With costs of pig production under increasing pressure, the nutrition of young pigs is of increasing interest, as this period is critical to the subsequent performance of the animals through to market. Optimising growth rate and feed efficiency at this time are therefore key requirements for success in today´s animal production systems. While antibiotics are available to assist in improving growth during this phase, there are a range of concerns from world-wide pig producers about their use, including bacterial resistance, palatability and the accuracy of antibiotic dosage if feed intake is compromised. Furthermore, animal production is viewed critically for its use of in-feed antibiotics, both from consumers and regulatory authorities. As a result, various feed additives have been studied as alternatives. Organic acids, particularly salts of organic acids, have been reported by many experts to enhance growth performance in the absence of antibiotic growth promoters (AGPs) in pigs, as well as poultry and aquaculture.
A market report from Global Feed Analysts (2008) indicated that the European market for feed acids is the fastest growing acidifier market in the world, growing by 6.6% in the period 2008-2012 and is likely to cross US$500 million by 2012. More recently (2010), the same source reported that the global market for feed acidifiers is projected to reach US$1.4 billion by 2015, driven by an increasing demand in developing economies, stable demand for meat and meat products from developed economies and, of course, a swelling world population.
The potential application of organic acids to livestock nutrition and forage preservation has been known for decades and is documented by many scientific studies. Acids make a fundamental contribution to feed hygiene, since they suppress the growth of mould and thus restrict the potential production and detrimental effects of mycotoxins. Consequently the feed´s safety is guaranteed by adding organic acids. A strong bactericidal and bacteriostatic effect has also been demonstrated for formic acid, the shortest-chain organic acid. These effects are based on reduction of the pH in both the feed and in the gut and also by the antimicrobial effect of the acid. The antimicrobial effect of organic acids varies widely and is based chiefly on the acid´s degree of dissociation, as indicated by its pK-value, which states the pH at which the acid is 50 per cent dissociated and can be used to determine the action of an acid at a given pH. This is based chiefly on the capacity of organic acids in their un-dissociated state to cross the cell walls of gram-negative bacteria such as E.coli and Salmonella and penetrate into the cell.
Inside the bacterial cell, acids dissociate into a hydrogen cation and an acid anion. The cation also reduces the pH-value in the interior of the cell. Restoring intercellular pH is expensive in terms of energy, while the anion disrupts DNA synthesis in the nucleus. This dual impact mechanism effectively obstructs bacterial replication.
Formic acid is often described as being the strongest organic acid against pathogen gram negative bacteria; however certain disadvantages, like its unfavourable pungent smell and corrosiveness limit its use in feed production.
The potassium salt of formic acid, potassium diformate (KDF), on the other hand, also has a strong anti-microbial effect, but additionally is proven safe for humans and has no adverse smell. In contrary to formic acid, potassium diformate is a solid product (composition: 35.4% formic acid, 34.6% formate and 30% potassium), which is non-corrosive. Because of its unique chemical structure, potassium diformate combines the chemical properties of an acid and a salt. It is registered as Formi®, the first non-antibiotic performance enhancer for pigs and patented by the ADDCON Group.
In order to fulfil the EU-registration requirements, KDF passed standards in several trials with weaners, fatteners and sows - the inclusion of potassium diformate in the feed of weaner piglets for instance has been shown in many experiments to have a substantial positive effect on animal performance (Roth et al. 1996; Kirchgessner et al. 1997; Partanen 2001; Diebold and Eidelsburger 2006). The benefit on production performance from supplementing pig diets with potassium diformate seems to originate to a certain extent from enhanced body protein retention (Roth et al. 1998), thus supporting improvements in feed conversion.
In the following several trials, from Europe and Asia, prove the aforementioned benfecial effects on feed conversion ratio.
A trial was carried out at a large pork producing co-operative in UK. Pigs were selected from a single-source high health status outdoor breeding unit. Pig genetics were: 25% Landrace, 25% Duroc, 50% PIC synthetic sire line (337). A total of 420 piglets with equal numbers of males and females were weaned at 28 days and randomly allocated to two groups. Piglets in the treated group received 1.2% potassium diformate. Pigs were housed in pens with solid concrete floors, each with a floor area of 1.2 m² per animal, whereof 70% was bedded lying area. Feed was offered ad libitum throughout the trial as pellets by dual-space ad lib feed hoppers. Feed did not contain any zinc or prophylactics. Free access to water was available all the times.
Piglets had an average growth rate of 195 g/d in the starter phase with a daily feed intake of 231 g/d. The addition of 1.2 % KDF resulted in a significantly improved daily weight gain (+20%) and feed conversion rate (-12.4%). The feed intake was 7.2% higher in the KDF treatment group. In the weaner phase (weeks 3 to 7) the average weight gain was 534 g/d with a daily feed intake of 834 g/d. The addition of 1.2 % KDF resulted in a significantly improved daily live weight gain (+13.8%) and feed conversion rate (-8.5%). The feed intake increased by 3.7% in the treatment groups, supplemented with 1.2% KDF.
For the overall trial period of 7 weeks the addition of 1.2% potassium diformate resulted in a highly significant improvement of daily weight gain (+14.6%) and feed conversion rate (-9.4%). The daily feed intake was increased by 3.8% in the group supplemented with KDF. Piglets supplemented with KDF had a significant higher live weight at the end of the overall trial (30.76 kg vs. 27.65 kg, + 11.2%; Table 1).
Table 1. Effect of KDF (FORMI) on performance parameters of weaned piglets (data from Eidelsburger et al. 2007)
A trial in the tropics (Kasetsart University, Thailand) backed the aforementioned data and thus showed that the additive is working under humid and hot climates as well. Eighty growing pigs (Duroc x Large White x Landrace crossbreeds) were fed from week 10 till week 17 a typical corn-soy commercial diet with wheat bran as binder, either without or with KDF (0.6%). The initial weight of tested pigs was around 21 kg, while the trial lasted till >50 kg of body weight. The actual data are displayed in Table 2.
Table 2. Performance of Duroc x Large White x Landrace crossbreeds from week 10 to 17 fed with or without KDF (FORMI)
The data reveal a numerical increase of ADG in the KDF fed group by 4.4%, while the fed conversion ratio was improved by 4.4% as well, thus suggesting improved economics during the period potassium diformate was used.
A further trial under tropical conditions was conducted on a commercial pig farm in Thailand under the supervision of the Department of Animal Science of the Khon Kaen University. The aim of the trial was to test potassium diformate in different dosages against a commercial piglet diet containing an antibiotic growth promoter (AGP). Feed and water were available ad libitum. 240 crossbred weaned piglets (21 days of age, average weight 6.3 kg) were randomly selected and divided into 5 treatment groups. Piglets were housed over a 35-day trial period in pens with 4 replicates. Performance data were measured at the end of the trial. The positive control group received 110 mg Tylosin, 110 mg Sulfamethazine and 100 mg Colistin per t of feed, while the trial groups containing potassium diformate (FORMI) received 0.3%, 0.6% and 0.9% as well as 1.2% KDF. During the trial all data have been recorded (Table 3).
Table 3. Performance of crossbreeds weaned piglets fed with or without KDF (FORMI)
As it can be seen from the table, overall performance in the groups fed with potassium diformate was significantly improved. The addition of KDF resulted in dose-dependent improvements in daily weight gain, FCR as well survival rate. Especially the FCR was already significantly improved at the lowest offered dosage of potassium diformate, and could be reduced by more than 4% with 0.3% KDF-inclusion only - while the addition of 0.6% KDF lead even to an improvement of feed conversion of 11%.
Discussion and conclusion
The use of potassium diformate as non antibiotic growth promoter has been demonstrated widely to enhance the production performance of growing pigs (Roth et al. 1996; Kirchgessner et al. 1997; Partanen 2001; Eidelsburger et al. 2005; Diebold and Eidelsburger 2006). The mode of action of potassium diformate and other organic acid products based on formic acid has been intensively investigated and documented in the scientific literature (Partanen and Mroz 1999; Eidelsburger 2001; Diebold and Eidelsburger 2006). It is well-known and accepted in the scientific literature, that acidifier have positive effects on reduced buffer capacity in the feed, accelerated and improved decrease of pH value in stomach contents with the subsequent better development of digestive enzymes (Roth et al. 1996; Kirchgessner et al. 1997; Partanen and Mroz 1999; Eidelsburger 2001; Partanen 2001). In combination with the well documented positive effects of potassium diformate on digestibility of nutrients (e.g. protein), reducing E. coli, salmonella and other pathogenic bacteria and therefore optimizing the digestion process in the small intestine and hindgut of piglets (Diebold and Eidelsburger 2006), there might be an explanation for such more pronounced effects of potassium diformate on feed conversion of piglets and growing pigs.
This paper was presented at the Pig Feed Quality Conference, Cebu, Philippines, May 2011.