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Background Unmanned aerial vehicle (UAV)-based remote sensing provides a flexible, low-cost, and efficient approach to monitor crop growth status at fine spatial and temporal resolutions, and has a high potential to accelerate breeding process and improve precision field management. Method In this study, we discussed the use of lightweight UAV with dual image-frame snapshot cameras to estimate aboveground biomass (AGB) and panicle biomass (PB) of rice at different growth stages with different nitrogen (N) treatments. The spatial–temporal variations in the typical vegetation indices (VIs) and AGB were first investigated, and the accuracy of crop surface model (CSM) extracted from the Red Green Blue (RGB) images at two different stages were also evaluated. Random forest (RF) model for AGB estimation as well as the PB was then developed. Furthermore, variable importance and sensitivity analysis of UAV variables were performed to study the potential of improving model robustness and prediction accuracies. Results It was found that the canopy height extracted from the CSM (Hcsm) exhibited a high correlation with the ground-measured canopy height, while it was unsuitable to be independently used for biomass assessment of rice during the entire growth stages. We also observed that several VIs were highly correlated with AGB, and the modified normalized difference spectral index extracted from the multispectral image achieved the highest correlation. RF model with fusing RGB and multispectral image data substantially improved the prediction results of AGB and PB with the prediction of root mean square error (RMSEP) reduced by 8.33–16.00%. The best prediction results for AGB and PB were achieved with the coefficient of determination (r 2 ), the RMSEP and relative RMSE (RRMSE) of 0.90, 0.21 kg/m 2 and 14.05%, and 0.68, 0.10 kg/m 2 and 12.11%, respectively. In addition, the result confirmed that the sensitivity analysis could simplify the prediction model without reducing the prediction accuracy. Conclusion These findings demonstrate the feasibility of applying lightweight UAV with dual image-frame snapshot cameras for rice biomass estimation, and its potential for high throughput analysis of plant growth-related traits in precision agriculture as well as the advanced breeding program. Electronic supplementary material The online version of this article (10.1186/s13007-019-0418-8) contains supplementary material, which is available to authorized users.

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This review critically examines the literature on the current status of trace mineral nutrition and the effect of organically complexed trace minerals, focusing on copper (Cu), iron (Fe), manganese (Mn) and zinc (Zn), on broiler chicken production. The requirements of Cu, Fe, Mn and Zn by broiler chickens need to be redefined due to today’s fast growing birds and the availability of organic trace minerals. Zn is one of the key trace minerals for chickens and although it maintains a relatively stable tissue concentration, dietary deficiency of Zn strongly depresses the feed intake, and hence the growth, of broiler chickens. Based on studies using a semiconventional diet, it is reasonable to conclude that the total Zn requirement for broiler chickens is around 60 mg/kg up until day 14 and 70 mg/kg from 14 day onwards, including the Zn content in the basal diet. However, it is difficult to determine the requirements of other organic trace minerals such as Cu, Fe and Mn because under a Zn adequate condition, it is impossible to produce deficient symptoms of these minerals on the basis of growth response. It also identifies gaps in knowledge of inorganic and organic trace mineral nutrition for the modern broiler chicken.

Hydrothermal synthesis of tetraborate, B 4 O 5 (OH) 4 2-, -pillared hydrotalcites was investigated, and an efficient way of preparing them was found. The structures of the pillared materials were characterized using a combination of techniques such as powder X-ray diffraction, FT-IR, 11 B and 27 Al MAS NMR, DTA/TGA, and chemical analysis. The results show that the structure of the coprecipitate is important in controlling the formation of B 4 O 5 -(OH) 4 2--pillared hydrotalcites. With a slurrylike precipitate, a more ordered structure of the pillared hydrotalcite is obtained, while with a wet cakelike precipitate, a disordered structure of the pillared hydrotalcite is formed. The tetraborate anions in the interlayer space orient with their tetrahedral BO 4 linkage perpendicular to the sheets of hydrotalcite. The tetraborate pillared material has a chemical composition of [Mg 0.70 Al 0.30 (OH) 2 ][B 4 O 5 -(OH) 4 ] 0.15 ‚H 2 O and a surface area of ∼47 m 2 /g.

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1. The effect of potassium diformate (KDF) on mortality, growth performance, microbial populations, pH and short chain fatty acid concentrations in the intestinal tract of broiler chickens challenged with necrotic enteritis was investigated. 2. An experiment with 1050 Cobb male broiler chickens was conducted from 1 to 35 d of age. There were 7 treatment groups: (1) unchallenged negative control, (2) unchallenged KDF (4.50 g/kg feed), (3) challenged negative control, (4) challenged positive control (100 ppm monensin and 45 ppm Zn-bacitracin), and (5) to (7) challenged KDF (inclusion rate 2.25, 4.50 and 6.75 g/kg feed, respectively). 3. The necrotic enteritis challenge caused significant growth depression except in the challenged positive control group. Inclusion of KDF in feed had no significant effect on weight gain or feed conversion ratio, neither under challenged nor unchallenged conditions. Necrotic-enteritis-related mortalities were reduced in response to the positive control feed and KDF at 2.25 and 4.50 g/kg rates, but with no effect at the 6.75 g/kg rate. 4. There was no effect of KDF on Clostridium perfringens numbers in jejunum during the necrotic enteritis challenge (d 15). Post challenge (d 35), 4.5 g/kg KDF reduced the number of C. perfringens and Enterobacteria in jejunum compared with the negative control group. 5. Intestinal pH was not affected by adding KDF to the feed. The challenge reduced jejunum pH compared with the unchallenged treatment groups and challenged positive control group. 6. Chickens fed the KDF diets had detectable concentrations of formic acid in the jejunum. There was a tendency towards higher concentrations of acetic acid and lactic acid in the small intestine of unchallenged birds, whereas challenged birds had higher concentrations of butyric acid in the caeca. 7. It is concluded that KDF holds promise as an agent to control necrotic enteritis in broiler chickens and it may be possible to enhance the efficacy of KDF by manipulating dietary properties that may influence the dissociation kinetics of KDF in the gut.

1. The aim of the present study was to demonstrate trace mineral interactions among organic copper, iron, manganese and zinc (Cu, Fe, Mn and Zn) in broiler chickens. 2. Three experiments were conducted using a control diet which was deficient in Cu, Fe, Mn and Zn. 3. In experiment 1, the control diet, supplemental organic Cu, Fe alone and combined diets, were randomly fed to 4 groups of one-day-old Cobb broilers (each group had 6 replicates of 4 birds). 4. In experiment 2, the control diet, supplemental organic Mn and Zn alone or combined with Cu, Fe diets and corresponding inorganic combined diet, were randomly fed to 6 groups (each group had 8 replicates of 6 birds). 5. In experiment 3, the depletion of organic Zn, the depletion of inorganic Zn and normal Zn treatments were carried out in three groups of one-day-old Cobb broilers (each group had 8 replicates of 6 birds). 6. Adding organic Cu, Fe and Mn alone or combined to Zn deficient diets did not significantly improve bird performance and were mostly excreted. Supplemental organic Zn alone or combined with other elements significantly increased feed intake, body weight gain and tibia bone length. However, supplemental organic Fe alone or combined with Cu significantly increased feed intake but had no obvious effect on body weight gain. The organic Fe supplementation resulted in a wider tibia. 7. Depletion of organic and inorganic Zn resulted in decreased feed intake, body weight gain and total tibia bone Zn content. Zinc deficiency did not affect the uptake of organic Fe by tibia bone but reduced its total Fe content. 8. Zinc is the first limiting element among these 4 trace minerals. Adding Mn, Cu and Fe to Zn deficient diets did not stimulate bird performance. Surplus organic Fe and Cu resulted in increased feed intake and increased tibia bone Fe content but did not contribute to bird performance.