Effects Of Various Dietary Selenium Levels And Source On Growth Performance And Health Of Broilers

This experiment was conducted to investigate the most optimum selenium addition level for broiler by studying the effect of supplementation of broiler diets with various dietary levels of both Sodium Selenite (SS) and Se-enriched yeast (SY) on the growth performance, serum biochemical parameters, the antioxidative function and the content of Se in tissues and faeces. Three hundred and thirty one-day-old healthy broilers were allotted to eleven groups randomly with five replicates with six broilers each. The research lasted 42 d for a two-phase trial (2-4 weeks,5-7 weeks).The first group fed a corn-soybean meal basal diet. The other ten treatments were fed the basal diets with addition of two different selenium sources (SS,SY) and 5 levels 0.15,0.30,1.00,5.00, 10mg/kg of each. The results were as follows:Clinical manifestation:Broilers appeared the average daily feeds intake reduction,spirit depressed and growth slowed after 28d feeding with 10.00mg/kg SS;These appeare distinct the clinic features after 49ds feeding with 10.00mg/kg SS. including:low spirit, feather disheveled and drop, appetite decrease.lean.move maladjust. Broiler appear slight symptom of poisoning after 49d feeding with 5.00mg/kg SS and 10.00mg/kg SY feed; and those broilers reduced the average daily feeds intake and has depressed spirit and slow growth.The growth performance:ADFI, ADG and F/G had significant difference of broilers by dietary Se levels of both SS and SY (P<0.05).During the first period, ADG in treatment 5 decreased dramatically compared with control groups (P<0.05).In the later period, ADG decreased dramatically and feed conversion rate increased in treament 4.5.9.10 compared with control groups.The slaughter performance:Throughout the whole experiment, the addition of SS and SY diets showed no significantly effects on the dressing percentage, eviscerated.carcass rate, semi-eviscerated, carcass rate, breast muscle rate, leg muscle rate compared with control groups (P>0.05).The muscle water holding capacity:The muscle water holding capacity of broilers was affected by dietary Se levels both SS and SY (P<0.05).During the first period,there were significant decrease on muscle water holding capacity in treatment 1,2,6,7,8 compared with control groups(P< 0.05),while there has oppisition reasults of the muscle water holding capacity in treament 1,2,6,7,8.In the later period, there has the similar results of muscle water holding capacity compared with the first period.The biochemical parameters in serum:Throughout the whole experiment,the supplementation of dietary Se levels of both SS and SY showed no significantly effects on ALT,AST,AKP,and LDH in serum of broilers (P<0.05).The antioxidative function:The supplementation of dietary Se levels of both SS and SY showed significantly effect on SOD and GSH-Px activities and the content of MDA in serum of broilersv (P<0.05).During the first period, treatment 2,3,7,8 SOD and GSH-Px activities in blood serum were significantly increased (P<0.05),and the content of MDA in blood serum was significantly decreased compared with control groups(P<0.05).In the later period,treatment 1,6, SOD and GSH-Px activities in blood serum were significantly increased (P<0.05), the content of MDA in blood serum was significantly decreasedcompared with control group (P<0.05).The content of Se in tissues and faeces:The content of selenium in tissues and faeces increased as dietary Se levels increased of both SS and SY (P<0.05).And SY had more obvious effect than SS on the content of Se in the tissues (P<0.05).on the contrast, SS had more obvious effect than SYon the residue level selenium in faeces (P<0.05).Above-mentioned results showed:(1)The addition of Se levels (0.15 mg/kg and 0.30mg/kg) of both SS and SY showed positive effects on the antioxidative function, the growth performance and muscle's water holding capacity in broilers, SY is better than SS. However, the addition of Se levels (5.00 mg/kg and 10.00mg/kg) of both SS and SY has negative effects on the health of broilres. Furthermore, broilers fed with 10mg/kg of SS appeared distinct signs of toxicity, broilers fed with 10mg/kg of SS showed no distinct toxic symptoms.Therefore, SS should be more toxic than SY. (2) The content of selenium in tissues and faeces increased (P<0.05)as dietary Se levels increased of both SS and SY. The content of selenium in tissues of broilers fed with SY was higher than broilers fed with SS.which indicates that SY has higher deposition rate than SS.Therefore, the selenium residue level in faeces of SY was lower than SS.