Maternal zinc alleviates tert-butyl hydroperoxide-induced mitochondrial oxidative stress on embryonic development involving the activation of Nrf2/PGC-1α pathway.

BACKGROUND: Mitochondrial dysfunction induced by excessive mitochondrial reactive oxygen species (ROS) damages embryonic development and leads to growth arrest. OBJECTIVE: The purpose of this study is to elucidate whether maternal zinc (Zn) exert protective effect on oxidative stress targeting mitochondrial function using an avian model. RESULT: In ovo injected tert-butyl hydroperoxide (BHP) increases (P < 0.05) hepatic mitochondrial ROS, malondialdehyde (MDA) and 8-hydroxy-2-deoxyguanosine (8-OHdG), and decreases (P < 0.05) mitochondrial membrane potential (MMP), mitochondrial DNA (mtDNA) copy number and adenosine triphosphate (ATP) content, contributing to mitochondrial dysfunction. In vivo and in vitro studies revealed that Zn addition enhances (P < 0.05) ATP synthesis and metallothionein 4 (MT4) content and expression as well as alleviates (P < 0.05) the BHP-induced mitochondrial ROS generation, oxidative damage and dysfunction, exerting a protective effect on mitochondrial function by enhancing antioxidant capacity and upregulating the mRNA and protein expressions of Nrf2 and PGC-1α. CONCLUSIONS: The present study provides a new way to protect offspring against oxidative damage by maternal Zn supplementation through the process of targeting mitochondria involving the activation of Nrf2/PGC-1α signaling.

In vitro evaluation of efficacy of nonstarch polysaccharides enzymes on wheat by simulating the avian digestive tract.

In this study, the efficacy of different nonstarch polysaccharide (NSP) enzyme sources on wheat ingredients and wheat basal diets in vitro were evaluated by simulating the avian digestive tract. In Exp. 1, pH level was increased from 2.0 to 8.0 by simulating the avian digestive tract. The relative enzyme activities of xylanase A, B, and C and ß-glucanase X at pH 3.0-3.5 were higher (P < 0.05) than those at pH 2.0 or 7.0-8.0. The optimal pH levels of 3.5 and 7.0 were screened by simulating the proventriculus and small intestine, respectively to evaluate the efficacy of NSP enzyme on wheat sources. In Exp. 2, wheat 1 contained the highest content of NSP fractions and the lowest digestibility in vitro dry matter (IVDMD) and energy (IVED) in wheat samples. Therefore, wheat 1 was selected for hydrolysis research under different NSP enzyme sources and levels (1,500, 4,500, 13,500, 40,500, 121,500 U xylanase/kg and 250, 500, 1,000, 2,000, 4,000 U ß-glucanase/kg) in vitro. The hydrolysis of wheat on the basis of the released reducing sugar content was determined by xylanase sources A > B > C (P < 0.05) and ß-glucanase sources of X > Y (P < 0.05). On the basis of the hydrolysis, the optimum dose of xylanase A and ß-glucanase X were 40,500 U/kg and 2,000 U/kg, respectively. Subsequently, the completely randomized designs involving 2 NSP enzymes treatments × 2 endogenous digestive enzymes treatments (Exp. 3), as well as 2 wheat basal diets × 2 NSP enzymes treatments (Exp. 4) were used to evaluate the efficacy of NSP enzymes on dietary nutrient digestibility. The addition of NSP enzymes (40,500 U xylanase A/kg and 2,000 U ß-glucanase X/kg) increased the IVDMD and IVED of wheat 1 without endogenous enzymes (P < 0.05), while the IVDMD and IVED of wheat 1 with endogenous enzyme were only slightly increased (P > 0.05). The addition of NSP enzymes could increase the IVDMD and IVED of corn-wheat-soybean meal diet (P < 0.05), but had no effect on those of wheat-cottonseed meal rapeseed meal diet (P > 0.05). In conclusion, xylanase and ß-glucanase additions could effectively eliminate the adverse effects on wheat and wheat basal diets at the optimal pH levels of 3.5 and 7.0 by simulating the proventriculus and small intestine parts, respectively. The efficacy of NSP enzymes was influenced by the enzyme sources, dietary type, and the interaction of endogenous enzymes.

The inclusion level of wheat in poultry feeds is limited by nonstarch polysaccharides (NSP). Feeding NSP will increase the intestinal viscosity and residence time of the digesta, reduce nutrient digestion, and absorption of nutrients by birds, thereby damaging the intestinal function and growth performance. The degradation of NSP in feed by supplementing NSP enzymes has a positive effect on nutrient availability and growth performance. Therefore, there is a need for a quick and reliable method to assess the efficacy of NSP enzymes from different types, sources, and processing techniques. Compared with the expensive and time-consuming in vivo method for animal feeding experiments, in vitro digestion has been proved to be a rapid method for predicting the efficacy of exogenous enzymes in various parts of the avian digestive tract. Therefore, in this study, the efficacy of different NSP enzyme sources on wheat ingredients and wheat basal diets were evaluated in vitro by simulating the avian digestive tract.

Effect of Maternal Marginal Zinc Deficiency on Development, Redox Status, and Gene Expression Related to Oxidation and Apoptosis in an Avian Embryo Model.

Maternal severe zinc (Zn) deficiency resulted in growth retardation and high mortality during embryonic development in human. Therefore, this study is aimed at evaluating the effect of maternal marginal Zn deficiency on the development and redox status to avoid severe Zn deficiency using an avian model. A total of 324 laying duck breeders at 214 days old were randomly allotted into 3 dietary Zn levels with 6 replicates of 18 ducks per replicate. The birds were fed experimental diets including 3 dietary supplemental Zn levels of 0 mg/kg (maternal Zn-deficient group, 29.2 mg Zn/kg diet), 60 mg/kg (maternal Zn-adequate group), and 120 mg/kg (maternal Zn-high group) for 6 weeks. Dietary Zn levels had on effect on egg production and fertility (P > 0.05), whereas dietary Zn deficiency decreased breeder plasma Zn concentration and erythrocytic alkaline phosphatase activity at week 6 and inhibited erythrocytic 5'-nucleotidase (5'-NT) activity at weeks 2, 4, and 6 (P < 0.05), indicating that marginal Zn-deficient status occurred after Zn depletion. Maternal marginal Zn deficiency increased embryonic mortality and contents of superoxide anion radical, MDA, and PPC and reduced MT content and CuZnSOD activity in duck embryonic livers on E29. The MDA content was positively correlated with embryonic mortality. Maternal marginal Zn deficiency increased BCL2-associated X protein and Caspase-9 mRNA expressions as well as decreased B-cell lymphoma-2 and MT1 mRNA and signal AKT1 and ERK1 protein expressions (P < 0.05). Breeder plasma Zn concentration and erythrocytic 5'-NT activities at week 6 were positively correlated with GSH-Px activity and GPx, MT1, and BCL2 mRNA expressions in embryonic livers on E29. In conclusion, erythrocytic 5'-NT activity could be more rapid and reliable to monitor marginal Zn-deficient status. Marginal Zn deficiency impaired hatchability and antioxidant defense system and then induced oxidative damage and apoptosis in the embryonic liver, contributing to the greater loss of duck embryonic death.

Effects of Selenium-Enriched Yeast on Performance, Egg Quality, Antioxidant Balance, and Egg Selenium Content in Laying Ducks.

This study investigated the effects of dietary selenium-enriched yeast (Se yeast) supplementation on the laying performance, egg quality, plasma antioxidant balance, and egg selenium (Se) content in laying Longyan ducks. A total of 480 32-week-old ducks were randomly divided into four dietary treatments, each consisting of six replicates of 20 ducks. The dietary treatments were a control basal diet and basal diets with supplementation of 0.05, 0.15, and 0.25 mg Se/kg via Se yeast. The analyzed Se contents of the four diets were 0.15, 0.21, 0.36, and 0.43 mg Se/kg, respectively. Dietary Se yeast supplementation had no apparent effects on laying performance and egg quality (p > 0.05), but it improved the antioxidant balance of ducks, as inferred by greater glutathione peroxidase and catalase activities, and decreased the malondialdehyde content in plasma of ducks (p < 0.05). It was suggested that the Se content in the basal diet containing 0.15 mg/kg of Se requirement is adequate for productive performance, but not for the antioxidant balance of laying ducks. Besides that, the Se contents in the yolk, albumen, and whole egg increased linearly as the Se supplementation levels increased. With more feeding days, the Se contents in the yolk and whole egg from non-Se-yeast-supplemented ducks increased linearly (p < 0.05), while those from Se-yeast-supplemented ducks showed a quadratic relationship (p < 0.05). In conclusion, the Se content of the basal diet at 0.15 mg/kg was adequate for laying performance and egg quality traits in laying ducks. Dietary Se yeast supplementation is beneficial to improve the antioxidant balance of laying ducks and increase the Se deposition in eggs for producing Se-enriched eggs. Based on the quadratic model or the quadratic broken-line model analyses, supplemental 0.19 mg Se/kg via Se yeast, with a total equivalent of 0.34 mg Se/kg in the diet, could provide the optimum antioxidant balance in laying ducks. Dietary supplementation of 0.25 mg Se/kg via Se yeast, with a total equivalent of 0.40 mg Se/kg in the diet, could lead to achieving the desired Se content in the whole egg.

Effect of Dietary Zinc Level on Egg Production Performance and Eggshell Quality Characteristics in Laying Duck Breeders in Furnished Cage System.

In order to investigate the effect of dietary Zn levels on laying performance, eggshell quality, and eggshell microstructure in Muscovy duck breeders under furnished cages. Firstly, the effects of age (35 weeks vs 40 weeks) and rearing system (littered floor vs furnished cage) on eggshell quality of laying duck breeders were studied (Exp. 1). Then, a total of 324 30-week-old Muscovy duck breeders were allotted into 3 dietary Zn groups with 6 replicates (18 ducks per replicate), including 0 mg Zn/kg (control-Zn group, C-Zn), 40 mg Zn/kg (normal-Zn group, N-Zn), and 140 mg Zn/kg (high-Zn group, H-Zn). The experimental period for 6 weeks was divided into 3 periods of 30-32, 32-34, and 34-36 weeks of age (Exp. 2). In Exp. 1, duck breeder eggs in the furnished cage system had lower the average shell thickness than birds in the littered floor system at 40 weeks of age (P < 0.05), not at 35 weeks of age. In Exp. 2, N-Zn and H-Zn groups had greater egg weight, egg production, and egg to feed ratio of duck breeders than C-Zn group (P < 0.05). Additionally, H-Zn group had higher laying rate, qualified egg ratio, and Haugh unit as well as lower mammillary cone width than C-Zn group (P < 0.05), with no differences between C-Zn and N-Zn groups (P > 0.05). Diet supplemented with 140 mg Zn/kg increased shell thickness and palisade layer thickness of duck breeders at 36 weeks of age (P < 0.05), but not at 32 and 34 weeks of age. In conclusion, diets with 40 or 140 mg Zn/kg improved egg production performance and egg quality of laying duck breeders during 30-36 weeks of age in a furnished cage system. Dietary supplementation of 140 mg Zn/kg level increased the ultrastructural palisade layer thickness contributing to greater eggshell thickness of duck breeders at 36 weeks of age.

The Role of Zinc in Poultry Breeder and Hen Nutrition: an Update.

Zinc (Zn) is an essential trace mineral in breeder hen diets and functions in diverse physiological processes, including reproduction, immunity, antioxidant ability, and epigenetic processes. In this paper, five main aspects of Zn nutrition in poultry breeder birds and hens, including semen quality, molting, egg production and egg quality, hatchability and embryonic development, and offspring performance, are reviewed. Zn deficiency in poultry breeder birds led to lower semen quality (reducing around 10% sperm motility) and egg production (lowering 3-10 g/day/bird egg mass) as well as poor offspring development and growth performance (increasing 9-10% weak chick ratio and 10% mortality of progeny). Adequate maternal or higher Zn supplementation was adopted not only to induce molting with a greater postmolt performance (rising 4-7% laying rate) but also to enhance progeny immune response and antioxidant ability via epigenetic mechanisms. Therefore, it is necessary to reevaluate the optimal Zn requirement for egg production as well as the embryonic development and offspring chick performance of breeder hens. In the last 10 years, greater attention has been focused on the effectiveness of organic Zn for improving the reproductive performance of breeders and progeny viability and immune status. In fact, organic Zn sources are not always beneficial to the above aspects. So far, it has been very important to know the exact mechanisms of greater bioavailability and the epigenetic role of organic Zn sources in the augmentation of immune status and antioxidant abilities in poultry breeder birds and offspring. Therefore, a comprehensive analysis of these key points will not only aid in maintaining the beneficial effects of Zn nutrition for breeders and their progeny under stable conditions but will also support birds under stressful conditions such as disease as well as provide a better understanding of the integrated nutrition of breeder-offspring.

Effects of dietary arginine and glutamine on alleviating the impairment induced by deoxynivalenol stress and immune relevant cytokines in growing pigs.

Deoxynivalenol (DON) is a mycotoxin that reduces feed intake and animal performance, especially in swine. Arginine and glutamine play important roles in swine nutrition. The objective of this study was to determine the effects of dietary supplementation with arginine and glutamine on both the impairment induced by DON stress and immune relevant cytokines in growing pigs. A total of forty 60-d-old healthy growing pigs with a mean body weight of 16.28±1.54 kg were randomly divided into 5 groups, and assigned to 3 amino acid treatments fed 1.0% arginine (Arg), 1.0% glutamine (Gln) and 0.5% Arg+0.5% Gln, respectively, plus a toxin control and a non-toxin control. Pigs in the 3 amino acid treatments were fed the corresponding amino acids, and those in non-toxin control and toxin control were fed commercial diet with 1.64% Alanine as isonitrogenous control for 7 days. The toxin control and amino acid treatments were then challenged by feeding DON-contaminated diet with a final DON concentration of 6 mg/kg of diet for 21 days. No significant differences were observed between toxin control and the amino acid groups with regard to the average daily gain (ADG), although the values for average daily feed intake (ADFI) in the amino acid groups were significantly higher than that in toxin control (P<0.01). The relative liver weight in toxin control was significantly greater than those in non-toxin control, arginine and Arg+Glu groups (P<0.01), but there were no significant differences in other organs. With regard to serum biochemistry, the values of BUN, ALP, ALT and AST in the amino acid groups were lower than those in toxin control. IGF1, GH and SOD in the amino acid groups were significantly higher than those in toxin control (P<0.01). The IL-2 and TNFα values in the amino acid groups were similar to those in non-toxin control, and significantly lower than those in toxin control (P<0.01). These results showed the effects of dietary supplementation with arginine and glutamine on alleviating the impairment induced by DON stress and immune relevant cytokines in growing pigs.

Dietary arginine supplementation increases mTOR signaling activity in skeletal muscle of neonatal pigs.

Dietary arginine supplementation increases growth of neonatal pigs, but the underlying mechanisms are unknown. This study was conducted to test the hypothesis that the arginine treatment activates translation initiation factors and protein synthesis in skeletal muscle. Piglets were fed milk-based diets supplemented with 0 or 0.6% L-arginine between 7 and 14 d of age. Following a 7-d period of arginine supplementation, at 1 h after the last meal, jugular venous blood samples were obtained for metabolite analysis, whereas longissimus muscle and liver were collected to determine the abundance and phosphorylation state of the mammalian target of the rapamycin (mTOR), ribosomal protein S6 kinase 1 (S6K1), eukaryotic initiation factor (eIF) 4E-binding protein-1 (4E-BP1), eIF4E, and eIF4G. Fractional rates of protein synthesis were measured in muscle and liver using the [(3)H]phenylalanine flooding-dose technique. Arginine supplementation increased (P < 0.05) daily gain, the plasma insulin concentration, and protein synthesis in skeletal muscle but not in liver. The arginine treatment enhanced the formation of the active eIF4E x eIF4G complex but reduced the amount of the inactive 4E-BP1 x eIF4E complex in muscle. These changes were associated with elevated levels of phosphorylated mTOR and 4E-BP1 in muscle of arginine-supplemented piglets (P < 0.05). Neither the total amounts nor phosphorylation levels of the translation initiation factors in the liver differed between control and arginine-supplemented piglets. Collectively, these results suggest that dietary arginine supplementation increases mTOR signaling activity in skeletal muscle, but not in liver, of milk-fed neonatal pigs. The findings provide a molecular mechanism for explaining the previous observation that increased circulating arginine stimulated muscle protein synthesis and promoted weight gain in neonatal pigs.