Effects of oregano oil on growth performance of nursery pigs

Efectos del aceite de orégano en el desempeño del crecimiento de cerdos de destete

Effets de l’huile d’origan sur les performances de croissance des porcelets en pouponnière

Casey R. Neill, MS; Jim L. Nelssen, PhD; Mike D. Tokach, PhD; Robert D. Goodband, PhD; Joel M. DeRouchey, PhD; Steve S. Dritz, DVM, PhD; Crystal N. Groesbeck, MS; Kelly R. Brown, MS

CRN, JLN, MDT, RDG, JMDR, CNG, KRB: Department of Animal Sciences and Industry, Kansas State University, Manhattan, Kansas. SSD: Food Animal Health and Management Center, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas. Corresponding author: Dr Robert D. Goodband, Department of Animal Sciences, Kansas State University, 242 Weber Hall, Manhattan, KS 66506-0201; Tel: 785-532-1228; Fax: 785-532-7059; E-mail: goodband@ksu.edu. Contribution no. 06–124-J of the Kansas Agricultural Experimental Station.

Cite as: Neill CR, Nelssen JL, Tokach MD, et al. Effects of oregano oil on growth performance of nursery pigs. J Swine Health Prod. 2006;14(6):312–316.
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Keywords: swine, oregano oil, neomycin, oxytetracycline, feed antimicrobial
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Received: November 28, 2006
Accepted: February 23, 2006

Several ingredients have been proposed to partly or fully replace antibiotics as growth-promoting agents in swine diets. These include additives such as egg immunoglobulins, mannan oligosaccharide, probiotics, fructo-oligosaccharide, spices, botanicals, essential oils, and herbs.^1-3 Many human food products use oregano for seasoning, for example, pizza toppings. Oregano (Origanum vulgare) is a perennial herb grown in many countries, with oregano from the Mediterranean region, especially Turkey and Greece, reputed to be of the highest quality.⁴ Oregano’s unique odor and taste is attributable to the essential oil produced.⁴ Oregano oil has antimicrobial-like activity,^5,6 making it a natural feed additive with the potential to enhance palatability of feed as well as ADG and feed efficiency (gain:feed; G:F) in pigs. Therefore, the objective of this trial was to compare the effects of oregano oil (ORG) and the in-feed antimicrobial combination of neomycin and oxytetracycline (NT) on growth performance in nursery pigs.

Materials and methods

Animals

A total of 434 pigs (PIC L327 × L42) were housed at the Kansas State University Swine Teaching and Research Center in an environmentally controlled nursery in pens (1.17 m × 1.52 m) with woven wire flooring. One self feeder and one nipple waterer in each pen allowed ad libitum access to feed and water. Pigs were observed daily for signs of diarrhea. All experimental protocols used in this study were approved by the Kansas State University Institutional Animal Care and Use Committee.

Experimental design

Two 28-day experiments were conducted, using a total of 224 pigs in Experiment One (initial mean body weight 5.9 kg) and a total of 210 pigs in Experiment Two (initial mean body weight 5.4 kg). Pigs were blocked by weight at weaning (Day 0; 21 ± 2 days of age) and randomly assigned to dietary treatment within weight block. Pigs were housed seven per pen, with eight pens per treatment in Experiment One and six pens per treatment in Experiment Two. Either four barrows and three gilts or three barrows and four gilts were included in each pen. The numbers of barrows and gilts per pen was constant within a weight block, with equal numbers of blocks including each gender ratio in each experiment. In both experiments, pigs were weighed on Days 0, 7, 14, 21, and 28 to determine ADG, ADFI, and G:F.

Experiment One. The four dietary treatments were arranged in a 2 × 2 factorial. Pigs were fed the control diet, the control diet with NT, the control diet with ORG, or the control diet with both ORG and NT. Oregano premix was added at 1 kg per tonne to Phase 1 diets (Days 0 to 14) and at 0.5 kg per tonne to Phase 2 diets (Days 15 to 28) to provide ORG at a rate of 50 g per tonne in Phase 1 and 25 g per tonne in Phase 2.

Experiment Two. The five dietary treatments were the control diet, the control diet plus NT, and the control diet plus oregano oil at 25, 50, and 100 g per tonne of the diet. Oregano oil concentration remained constant for the 28-day trial.

Dietary treatments

The control diets, provided in a meal form, were based on corn-soybean meal and fed in two phases (Table 1). The Phase 1 diet was formulated to contain 1.55% lysine and included 15% dried whey and 3.75% fish meal. The Phase 2 diet was formulated to contain 1.45% lysine with no specialty protein sources. The control diet for each phase, excluding the corn starch, was mixed in one batch and divided into four aliquots for Experiment One and five aliquots for Experiment Two. Premixes for each diet were then made with corn starch and the appropriate additive, and each premix was then mixed into an aliquot of the control diet. Diets were analyzed for crude protein content and were correct within normal expected analytic variation.

The oregano premix was a commercially available product (Regano 500; Ralco-mix Products, Marshall, Minnesota) consisting of 5% oregano oil and 95% inert carrier. Information provided by the premix provider indicated that the oregano oil used in the product contained from 75.0% to 84.0% carvacrol and 0.7% to 4.0% thymol.⁴ According to company literature, the oregano used in these two experiments was cultivated in Greece and harvested from June to July when the plants are mature and expected to produce the most oil.⁴

The NT in-feed antimicrobial was provided as a premix containing neomycin sulfate (22 mg per kg) and oxytetracycline (22 mg per kg) (Neo-Oxy 10/10; Penfield Animal Health, Omaha, Nebraska). The premix was substituted at the expense of corn starch to provide 154 mg per kg neomycin sulfate and 154 mg per kg oxytetracycline in the complete feed in Phase 1 and 2.

Statistical analysis

Each experiment was analyzed as a randomized complete block design with pen as the experimental unit and pigs blocked on the basis of weaning weight. Analysis of variance was performed using the Mixed procedure of SAS (SAS Institute Inc, Cary, North Carolina) with block as a random effect and treatment as a fixed effect. In Experiment One, the effects of treatment were partitioned into the main effects of ORG, NT, and their interaction. In Experiment Two, preplanned contrasts were used to evaluate the effects of control versus NT, control versus ORG, and NT versus ORG, and linear and quadratic polynomial contrasts to determine the effects of increasing ORG dose. In all analyses, a P value of < .05 was considered significant.

Results

In Experiment One, no ORG by NT interactions were observed (P > .05; Table 2). All growth parameters measured Day 0 to 28 were better (P < .01) for pigs fed NT compared to those fed all other treatments: ADG was 420 g for pigs fed NT and 361 g for pigs not fed NT (SE 12.2 g); ADFI was 542 g for pigs fed NT and 481 g for pigs not fed NT (SE 18.4 g); and G:F was 0.78 for pigs fed NT and 0.75 for pigs not fed NT (SE 0.007). Growth parameters measured Days 0 to 28 for pigs fed diets with or without ORG did not differ (P > .05): ADG was 393 g for pigs fed ORG and 388 g for pigs not fed ORG (SE 12.2 g); ADFI was 512 g for pigs fed ORG and 511 g for pigs not fed ORG (SE 18.4 g); and F:G for pigs fed ORG was 0.77 and 0.76 (SE 0.007) for pigs not fed ORG.

In Experiment Two, ADG and ADFI were greater for pigs fed NT at all data points and for Days 0 to 14, G:F was greater for pigs fed NT than for pigs fed the control or ORG diets (Table 3). For Days 0 to 28, G:F was better for pigs fed NT and these pigs were heavier than those fed ORG (Table 3). The ADG, ADFI, G:F, and 28-day weights of pigs fed ORG (25, 50, or 100 g per tonne) were similar to those of pigs fed the control diet (P > . 05), and there was no effect on growth parameters of increasing dose of ORG (linear ORG, P > .05; quadratic ORG, P > .05).

Discussion

Antibiotics are commonly added to swine diets to increase growth rate and feed efficiency and for disease prevention.⁷ The response to feeding antibiotics is greater in nursery pigs than in finishing pigs and in unhygienic environments than in hygienic environments.⁷ With widespread use of antibiotics, health officials are concerned about antimicrobial resistance when humans consume meat from livestock that have been fed antibiotics.⁸ The use of antimicrobials in livestock feed is being debated as a public health issue.⁸ Therefore, there is a need for in-feed antimicrobial substitutes. Many studies have evaluated various feed additives to replace antimicrobials. However, no results have demonstrated the same growth performance and feed efficiency responses to these “substitutes” compared to in-feed antimicrobials.

Natural oregano oil has many components. Two of these, carvacrol and thymol, have been shown to have the strongest antimicrobial activity.⁴ In their evaluation of 50 essential oils, Deans and Ritchie⁵ placed thymol among the 10 with the greatest antimicrobial activity. A research trial conducted by Baratta et al⁶ examined the antimicrobial activity of laurel, sage, rosemary, oregano, and coriander oils. Microbial growth inhibition of the microorganisms tested was greatest for oregano oil.

In a study by Gunter and Bossow,⁹ in which weaned pigs were fed a diet containing oregano premix (5% etheric oil and 95% carrier) at 500 g per tonne, ADG and F:G were better in pigs fed the diet containing the oregano premix than in pigs fed the same diet without oregano. No antibiotics were fed in this study.

Oregano also has been reported to enhance sow reproductive performance. Amrik and Bilkei¹⁰ reported enhancements in mortality rate, sow culling rate, farrowing rate, and number of liveborn pigs when sows were fed gestation and lactation rations containing oregano premix at 1000 g per tonne. In this study, each kg of oregano premix contained 500 g oregano oils (60 g carvacrol and 55 g thymol per kg), mixed with dried leaf and flower of Origanum vulgare up to 1 kg. Khajarern and Khajarern¹¹ also reported an increase in daily feed intake in lactating sows when origanum essential oil was added to the diet at 250 g per tonne, and in addition, daily weight gain was higher in pre-weaned pigs from these sows than in litters from sows not fed oregano oil.

Utiyama et al¹² evaluated growth performance in weanling pigs (21 days of age) fed a diet containing a combination of herbal extracts of garlic, clove, cinnamon, pepper, and thyme at 500 g per tonne. No enhanced growth performance was observed when the herbal extracts were fed. Cloves and spices have been used for many years as food preservatives because of their antimicrobial activity. Main et al¹³ evaluated cloves as a substitute for antimicrobials in nursery pig diets in two experiments. Results were inconsistent, with ADG better in pigs fed the lowest concentration of cloves only during Days 0 to 21 in the first experiment and no growth enhancement in the second experiment. Iowa State University has published numerous reports evaluating several botanicals: echinacea,^14,15 garlic,^16,17 goldenseal,¹⁸ and peppermint.^19,20 Growth performance of nursery pigs was assessed when diets contained either increasing levels of one of the botanicals or an in-feed antibiotic. Results of these trials showed either no growth-performance enhancement or inconsistent results among experiments. Turner et al² reviewed studies evaluating the effects of probiotics, oligosaccharides, spices, and plant extracts on growth performance of swine, as well as effects on gut function and health. Results were inconsistent and no true substitute for antimicrobials was identified. These reports, together with the results of our current studies, suggest that no herbal or plant-based substance tested is an effective substitute for nursery feed antimicrobials.

Implication

• Under the conditions of this experiment, addition of in-feed antimicrobials enhanced growth performance of nursery pigs, but addition of oregano at a range of dosages did not.

References

1. Keegan TP, Dritz SS, Nelssen JL, DeRouchey JM, Tokach MD, Goodband RD. Effects of in-feed antimicrobial alternatives and antimicrobials on nursery pig performance and weight variation.
J Swine Health Prod. 2005;13:13–18.

2. Turner JL, Dritz SS, Minton JE. Review: Alternatives to conventional antimicrobials in swine diets. Professional Animal Scientist. 2001;17:217–226.

3. Stahl CH. Alternatives to antibiotics in feed for pigs. Pig News Info. 2005;26:9N–15N.

*4. Ralco-Mix Products, Inc. Where does your oregano come from? Available at: http://www.ralconutrition.com/poultry/oregano.aspx?n=p. Accessed September 8, 2006.

5. Deans SG, Ritchie G. Antibacterial properties of plant essential oils. Int J Food Microbiol. 1987;5:165–180.

6. Baratta MT, Dorman HJD, Deans SG. Chemical composition, antimicrobial and antioxidative activity of laurel, sage, rosemary, oregano and coriander essential oils. J Essential Oil Res. 1998;10:618–627.

7. National Research Council. Nutrient Requirements of Swine. 10^th ed. Washington, DC: National Academy Press; 1998.

8. Gorbach SL. Antimicrobial use in animal feed – time to stop. New Engl J Med. 2001;345:1202–1203.

*9. Gunter KD, Bossow H. The effect of etheric oil from Origanum vulgaris (Ropadiar^®) in the feed ration of weaned pigs on their daily feed intake, daily gains and food utilization [abstract]. Proc 15^th IPVS Cong. Birmingham, UK. 1998;223.

10. Amrik B, Bilkei G. Influence of farm application of oregano on performances of sows. Can Vet J. 2004;45:674–677.

*11. Khajarern J, Khajarern S. The efficacy of origanum essential oils in sow feed. Int Pig Topics. 2002;17:17.

*12. Utiyama CE, Oetting LL, Giani PA, Ruiz US, Miyada VS. Antimicrobials, probiotics, prebiotics, prebiotics and herbal extracts as growth promoters on performance of weanling pigs [abstract]. J Anim Sci. 2004;82(Suppl 1):26.

*13. Main RG, Minton JE, Dritz SS, Tokach MD, Goodband RD, Nelssen JL. Evaluating cloves as a potential substitute for antimicrobials in nursery pig diets. Kansas Agricultural Experiment Station Report Progress. No. 880. 2001; 32–34. Kansas State Swine Day Report.

*14. Holden P J, McKean J, Franzengurg E. 1998. Botanicals for pigs – Echinacea. Iowa State University Swine Research Report. ASL-R1560. Available at: http://www.extension.iastate.edu/Pages/ansci/swinereports/asl-1560.pdf. Accessed September 12, 2006.

*15. Holden PJ, McKean J. 2000. Botanicals for pigs – Echinacea II. Iowa State University Swine Research Report. ASL-R647. Available at: http://www.ipic.iastate.edu/reports/00swinereports/asl-647.pdf. Accessed September 12, 2006.

*16. Holden PJ, McKean J, Franzengurg E. 1998. Botanicals for pigs – Garlic. Iowa State University Swine Research Report. ASL-R1559. Available at: http://www.extension.iastate.edu/Pages/ansci/swinereports/asl-1559.pdf. Accessed September 12, 2006.

*17. Holden PJ, McKean J. 2000. Botanicals for pigs – Garlic II. Iowa State University Swine Research Report. ASL-R648. Available at: http://www.ipic.iastate.edu/reports/00swinereports/asl-648.pdf. Accessed September 12, 2006.

*18. Holden PJ, McKean J, Franzengurg E. 1998. Botanicals for pigs – Goldenseal. Iowa State University Swine Research Report. ASL-R1558. Available at: http://www.extension.iastate.edu/Pages/ansci/swinereports/asl-1558.pdf. Accessed September 12, 2006.

*19. Holden PJ, McKean J, Franzengurg E. 1998. Botanicals for pigs – Peppermint. Iowa State University Swine Research Report. ASL-R1561. Available at: http://www.extension.iastate.edu/Pages/ansci/swinereports/asl-1561.pdf. Accessed September 12, 2006.

*20. Holden PJ, McKean J. 2000. Botanicals for pigs – Peppermint II. Iowa State University Swine Research Report. ASL-R649. Available at: http://www.ipic.iastate.edu/reports/00swinereports/asl-649.pdf. Accessed August 30, 2006.

*Non-refereed references.