A Meta-analysis of Responses of Broiler Chickens to Dietary Zinc Supplementation: Feed Intake, Feed Conversion Ratio and Average Daily Gain

Productive, internal organ and intestinal histomorphological characteristics of broiler chickens in response to dietary rapeseed meal: A meta-analysis

The use of rapeseed as a source of protein in broiler chicken diets has been highlighted. However, there are inconsistent findings on the performance data of broiler chickens fed rapeseed meal (RSM). Therefore, this meta-analysis aimed to resolve the inconsistent findings on the effect of RSM on growth performance, carcass characteristics, internal organs, and intestinal histomorphology of broiler chickens, identify knowledge gaps and create new insights using published data. Fourteen studies on the topic were identified via a systematic search performed on bibliographic databases, and the data generated was analysed using OpenMEE software. A random-effects model was used, and effect sizes were presented as standardised mean difference (SMD) at a 95% confidence interval (CI). Sources of heterogeneity were evaluated using broiler strains, inclusion levels, processing methods, rearing phases and sex as moderators. In comparison with the controls, the results showed that RSM decreased feed intake (SMD = -0.29; 95% Cl: -0.41, -0.18; p < 0.001), average daily gain (SMD = -0.48; 95% Cl: -0.63, -0.32; p < 0.001), and liver weight (SMD = 1.24; 95% Cl: 0.78, 1.71; p < 0.001), but had no effect on feed conversion ratio (SMD = 0.10; 95% Cl: -0.05, 0.23; p = 0.19). Likewise, broiler chickens fed RSM had significantly reduced carcass yield, weights of thigh, abdominal fat and heart when compared with the control. Results indicate that duodenum villus height (DVH) and jejunum villus height (JVH)/crypt depth (CD) ratios were improved in broiler chickens fed RSM. Meta-regression revealed that the analysed moderators are significant predictors of feed intake, average daily gain and feed conversion ratio in broiler chickens. In conclusion, dietary RSM negatively influenced growth performance, liver weight and carcass characteristics in broiler chickens, but improved aspects of intestinal histomorphology traits. Therefore, innovative research on processing methods that will improve the feeding value of rapeseed meal in broiler chickens is recommended.

A novel consensus bacterial 6-phytase variant supplemented to an all-vegetable broiler diet totally replaced added trace minerals including zinc, iron, copper and manganese in two experiments

Two experiments tested the effect of a bacterial 6-phytase (PhyG) supplemented to a vegetable broiler diet without or with added trace minerals (TM), on growth performance and TM utilization. Each tested 12 treatments in a 2 × 6 factorial arrangement with 3,360 Ross 308 males (35 birds/pen, 8 pens/treatment) in a randomized complete block design. Phytase levels comprised no PhyG or PhyG at 2,000, 1,500 and 1,000 FTU/kg during 0 to 10, 10 to 20 and (Experiment 2) 20 to 35 d of age, respectively; TM diets comprised: no added TM (diet 1); 10, 15, 3 and 10, or 20, 30, 6 and 20 mg/kg of Zn, Fe, Cu and Mn as sulphate (diets 2 and 3); 15, 3 and 10 mg/kg of Zn, Cu and Mn as oxide and 15 mg/kg Fe as sulphate, or 30, 6 and 20 mg/kg of Zn, Cu and Mn as oxide and 30 mg/kg Fe as sulphate (diets 4 and 5), and; 10, 3, 15 and 10 mg/kg of organic Zn, Cu, Fe and Mn (diet 6). Apart from no added TM, basal diets were nutritionally adequate; phytase-supplemented diets were reduced in Ca and retainable P. All diets were pelleted and fed ad libitum. In both experiments during all phases there were interactions (P < 0.05) between phytase and TM on BW, BW gain (BWG), feed intake (FI), FCR (experiment 2 only) and tibia Zn. Without phytase, TM improved (P < 0.05) these measures. Phytase without TM increased (P < 0.05) d 35 BW, overall BWG and FI, equivalent to or beyond the level achieved by TM without phytase. Tibia Zn at d 10 and 20 in Experiment 2 was increased by phytase beyond the level achieved by TM without phytase (P < 0.05). Phytase also increased (P < 0.05) liver Zn, Fe, and Mn at d 10 and 20 and plasma Zn at d 20 d. There was no consistent effect of TM source or dose on bird responses. In conclusion, PhyG phytase replaced the effect of added TM on performance during 0 to 35 d of age and could support a reduction in commercial dose levels of added TM in all-vegetable broiler diets.

Effect of dietary β-mannanase supplementation on growth performance, intestinal morphology, digesta viscosity, and nutrient utilization in broiler chickens: Meta-analysis and meta-regression

OBJECTIVE

The present study aimed to investigate the effectiveness of dietary β-mannanase supplementation on growth performance, intestinal morphology, digesta viscosity, and dietary nutrient utilization in broiler chickens through a meta-analysis. The effects were further examined by a meta-regression analysis with activity levels of β-mannanase in broiler diets.

METHODS

A total of 23 studies, which were conducted in 11 countries and completed between December 2003 and August 2023, were selected for this meta-analysis. The standardized mean difference and its 95% confidence interval were calculated as the effect size metrics using random effect model, with I2 value being utilized to measure heterogeneity. Investigated measurements included body weight gain (BWG), feed intake, feed conversion ratio (FCR), villus height (VH), crypt depth (CD), VH:CD ratio, digesta viscosity, nitrogencorrected metabolizable energy (n), apparent ileal digestibility (AID), and apparent total tract retention (ATTR) of dry matter (DM), gross energy (GE), and nitrogen (N). All statistical analyses were performed using R version 4.3.3.

RESULTS

Results revealed significant positive effects of dietary β-mannanase supplementation on BWG (p = 0.005), FCR (p<0.001), VH (p<0.001), VH:CD (p<0.001), digesta viscosity (p<0.001), AMEn (p = 0.011), AID of GE (p = 0.002) and N (p = 0.003), and ATTR of DM (p = 0.019), GE (p = 0.002), and N (p = 0.005) in broiler chickens. In the meta-regression analysis, increasing activity levels of β-mannanase in broiler diets increased VH:CD (p< 0.001; R2 = 79.2%) and AID of N (p = 0.038; R2 = 67.4%).

CONCLUSION

The current meta-analysis indicates that dietary β-mannanase supplementation improves energy and nutrient utilization in broiler diets possibly by decreasing digesta viscosity and enhancing intestinal morphology in broiler chickens. These beneficial effects can contribute to improved growth performance in broiler chickens.

Effect of Zinc Amino Acid Complexes on Growth Performance, Tissue Zinc Concentration, and Muscle Development of Broilers

The present study aimed to evaluate the effects of zinc amino acid complexes on growth performance, tissue zinc concentration, and muscle development in broilers. A total of 504 day-old male arbor acres broilers were randomly divided into seven treatments (fed with a basal diet or a basal diet supplemented with 120 mg kg-1 Zn as ZnSO4, 30, 60, 90 or 120 mg kg-1 Zn as ZnN, or 30 mg kg-1 Zn as ZnA separately). Each group had six replicates, with 12 birds per replicate. The results showed that the addition of 60 mg kg-1 ZnN significantly increased (P < 0.05) the average daily gain (ADG) and breast muscle percentage of broilers. Zinc concentration of ZnN and ZnA added groups were higher than (P < 0.05) that in the Zn sulfate group under the same addition dose. Except for the 30 mg kg-1 ZnN group, the muscle fiber diameter and cross-sectional area (CSA) were significantly increased (P < 0.05) in the ZnN addition groups. Compared with the basal diet group, adding ZnN significantly increased (P < 0.05) the expression of MTOR, MYOD, and MYOG at day 21 and decreased (P < 0.05) the expression of Atrogin-1. The expression levels of AKT, MTOR, P70S6K, and MYOD were increased at day 42, while the expression levels of MuRF1 and Atrogin-1 were decreased. Adhesion, backbone regulation of actin, MAPK, mTOR, and AMPK were significantly enriched as indicated by KEGG pathway enrichment analysis. In conclusion, zinc amino acid complexes could improve growth performance, tissue zinc concentration, and regulate breast muscle development.

Integrated evaluation of the requirements and excretions of Cu, Fe, Zn, and Mn for broilers via a uniform design method

This study aimed to determine the ideal balance profile of Cu, Fe, Zn, and Mn for broilers of 1-21 days of age via a uniform experimental design. In Experiment 1, 900 1-day-old Arbor Acres male broilers were randomly allotted to 15 dietary treatments with six replicates of 10 birds. A total of 14 experimental diets were formulated with the supplementation of 8~16, 123~160, 40~80, and 60~120 mg/kg of Cu, Fe, Zn, and Mn, respectively, in the basal diet, according to the uniform design method. The excretion of Cu, Fe, Zn, and Mn in the manure and the broiler performance were determined to build the ideal balance profile of these elements. Experiment 2 was conducted based on the ideal balance profile built in Experiment 1, to test its practicability using 720 broilers with two treatments. The dietary concentrations of Cu, Fe, Zn, and Mn in the control group were 15.19, 203.08, 76.78, and 86.13 mg/kg, respectively. In Experiment 1, the concentrations of Cu, Fe, Zn, and Mn in the diets were 16.96, 166.66, 46.01, and 60.26 mg/kg, respectively, when the average daily gain reached the optimum value. When the dietary concentrations of Cu, Fe, Zn, and Mn were 8.54, 130.66, 38.19, and 64.07 mg/kg, respectively, the total excretion of Cu, Fe, Zn, and Mn got the minimum value. There are corresponding ideal balance profiles for minimum excretion of a certain element. In Experiment 2, the dietary levels of Fe, Zn, and Mn were decreased by 17.93%, 40.08%, and 30.04%, respectively, which had no significant effect on average daily gain, average daily feed intake, and feed gain for 1~21 day-old broilers but markedly decreased the excretion of Cu and Mn and total excretion. It was concluded that there is a dilemma between growth performance and mineral excretion. Although dietary levels of Cu, Fe, Zn, and Mn supporting optimal growth are higher than those for minimizing mineral excretion, supplementing too many trace elements in the diets of broilers is unnecessary.

Effect of Two Particle Sizes of Nano Zinc Oxide on Growth Performance, Immune Function, Digestive Tract Morphology, and Intestinal Microbiota Composition in Broilers

The effects of dietary supplementation with two particle sizes of nano zinc oxide (ZnO) on growth performance, immune function, intestinal morphology, and the gut microbiome were determined in a 42-day broiler chicken feeding experiment. A total of 75 one-day-old Arbor Acres broilers were randomized and divided into three groups with five replicates of five chicks each, including the conventional ZnO group (NC), the nano-ZnO group with an average particle size of 82 nm (ZNPL), and the nano-ZnO group with an average particle size of 21 nm (ZNPS). Each group was supplemented with 40 mg/kg of ZnO or nano-ZnO. Our results revealed that birds in the ZNPS group had a higher average daily gain and a lower feed-to-gain ratio than those in the NC group. ZNPS significantly increased the thymus index and spleen index, as well as the levels of serum metallothionein (MT), superoxide dismutase (SOD), and lysozyme (LZM). The ZNPS treatments reduced interleukin (IL)-1β and tumor necrosis factor-alpha (TNF-α) levels and increased IL-2 and interferon (IFN)-γ levels compared to that in the NC group. Additionally, compared with the birds in the NC group, those in the nano-ZnO group had a higher villus height to crypt depth ratio of the duodenum, jejunum, and ileum. Bacteroides increased in the ZNPS group at the genus level. Further, unidentified_Lachnospiraceae, Blautia, Lachnoclostridium, unidentified_Erysipelotrichaceae, and Intestinimonas were significantly increased in the ZNPL group. In conclusion, nano-ZnO improved the growth performance, promoted the development of immune organs, increased nonspecific immunity, improved the villus height to crypt depth ratio of the small intestine, and enriched the abundance of beneficial bacteria. Notably, the smaller particle size (21 nm) of nano-ZnO exhibited a more potent effect.