Can acidification replace zinc oxide in piglet diets?

Restrictions on feeding high levels of zinc oxide will become effective in the EU in June 2022. Anticipating these changes, Trouw Nutrition has conducted multiple studies to evaluate products that support piglet performance without zinc oxide, AGPs or antibiotics. Two interesting research studies conducted in Canada in 2018, demonstrate that water acidification is an effective alternative to including high levels of ZnO in piglet feed.

Should pig farmers be concerned about restrictions on feeding high levels of zinc oxide (ZnO) to manage post-weaning diarrhea and gut health? Research findings from two studies carried out in Canada show that adding an acidifier to piglets’ water may deliver better results than feeding high levels of zinc, when it comes to improving feed intake, average daily gain, feed conversion ratio (FCR) and final bodyweight. As the EU deadline for restricting the practice of feeding high levels of zinc approaches, Feed & Additive caught up with Jeanine de Nysschen, an animal scientist and Selko global product manager for a conversation about research on alternative approaches to support piglet health.

How are regulatory changes accelerating efforts to find alternatives to AGPs and zinc oxide?
Efforts to reduce the use of antibiotics and AGPs in swine production have been underway for many years. Ongoing research to identify effective replacements for zinc oxide, AGPs and antibiotics is driven by concerns about the risk antimicrobial resistance presents to human health as well as ongoing efforts to reduce the environmental footprint of farming.

Restrictions on feeding high levels of zinc oxide will become effective in the EU in June 2022. Anticipating these changes, Trouw Nutrition has conducted multiple studies to evaluate products that support piglet performance without zinc oxide, AGPs or antibiotics. Two interesting research studies conducted in Canada in 2018, demonstrate that water acidification is an effective alternative to including high levels of ZnO in piglet feed.

What purpose has ZnO traditionally played in the piglets’ diet?
High levels of ZnO – about – 1,500 to 3,000 mg/kg feed – have long been added to piglets’ diets to help stabilize the intestinal microflora during the critical weeks post-weaning when piglets lose the protection supplied by sow’s milk and are exposed to new environmental threats. Adding ZnO to feed also aims to inhibit the growth of some pathogenic bacteria and create conditions in the animal’s GI tract for beneficial microflora to grow, but research is showing other strategies can effectively replace ZnO when it comes to managing gut health and animal performance.

What are alternative strategies to support piglets’ gut health and digestion?
Much research has focused on the role of acidification to support gut health. Scientists continue to study how carefully selected blends of organic acids can optimize digestive processes in piglets. Selko®-pH is a water additive that has been evaluated in several studies for its efficacy in supporting digestion. Containing a blend of free and buffered organic acids, Selko®-pH was developed by Selko to provide the gut enhancing effects long associated with feeding high levels of ZnO, without the corresponding environmental concerns. Understanding mode of action is essential. Researchers formulated Selko®-pH as an organic acid blend that lowers the pH of piglets’ water and works inside the animal’s gastrointestinal tract to lower the stomach pH and support digestion. Lowering the pH of water and of the stomach has a bacteriostatic effect on some pathogenic species, while organic acids are also known for their antimicrobial effect.

What research has been conducted to evaluate the efficacy of Selko®-pH in piglets?
Researchers conducted two studies with Selko®-pH to evaluate its efficacy in improving piglet performance in reduced ZnO feeding programs. The studies were carried out at the Burford Research Centre and the Magiporc commercial validation farm in 2018. A total of 1,200 piglets were included in the comparison trials and randomly allocated to one of four treatment group diets over a three-week post-weaning period.

The four diets included a high-zinc diet containing 2,500mg/kg with no acidifier in the water, a low-dose zinc diet containing 150mg/kg zinc and no water acidifier, a high dose zinc diet with an acidifier (Selko®-pH) added to the water, and a low-dose zinc diet that also included an acidifier (Selko®-pH). The researchers used water titration to determine inclusion rates of the acidifier and bring the water pH to 3.8. At this pH level, harmful bacteria find it difficult to survive. Food and water were provided ad libitum to piglets throughout the studies. While acidification of water was limited to three weeks, the piglets were monitored for an additional three weeks.

What piglet performance parameters were evaluated in the studies conducted in Canada?
Researchers tracked piglets to assess average daily gain (ADG), average daily feed intake (ADFI), feed conversion ratio (FCR) and final bodyweight (BW).

What were some key findings from the studies?
The raw data from the two studies were combined into one dataset and analyzed using a model procedure to assess ADG, ADFI, FCR and BW. (See Table 1).

Except for the first week, piglets receiving the high zinc diet tended to have a higher ADG compared to piglets receiving the low zinc diet. By week three, the pigs fed a high-zinc diet had an average daily gain of 453g/d compared to pigs fed the low-zinc diet that gained 452g/d. Although supplementation was only for the first three weeks of the diet, the trend continued through week six. Piglets receiving the water acidifier in both the high- and low-dose treatment groups had increased weight gain compared to piglets that did not receive an acidifier. Piglets on the low zinc and Selko®-pH diet tended to gain more weight than animals that received the high-zinc diet and Selko®-pH. (See Figure 1).

It’s always important to consider the efficiency of the feed investment, and results were promising here as well. By week three, feed conversion tended to be lower for pigs on the low-zinc and Selko®-pH diet compared to pigs in the high-zinc diet treatment group. (See Table 1.) Pigs in both the high-zinc and low-zinc diets that received Selko-pH performed better in terms of FCR than pigs not receiving an acidifier, regardless of the level of zinc fed.

Looking at final body weight, over the six-week trial, piglets on the high-zinc diets tended to outperform those on only the low-zinc diets (Figure 2). But again, both groups of piglets receiving the acidifier outweighed the pigs that did not receive it. Animals in the low-zinc diet treatment group that received Selko-pH were heavier than their high zinc counterparts. (See Figure 2.)

How did acidification affect daily feed intake?
Given the stress of the transition from sow’s milk to solid feed, assuring adequate intake is always a concern. Study findings shown in Table 1 show that feeding high doses of ZnO negatively affected piglets’ average daily feed intake (ADFI, 166 vs 178 g/d) and improved average daily gain (ADG, 165 vs 167 g/d) during the first week post-weaning for high and low ZnO diets respectively. However, piglets that received a low dose of ZnO in their feed along with Selko-pH (LZ+PH) showed significantly higher ADFI (+13 g/d and +14 g/d) compared to high ZnO treatments. The LZ+PH animals also had higher ADG (+14 g/d and +22 g/d) compared to piglets receiving high doses of ZnO.

Were there any performance factors noticed in the studies?
Survivability is always a concern, and mortality among different groups showed some differences. At the end of three weeks, piglets receiving the high-zinc diet had the highest mortality rate, whereas both groups receiving the combination of high- or low-zinc along with the acidifier had lower levels of mortality.

What is a final summary from the trials?
Setting piglets up for long-term performance without zinc oxide, AGPs or antibiotics demands an integrated strategy including feed, farm, and health management. However, these trials demonstrate the value that Selko-pH brings to the post-weaning diets of piglets. The results of these studies show that acidification can be an effective alternative to adding high levels of zinc oxide to piglet diets.

About Jeanine de Nysschen
Jeanine de Nysschen is the Global Product Manager of Selko-pH with a Master of Agricultural Science degree in Animal Science: Production Physiology and Product Quality and Bachelor’s degree in Animal Science from the University of Pretoria in South Africa. During her professional career she gained on-farm experience and knowledge on animal nutrition and feed additives aimed at controlling Salmonella, reducing the use of antibiotics, and improving production efficiency.