Effects of Dietary Selenium and Vitamin E on Growth Performance, Meat Yield, and Selenium Content and Lipid Oxidation of Breast Meat of Broilers Reared Under Heat Stress.

This study was conducted using 360 broiler chickens to evaluate the effects of dietary vitamin E (0, 125, and 250 mg/kg), selenium (0, 0.5, and 1 mg/kg), or their different combinations on performance, meat yield, and selenium content and lipid oxidation of breast meat of broilers raised under either a thermoneutral (TN, 24 °C constant) or heat stress (HS, 24 to 37 °C cycling) condition. There was a reduction (P < 0.05) in body weight and feed intake and an increase (P < 0.05) in feed conversion ratio when broilers exposed to HS. In the overall period of the study (1 to 49 days), growth performance of TN broilers was not affected (P < 0.05) by vitamin E and selenium supplementation. However, under HS condition, broilers receiving 250 mg/kg vitamin E and 0.5 mg/kg selenium consumed more (P < 0.05) feed than that of broilers receiving 250 mg/kg vitamin E alone, but similar (P > 0.05) to that of broilers receiving 250 mg/kg vitamin E and 1 mg/kg selenium. The malondialdehyde (MDA) content of the breast meat was increased (P < 0.05), but its selenium content was decreased (P < 0.05) by exposure to HS. The breast meat selenium content was increased (P < 0.05) by selenium supplementation. The breast meat selenium content was decreased (P < 0.05) by supplementation of 250 mg/kg vitamin E to diet of TN birds. However, the breast meat selenium content was increased (P < 0.05) by supplementation of vitamin E under HS condition. The breast meat MDA content was not affected (P > 0.05) by dietary treatments under TN condition. However, the breast meat MDA content was decreased (P < 0.05) by both vitamin E and selenium supplementation under HS condition, and the lowest MDA content was observed in the breast meat of broilers receiving combination of 125 mg/kg vitamin E and 1 mg/kg selenium. The results showed that supplementation of selenium and vitamin E was capable of increasing the selenium content of the breast meat and could improve the lipid oxidation of the breast meat when broilers reared under HS condition.

Selenium as a feed supplement for heat-stressed poultry: a review.

Heat stress is associated with compromised performance and productivity in poultry due to declines in feed intake, nutrient utilization, growth rate, egg production and quality, and feed efficiency. Emerging evidences have shown that acute heat exposure results in increased production of free radicals and causes oxidative damage to lipids, proteins, and DNA. Additionally, heat stress can influence immune response by changing the expression of cytokines and by making the immune cells more susceptible to oxidative stress. Selenium, as a part of specific selenoproteins, can help to maintain antioxidant defenses, thereby preventing damages to tissues. An optimum response with supplementation of selenium in diet has been found to improve feed intake, body weight gain, feed efficiency, egg production and quality, and antioxidant status in heat-stressed poultry. Selenium compounds are also known to improve immune responses by altering the production of certain cytokines secreted by cells of the immune system and by enhancing the resistance of the immune cells to oxidative stress. It was reported that selenium supplementation had inhibitory effects on tumor necrosis factor alpha levels in heat-stressed broiler chicks, but the details are not completely elucidated. In the present review, the effect of selenium on production performance, nutrient utilization, antioxidative status, and immune responses of heat-stressed poultry is summarized.

Effects of dietary selenium and vitamin E on immune response and biological blood parameters of broilers reared under thermoneutral or heat stress conditions.

A study was conducted using 360 broiler chickens to evaluate the effects of dietary vitamin E (0, 125 and 250 mg/kg), selenium (Se, 0, 0.5 and 1 mg/kg), or their different combinations on immune response and blood biological parameters of broilers raised under either thermoneutral (TN, 23.9 °C constant) or heat stress (HS, 23.9 to 37 °C cycling) conditions. Humoral immunity was assessed by intravenous injection of 7% sheep red blood cell (SRBC) followed by evaluation of serum for antibody titers in primary and secondary responses. Heterophil to lymphocyte (H/L) ratio also determined as an indicator of stress. Furthermore, at the end of the experiment, birds were bled for determination of some biological parameters. There was a significant reduction in body weight and feed intake, but the feed conversion ratio increased when the birds were exposed to HS (P<0.05). Body weight and feed intake were not influenced significantly by dietary vitamin E and Se (P>0.05), whereas feed conversion was improved significantly by 125 mg/kg vitamin E (P<0.05). The liver and lymphoid organ weights as well as IgM and IgG, antibody titers for primary and secondary antibody responses to SRBC were reduced significantly under HS (P<0.05). Heat stress also resulted in a significant increase in H/L ratio (P<0.05). Dietary vitamin E resulted in improvement of primary and secondary antibody responses both in TN and HS broilers (P<0.05). The HS birds also showed an improved antibody titer in secondary response with high concentration of Se (P<0.05). Vitamin E and Se had interactive effects on anti-SRBC titers; however, no consistent differences were found between dietary levels during the study. The H/L ratio decreased by feeding vitamin E at both levels either under HS or TN conditions (P < 0.05). The serum concentrations of glucose, triglycerides, total cholesterol, and LDL-cholesterol were increased but serum HDL-cholesterol decreased in HS broilers (P<0.05).

Lack of effect of dietary chromium supplementation on growth performance and serum insulin, glucose, and lipoprotein levels in broilers reared under heat stress condition.

This study evaluated the effects of supplemental dietary chromium (Cr) on the performance, carcass traits, and some serum parameters of broilers under a heat stress (23.9 to 37 °C cycling) condition. A total of 150 1-day-old broiler chicks (Cobb 500) according to a completely randomized design were assigned into five treatment groups. Each treatment consisted of three replicates and each replicate contained ten chicks. Treatments were supplemented with 0 (control), 600, and 1,200 µg kg(-1) Cr in the form of Cr chloride (CrCl3) and Cr L-methionine from 1 to 49 days of age. Blood samples were collected from two birds in each replicate to determine serum parameters at 35 and 49 days of age. The body mass, feed intake, and conversion ratio were not influenced by dietary Cr (P > 0.05). Dietary supplementation of Cr from either CrCl3 or Cr L-methionine caused increased serum concentrations of Cr (P < 0.05), but had no effect on serum insulin and glucose concentrations at both sampling times (P > 0.05). Serum triglycerides, very low-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol were also not significantly affected (P > 0.05) by dietary treatments, whereas total cholesterol concentration decreased in chicks fed Cr L-methionine compared to the control (P < 0.05).

Effects of dietary selenium, vitamin E, and their combination on growth, serum metabolites, and antioxidant defense system in skeletal muscle of broilers under heat stress.

This experiment was conducted to evaluate the effects of dietary vitamin E, selenium (Se), and a combination of the two, on the performance, serum metabolites and oxidative stability of skeletal muscle of broilers during heat stress. The broilers raised in either a thermoneutral (23.9°C constant) or heat stress (23.9°C to 37°C cycling) environment were assigned to 6 dietary treatments (0, 0.5, or 1 mg/kg Se; 125 and 250 mg/kg vitamin E; or 0.5 mg/kg Se plus 125 mg/kg vitamin E) from 1 to 49 days of age. At the end of the experiment, blood samples were collected from chicks, the chicks sacrificed, and pectoralis superficialis muscle was used for measurement of malondialdehyde (MDA) concentration and enzyme activities of glutathione peroxidase (GPx) and superoxide dismutase (SOD). The heat-stressed chicks consumed less feed, gained less weight, and had higher feed conversion ratio when compared to thermoneutral chicks (P<0.05). Serum concentrations of iron (Fe) and zinc (Zn) were decreased by heat stress (P<0.05), whereas the serum concentrations of copper (Cu), glucose, and uric acid were significantly increased under heat stress (P<0.05). The chicks that received supplemental of vitamin E exhibited significantly higher serum concentrations of Zn (P<0.05) and significantly lower concentrations of Cu, glucose, and uric acid (P<0.05) when exposed to heat stress. Dietary Se also caused a significant decrease in serum glucose, uric acid, and Cu concentrations of heat-stressed broilers (P<0.05), but had no significant effect on Zn concentration (P>0.05). The GPx activity remained relatively constant (P>0.05), though SOD activity and MDA levels in skeletal muscle were enhanced on exposure to heat stress (P<0.05). The heat-stressed chicks that received the combined supplementary level of vitamin E and Se had the lowest concentration of MDA and the highest activity of SOD in the skeletal muscle (P<0.05). Dietary Se also caused a significant increase in enzyme activity of GPx in the skeletal muscle (P<0.05). These results indicate that the derangement of blood parameters and oxidative stability in broilers under heat stress are improved by supplemental vitamin E and Se.

Effect of prepartum supplementation of selenium and vitamin E on serum Se, IgG concentrations and colostrum of heifers and on hematology, passive immunity and Se status of their offspring.

Forty heifers at the late stage of gestation were randomly assigned into five groups. Heifers were balanced for age, weight, and time of calving in each group. Four and 2 weeks before expected time of calving, the heifers were injected with 0 ml (C), 10 ml (T1), 20 ml (T2), 30 ml (T3), and 40 ml (T4) Se and VE supplements, respectively. Each milliliter of the supplement contained of 0.5 mg Se as sodium selenite and 50 IU of dl-alpha-tocopheryl acetate. Blood samples were collected from the heifers 4 weeks before expected calving and at calving day and from the calves at birth and 7 days of age. The serum Se and immunoglobulin G (IgG) concentrations, white blood cell and differential leukocyte counts were measured. The Se concentrations in the sera of the heifers before the injections of Se and VE supplements were the same among the groups (P > 0.05), but after calving were significantly increased in the treated heifers (P < 0.05). Similarly, the serum Se levels of calves of the treated heifers were higher (P < 0.05). The Se concentrations in the colostrums of the heifers were affected by treatments (P < 0.05). Colostrum and daily milk productions at 8-week lactation were increased in treated heifers compared with the controls (P < 0.05). Likewise, the milk somatic cell counts decreased in the treated heifers compared with the controls. The changes of the mean serum IgG levels did not differ among calves (P > 0.05). The white blood cell counts were higher in calves of heifers in groups T3 and T4 compared with the control group at 7 days of age (P < 0.05).

The effect of different levels of organic and inorganic chromium supplementation on production performance, carcass traits and some blood parameters of broiler chicken under heat stress condition.

A total of 250 broilers in a completely randomized design selected to evaluate the effect of different levels of chromium (Cr) supplementation on performance, carcass traits and some blood parameters of heat-stressed broiler chicks. All birds were kept under heat stress temperature (33 ± 3°C) and divided into five treatments groups. Each treatment consisted of five pens with 10 birds in each pen. The basal diets were supplemented with 0 ppb (control), 800 ppb Cr-L-Met (T(1)), 1,200 ppb Cr-L-Met (T(2)) or 800 ppb CrCl(3) (T(3)), and 1,200 ppb CrCl(3) (T(4)). The feed intake and body mass were measured at 10, 21, and 42 days of age. Blood samples were collected from two birds in each replicates to determine biological and hematological values at 28 and 42 days of age. There were no significant difference in mass gain and feed conversion of broilers that received Cr supplementations compared with controls. The serum glucose concentration decreased in broilers received organic chromium methionine supplements compared with other treatments groups. Slight but not significant increases were observed in serum high-density lipoprotein (HDL) concentration of treated groups than controls while the mean serum HDL concentration was significantly higher in T(2) group compared with control group. Serum low-density lipoprotein level decreased in broiler received organic Cr supplements (p < 0.05).