Natural feed additives as alternatives to in-feed antibiotics in nursery pigs

Intensive pig production puts additional stress on the weaned piglet at a time of already heightened vulnerability to infections. With a global trend towards the reduction and elimination of antibiotics for growth promotion from pig diets, can natural alternatives really close the performance gap?
calendar icon 25 October 2018
clock icon 6 minute read

Author: Roger Berríos B Vet Med, Product Manager Acids and Santa Maria Mendoza PhD, Swine Technical Sales Manager

Commercial pig production has changed dramatically in the last decades. A transition from extensive housing systems with low animal density to intense production systems with a high degree of confinement was driven by the need to increase meat production and satisfy the demands of a growing population. The production cycle of a pig is divided into stages, each with different housing systems, management styles and challenges.

Intensive production adds stress to piglets

Within swine production, the weaner unit represents a big challenge. Under natural conditions, the sows wean their litters gradually over the first 17 weeks of lactation, yet in intensive production, the weaning process is abrupt and can start as early as 3-4 weeks. Weaning at this young age often means that the piglets are not physiologically, immunologically or behaviorally ready. And at the same time, they suffer a large variety of stressors including abrupt separation from the mother, transport, handling and social stress caused by regrouping several litters, changes in environment, change of water supply, change of feed source from a milk-based diet to solid feed with high levels of protein from plant origin, and exposure to pathogens among others. A fasting period is commonly observed immediately after weaning due to adaptation to dietary changes; this weaning anorexia might contribute to gastrointestinal inflammation.

Consequently, the weaned piglet is both vulnerable to infections and weaker to fight them. All this affects piglet health, leading to decreased performance and, in extreme cases, mortality. During the weaning process, a dysbiosis in the gut microbiota leads to post-weaning diarrhea and gastrointestinal infection where colibacillosis diarrhea is of greatest concern. Antibiotics are used in the swine industry for their growth promotion effects, prophylaxis or metaphylaxis and therapeutic purposes.

Regulation of antibiotic usage

Overuse of antibiotics is linked to an increase in antimicrobial-resistant agents which concerns animal and human health authorities. The use of antibiotics as growth promoter agents has been banned in Europe since 2006 and the ban is gradually being extended to other regions. Nevertheless, in-feed antibiotics are still used in some regions as a prophylaxis / metaphylaxis measure to prevent a drop in growth performance and health issues in weaned piglets. In the United States (USA), carbadox is commonly used in the weaner phase to control enteric disease (colibacillosis). It is usually alternated among dietary phases during the weaner period because it does not require veterinary feed directive. However, research suggests that carbadox inhibits bacteria by intercalating DNA and causing mutation in bacteria. This mutagenic property has led to its ban in Europe and Canada, and might influence the USA regulations in the near future. The combination of oxytateracycline and neomycin is used to treat bacterial enteritis and bacterial pneumonia. The use of sub-therapeutic doses of oxytateracycline and neomycin for growth promotion are banned in many countries including the USA, because the overuse has led to higher antibiotic resistance gene levels and prevalence.

Antibiotic alternatives

Therefore, it has become critical to find antibiotic alternatives to support growth performance and maintain piglet health during the weaning period. Producers are opting for the use of natural feed additives to prevent bacterial infections such as organic acids and phytogenics. However, the alternatives are evaluated directly against the effects of antibiotics on growth performance as a benchmark to overcome. The effect of antibiotics on growth performance enhancement is linked to their antimicrobial and anti-inflammatory effects.

The aim of this article is to present the results of a study where weaners were fed different antimicrobial programs (Table 1): a control diet (C) containing no antibiotic or antimicrobial feed additives, a positive control (PC) with antibiotic added to promote growth, an antibiotic reduction treatment (C-OA) containing antibiotics for the first phase and a natural feed additive for the second phase, and a holistic approach (OA-EO) where only natural feed additives were added to the diet.

Table 1. Study design

Table 2. Diet composition

ME = metabolisable energy, SID Lys = standardised ileal digestible lysine.

Study design

A total of 480, 22-day-old weaned piglets (body weight (BW) = 6.22 ± 1.4 kg) of PIC 280 X 1050 breed were used. Pigs were allocated to one of 48 pens (ten animals per pen) and assigned within weight blocks to one of four dietary treatments (12 pens per diet) as described in Table 1. The pigs were fed a corn-soybean meal based diet formulated in two phases as described in Table 2. Body weight (Figure 1) and feed intake were measured at day 8, 15 and 22. Average daily gain (Figure 2), average daily feed intake (Figure 3) and gain:feed ratio (Figure 4) were calculated. A mixed model was used to examine the effect of diet, weight block was used as the random effect, and multiple comparisons were evaluated using a t-test method.

Figure 1. Average body weight (kg)

Figure 2. Average daily gain (kg/d)

Figure 3. Average daily feed intake (kg/d)

Figure 4. Gain:feed ratio data


Pigs in the PC group had a greater BW (11.19 kg, P=0.001) compared to the C group (10.53 kg), but it did not differ between the C-OA group (11.03 kg, P=0.382) or the OA-EO group (10.85 kg, P=0.074). Body weight did not differ between the OA-EO and C groups (P=0.100).


The results of this experiment showed that it is possible to reduce or replace in-feed antibiotics with natural alternatives and enhance performance parameters in weaned piglets. Pigs fed carbadox followed by a Biotronic® Top3 (C-OA) did not differ in performance compared to pigs fed carbadox followed by neomycin and oxytetracycline (PC). In addition, the combination of Biotronic® Top3 (a blend of formic, propionic, and acetic acids combined with cinnamaldehyde and Permeabilizing Complex™ mixture) and Digestarom® P.E.P. (a phytogenic blend of oregano, anise, and citrus oil, and fructo oligosaccharide with antioxidative and anti-inflammatory properties) provided a viable natural alternative to in-feed antibiotics. A more extensive approach is necessary in order to replace antibiotics in animal production. Consideration has to be taken for improvements in production management and animal welfare, feeding systems and feed quality, biosecurity and vaccination programs, improvement of facilities and a more responsible use of the resources we have available.

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