The information is part of an attempt to understand potential consequences for the use of arsenic-containing feed additives on other parts of the biosphere including human health and the environment.
The research team published its work, which they said is the first study to describe mass balance of arsenic intake and excretion by chickens, in Science of the Total Environment.
“In our study, we conducted an experiment growing two strains of chicken on rox-supplemented feed or feed devoid of rox [Roxarsone],” the researchers said. “We report mass balance that determines the amount of total As taken in by chickens with feed consumption and the amount of total As excreted in poultry litter to assess the possible retention of As inside the chicken body.”
They found "no significant retention of As in the chickens."
The said the majority of the arsenical element in the feed additive moved through the bird, leaving the poultry protein produced safe for human consumption. Chickens receiving the feed additive had similar growth to those on the control diet.
They concluded that poultry litter enriched in arsenic warrants investigations if used in crop production.
Because poultry litter is commonly used as an organic amendment to fertilize soil (Wilkinson, 1979) for crop production, arsenic and its different metabolites/species can be transferred to different plant parts that may generate some public health issues (Rutherford et al., 2003; Yao et al., 2009; Yao et al., 2016), wrote the researchers.
“The results are important in evaluating the fate of feed additive used in poultry production and its potential environmental implications if As containing poultry litter is applied to soil for crop production,” the researchers said.
Why track in-feed arsenic use?
Arsenic (As) is a known carcinogen and is considered a toxic element. The researchers said. Sources of As contamination include as a content in some earth crust minerals and industrial activities.
Drinking water and food contamination are the primary pathways for animals to come into contact with the element, they said. However, Roxarsone (rox; 3-nitro-4-hydroxyphenylarsonc acid) is an arsenic-containing organic compound that was often added to poultry feed to prevent parasitic disease and improve growth, feed efficiency and meat pigmentation.
Use or sale of the feed additive was halted in the EU in 1999, the US in 2013 and Canada in 2011, they said.
“When the United States Food and Drug Administration (FDA) approved rox in 1944 as a feed additive, it was believed that the non-toxic organic As present in rox would not change into toxic inorganic As inside the chicken body; rather organic As would be excreted unchanged into the poultry manure leaving chicken meat safe for human consumption,” the researchers said. “However, higher than tolerable amounts of total As (>2.0 mg kg−1) established by FDA before 1963 (FDA, 1963) were found in the livers of rox-fed chickens compared to the ones fed without rox.”
Testing found different types of As in different parts of chickens and that the toxicity of As can be highly dependent on the chemical species, they said. Research also found that the feed additive could be changed into metabolites in chicken manure and lead to increased concentration of those As species in plants grown in soil fertilized with chicken manure.
However, no work has been done evaluating the mass balance of As moving from poultry feed to poultry litter, they said. “Though rox containing poultry feed has been discontinued in Europe and North America, many other countries continue to use phenylarsenicals in the poultry industry,” they added.
“The mass balance of As from poultry feed to poultry litter reported in this manuscript is a part of a comprehensive study envisaged to track As from rox containing poultry feed to poultry litter including its metabolism in the chicken meat,” they said.
Methods and materials
In the feeding trial, more than 1,600 birds of two different commercial poultry lines, Cobb or Ross, were given one of two diets for a period of 35 days, the researchers said. The diets included a corn-, wheat-soybean meal-based control, and that diet with the feed additive 3-NITRO.
“For the rox treatment, 3-NITRO® (Alpharma Canada Corporation) containing 20% rox was added to the feed at 250g ton−1,” they said. “Because rox contains 28.48% As, the As content was 14.24mg kg−1 of the feed prepared for the rox treatment.”
Birds also saw the diet change from starter, to grower to finisher during the feeding trial, they said. The rox feed additive was only added during the starter and grower diets.
Bird survival, body weight change and feed intake were noted during the trials, the researchers said. Samples of poultry litter and excreta were collected on days 14, 28 and 35 during the trial and total litter amount generated was established.
The mass balance of As eaten in the feed and excreted into the litter also was calculated, they said.
At the end of the trial, slightly more Ross chickens had survived, especially those getting the rox diet, the researchers said.
Feed consumption tended to be slightly higher for Ross birds, and both lines tended to have greater feed intake from birds on the control diet, however, differences were not significant in average body weight.
Arsenic intake through feed was calculated for both types of birds on the trials diets and found to be similar, they said.
Overall, results indicated that there was no significant retention of As in body of the chickens getting the supplemented feed, they said.
“The results of our study show that arsenic from poultry feed ends up in poultry litter when two poultry stains are fed with rox-amended feed,” they said. “Our mass balance calculations showed As recovery between 86 and 108% during the growth period of 28 days, which suggested no significant retention of As in the chickens.”
However, the levels of arsenic in poultry litter may need additional exploration regarding the environmental implications if that material is applied to soils used for crop production, said the researchers.
“At [the] 14th day, As intake was 661 ± 10 and 680 ± 8mg pen−1 which increased cumulatively to 2,669 ± 128 and 2,730 ± 92mg pen−1 in Cobb and Ross, respectively at 28th day,” they said.
The weight of the poultry litter increased over time, they said. By day 28, when the feed additive supplementation ended, Cobb birds produced 80 ± 5 and 73 ± 3kg litter pen−1, in control and rox-fed pens, respectively.
Ross birds on the control diet generated 76 ± 4kg litter pen−1 by the 28th day, while those getting the supplemented diet produced 74 ± 17kg litter pen-1, they said.
Some As levels were found in the litter of birds on the control diet, although the amounts in the rox-fed birds were significantly higher.
The fishmeal used in the control diet was determined to have been the source of the As levels found in the control group, said the researchers.
“At 14th day, As excretions by Cobb and Ross were 703 ± 149 and 625 ± 185mg pen−1, which increased to 2,896 ± 414 and 2,362 ± 228mg pen−1, respectively, by 28th day,” they said of total As excreted in the litter.
The amount of As declined from day 28 through the end of the trial on day 35, because the feed additive was not used in the finisher diet.
According to the mass balance calculation, during the first 14 days of the feeding trial the majority of the arsenic was excreted, they said. “During the first 14 days, 106 ± 21% and 92 ± 26% of ingested As was recovered from the poultry litter produced by Cobb and Ross strains, respectively,” they added.
“Similar recovery of As (86 ± 5 to 108 ± 11%) was achieved at 28th day when feeding chicken with rox containing grower diet was stopped and cumulative As excreted in poultry litters produced by Cobb and Ross was determined,” they said.
Source: Science of the Total Environment
Title: Transfer of arsenic from poultry feed to poultry litter: A mass balance study
Authors: S Gupta, X. C Le, G Kachanosky, M Zuidhof, T Siddique