Toxicity of dietary melamine to laying ducks: biochemical and histopathological changes and residue in eggs

Effects of photoperiod on performance, ovarian morphology, reproductive hormone level, and hormone receptor mRNA expression in laying ducks

We investigated the effect of photoperiod on performance, ovarian morphology, reproductive hormones levels, and their receptors mRNA expressions in laying ducks. After adaption, 300 252-day-old Jinding laying ducks were randomly allocated to 5 groups, receiving 12L:12D, 14L:10D, 16L:8D, 18L:6D, or 20L:4D, respectively. Each treatment had 6 replicates of 10 birds each. The feeding trial lasted 8 wk. Egg production, egg mass, and ADFI increased linearly and quadratically with increasing photoperiods (P < 0.05), and the higher values of them occurred in photoperiods ≥ 16 h, compared with 12L:12D (P > 0.05). Initial and bare stroma weight increased quadratically, while total large white follicle (LWF) number and weight increased linearly and quadratically, with increasing photoperiods (P < 0.05). The higher values of them occurred in 16L:8D and 18L:6D treatments as well as the higher total LWF weight also occurred in 20L:4D, compared with 12L:12D (P > 0.05). Besides, 16.93 and 16.93 h were the optimal photoperiods for bare stroma (follicles ≥ 2 mm in diameter removed) weight and total LWF weight, respectively, calculated from reliable regression equations (R² ≥ 0.5071). Compared with 12L:12D, the higher levels of estradiol, progesterone, follicle-stimulating hormone (FSH) as well as the higher expressions of estrogen, luteinizing hormone (LH) and progesterone receptors were observed in ≥16 h photoperiods (P < 0.05), while the higher LH level and FSH receptor expression only occurred in 16L:8D and 18L:6D (P < 0.05). In the hypothalamus, higher mRNA expression of gonadotropin-releasing hormone occurred in 16L:8D and 18L:6D groups (P < 0.05). Meanwhile, gonadotropin-inhibitory hormone and prolactin increased in 20-hour photoperiod (P < 0.05), and the latter may be due to theup-regulation of vasoactive intestinal peptide expression (P < 0.05). To sum up, an appropriate photoperiod could improve the performance and reproductive organ and ovarian follicles development through reproductive hormones and their receptors, and 16.56 to 10.93 h is an adequate photoperiod for laying ducks.

Benchmark dose analysis framework for developing wildlife toxicity reference values

The effects characterization phase of ecological risk assessments (ERAs) often includes the selection or development of toxicity reference values (TRVs) for chemicals under investigation. In wildlife risk assessments, TRVs are thresholds represented by a dose or concentration associated with a specified adverse response. Traditionally, a TRV may be derived from an estimate of the no-observed-adverse effect level or lowest-observed-adverse-effect level, identified from a controlled toxicity study. Because of the limitations of this approach, risk assessors are increasingly developing TRVs using alternative methods. Benchmark dose (BMD) analysis is widely recognized as one approach for developing TRVs. A BMD is derived using the full dose-response relationship from all experimental doses and may represent a user-specified response level (e.g., 5, 10, 20, or 50%). Although many regulatory programs consider the use of BMD-derived wildlife TRVs, there is limited guidance available for implementing the BMD approach, particularly for ERA. The present study provides a framework for ecological risk assessors to identify appropriate data, examine dose-response relationships, estimate BMDs, and document the results for use in risk analysis. This framework demonstrates the process of developing a TRV using BMD analysis and identifies applications for which this approach may enhance ERAs (e.g., site assessment, chemical or pesticide registration programs). Environ Toxicol Chem 2018;37:1496-1508. © 2018 SETAC.

Broiler chickens exposed to melamine and cyanuric acid-contaminated diets

The objective of this study was to investigate whether melamine (MEL) is biotransformed into cyanuric acid (CYA) in male broiler chickens. The effects of the dietary addition of MEL and CYA alone and in combination on the growth performance and mortality of the chickens were also investigated. The chickens were divided into six experimental groups and were fed diets with an addition of 50 or 100 mg/kg MEL or 50 or 100 mg/kg CYA of diet, with the contaminants added separately or in combination. The control group was fed a diet without MEL or CYA. At the end of the experiment (day 40), samples of liver, kidney and breast and thigh muscles were collected from 12 birds per treatment group and were analysed for the presence of MEL and CYA. This study showed that MEL is biotransformed into CYA in broilers. Higher concentrations of MEL or CYA in the diet increased the presence of their residues in tissues, and the CYA residue concentration was several times higher in the respective tissues than the MEL residue concentration. The dietary addition of MEL and CYA did not affect the mortality rate, feed conversion ratio or body weight of the chickens.

Effect of dietary phytase transgenic corn on physiological characteristics and the fate of recombinant plant DNA in laying hens

The study aimed to evaluate the potential effects of feeding with phytase transgenic corn (PTC) on organ weight, serum biochemical parameters and nutrient digestibility, and to determine the fate of the transgenic DNA in laying hens. A total of 144 50-week-old laying hens were grouped randomly into 2 treatments, with 8 replicates per treatment and 9 hens per replicate. Each treatment group of hens was fed with diets containing 62.4% non-transgenic conventional corn (CC) or PTC for 16 weeks. The phytase activity for CC was 37 FTU/kg of DM, whereas the phytase activity for PTC was 8,980 FTU/kg of DM. We observed that feeding PTC to laying hens had no adverse effect on organ weight or serum biochemical parameters (p>0.05). A fragment of a poultry-specific ovalbumin gene (ov) was amplified from all tissues of hens showing that the DNA preparations were amenable to PCR amplification. Neither the corn-specific invertase gene (ivr) nor the transgenic phyA2 gene was detected in the breast muscle, leg muscle, ovary, oviduct and eggs. The digestibility data revealed no significant differences between the hens that received the CC- and PTC-based diets in the digestibility of DM, energy, nitrogen and calcium (p>0.05). Phosphorus digestibility of hens fed the PTC-based diet was greater than that of hens fed the CC-based diet (58.03% vs 47.42%, p<0.01). Based on these results, it was concluded that the PTC had no deleterious effects on the organ weight or serum biochemical parameters of the laying hens. No recombinant phyA2 gene was detected in muscle tissues and reproductive organs of laying hens. The novel plant phytase was efficacious in improving the phosphorus digestibility of laying hens.

Toxicity of melamine: the public health concern

Melamine contamination in food has resulted in sickness and deaths of human infants, pets, and farm animals in the past decade. The majority of the victims suffered from acute kidney injury, nephrolithiasis, and urolithiasis. Since then, animal studies have revealed the possible target organs of the melamine toxicity and the extent of the adverse effects of the contaminant. State-of-the-art analytical methods have been developed to achieve the "zero tolerance" aim for such economically motivated adulteration. These studies provide in-depth understanding of the melamine toxicity and promising analytical methods, which can help us safeguard our dairy food source.

Comparison of blood variables, fiber intensity, and muscle metabolites in hot-boned muscles from electrical- and gas-stunned broilers

The aim of this study was to compare the effects of gas stunning (GS) and electrical stunning (ES) on energy metabolism in Arbor Acres broilers. Thirty-six birds were slaughtered without stunning (control) or after stunning with the following treatments: 40% CO(2) + 21% O(2) + N(2) (G40%); 60% CO(2) + 21% O(2) + N(2) (G60%); 35 V, 47 mA, 400 Hz (E35V); 50 V, 67 mA, 160 Hz (E50V); and 65 V, 86 mA, 1,000 Hz (E65V). Muscle samples were obtained from the pectoralis major (breast) and tibialis anterior (leg) muscles in ambient temperature within 45 min postmortem and stored at -80°C. Blood pH decreased consistently with GS (G40% and G60%) compared with ES and the control (P < 0.01). No consistent differences were observed between GS and ES in the plasma variables, glycolytic potential, adenosine phosphates, or fiber intensities. Plasma lactate increased with G40% and E35V (P < 0.05), whereas plasma uric acid and urea nitrogen increased with E35V (P < 0.05) compared with the control. Compared with the control, the intensity of type IIB fibers decreased in broilers stunned with E35V and E50V (P < 0.05) and glycolytic potential increased (P < 0.01) with G60% in the breast muscle and decreased (P < 0.01) in the leg muscle with all the stunning treatments except for E50V. Energy decreased (lower adenosine triphosphate, higher adenosine monophosphate, and adenosine monophosphate:adenosine triphosphate ratio, P < 0.05) in breast muscle with G40% compared with ES at high currents (E50V and E65V). However, the adenosine phosphates with GS were not significantly different (P > 0.05) from ES at low current (E35V) in either breast or leg muscle. In conclusion, no essential difference in energy metabolism was found in broilers stunned with ES and GS when ES was based on low current and high frequency and GS was based on hypercapnic moderate oxygenation. This study indicated that G40% was potentially a superior stunning variable.

Toxicity of cyanuric acid to broilers on hepatic and renal health with and without melamine

The purpose of this study was to evaluate the toxicity potential of cyanuric acid (CYA) and a combination of melamine (MEL) and CYA in broilers. A total of 1200 male COBB 500 broilers were randomly allocated into 1 of 10 treatment groups by a 5 × 2 factorial design in a 42-d experiment. The dietary treatments were as follows: T1 to T5: basal diets with 0, 10, 20, 33.3, and 50 mg CYA per kg diet; T6 to T10: basal diet with CYA regimens similar to T1 to T5 but with 100 mg MEL per kg diet. There were 6 replication pens with 20 chicks per pen. No differences were observed in alanine transaminase (ALT) and aspartate aminotransferase (AST) activities. But on d 22, uric acid (UA) and creatinine (Crea) concentrations were significantly greater when birds were fed CYA at 33.3 mg/kg with MEL 100 mg/kg, and Crea concentration was also higher when birds were fed CYA at 50 mg/kg. No crystals were found in kidneys but dilated renal tubules and small blood vessel expansion were found in kidneys of birds fed CYA at 50 mg/kg and CYA at 33.3 mg/kg with MEL 100 mg/kg. The apoptosis rate (AR) of kidneys of all birds fed CYA and MEL contaminated diets were higher than the control group. These results indicated that the dietary addition of CYA and MEL could induce kidney damage, and the effects were harmful when the ratio of CYA/MEL was 1:3.

Bioaccumulation of melamine in catfish muscle following continuous, low-dose, oral administration

In this study, catfish muscle was analyzed for melamine (MEL) and cyanuric acid (CYA) residues following experimental feeding with low doses of MEL and MEL and CYA (MEL+CYA) and with the insoluble melamine-cyanurate complex (MEL=CYA). Catfish were daily fed 0.1 mg/kg BW of MEL for 15, 28, or 42 days, 0.1 mg/kg BW of MEL+CYA for 28 days, 2.5 mg/kg BW of MEL+CYA for 14 days, or 400 mg/kg BW of MEL=CYA for 3 days. Residues in the tissue were determined by LC-MS/MS. MEL was extracted with acidic acetonitrile, followed by defatting with dichloromethane, and isolated with cation exchange solid phase extraction (SPE). For CYA analysis, fish were extracted with dilute acetic acid, defatted with hexane, and cleaned up with a graphitic carbon SPE. Catfish fed 0.1 mg/kg BW of MEL reached a maximum muscle residue concentration of 0.33 ± 0.04 mg/kg (ppm) after 28 days of continuous feeding. The same concentration was found for MEL+CYA feeding at the 0.1 mg/kg BW level for 28 days. Feeding at 2.5 mg/kg BW of MEL+CYA yielded muscle concentrations above the 2.5 mg/kg level of concern for most of the study fish. Finally, catfish fed high levels of the MEL=CYA complex (400 mg/kg BW) accumulated relatively little MEL in the muscle (0.14 ± 0.07 mg/kg) and, unlike treatment with MEL+CYA, did not form renal melamine-cyanurate crystals. Appreciable concentrations of CYA were not detected in any of the muscles tested. These studies provide data to model the bioaccumulation of triazine residues into edible fish tissue as a result of the continuous consumption of adulterated feed.