface area, high surface activity, a lot of surface active centres, high catalytic efficiency and strong adsorbing ability and over and above the character of low toxicity of Se0. Dietary selenium is an essential trace element for animals and humans with a variety of biological functions. It plays important roles in the regulation of thyroid hormone metabolism, cell growth and antioxidant defence systems thus, together with alpha-tocopherol prevents cells against oxidative stress damage, also these compounds are necessary for growth, fertility, and immune system health in animals and humans. The in situ and in vitro usually use for determining of effect of additives on digestibilities of t feeds. Regarding to the importance of TMR feeding on dairy cattle nutrition, determining of its digestibilities with additive and without additive is necessary. The aim of this study was to investigate the effects of different forms of selenium sources on digestibility of high production lactating dairy cows TMR in vitro and in situ Techniques. Materials and Methods: 3 male ruminally cannulated sheep, average 43±4.8 kg of BW, were used in a replicated 3×3 Latin square experiment. Sheep were fed twice daily (08:00 and 18:00 h) at maintenance nutrition requirements with a basal diet consisting of 400 g/kg (dry matter) DM of basal concentrates and 600 g/kg DM of forage. Sheep were placed in metabolic cages individually and fresh water was freely available during the experimental period. This experiment was conducted in three periods of 28 days with 21 d adaptation period and 7 d for data tacking. Treatments were: 1. Basal diet + 0.3 ppm nano selenium, 2. Basal diet + 0.3 ppm organic selenium, 3. Basal diet + 0.3 ppm inorganic selenium. In gas production method, 300 mg of each treatment weighted and incubated for 2, 4, 6, 8, 12, 16, 24, 36, 48, 72, 96 hours. The Nylon bag method used to estimate ruminal disappearance of dry matter. Ruminal degradability was measured using nylon bag technique on day 22–28 of the experimental period. The samples 5 g of feed were weighed in 6 cm×12cm nylon bags made of monofilament Pecap polyester . Samples were incubated separately in duplicate bags and suspended in the rumen of each sheep and removed after 0, 2, 4, 8, 12, 16, 24, 36, 48 and 72 hours. All removed bags were rinsed in cold water until the bags were clean; the bags immediately were dried in an oven at 65◦C for 12 h, then 105 ◦C for 24 h in order to determine DM disappearance. in three steps digestion method, about 5 g of feed stuffs weighted in 6 cm×10cm nylon bags made of monofilament Pecap polyester . Samples were incubated separately in duplicate bags and suspended in the rumen of each sheep and removed after 12 hours. All removed bags were rinsed in cold water until the bags were clean; the bags immediately were dried in an oven to determine DM disappearance. Results and Discussion: During most of incubation hours, the volume of produced gas was higher in nano selenium, organic selenium, inorganic selenium and control treatments, respectively. However, significant differences between treatments were occurred after 36 h of incubation. The most gas production potential (A) was measured in nano selenium, organic selenium and inorganic selenium compared with control treatments. There were not any significant differences between nano selenium and organic selenium in gas production potential. there wasn’t any significate differences between treatments in degradability of TMR dry matter. In three steps digestion experiment, nano treatment was higher than inorganic treatment in post ruminal digestion of TMR dry matter. CONCLUSIONS: The results showed that the addition of various sources of selenium to the diet may improve rumen function.
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