Eggs were collected over two weeks from 1 to 25 February 2022 in areas with large commercial egg production and in villages where households keep backyard hens. The sample included 10 eggs from each of five housing systems: backyard, organic, free-range, soil/litter and cages. Forty eggs came from commercial producers and 10 from village households.

Commercial hens received feed with equal mineral content, while backyard hens could receive household food leftovers without additional vitamins or minerals. Organic and free-range birds had access to yards with grass and soil for five to six hours daily, and backyard hens had access to their yards and surrounding areas for more than eight hours. These dietary and environmental differences were associated with, but did not establish the cause of, the measured differences in albumen composition.

Albumen was separated from the yolks, dried at 104 °C, ground and homogenized. Five-gram portions underwent acid digestion before analysis with a high-resolution radial-viewing ICP-OES system. The researchers used one-way analysis of variance followed by the Tukey-HSD test, with differences considered statistically significant at p < 0.05.

Average chromium concentration was reported as 0.05546 mg/kg for eggs from ecological housing—backyard, organic and free-range—compared with 0.02166 mg/kg for intensive systems. Copper averaged 1.1749 mg/kg in the ecological group and 0.7100 mg/kg in intensive systems. Iron showed the largest difference among the essential elements, averaging 5.1993 mg/kg in ecological eggs and 0.8753 mg/kg in the other systems.

Manganese concentrations were frequently below the method’s detection limit. Zinc concentrations were more similar between housing groups, although the reported average was slightly higher in ecological eggs. The study also measured aluminium, cadmium, nickel and lead. Reported maximum concentrations were 1.551223 mg/kg for aluminium, 0.051892 mg/kg for cadmium, 0.235058 mg/kg for nickel and 0.272676 mg/kg for lead.

All measured concentrations remained below the toxicity thresholds listed in the study’s tables. Lead was undetectable in backyard and free-range samples, while detectable concentrations occurred in organic and cage samples. Cadmium concentrations were higher in the intensive categories than in the ecological grouping, but the observational design did not establish whether feed, housing equipment or another factor produced that pattern.

The comparative study provides baseline measurements for a limited Romanian sample collected during a two-week period. It did not report feed and environmental metal measurements, random allocation of hens to housing systems or a long-term assessment of egg products. Consequently, the results show differences among sampled eggs and cannot by themselves establish that outdoor access, feed composition or a particular husbandry system caused the observed mineral concentrations.

Subject of Research: Comparison of metal concentrations in egg albumen from five hen housing systems in Romania

Article Title: Comparative study of metal concentration determination in albumen of hen eggs originating from industrial poultry farms, backyard and free-range hens using ICP-OES technique

Article References: Kirov, P. M., Karadjov, M., Hristov, H. K., & Alexandrova, R. (2023). Comparative study of metal concentration determination in albumen of hen eggs originating from industrial poultry farms, backyard and free-range hens using ICP-OES technique. BioRisk, 20, 129-138. https://doi.org/10.3897/biorisk.20.97322

Image Credits: AI Generated

DOI: 10.3897/biorisk.20.97322

Keywords: egg albumen, hen housing, metal concentrations, ICP-OES, essential elements, heavy metals, Romania, poultry farming, comparative study, Comparative, metal, concentration