Cart 0 items $0.00
Cart 0 items $0.00

What is in feather meal? The American studies that put us off it

by Seacliff Organics in Information

Feather meal is poultry feathers that have been pressure cooked, dried and ground, then sold as a high nitrogen organic fertiliser. When Johns Hopkins researchers tested 12 samples for drug residues in 2012, every one was positive, and seven of the 12 were fertiliser products. A companion study found arsenic in all 12 of its samples. Nobody has shown that this harms gardeners or crops, and nobody has published a test of feather meal made or sold in New Zealand. Seacliff does not sell it.

What feather meal is

Feathers are a slaughterhouse by-product. Renderers cook them under high pressure, then press, dry and grind them (Bland 2012), and the meal is sold as animal feed and as fertiliser (Love et al. 2012a). What a bird was dosed with can stay in its feathers. In a Belgian trial, breeder birds given the antibiotic enrofloxacin for three days all still had it in their feathers 15 weeks later, above 5 µg/kg (Ringenier et al. 2025).

The drug residue study

Love and colleagues bought 12 feather meals in six American states and in China (JHCLF 2012). Two were Chinese, seven of the 12 were fertiliser products and five were feed grade (Bland 2012; Chen 2015). Each was screened for 59 pharmaceuticals and personal care products (Love et al. 2012a). They found:

  • Antimicrobial residues in all 12 samples, two to ten per sample, from six drug classes (Love et al. 2012a).
  • Fluoroquinolones in 8 of the 12 (JHCLF 2012), including 60% of the American samples (EHP 2012). The United States withdrew approval for the fluoroquinolone enrofloxacin in poultry from 12 September 2005 (FDA 2005).
  • Caffeine and paracetamol (acetaminophen) in 10 of the 12 (Love et al. 2012a), plus the antihistamine diphenhydramine and the antidepressant fluoxetine (JHCLF 2012).
  • In the laboratory, sterilised feather meal slowed the growth of ordinary E. coli (p = 0.01) but not of a drug resistant strain (Love et al. 2012a). The authors said one sample held enough to select for resistant bacteria (JHCLF 2012).

The blunt version: across 12 bags of feather meal, most of them sold as fertiliser, the laboratory found antibiotics in every one, and caffeine, paracetamol, an antihistamine and an antidepressant among them.

What the paper did not do matters as much. It tested the meal. It did not follow the residues into soil, crops or people (Bland 2012), and its own conclusion was that more studies were needed to understand the risk (Love et al. 2012a).

The amounts were small. The paper's results table is behind a paywall and we have not read it, so we quote no top figure. A later thesis that cites the table gives 0.6 to 16.6 µg/kg for three of the compounds in samples from California, Idaho and Tennessee (Chen 2015). One µg/kg is one part per billion.

Two members of the American Association of Avian Pathologists wrote to the journal. Their points: most compounds sat at or near the limit of detection; only two American samples showed enrofloxacin, both near that limit; the feed grade conclusions rested on three 2.5 g samples; town water used in rendering could explain trace drugs; and nothing showed residues moving from fertiliser into crops (Bland 2012; Kelly 2012). The authors replied in the same journal (Love et al. 2012b; 2012c). We could not get those replies to read.

The arsenic study

Nachman and colleagues measured arsenic in 12 feather meals from six American states and China. All 12 contained it, at 44 to 4,100 µg/kg, and 37 to 83% of it was inorganic (Nachman et al. 2012), the more toxic form (FDA 2022). Arsenic based drugs such as roxarsone were then widely fed to American broilers, although roxarsone itself was not detected in the meal (below 20 µg/kg as arsenic). The authors wrote that feather meal used as fertiliser "may" add to human risk. What they measured was the meal, not soil or crops (Nachman et al. 2012).

Worked example: how much arsenic is that?

Take the worst sample and a heavy dressing. The rate, depth and soil density are our assumptions.

  • Worst sample: 4,100 µg/kg = 4.1 mg/kg.
  • Dressing: 100 g/m² = 0.1 kg/m². Arsenic added: 0.1 × 4.1 = 0.41 mg/m².
  • Soil to 150 mm at 1.0 t/m³: 0.15 m³ × 1,000 kg/m³ = 150 kg/m².
  • Rise in soil arsenic: 0.41 ÷ 150 = 0.0027 mg/kg per dressing. Twenty yearly dressings with no losses: 20 × 0.41 ÷ 150 = 0.055 mg/kg.

New Zealand's soil contaminant standard for arsenic is 20 mg/kg for a residential section growing 10% of its produce (MfE 2011, Table 54). On these numbers, arsenic from feather meal will not move a garden towards it. The worst sample held less arsenic per kilogram than the standard allows in the soil itself.

What has changed since 2012

Both studies are 14 years old and the samples were American and Chinese. Three things have happened since.

  • The arsenic drugs are gone from the United States. Approvals for roxarsone, arsanilic acid and carbarsone were withdrawn in February 2014, and for nitarsone, the last, on 31 December 2015 (FDA 2022; FDA 2015). We found no published retest of American feather meal, so the improvement is expected, not measured.
  • One follow-up used the same laboratory. A Clemson University thesis, funded by the Animal Co-Products Research and Education Center and not published in a journal, tested fresh feed grade feather meal from three American rendering plants for 60 compounds. Four were above reporting limits: ormetoprim (3.02 µg/kg), sulfadimethoxine (0.71 to 13.5 µg/kg) and two chlortetracycline derivatives (32.9 and 41.7 µg/kg). No fluoroquinolone, caffeine or paracetamol was reported in the meal. That is fewer compounds than Johns Hopkins found, though these four ran higher (Chen 2015).
  • Europe finds residues too. Of 55 rendered animal protein samples from European makers, 40 contained tetracyclines at 25.59 to 456.84 µg/kg (Morello et al. 2021).

Drug residues keep turning up when someone looks, and the amounts stay in the parts per billion.

New Zealand and Australia

We could not find any published testing of feather meal made or sold in New Zealand or Australia, for drug residues or for arsenic. What is known is about the birds:

  • Fluoroquinolones are not registered for use in poultry in New Zealand, and bacitracin was phased out of poultry feed in 2023, with antibiotics kept for treating infections (Sircombe et al. 2026).
  • Australia had not approved quinolones for any food-producing animal when the question was reviewed in 2012 (Cheng et al. 2012).
  • New Zealand's register of veterinary medicines lists no product containing roxarsone, nitarsone, arsanilic acid or carbarsone today (MPI 2026). We could not find out whether any was used here, or in Australia, in the past.

So a local feather meal may well be cleaner than the 2012 American samples. Nobody has measured it, and a bag sold here may not have been rendered here.

How it works as a fertiliser

Feather meal is good at its job. A University of California sample held 14.2% nitrogen and, at 2004 Californian prices, cost the least per kilogram of available nitrogen of four organic fertilisers tested (Hartz and Johnstone 2006). It is also quick:

Weeks in moist soil Organic nitrogen mineralised at 10 °C Organic nitrogen mineralised at 15 °C
1 30% 42%
2 48% 49%
4 51% 56%
8 55% 59%

Source: Hartz and Johnstone (2006, Table 2). A wider survey found 50 to 65% released within 100 days in warm, moist soil, most of it in the first 20 days (Geisseler n.d.).

The arithmetic for 100 g/m² at 15 °C: 100 g × 14.2% = 14.2 g of nitrogen. In two weeks, 14.2 × 0.49 = 7.0 g/m². In eight weeks, 14.2 × 0.59 = 8.4 g/m², or 84 kg/ha. The rest had not been released by week eight.

What Seacliff uses for nitrogen

Our nitrogen comes from Mussel Meal, Fish Meal, lucerne meal, neem and karanja seed meals, flaxseed meal and mealworm frass, alone and in our blends. We do not sell feather meal because we cannot answer the questions below for it, and we will not sell an animal by-product we cannot answer for.

That does not make our own inputs clean by default. Fish and shellfish meals are animal by-products too, and the same questions apply to us. [LAB RESULT NEEDED: Mussel Meal and Fish Meal nitrogen %, heavy metals (arsenic, cadmium, lead, mercury) and pathogen screen]. We cover the wider picture in Natural does not mean clean, and our fertiliser calculator gives rates for the inputs we do sell.

What to do

  • If you already use feather meal, do not panic. The measured amounts are tiny and we found no study showing harm to a garden or its produce.
  • Treat it as a quick nitrogen source and apply it close to planting.
  • If you grow medical cannabis under licence, or sell produce, ask for paperwork before any animal by-product goes into the mix.
  • You may not need extra nitrogen at all. A soil test and the crop's own growth are better guides than habit.

Questions to ask any supplier of an animal by-product, Seacliff included:

  1. What animal is it from, and in which country was it raised and rendered?
  2. Which antibiotics and feed additives are permitted for those animals there?
  3. Is there a heavy metal result for this batch, including arsenic?
  4. Has it ever been screened for drug residues?
  5. What heat treatment did it get, and is there a pathogen test?
  6. Can I see the lab sheet, with a date and a batch number?

References

← Older Post Newer Post →

0 comments

Leave a comment

Please note, comments must be approved before they are published