Y. N. Min

Dietary vitamin E improves meat quality and antioxidant capacity in broilers by upregulating the expression of antioxidant enzyme genes

ABSTRACT A total of 240 one-day-old broiler chicks were divided into 3 treatments with 4 replicates of 20 birds. The birds were fed a corn–soybean meal diet supplemented with 0, 100, and 200 mg/kg vitamin E (VE), respectively. The results indicated that VE supplementation led to a significant decrease in shear force (P < .05), and showed higher b* values and lower a* values (P < .05). Dietary supplementation with VE significantly increased VE concentration in serum compared to that in the control group (P < .05). Total antioxidant capacity activity in breast muscle or serum was increased with the increase in dietary VE supplementation in a dose-dependent manner (P < .05). Total superoxide dismutase (T-SOD) and glutathione peroxidase (GSH-Px) activity were linearly increased with the increase in dietary VE (P < .05), while malondialdehyde content decreased linearly (P < .05). The mRNA expression of SOD and GSH-Px in liver was linearly increased with the increase in dietary VE (P < .05). These findings suggest that dietary VE could increase meat quality by upregulating the expression of antioxidant enzyme genes in broilers.

Vitamin E and vitamin C supplementation improves antioxidant status and immune function in oxidative-stressed breeder roosters by up-regulating expression of GSH-Px gene

ABSTRACT This study aimed to evaluate the effects of vitamin C and vitamin E on antioxidant capacity and immune function in oxidative‐stressed breeder roosters. One hundred twenty 45‐week‐old Lveyang black‐boned breeder roosters were randomly assigned to 5 dietary treatments, including negative control group (NC), positive control group (PC), and 3 trial groups, which were fed the diets containing 300 mg/kg VC, 200 mg/kg VE, or 300 mg/kg VC and 200 mg/kg VE (VC+VE). At 47 wk of age, the positive control and trial groups were subcutaneously injected 3 times every other d with dexamethasone (DEX) 4 mg/kg of body weight, the negative control group was injected with saline. The experiment lasted for 35 d. The results showed that at 50 wk of age, average daily feed intake of birds challenged with DEX significantly increased (P < 0.05). During post‐stress recovery period (52 wk of age), dietary supplemental VE or VC+VE notably increased body weight under oxidative stress (P < 0.01). Oxidative stress induced by DEX could significantly decrease superoxide dismutase (SOD), IgM, antibody titer of ND and mRNA expression of SOD or glutathion peroxidase activity (GSH‐Px), increase serous malondialdehyde (MDA) (P < 0.05). Supplementation of VC or VE significantly decreased serous MDA, and increased SOD under oxidative stress (P < 0.05). Supplementation of VC or VE, or their combination significantly increased the relative expression of GSH‐Px mRNA when compared to the oxidative‐stressed control treatment (P < 0.05), whereas did not alleviate the relative expression of SOD mRNA (P > 0.05). Therefore, the results suggest that addition of 300 mg/kg VC, 200 mg/kg VE or their combination could improve antioxidant ability and immune performance in oxidative‐stressed breeder roosters through up‐regulating the expression of GSH‐Px gene.

Effects of dietary threonine levels on growth performance, serum biochemical indexes, antioxidant capacities, and gut morphology in broiler chickens

&NA; A dose‐response experiment was conducted to investigate the impacts of dietary threonine (Thr) levels on growth performance, serum biochemical indices, antioxidant capacities, and gut morphology of broiler chickens. Four hundred and thirty‐two 1‐d‐old commercial broilers were allocated to 4 treatments consisting of 6 replicates of 18 birds. The experimental treatments received the same Thr‐deficient basal diet and were labeled as follows: 85%, 100%, 125%, and 150% of NRC (1994) recommendations. The results demonstrated that on 21 d and 42 d, average daily weight gain (ADG, 22 to 42 d, 0 to 42 d) increased quadratically or cubically as the inclusion of Thr increased, while feed conversion ratio (FCR, 0 to 21 d, 0 to 42 d) decreased quadratically or cubically as dietary Thr increase from 85% to 150%. Excess dietary Thr levels triggered plasma aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities. The concentrations of total protein (TP) and globulin (GLO) increased quadratically with increasing Thr level, and the highest concentrations of TP and GLO were obtained at the 125% Thr level. Moreover, the plasma uric acid (UA) concentration decreased linearly or quadratically with the increase in dietary Thr level. Likewise, the serum glutathione peroxidase (GSH‐Px) and total superoxide dismutases (T‐SOD) activities increased quadratically as dietary Thr increased, and the highest activity of GSH‐Px was obtained at the 125% Thr level, while the highest T‐SOD level occurred in the 100% Thr group. Gut morphology of birds showed significant response to different graded concentrations of Thr level. Villus height (VH), crypt depth (CD), and VH:CD ratio (VH/CD) were increased linearly or quadratically by Thr supplementation. Therefore, the present study suggests that the NRC (1994) recommendations Thr level that was optimum for growth performance, and 125% of the NRC (1994) recommendations Thr level had better effects on biochemical indices, antioxidant function, and gut morphology of broilers.

On oxidation resistance and meat quality of broilers challenged with lipopolysaccharide

Effects of preslaughter immunological stress induced by lipopolysaccharide (LPS) on antioxidant performance and meat quality of broilers were investigated. Twenty-four broiler chickens (39 days old) with near-mean body weight (BW) were randomly divided into three following treatments: sham injection of saline (control), daily subcutaneous (s.c.) injection of LPS (3 mg/kg or 6 mg/kg of BW, respectively.) for three days. The results showed that average daily feed intake and daily gain of chickens were significantly decreased in the LPS treatment (P < 0.05). The F/G was significantly enhanced (P < 0.01). The LPS treatment had no significant influence on carcass performance (P > 0.05). The LPS treatment significantly decreased the pH at 24 h postmortem in breast muscle (P < 0.05) and significantly increased the water-holding capacity (WHC) of breast muscle (P < 0.01). It was the same as the change of yellowness (b*) at day 3 postmortem and lightness (L*) at day 6 postmortem in breast muscle (P < 0.05), but had no significant influence on shear force of breast muscle (P > 0.05). The pH at 45 min or 24 h postmortem of thigh muscle was significantly dropped in the LPS treatment (P < 0.01), however, the WHC and shear force of thigh muscle were not significantly different (P > 0.05). The yellowness (b*) significantly increased at day 3 postmortem of thigh muscle (P < 0.05). The plasma, breast muscle and thigh muscle MDA were significantly enhanced in the LPS treatment (P < 0.05). The total antioxidant capacity (T-AOC) level was significantly suppressed (P < 0.05); however, the plasma activity of glutathione peroxidase (GSH-Px) was slightly decreased (P > 0.05). The results of present study suggested that LPS-induced preslaughter immunological stress could increase body oxidative damage and decrease oxidation resistance, resulting in a decrease in growth performance and meat quality of broilers; also these adverse effects could be rested with the stress intensity.

Effects of organic zinc on tibia quality, mineral deposit, and metallothionein expression level of aged hens

&NA; The study aimed to determine the effects of methionine hydroxy analog chelate zinc on the tibia quality, mineral deposit, apparent retention of nutrients, and liver metallothionein (MT) expression level of aged laying hens. A total of 960 layers (Hy‐Line Grey, 57 wk old) were randomly assigned into 4 groups, and each group had 8 replicates of 30 hens. During the first 2 wk, groups were fed a basal diet without extra zinc (Zn: 35.08 mg/kg). During the ensuing 14 wk, 4 levels of Zn (inorganic Zn: 80 mg/kg; organic Zn: 20, 40, 80 mg/kg) were added to the diet. The results indicated that both the Zn source and level did influence tibia strength and calcium (Ca) and Zn concentrations of tibia (P < 0.05), whereas there were no differences in the copper (Cu) and phosphorus (P) concentrations of the tibia and the tibia length (P > 0.05). Moreover, dietary supplementation with 40 or 80 mg/kg of organic Zn showed higher Zn and Ca concentrations in the tibia and higher tibia strength. The Cu concentration in the liver showed no difference among the 4 treatments, whereas the Zn concentration in the liver increased with the increasing Zn level. The apparent retention of P, iron (Fe), and manganese (Mn) was not affected by the Zn level or source (P > 0.05). However, the organic Zn group increased the apparent retention of Cu, Zn, Ca, crude protein (CP), and energy, and the group supplemented with 40 or 80 mg/kg of organic Zn obtained significant effects (P < 0.05). Moreover, dietary supplementation with 40 or 80 mg/kg organic Zn increased the MT mRNA expression of the liver at week 72, whereas 20 mg/kg of organic Zn decreased it (P < 0.05). In conclusion, this study suggested that an optimum dietary (40 mg/kg) organic Zn level plays a key role in promoting the apparent retention of minerals and nutrients, trace element deposit, and MT mRNA expression.

The association of very low-density lipoprotein receptor (VLDLR) haplotypes with egg production indicates VLDLR is a candidate gene for modulating egg production

The very low-density lipoprotein receptor (VLDLR) transports egg yolk precursors into oocytes. However, our knowledge of the distribution patterns of VLDLR variants among breeds and their relationship to egg production is still incomplete. In this study, eight single nucleotide polymorphisms (SNPs) that account for 87% of all VLDLR variants were genotyped in Nick Chick (NC, n=91), Lohmann Brown (LohB, n=50) and Lueyang (LY, n=381) chickens, the latter being an Chinese indigenous breed. Egg production by NC and LY chickens was recorded from 17 to 50 weeks. Only four similar haplotypes were found in NC and LohB, of which two accounted for 100% of all NC haplotypes and 92.5% of LohB haplotypes. In contrast, there was considerable haplotypic diversity in LY. Comparison of egg production in LY showed that hens with NC-like haplotypes had a significantly higher production (p < 0.05) than those without the haplotypes. However, VLDLR expression was not significantly different between the haplotypes. These findings indicate a divergence in the distribution of VLDLR haplotypes between selected and non-selected breeds and suggest that the near fixation of VLDLR variants in NC and LohB is compatible with signature of selection. These data also support VLDLR as a candidate gene for modulating egg production.Abstract The very low-density lipoprotein receptor (VLDLR) transports egg yolk precursors into oocytes. However, our knowledge of the distribution patterns of VLDLR variants among breeds and their relationship to egg production is still incomplete. In this study, eight single nucleotide polymorphisms (SNPs) that account for 87% of all VLDLR variants were genotyped in Nick Chick (NC, n=91), Lohmann Brown (LohB, n=50) and Lueyang (LY, n=381) chickens, the latter being an Chinese indigenous breed. Egg production by NC and LY chickens was recorded from 17 to 50 weeks. Only four similar haplotypes were found in NC and LohB, of which two accounted for 100% of all NC haplotypes and 92.5% of LohB haplotypes. In contrast, there was considerable haplotypic diversity in LY. Comparison of egg production in LY showed that hens with NC-like haplotypes had a significantly higher production (p < 0.05) than those without the haplotypes. However, VLDLR expression was not significantly different between the haplotypes. These findings indicate a divergence in the distribution of VLDLR haplotypes between selected and non-selected breeds and suggest that the near fixation of VLDLR variants in NC and LohB is compatible with signature of selection. These data also support VLDLR as a candidate gene for modulating egg production.