Vitamin D insufficiency during winter is a common problem for humans in Europe. One way to ease this problem is through the production of vitamin D-fortified eggs. To evaluate such a production process, the effects of vitamin D supplementation during an entire production period were assessed. Transfer of vitamin D3 (cholecalciferol) and vitamin D2 (ergocalciferol) from the diet to egg yolks was measured using 2 different levels of both vitamins (6,000 and 15,000 IU/kg feed) relative to a control treatment (2,500 IU vitamin D3/kg feed). During the experiment, production parameters, egg quality (egg weight, Haugh unit, specific gravity, eggshell fracture force, and Ca content of eggshell), and the condition of hens were monitored. At the end of the experiment histopathological tests were performed. Supplementing diets with vitamin D3 increased egg yolk vitamin D content more effectively than did supplementation with vitamin D2. For groups of hens receiving 6,000 or 15,000 IU of vitamin D3/kg feed, egg yolk vitamin D3 content ranged from 9.1 to 13.6 and from 25.3 to 33.7 microg/100 g, respectively. Corresponding values for birds fed vitamin D2 were 4.7 to 7.0 and 13.3 to 21.0 microg/100 g. Both supplements enhanced vitamin D3 content of egg yolks relative to the control diet (2.5 to 5.0 microg/100 g of egg yolk). Vitamin D supplements had no effects on production parameters compared with the control diet. However, especially vitamin D3 improved bone strength (P < 0.05). Autopsy at the end of the experiment indicated no detrimental accumulation of calcium in the kidneys, liver, heart, muscles, or lungs.

BackgroundAlthough modern commercial poultry production today is based on large farms and intensive husbandry, keeping backyard poultry has regained popularity in industrialized countries. However, the health status of backyard flocks is still relatively poorly documented. A questionnaire was sent to the owners of 376 backyard poultry flocks (<500 birds) in order to study health management procedures and characterize backyard poultry populations in Finland. Information was also collected on the postmortem findings from non-commercial flocks using necropsy data from the Finnish Food Safety Authority (Evira).ResultsBackyard flocks in Finland are small in size (<50 birds), comprising mainly chickens. Based on the results of the questionnaire, the health of such flocks is good, mortality low and vaccinations are not commonly used. Most of the flocks were registered in the national poultry register. The standard biosecurity practices are not generally applied and contact with wild birds, pets and farm animals is frequent, which can make the flocks more prone to infectious diseases. We conducted an 11-year retrospective study of the postmortem necropsy findings of the Evira in order to document the diseases, which caused mortality in backyard chickens in Finland. Necropsy was performed on a total of 132 non-commercial laying hens during 2000 – 2011. The most common postmortem findings were Marek’s disease (27%) and colibacillosis (17%).ConclusionsThis study is the first to report data on characteristics of and management practices for backyard chicken flocks in Finland. Close connections with commercial flocks are rare and farms are usually distantly located suggesting that the risk that these backyard flocks pose to commercial poultry is low.

This study examined the effects of dietary energy content on the egg production and egg quality of hens kept in 3-hen conventional cages or 8-hen furnished cages. A total of 1,088 Lohmann Selected Leghorn hens were housed in either furnished or conventional cages and offered low- or high-energy diets (from 2,342 to 2,414 kcal/kg or from 2,581 to 2,629 kcal/kg) during 3 consecutive feeding phases of 20, 16, and 16 wk, respectively. The same dietary energy effects were observed in both cage systems. The hens that received the low-energy diet consumed more feed (P < 0.01) and produced fewer eggs per day (P < 0.05) than the birds fed the high-energy diet. Over the entire experiment, housing had no significant effects on production parameters, but during the third feeding phase, the production rate was smaller in furnished cages than in conventional cages (P < 0.01). Because of the greater live weight of the hens in furnished cages at the beginning of the experiment, these hens consumed more feed during the first feeding phase than the hens in conventional cages. During the third feeding phase, the hens in furnished cages consumed less feed than those in conventional cages (P < 0.01), probably because of their better feather cover. No differences in feed conversion ratio were found between the cage types. The results of this study confirm the results of previous studies providing evidence of equal production rates and feed conversion ratios in furnished and conventional cages.

Eggs are one of the most important sources of vitamin D in the human diet, and their vitamin D content can be further increased by adding more vitamin D to hen feed. To investigate this issue more closely, we performed two feeding experiments. In both, zero egg samples were collected while the hens were fed regular feeds with a vitamin D content of 1720 or 4280 IU/kg. In experiment 1, egg samples were collected 2, 4, 7, 9, 11, 13, 16, 23, and 30 days after beginning the high-cholecalciferol (11 200 IU/kg) feeding period. In experiment 2, samples were collected 2, 4, 6, 8, 13, 28, 56, 84, 112, 140, and 168 days after beginning the high-cholecalciferol (12 000 IU/kg) diet. The egg samples were then assayed for their cholecalciferol content, and some samples, also for the presence of 25-hydroxycholecalciferol by an HPLC method. Further, the vitamin D-fortified eggs were compared with the controls by a sensory evaluation, by conducting fatty acid and functional analyses (emulsion capacity, gel forming capacity, foaming properties) and by measuring eggshell strength. Because vitamin D can be toxic in high doses, we also performed histopathological tests on the hens at the end of experiment 2. The top cholecalciferol contents in egg yolk (ca. 30 microg/100 g) were reached 8-13 days from starting the high-cholecalciferol diet. After 112 days feeding the cholecalciferol content gradually decreased to ca. 22 microg/100 g. When added to eggs as described above, vitamin D did not affect their sensory or functional properties or their fatty acid composition. Moreover, the cholecalciferol levels used in this study appeared not to affect eggshell strength or to be harmful for hens.

Laying hens were fed contaminated feed containing narasin 2.5 mg/kg for 21 days followed by a 7 day withdrawal period, hens in the control group were fed unmedicated feed. Eggs were collected during trial days 0, 3, 7, 14, 21 and after the withdrawal period of 7 days. The concentration of narasin in yolks and egg whites was analyzed by a liquid chromatography-mass spectrometry method. Narasin was found to accumulate in yolks, where the narasin concentration increased during the treatment. The concentration of narasin varied from 5.9 to 13.8 microg/kg (mean 10.6 microg/kg) in yolks after 21 day feeding periods. The concentrations of narasin ranged from < 0.9 to 1.4 microg/kg after the withdrawal period. Narasin residues were not found in egg whites of the laying hens fed contaminated feed nor in either yolks or egg whites of the laying hens fed unmedicated feed. The effect of cooking was also tested on the amount of narasin residues in eggs. Cooking for 10 min did not significantly influence the narasin residues in eggs. Traces of lasalocid were also found in the yolks. The traces of lasalocid are attributable to an accidental contamination of the feed during its manufacture.