Abstract
This experiment was conducted to evaluate the effects of different selenium (Se) products (inorganic, organic A, organic B) added at two supplemental dietary Se levels (0.1 and 0.3 mg/kg) on growth performance, nutrient digestibility and Se retention in growing-finishing pigs. A 3×2 factorial arrangement of treatments was used in a RCB design, with a non-Se-fortified basal diet serving as the negative control. A total of 56 crossbred pigs (28 male and 28 female pigs) initially weighing an average 28.45±0.53 kg BW were allotted to each treatment with four pigs per pen on the basis of sex and weight. Two pigs per pen were selected and bled from the anterior vena cava at 3- weekly intervals to analyze Se concentration. In the growing phase (0-6 weeks), increased ADFI was observed when pigs were fed organic Se compared to those fed the control diet or inorganic Se treatment (p<0.05). Pigs fed inorganic Se had a great ADFI than pigs fed organic Se (p<0.05) in the late finishing phase (7-12 weeks), although there were no differences in whole period ADFI between organic or inorganic Se products. During 12 weeks of the whole experimental period, serum Se concentration increased linearly when dietary Se level increased regardless of Se products (p<0.05). Both dietary Se source (p<0.05) and Se level (p<0.01) influenced the Se concentration of various pig tissues at end of this experiment and Se content was the highest in the kidney. For the determination of nutrient digestibility, a metabolic trial was conducted in 3 replicates in randomized complete block (RCB) design. A total of 21 barrows (50.21±0.62 kg of average BW) were used in the metabolic study. Selenium supplementation had no effect on nutrient digestibility except for crude protein. Crude protein digestibility increased with dietary supplementation of organic Se (A) compared with other forms of Se products or control diet (p<0.05). Consequently, this experiment indicated that dietary Se products and levels had no effect on growth performance of pigs. Se concentration in tissues and serum was increased in proportion to dietary Se level, especially when organic Se was provided. Although pigs were fed organic forms of Se, bioavailability of organic forms varied among products, consequently bioactivity of organic products to the animals should be evaluated before practical application in animal feed. (Asian-Aust. J. Anim. Sci. 2006. Vol 19, No. 1 : 61-66)
Highlights
In 1987, the FDA approved 0.3 mg/kg of inorganic Se added to animal feed, and restricted Se added to free mixed products to 200 mg/kg
Selenomethionine is found in livestock feed, increasing Se retention delivered to humans through livestock products
This experiment was conducted to evaluate the efficacy of the three Se products (sodium selenite, Se-enriched yeast-organic Se (A), organic Se (B) each at two supplemental dietary Se levels (0.1, 0.3 mg/kg) on serum Se, and tissue Se concentration in growing-finishing pigs
Summary
In 1987, the FDA approved 0.3 mg/kg of inorganic Se (sodium selenite or sodium selenate) added to animal feed, and restricted Se added to free mixed products to 200 mg/kg. Sodium selenite and sodium selenate had similar effects on animals but considering cost, sodium selenite is favored (Mahan, 2001). Development and research on organic Se products have shown progress. Inorganic Se forms, selenite or selenate, are effective sources in preventing Se deficiencies of livestock, but are ineffective in synthesis of selenocysteine containing selenoprotein, found in meats, milk and eggs. Numerous Se products for supplementing animal feed have been introduced in the feed industries. Their efficacies and retention in animals should be evaluated.
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