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AbstractThis study aimed to investigate the effects of dietary supplementation with 5-aminolevulinic acid (5-ALA) on growth performance, blood parameters, iron status, nutrient digestibility, and antioxidant capacity in broilers. A total of 600 one-day-old Arbour Acres broilers were distributed into 5 groups with 6 replicates of 20 birds by a completely randomised design. The birds in the 5 groups were fed the basal diets with 0, 15, 30, 45, and 60 mg/kg 5-ALA, respectively. Dietary supplementation with 60 mg/kg 5-ALA significantly reduced the feed to gain ratio during days 1–21 and days 22–42. Moreover, compared with the control group, dietary supplementation with 30 mg/kg 5-ALA elevated haemoglobin concentrations during days 1–21. Furthermore, dietary supplementation with 45 and 60 mg/kg 5-ALA increased the digestibility of crude protein and decreased serum uric acid levels. At 21 days of age, dietary supplementation with 45 and 60 mg/kg 5-ALA increased liver catalase activity and decreased liver malondialdehyde concentrations, and upregulated the liver mRNA expression of ferritin light chain and nuclear factor erythroid 2-related 2. In addition, the liver mRNA expression of haem oxygenase-1 and divalent metal transporter were upregulated in the 60 mg/kg 5-ALA supplementation group, while the liver mRNA expression of Kelch-like ECH-associated protein 1 was decreased in the 5-ALA supplementation groups. In conclusion, dietary supplementation with 60 mg/kg 5-ALA improved the growth performance, nutrient digestibility, iron status and antioxidant capacity of 21-d-old broilers.HighlightsAddition of 60 mg/kg 5-ALA to broiler diets reduced the feed to gain ratio.Addition of 45 and 60 mg/kg 5-ALA to broiler diets improved crude protein digestibility and decreased serum uric acid levels.5-ALA exhibited antioxidant properties by enhancing the Nrf2 and HO-1 expression

The negative effects of dietary antibiotics have become a widespread concern. It is imperative to search for a new type of green, safe, and efficient feed additive that can replace antibiotics. This study was to investigate the effects of glucose oxidase (GOD) on growth performance, immune function, and intestinal barrier in ducks infected with Escherichia coliO88. First, we established the E. colichallenge model of ducks through a preliminary experiment and then carried out the formal experiment by using 144 1-day-old male lean Peking ducklings (50 ± 2.75 g). All ducks were randomly assigned to 1 of 3 dietary treatment groups of basal diet (control), 30 mg/kg virginiamycin (antibiotic), and 200 U/kg GOD (1,000 U/g). Each group consisted of 6 replications with 8 birds per replicate. At day 7, all ducks were orally administered 0.2 mL E coliO88 (3 × 109 cfu/mL) twice, 8 h apart based on the preliminary experiment. The experiment lasted for 28 d. Dietary supplementation with GOD improved growth performance of ducks infected with E. coli. The GOD increased contents of Ig in plasma and secreted Ig A in jejunal mucosa. The GOD group had lower concentrations of inflammatory cytokines (tumor necrosis factor-α, IL-1β, and IL-6) and their upstream regulator Toll-like receptor 4 in the jejunum of ducks than the control group. Supplementation with GOD increased villus height and decreased crypt depth in the jejunum. The gene expression of tight junction proteins (zonula occludens-1, claudin-1 and claudin-2) was enhanced by adding GOD. The GOD decreased intestinal permeability by reducing the concentrations of diamine oxidase and D-lactic in plasma of ducks. There were no significant differences in almost all the indices tested between the GOD and the antibiotic groups. In conclusion, supplementation of GOD improved growth performance, immune function, and intestinal barrier of ducks infected with E. coliO88. Glucose oxidase may serve as a promising alternative therapy to antibiotics to relieve or prevent colibacillosis in ducks.

This experiment was to investigate the effects of dynamic segmentation of interval nutrient supply phase feeding on the growth performance, carcass characteristics, immune organs indexes and intestinal morphology of broilers. A total of 320 one-day-old broilers were randomly assigned into 4 feeding treatments, which included 4 interval nutrient supply phases as follows. Treatment A: a nutrient supply standard was used for every 14 d. Treatment B: a nutrient supply standard was used for every 7 d. Treatment C: a nutrient supply standard was used for every 3.5 d except that one nutrient supply standard was used for d 1 to 7. Treatment D: a nutrient supply standard was used for every 3.5 d including d 1 to 7. Each treatment was represented by 8 replicates with 10 broilers per replicate. The trial lasted for 42 days. Throughout the 42 d trial period, treatment A showed significantly higher average daily gain than treatments B and C (P < 0.05). The feed:gain ratio of treatment A was significantly lower than those of treatments C and D (P < 0.05). On d 28 and 42, body weight of broilers in treatment A was much higher than those of treatments B and C (P < 0.05). The slaughter rate of treatment A was significantly higher than that of treatment B (P < 0.05). Eviscerated percentage of treatment A was significantly higher than those of treatment B and D (P < 0.05). There were no significant differences among 4 treatments in immune organs indexes (P > 0.05). The crypt depth of duodenum was significantly greater in treatments A and B than in treatment C on day 42 (P < 0.05). Meanwhile, the ratio of villus height to crypt depth (V:C ratio) of treatment D was significantly higher than that of treatment A (P < 0.05). No significant differences were found between treatments C and D in growth performance, carcass performance, immune organs indexes and intestinal structure (P > 0.05). In conclusion, this study revealed that the growth and carcass performance of broilers is the best for 14 days segmentation phase feeding, and 3.5 days segmentation interval phase feeding can promote small intestinal development of broilers. Dynamic segmentation of dietary supply fails to affect the immune function of broilers.

This study aims to evaluate the effects of aflatoxins on growth performance and skeletal muscle of Cherry Valley meat male ducks as they grow and develop. One-day-old healthy meat male ducks (n = 180) were randomly divided into 2 groups; there were 6 replicates in each group and 15 ducks in each replicate. The control group was fed a basic diet, and the experimental group was fed a mold-exposed cottonseed meal diet containing aflatoxins instead of normal cottonseed meal. The experimental period was 35 days, and divided into two stages of 1 to 14 days (early stage) and 15 to 35 days (late stage). During the experimental period, live weight, breast muscle weight and thigh muscle weight of meat male ducks were measured weekly. Results showed as follows: 1) aflatoxins contained in the mold-exposed diet significantly reduced daily weight gain and feed intake, and increased feed-to-gain ratio of meat male ducks at different ages (P < 0.05); 2) the Gompertz equation (Wt = Wmexp {−exp [−B (t − t*)]}) could successfully fit the growth curve and growth and developmental patterns of skeletal muscles of Cherry Valley meat male ducks (R2 ≥ 0.97); 3) the relationship between chest muscle and live weight was the best described by a power regression and polynomial regression (R2 = 0.99); the relationship between live weight and thigh muscle weight was the best described by linear regression, polynomial regression, and power regression (R2 = 0.99); 4) aflatoxins in the mold-exposed diet significantly reduced live weight, breast muscle weight and thigh muscle weight of Cherry Valley meat male ducks at various ages; and 5) aflatoxins delayed the age at peak in growth of meat male ducks, and reduced weights at the peak for breast muscle, thigh muscle and whole body as well as the maximal daily weight gain. In summary, aflatoxins delayed growth of Cherry Valley meat male ducks and development of skeletal muscle.

This experiment was to investigate the effects of dietary leucine supplementation on the gene expression of mammalian target of rapamycin (mTOR) signaling pathway and intestinal development of broilers. A total of 384 one-day-old broilers were randomly assigned into 4 treatments with 6 replicates (16 broilers per replicate). Broilers in these treatment groups were offered the following diets with 1.37, 1.77, 2.17 and 2.57% of leucine. These diet treatments were named 1.37TM, 1.77TM, 2.17TM, and 2.57TM. The experiment lasted 21 days and all birds had free access to feed and water. Results indicated that there was no significant difference in body weight, average daily gain and average feed intake among all treatments (P > 0.05). The broiler duodenal villus height in 2.57TM was the lowest, but the highest occurred in 1.37TM on d 7 and 14 (P < 0.05). The villus height in the jejunum and ileum increased along with leucine level from 1.37 to 2.17%. The villus height of jejunum was significantly higher in 2.17TM than in 1.37TM on d 7 and 14, and the ratio of villus height to crypt depth (V:C) in the duodenum, jejunum and ileum increased significantly (P < 0.05) on d 21. The gene expression level of mTORin the duodenum decreased with increasing leucine level and was higher in 1.37TM than in 2.57TM on d 7 and 14 (P < 0.05). On d 14 and 21 of the trial, the expression of S6K1in the duodenum was higher in 1.37TM than in 2.57TM (P < 0.05), and the expression of mTOR, S6K1in the jejunum and ileum increased with increasing leucine level form 1.37 to 2.17%, whereas a significant difference occurred between 1.37TM and 2.17TM (P < 0.05). In conclusion, the addition of leucine fails to enhance the growth performance of broilers. However, leucine can improve intestinal development by enhancing villus height and V:C ratio in the jejunum and ileum. Moreover, the expression of mTOR, S6K1increased as the level of dietary leucine was elevated from 1.37 to 2.17%.

We studied the effects of Lactobacillus acidophilus(L. acidophilus) on the growth performance, intestinal morphology, barrier function, and immune response of broilers challenged with Escherichia coliO157 (E. Coli). A total of 360 1-day-old Cobb male broilers were tested in a 3 × 2 factorial arrangement with 3 dietary L. acidophiluslevels (0, 5 × 108CFU/kg, and 10 × 108CFU/kg of diet) and 2 disease challenge treatments (control or E. colichallenged). Results showed that E. colichallenge decreased the ADG, ADFI, and BW of broilers from 15 to 21 d (P< 0.05), increased the jejunum intestinal wall thickness, and significantly increased the mortality rate. E. colichallenge significantly (P< 0.05) decreased the serum IgA and IgM contents and peripheral blood CD3+ T cell counts (P< 0.05), increased the serum CRP, DAO, and LPS levels at 21 d; upregulated the mRNA expression of iNOS, IL-8, IL-1β in the jejunum and iNOS in the spleen, and downregulated the occludin and ZO-1 mRNA expression in the ileum at 21 d compared with uninfected birds (P< 0.05). Dietary L. acidophilussupplementation consistently showed higher BW, ADG, ADFI, and jejunum and ileum V:C ratio at 14 d and 21 d in the presence and absence of E. colichallenge (P< 0.05). L. acidophilussupplementation reduced the mortality rate caused by E. colichallenge (P< 0.05), decreased the serum CRP, DAO, and LPS levels at 14 d and 21 d; upregulated the mRNA expression of occludin and ZO-1 in the jejunum and ileum, and downregulated the mRNA expression of iNOS, IL-8, and IL-1β in the jejunum in E. colichallenged birds at 21 d (P< 0.05). Dietary supplementation with L. acidophiluscan improve the growth performance, intestinal health, and survival of broilers challenged with E. coli.