Strategies to reduce the use of ZnO by modulating the gut microbiota in pigs

Introduction

Zinc (Zn) plays an important role in the metabolism of swine and as such is an essential trace element for growing pigs.

During the late 1980s, it was discovered that pharmacological concentrations (1.500-3.000 ppm) of Zn oxide (ZnO) resulted in reduced diarrhea and increased growth in weanling pigs. To minimize the risk of environmental pollution, in the EU, the legal norm for Zn is 150 mg/kg (ppm) of Zn in complete animal feed (EU Regulation 1334/2003). Since 2005, ZnO at pharmacological levels has been reallowed in some European countries (under the Veterinary Medicines Regulations) as a means to reduce the use of antibacterial compounds in the period shortly after weaning.

Mode of action of ZnO

The mechanisms behind the beneficial effects of ZnO to prevent diarrhoea and promote growth in weaned piglets are not completely understood but recent advances in research suggest it is achieved through multiple regulatory pathways.

It has been shown that ZnO regulates secretion of brain-gut peptides that stimulate feed intake resulting in a growth promoting effect. In addition, it improves intestinal barrier function by increasing the expression of intestinal insulin-like growth factor-1 and reduces the release of pro-inflammatory molecules. Furthermore, reduces attachment of pathogenic bacteria such as enterotoxigenic E. coli (ETEC) to the intestinal villi and is demonstrated to diminish the translocation of (pathogenic) bacteria such as E. coli and Enterococcus spp. in the mesenteric lymph nodes of the small intestine.

Downsides of Zn usage

It is clear that the use of high levels of ZnO (1,500-3,000 ppm) has many positive effects on piglet health and performance. However, such use of pharmacological ZnO dosages has potentially some negative consequences as well.

Pharmacological usage of ZnO for short periods of time (max. 14 days) does not cause severe negative consequences for the health of the animal but if used for longer periods it has toxic effects, resulting in depression in feed intake.

High levels of Zn cause a risk for sub-deficiencies of some minerals and nutrients, as it interferes with the productin of transporter proteins, and can form a complexes with e.g. phytate.

In addition, impurities such as cadmium in commercial ZnO can be a considerable problem when Zn quality is not strictly controlled.

Moreover, intensive usage of Zn in animal diets may favor the development of bacterial resistance against other antimicrobials.

Search for alternatives - SANACORE^®EN

Because of these negative aspects of ZnO usage, producers are looking to find a suitable replacement.

When developing an antimicrobial support product, NUTRIAD has focused on products with a similar mode of action as ZnO. This research has resulted in the development of SANACORE^®EN, a multifunctional product with a broad spectrum antibacterial approach. The aim of using the product is to reduce the use of ZnO and/or antimicrobials while supporting health and welfare of the animals, as well as to improve production results.

The different components in SANACORE^®EN cover the same range of positive effects as described above for ZnO, such a growth promoting effect, improvement of intestinal barrier function, modulation of ion absorption and a broad antibacterial effect.

Field trial with SANACORE^®EN

To test whether SANACORE^®En can be used in a program with reduced levels of ZnO, a trial was performed with 68 crossbred piglets (LD-LW x Pietrain), weaned at 28 days of age. These piglets were allocated to one of two dietary treatments based on live weight (see Table 1).

Table 1: Dietary treatment groups evaluated.

	Pre-starter day 28-42	Starter day 42-76
standard ZnO inclusion	HiZ	ZnO 3 kg/T	ZnO 3 kg/T
Low ZnO inclusion + Sanacore	LoZ + S	ZnO 3 kg/T Sanacore 3 kg/T	Sanacore 2 kg/T

* Feeds also include 120 ppm of colistin

Table 2: Performance parameters measured during the trial.* Feeds also include 120 ppm of colistin

	Pre-starter day 28-42	Starter day 42-76	Pre-starter + Starter day 28-76
	HiZ	LoZ + S	HiZ	LoZ + S	HiZ	LoZ + S
end weight (kg)	9.1	9.2	21.6	25.2 *
feed intake (g/d)	266	314 *	605	661 *	513	560 *
ADG (g/d)	240	250	374	468 *	334	405 *
FCR	1.2	1.3	1.7	1.5 *	1.6	1.4 *

* indicates p < 0.05

When looking at the performance results throughout the complete trial period, SANACORE^®EN application in pre-starter and starter, resulted in a significant increase in feed intake, a significant higher ADG and lower FCR in comparison with a standard ZnO programme. At the end of the trial period at 76 days of age, piglets on the SANACORE^®EN weighed on average 3.6 kg heavier than the piglets from the straight ZnO programme.

The current study demonstrated the potential of SANACORE^®EN to be used in programmes with reduced ZnO levels in weaning piglet diets. Applying a sound SANACORE^®EN strategy can make a real difference for producers that want to limit the use of ZnO.