Introduction
Earlier than moving into the topic, you will need to level out that the impact of natural acids (OAs) on pigs’ gastrointestinal well being, digestibility, and manufacturing efficiency will depend on a number of exterior elements such because the kind of weight loss plan, the focus and mixture of OAs used, and the pigs’ age and well being standing. These elements have to be thought-about when evaluating outcomes from completely different scientific research and making use of the data on a sensible stage.
For instance, the buffering capability of the weight loss plan impacts the motion of natural acids, with a higher impact in decrease buffering capability diets (Clean et al., 1999; Wang et al., 2023). Alternatively, relying on the sampling time used on the gastrointestinal stage to guage the acidifying capability of an acid, the outcomes obtained could fluctuate (Canibe et al., 2005). Due to this fact, to use scientific data in follow, you will need to have an in depth understanding of the research’s methodology and our farm’s circumstances.
Formic acid
Formic acid (EFSA Registration Quantity 1k236) is a quick chain fatty acid (SCFA) with the chemical system CH2O2, licensed by EFSA as a technological additive to be used in animal feed as a preservative with a most inclusion of 10 g/kg in feed with 12% moisture content material for pigs.
It’s a clear liquid acid, is soluble in water and alcohol, and has a low molecular weight of 46.03 g/mol, a pKa of three.75, and a logP Kow of -0.54. Because of its low pKa worth, the acid has a excessive acidifying capability on the gastric stage, though it’s sophisticated to deal with attributable to its corrosiveness. To scale back corrosiveness, combining formic acid with salts to type formic acid salts corresponding to ammonium formate is a extensively used follow. Keep in mind that doing so modifies its mechanism of motion on the gastrointestinal stage.
A number of research (Desk 1, tailored from Luise et al., 2020) have noticed improved manufacturing efficiency within the nursery and ending phases by together with formic acid within the feed.
Within the nursery, particularly within the days after weaning, the usage of formic acid is fascinating attributable to its sturdy acidifying energy on the gastric stage to facilitate protein digestion and scale back the proliferation of pathogenic micro organism on the gastric stage (Tung and Pettigrew, 2006; M. Garcia, 2011). It has been proven {that a} 0.9% inclusion of a combination of 75% formic acid and 25% propionic acid within the feed of post-weaning piglets experimentally contaminated with Salmonella and E. coli lowered the focus of those pathogens on the gastric stage (Taube et al., 2009). On the microbiota stage, Maribo et al. (2000) noticed that together with 0.7% and 1.4% formic acid lowered the focus of lactobacilli within the small gut and caecum and coliforms within the abdomen in piglets post-weaning. Equally, Gedek et al. (1992) noticed a discount of lactobacilli within the small and huge gut and a discount of coliforms within the massive gut independently of the formic acid dose (1.2% to 2.4%), whereas the extent of coliforms within the small gut was dose-dependent. Alternatively, research corresponding to that by Gerritsen et al. (2010) didn’t observe any enchancment in manufacturing efficiency however did observe a rise within the in vivo obvious digestibility of crude fiber in post-weaning piglets supplemented with 5 kg/t feed of a combination of formic acid, propionic acid, lactic acid, citric acid, and sorbic acid.
In ending, the usage of formic acid mixed with lactic acid at 0.8% or 1.2% inclusion (50:50 lactic acid:formic acid) has confirmed to be technique to cut back the prevalence of Salmonella within the final 14 weeks of ending (Creus et al. 2007).
Desk 1. Abstract of the consequences of formic acid use on manufacturing outcomes throughout nursery and ending of pigs (desk tailored from Luise et al., 2020).
| Formic acid | ||||
|---|---|---|---|---|
| Inclusion, % | Manufacturing part | Common every day achieve | Feed conversion ratio | Reference |
| 0.5 | Nursery | = | = | Manzanilla et al. (2004) |
| 0.2 | Nursery | = | = | Kil et al. (2006) |
| 0.6 | Nursery | ↑1 | ↓ | Luise et al. (2017) |
| 0.14 | Nursery | ↑1 | ↓ | Luise et al. (2017) |
| 0.8 | Ending (growers) | ↑ | Siljander-Rasi et al. (1998) | |
| 0.8 | Ending (finishers) | = | Siljander-Rasi et al. (1998) | |
| 1.0 | Ending | ↑ | Øverland et al. (2000) | |
| 1.8 | Ending | ↑ | Canibe et al. (2005) | |
| 1.0 | Ending (growers) | = | ↑ | Øverland et al. (2007) |
| 0.8 | Ending | ↑ | ↑ | Partanen et al. (2002) |
| 1.0 | Ending (growers) | ↑ | ↑ | Øverland et al. (2008) |
| 1.0 | Ending (finishers) | = | ↑ | Øverland et al. (2008) |
1 Outcomes after three weeks of administration; no important variations after six weeks.
Lactic acid
Lactic acid (EFSA Registration Quantity 1a270) is a SCFA with the chemical system C3H6O3 licensed by EFSA as a technological additive to be used in animal feed as a preservative with a most inclusion of fifty g/kg in feed with 12% moisture content material for pigs.
It’s a yellowish clear viscous liquid OA, is soluble in water and ethanol, and has a molecular weight of 90.08 g/mol, a pKa of three.75, and a logP Kow of -0.70. Because of its low pKa worth, the OA has a powerful acidifying capability on the gastric stage in younger piglets, making it an acid of alternative to cut back the incidence of digestive pathology after weaning, though its impact on selling manufacturing has contradictory outcomes.
Within the Nineties, it was printed that lactic acid can lower gastric pH and the proliferation of enterotoxigenic Escherichia coli in piglets (Thompson and Lawrence, 1981; Partanen and Mroz, 1999). Just a few years later, Tsiloyiannis et al. (2001) noticed that together with 1.6% lactic acid within the post-weaning feed decreased the share of animals with diarrhea, improved manufacturing outcomes, and lowered coliform bacterial counts. More moderen research have noticed that the inclusion in feed of three.97 g/kg lactic acid along with 4.16 g/kg fumaric acid in feed in piglets from 7 to 18 kg BW positively modulates the gastrointestinal microbiota by growing the Bacteroides-Porphyromonas-Prevotella rely within the ileum and lowering the focus of Streptococcus spp within the colon however with no impact on manufacturing outcomes (Zentek et al., 2013).
Propionic acid
Propionic acid (1k280) is a SCFA with the chemical system C3H6O2, licensed by EFSA as a technological additive to be used in animal feed as a preservative with a most inclusion of 30 g/kg in feed with 12% moisture content material in pigs.
It’s a clear oily liquid acid, miscible in water and soluble in alcohol, and has a molecular weight of 74.08 g/mol, a comparatively excessive pKa worth of 4.88, and a logP Kow of 0.33.
Propionic acid is an efficient OA in inhibiting the expansion of fungi and micro organism, making it a very helpful OA as a feed preservative, though it’s sophisticated to deal with attributable to its corrosiveness.
A latest research noticed that preserving grain with 4 kg propionic acid/t after harvest positively impacted grain high quality by way of decrease mycotoxin focus, and the efficiency of 0-35 day post-weaning piglets with elevated progress and consumption. Whereas no impact on efficiency was noticed, a discount of pro-inflammatory cytokine expression within the small gut at day 10 post-weaning was noticed when the 4 kg/t propionic acid was dosed within the completed feed. The authors conclude that the enhancements in manufacturing outcomes obtained could also be a consequence of improved grain high quality, elevated consumption, and helpful affect on the intestinal microbiota (Connolly et al., 2024).
To arrange this knowledge sheet, research have been chosen to independently consider the actions of formic acid, lactic acid, and propionic acid on pigs’ gastrointestinal well being and manufacturing parameters. Nevertheless, in follow, their inclusion is usually finished together with different OAs, producing a synergistic or additive impact that enhances their advantages.
