Feedback, is a common practice used in the pork industry where infected deceased pigs and their manure are fed to breeding pigs. It it also called controlled oral exposure or sometimes oral controlled exposure. It is done in an attempt to make the breeding pigs garner some degree of immunity to circulating diseases.[1] There is no standard protocol resulting in some swine researchers calling the procedure potentially risky and noting that it is often done in an unsafe manner.[2][3] The practice has also been criticized by animal welfare and animal rights groups calling it disturbing and or unethical.


Feedback appears to have been originally researched in the 1950s. In the decades since, its usage in the pork industry has become widespread due to increases in the pork industry's size and increases in overcrowding. The change in the industry's size has led to a growing spread in diseases such as E. coli and PEDv. A lack of effective vaccines for these diseases in the past led to feedback being used in their place.[4][5]

However, feedback usage extends beyond diseases where vaccines do not yet exist. In 2012, while 45% of large US herds vaccinated young female pigs against PRRS, 26.6% used feedback (or did so in addition).[6]

Global usage

The usage of feedback is not limited to just one country or region. Widespread usage has been recorded in at least the 2010s in places such as the United States,[6] Taiwan,[7] Belgium,[8] Japan,[9] South Korea,[10] Thailand,[11] and more. Additionally, following a PEDv outbreak in the 1970s, feedback was commonly used across Europe.[12]

Some countries recommend against the practice, but those recommendations are not always followed. For instance, the Japanese government has issued guidelines that discourage the use of feedback. However, one report found that over half of the studied farms that were exposed to PEDv in the Kagoshima and Miyazaki prefectures used feedback.[9]


Some veterinarians such as Jim Reynolds recommend against its use due to the risk of exposing pigs to more diseases than intended.[1] The Humane Society of the United States has called the practice "beyond disturbing" and that its use is indicative of the rise of intensive pig farming.[13] The Animal Legal Defense Fund has called it "disgusting, unethical and unlawful" and has filed a lawsuit against one pig farm for its use.[14]

See also


  1. ^ a b Torrella, Kenny (2023-08-05). "A new investigation exposes the stomach-churning practice that goes into making your bacon". Vox. Retrieved 2023-08-14.
  2. ^ Niederwerder, M. C.; Hesse, R. A. (2018-02-02). "Swine enteric coronavirus disease: A review of 4 years with porcine epidemic diarrhoea virus and porcine deltacoronavirus in the United States and Canada". Transboundary and Emerging Diseases. 65 (3): 660–675. doi:10.1111/tbed.12823. PMC 7169865. PMID 29392870.
  3. ^ Jung, Kwonil; Saif, Linda J.; Wang, Qiuhong (2020-09-01). "Porcine epidemic diarrhea virus (PEDV): An update on etiology, transmission, pathogenesis, and prevention and control". Virus Research. 286: 198045. doi:10.1016/j.virusres.2020.198045. ISSN 0168-1702. PMC 7266596. PMID 32502552.
  4. ^ Arruda, Paulo Elias (2010). The Effects of Oral Controlled Exposure on Colostrum Characteristics in Swine (Thesis). Iowa State University. doi:10.31274/etd-180810-921.
  5. ^ "U.S. Hogs Fed Pig Remains, Manure to Fend Off Deadly Virus Return". Scientific American. 2015-12-14. Retrieved 2023-08-14.
  6. ^ a b Swine 2012 Part II: Reference of Swine Health and Health Management in the United States, 2012 (PDF) (Report). United States Department of Agriculture. February 2020 [February 2016].
  7. ^ Nguyen Thi, Thu Hien; Chen, Chi-Chih; Chung, Wen-Bin; Chaung, Hso-Chi; Huang, Yen-Li; Cheng, Li-Ting; Ke, Guan-Ming (7 March 2022). "Antibody Evaluation and Mutations of Antigenic Epitopes in the Spike Protein of the Porcine Epidemic Diarrhea Virus from Pig Farms with Repeated Intentional Exposure (Feedback)". Viruses. 14 (3): 551. doi:10.3390/v14030551. ISSN 1999-4915. PMC 8954129. PMID 35336958.
  8. ^ Bernaerdt, Elise (2023). BIOSECURITY: THE PATH TO RAISING PIGS WITHOUT ANTIBIOTICS? (PhD thesis). Ghent University.
  9. ^ a b YAMAGAMI, Taiki; MIYAMA, Takeshi; TOYOMAKI, Haruya; SEKIGUCHI, Satoshi; SASAKI, Yosuke; SUEYOSHI, Masuo; MAKITA, Kohei (2021). "Analysis of the effect of feedback feeding on the farm-level occurrence of porcine epidemic diarrhea in Kagoshima and Miyazaki Prefectures, Japan". Journal of Veterinary Medical Science. 83 (11): 1772–1781. doi:10.1292/jvms.21-0343. ISSN 0916-7250. PMC 8636866. PMID 34615808.
  10. ^ Jang, Guehwan; Park, Jonghyun; Lee, Changhee (2021-07-01). "Successful Eradication of Porcine Epidemic Diarrhea in an Enzootically Infected Farm: A Two-Year Follow-Up Study". Pathogens. 10 (7): 830. doi:10.3390/pathogens10070830. ISSN 2076-0817. PMC 8308665. PMID 34357980.
  12. ^ Sexton, B. (2022). "Utilizing vaccine to reduce the duration and impact of sow farm porcine epidemic diarrhea (PED) outbreaks". AASV Annual Meeting. Perry, Iowa, USA: American Association of Swine Veterinarians. doi:10.54846/am2022/173. S2CID 246926640.
  13. ^ Barclay, Eliza (February 20, 2014). "'Piglet Smoothie' Fed To Sows To Prevent Disease; Activists Outraged". NPR.
  14. ^ "Lawsuit Filed Against Pig Breeder Holden Farms Related to Feeding Dead Piglets' Intestines and Feces to Mother Pigs and Other Offenses". Animal Legal Defense Fund. Retrieved 2023-08-14.