Zinc methionine and laminarin have growth‐enhancing properties in newly weaned pigs influencing both intestinal health and diarrhoea occurrence
Since 2006, the EU prohibits the inclusion of in‐feed antimicrobial growth promoters (AGP) to ameliorate the negative effects of weaning. Consequently, the prescribed inclusion of ZnO at rates above nutritional requirements for the maintenance and growth of pigs has increased gradually, in an attempt to contain the aforementioned problems associated with weaning by pig producers (Pluske et al., 2007). The inclusion of ZnO decreases the severity of diarrhoea and improves growth performance post‐weaning (Kim et al., 2012). However, the high inclusion of ZnO exceeds requirements of the pigs. Hence, there are concerns about these high inclusion rates and Zn accumulation in the soil (Miller et al., 2009), which could lead to restrictions on the inclusion of high levels of ZnO in the future.
The seaweed‐derived β‐glucan laminarin (LAM) has shown potential as a growth enhancer. Heim et al. (2014) showed that LAM supplementation improved feed efficiency and enhanced nutrient digestibility in the immediate post‐weaning period, but had no effect on the occurrence of diarrhoea, when offered to newly weaned pigs fed AGP‐free diets. There may be a synergistic effect between LAM and Zn inclusion in reducing the occurrence of diarrhoea. However, O'Shea et al. (2014) reported an antagonistic effect on feed efficiency in pigs post‐weaning between ZnO (3100 mg/kg inclusion) and seaweed extracts containing LAM and fucoidan. This antagonistic effect was due to the high inclusions levels of ZnO. Organic zinc could be used as a substitute for ZnO, as organic zinc can be supplemented in lower doses (up to 500 mg/kg feed) than ZnO (1000–4000 mg/kg feed) due to its increased bioavailability. Organic zinc is a non‐ionic chemical bond between the Zn atom and a ligand such as an amino acid (Schlegel et al., 2013) and has been shown to improve pig performance and reduce diarrhoea in a comparable manner to ZnO (Case and Carlson, 2002; Carlson et al., 2004; Buff et al., 2005).
The current study was designed to study the effects of replacing ZnO with either zinc methionine (ZnM) or LAM or a combination of both ZnM and LAM. Three experiments were conducted: experiment 1 investigated the interaction between ZnM and LAM on intestinal morphology, microflora and immune response of newly weaned pigs while growth performance in the first 31 days post‐weaning was measured in experiment 2. In experiment 3, the growth performance of newly weaned pigs that were offered ZnM and LAM was compared to ZnO. The hypothesis of this experiment is that there would be an additive effect between LAM and ZnM, leading to reduced diarrhoea, improved growth performance and small intestinal architecture, while also reducing the abundance of potentially pathogenic bacteria and the inflammatory response and would result in a similar growth performance to pharmacological levels of ZnO.