Effects of a dietary added formaldehyde-propionic acid blend on feed enterobacteria counts and on growing pig performance and fecal formaldehyde excretion

Efeitos da adição de uma mistura de formaldeído e ácido propiônico na dieta sobre a contagem de enterobactérias na ração e sobre o desempenho e excreção fecal de formaldeído de suínos em crescimento

Abstracts

The purpose of this study was to evaluate the effects of a dietary added formaldehyde-propionic acid blend on feed enterobacteria counts and on growing pig performance and fecal formaldehyde excretion. Forty pigs (34.2±1.8kg BW) were used in a randomized complete block design experiment with four treatments, five replications per treatment and two animals per experimental unit (pen). The treatments were: 0.0, 1.0, 2.0, and 3.0g of blend kg^-1 of feed. No effects (P>0.05) of dietary added blend levels were observed on average daily gain, average daily feed intake and feed:gain ratio during 1 to 14 and 1 to 28 days of experiment. Increasing dietary levels of blend reduced quadratically (P<0.01) total Enterobacteriaceae counts on 1^st and 14^th day after feed mixing, allowing to estimate, respectively, 2.63 and 3.35g kg^-1 (average 2.99g kg^-1) as the formaldehyde-propionic acid blend levels with lowest feed Enterobacteriaceae counts. Therefore, formaldehyde-propionic acid blend can reduce and/or control feed Enterobacteriaceae growth. There was no effect (P>0.05) of blend on fecal formaldehyde excretion on the 28^th day of the experimental period. Therefore, the addition of dietary formaldehyde-propionic acid blend up to 3.0g kg^-1 of feed reduces the Enterobacteriaceae counts until the 14^th day after feed mixing, without any effects on growing pig performance and fecal formaldehyde excretion

feed additive; Enterobacteriaceae; swine

O objetivo deste estudo foi avaliar os feitos de um blend de formaldeído e ácido propiônico em dietas para suínos em crescimento sobre a contagem de enterobactérias na ração armazenada, o desempenho zootécnico e a excreção fecal de formaldeído. Quarenta suínos (34,2±1,8kg de peso vivo) foram utilizados em um experimento em blocos completos casualizados, com quatro tratamentos, cinco repetições por tratamento e dois animais por unidade experimental (baia). Os tratamentos foram: 0,0, 1,0, 2,0 e 3,0g de blend kg^-1 de ração. Não foram observados efeitos (P>0,05) dos níveis de blend sobre o ganho diário de peso, consumo diário de ração e conversão alimentar durante os períodos 1 a 14 e 1 a 28 dias de experimento. O aumento dos níveis de blend na dieta reduziu quadraticamente (P<0,01) a contagem total de Enterobacteriaceae no 1^o e 14^o dias após a fabricação das dietas, sendo estimados, respectivamente, 2,63 e 3,35g kg^-1 (média 2,99g kg^-1) como os níveis do blend de formaldeído e ácido propiônico com as menores contagens de Enterobacteriaceae na ração. Portanto, o blend de formaldeído e ácido propiônico pode reduzir e/ou controlar o crescimento de Enterobacteriaceae na ração. Não houve efeito (P>0,05) do blend sobre a excreção fecal de formaldeído no dia 28 do período experimental. Portanto, a inclusão de um blend de formaldeído e ácido propiônico até o nível de 3,0g kg^-1 de ração reduz a contaminação de Enterobacteriaceae até 14 dias após a fabricação da ração, sem quaisquer efeitos sobre o desempenho e a excreção fecal de formaldeído

aditivo tecnológico conservante; Enterobacteriaceae; suíno

INTRODUCTION:

The feed contamination of Enterobacteriaceae, mainly Salmonella sp., is one of great concern in commercial swine production, because it can be an important vehicle of pathogens to animals and humans (DAVIES & HILTON, 2000; KORSAK et al., 2003; MACIOROWSKI et al., 2006). In addition, the contamination of feed mills and feeding systems, especially in non-accessible areas, may be sources of feed and animal contamination (FURUTA et al., 1980; TORROELLA et al., 1987). Subclinical effects of pathogenic Enterobacteriaceae on weaned pigs are difficult to quantify, but their performance has been improved when the contamination of feed was lowered (DeROUCHEY et al., 2004). However, there are studies suggesting a potential link between the microorganisms in feed and microorganisms causing human and animal diseases, which may be a food safety problem (DAVIES & HILTON, 2000; KORSAK et al., 2003; MACIOROWSKI et al., 2006; EFSA, 2008). Thus, the availability of additives that can control recontamination of feed with potential pathogens is essential to the safety of food for animals.

Chemical products, such as formaldehyde-based feed additives, can help to decrease and/or prevent bacterial contamination in feed stuffs (KAISER, 1992; ANDERSON et al., 2001). Formaldehyde has been shown to have antimicrobial activity when added to animal feeds, and have been used as feed additive especially to control Salmonella sp. (MOLLER, 1983; MOUSTAFA et al., 2002). Blends of formaldehyde, propionic acid and other dispersing agents have been shown to achieve greater decontamination of inoculated feed with Salmonella sp. compared to several acid products (CARRIQUE-MAS et al., 2007). However, high levels of formaldehyde in the feed may affect the palatability of diets for pigs (PATTERSON et al., 1989; LY et al., 2000) and reduce feed intake (SCAN, 2002; EFSA, 2008).

The purpose of this study was to evaluate the effects of a dietary added formaldehyde-propionic acid blend on feed enterobacteria counts and on growing pig performance and fecal formaldehyde excretion.

MATERIAL AND METHODS:

Forty crossbred growing pigs of a commercial genetic line named Topigs^(r) were used in a randomized complete block (based on gender and initial BW) design experiment, with four treatments, five replications per treatment and two animals per experimental unit (pen). A barrow and a gilt were housed in 1.2x2.9m pens with partially slatted floors from 34.16±1.80kg to 61.08±2.76kg body weight (BW) in a naturally ventilated building. Feed and water were provided ad libitum to the pigs during the 28 days of experimental period.

The treatments consisted of four dietary levels of a formaldehyde-propionic acid blend: 0 (control), 1.0, 2.0, and 3.0g of blend kg^-1 of feed. The formaldehyde-propionic acid blend was a commercial liquid product (Salmex^(r), trade mark of Btech Tecnologias Agropecuárias e Comércio Ltda) composed by 33% formaldehyde, 9% propionic acid, terpenes and surfactants, and was applied using liquid aspersion equipment to guarantee dosage and homogeneity of the production the feed.

A two-phase feeding program was formulated according to the nutrient requirements for growing pigs (ROSTAGNO et al., 2005): grower 1 diet (from 1 to 14d of experiment) and grower 2 diet (from 15to 28d of experiment) (Table 1). Corn-soybean meal basal diets were mixed using recommended standard feed manufacturing method (feedstuffs batch, package, and storage conditions) a day before starting each phase-feeding period. Average daily gain, average daily feed intake, and feed:gain ratio were calculated for each pen during 1 to 14^th and 1 to 28 days of experiment. Feed samples were collected on the 1^st, 7^th and 14^th days after feed mixing for analysis of the blend recovery in the feed for treatment confirmation, and on the 1^st and 14^thd for analysis of total Enterobacteriaceae counts in the feed. At the 28^th day of the experimental period, feces samples were collected directly from the rectum of animals for formaldehyde quantification. The analysis of blend recovery in the diet and formaldehyde quantification in the feces was based on formaldehyde quantification using high-performance liquid chromatography (HPLC) (AOAC, 2005). For total Enterobacteriaceae counts, feed samples were diluted and transferred to the cultivation media of violet red bile agar with glucose (VRBG) to the selective isolation and identification of Enterobacteriaceae genus, and results were expressed as CFU (colony-forming unit)g^-1 (MAPA, 2003).

Table 1
: Composition of the experimental diets (as-fed basis).

• ^1Provided
  per kilogram of feed: manganese, 60mg; zinc, 150mg; iron, 100mg; copper, 10mg; iodine, 1.2mg.
• ^2Provided
  per kilogram of feed: vitamin A, 11,500UI; vitamin D₃, 5,850UI; vitamin E, 45UI; vitamin K₃, 3mg; thiamine, 1.8mg; riboflavin, 5.1mg; pyridoxine, 3.5mg; vitamin B₁₂, 24µg; folic acid, 0.82mg; pantothenic acid, 18mg; niacin, 37.5mg; biotin, 0.14mg; selenium, 0.35mg; ethoxyquin, 0.042mg.

Data were analyzed using the MIXED procedure of SAS^(r) (SAS Institute Inc., Cary, North Carolina, USA). The model for pig performance and formaldehyde in the feces data analysis included the fixed effects of the dietary blend levels and the random effect of block, as follows:

,where:

Y(ij) is the dependent response, μ is the overall mean, t(i)is the fixed effect of dietary blend levels (i = 0,...3), b(j)is the random effect of block (j = 1,...5) and ε(ij)is the experimental error.

Concerning total Enterobacteriaceae counts, data were transformed using the log₁₀ function to run the statistical analysis. The model for analysis of total Enterobacteriaceae counts and blend recovery data included the fixed effects of dietary blend levels and time:

, where:

Y(ij) is the dependent response, μ is the overall mean, t(i) is the fixed effect of dietary blend levels (i = 0,...3), p(j) is the fixed effect of time (total Enterobacteriaceae counts: j = 1, 2; blend recovery: j = 0,...3), t*p(ij) is the interaction between dietary blend levels and time, and ε(ij) is the experimental error.

The relationship between the dietary blend levels and the total Enterobacteriaceae counts was determined using polynomial regression analysis.

RESULTS AND DISCUSSION:NITSCHMAN & HADORN, 1941 DAVID et al., 1972 KHAN et al., 2003 SCAN, 2002

The pigs remained healthy throughout the trial and with no feed intake problems due to the added blend of formaldehyde and propionic acid.

No effects (P>0.05) of dietary formaldehyde-propionic acid blend levels were observed on average daily gain, average daily feed intake or feed:gain ratio of the growing pigs (Table 2).These results are an indication that formaldehyde-based additives may be used in corn-soybean meal diets for growing pigs as a way of decontamination of feed, feed mills and feeding systems, without affecting feed intake and pig performance. Beneficial effects of formaldehyde-based feed additive on pigs performance have been shown when feed is formulated with ingredients susceptible to high microbial degradation, such as meat and bone meal, spray-dried plasma (DeROUCHEY et al., 2004) and syrup (LY et al., 2000). For example, nursery pigs (6 to 10kg BW) fed with formaldehyde-treated plasma had improved performance compared to those fed diets with untreated plasma (DeROUCHEY et al., 2004). In addition, finishing pig (50 to 90kg BW) fed with formaldehyde-treated syrup, a by-product of raw sugar refining, had improved feed intake and weight gain when compared to those fed with untreated syrup, without any effects of formaldehyde-treatment on dry matter and organic matter digestibility, and nitrogen and energy retention (LY et al., 2000). These are indication that higher microbial challenge and fermentation rate might have occurred in untreated feed stuffs and depressed its palatability.

Table 2
:Effects of dietary levels of a formaldehyde-propionic acid blend on body weight (BW), average daily gain (ADG), average daily feed intake (ADFI), feed:gain ratio and formaldehyde excretion in the feces of growing pigs.

• ¹
  Standard error of the mean.

No effects (P>0.05) of the dietary formaldehyde-propionic acid blend levels were observed on the formaldehyde fecal excretion on the 28^th day of experiment (Table 2). These results could be an indication that formaldehyde may have been degraded in the gastrointestinal tract. However, the results of this study were different from others. In a trial with growing pigs (20 to 30kg BW) that had received feed treated with variable amounts of formaldehyde (from 0 to 990mg kg^-1) for six weeks, a dose dependent correlation with the fecal formaldehyde content (from 0.35 to 4.43mg kg^-1) was observed (SCAN, 2002). In addition, in two other experiments reported in the SCAN (2002) dossier, pigs fed with diets with or without formaldehyde (0 vs. 660mg of formaldehyde kg^-1) showed higher concentrations of fecal formaldehyde (0.07 vs. 0.34mg kg^-1, respectively), but the effect was lower than in the first study.

No interaction (P>0.05) between the dietary formaldehyde-propionic acid blend levels and storage time was observed on total Enterobacteriaceae counts in the feed. However, increasing the dietary formaldehyde-propionic acid blend levels reduced quadratically(P<0.01) total Enterobacteriaceae counts on the 1^st and 14^th day after feed mixing (Table 3), allowing to estimate, respectively, 2.63 and 3.35g kg^-1 (average 2.99g kg^-1) as the formaldehyde-propionic acid blend levels with lowest feed Enterobacteriaceae counts. Therefore, formaldehyde-propionic acid blend can reduce and/or control Enterobacteriaceae growth in the feed. The reduction of Enterobacteriaceae in the feed showed the bactericidal and/or bacteriostatic effects of formaldehyde-propionic acid blend in the period of 14d after feed mixing.

Table 3
: Effects of dietary levels of a formaldehyde-propionic acid blend on total Enterobacteriaceae counts in the feed on the 1^st and 14^th day after feed mixing and blend recovery in the feed on the 1^st, 7^th and 14^th day after feed mixing.

• ¹
  Standard error of the mean; Different small letters in line differ (P<0.05), and different capital letters in columns differ (P<0.05).
• ²
  CFU: Colony-forming unit.
• ³
  Quadratic effect of a blend on 1^st day Enterobacteriaceae counts: Y=0.26x²-1.37x+3.34; R²=0.999
• ⁴
  Quadratic effect of a blend on 14^st day Enterobacteriaceae counts: Y=0.115x²-0.771x+3.304; R²=0.986.

^{-1 -1}

CONCLUSION:

The use of a dietary formaldehyde-propionic acid blend up to 3.0g kg^-1 of feed reduces the Enterobacteriaceae counts in the feed until 14d after feed mixing, without any effects on growing pig performance and fecal formaldehyde excretion.

ACKNOWLEDGEMENTS

We acknowledge the "Fundação de Estudos Agrários Luiz de Queiroz (FEALQ)" and "Btech Tecnologias Agropecuárias e Comércio Ltda" for granting aid for this research.

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• ETHICS COMITTE AND BIOSECURITY The authors declare that this project was not submitted for evaluation to the "Committee of Ethics for the Use of Animals - CEUA/ESALQ/USP", but are aware of the resolutions of the "National Council for the Control of Animal Experimentation - CONCEA" <http://www.mct.gov.br/index.php/content/view/310553.html> and assume full responsibility for the presented data, as well as are available for possible questioning that should be required.

Publication Dates

• Publication in this collection
  28 Oct 2014
• Date of issue
  Mar 2015

History

• Received
  17 Dec 2013
• Accepted
  11 June 2014