Improving liquid feeding system hygiene to improve the feed efficiency of liquid-fed grow-finisher pigs
The feed efficiency of liquid-fed pigs can be up to 0.20 of an FCE unit poorer compared to dry feeding, which equates to an increase in feed cost of ~€5.10 per pig, based on the five year average finisher feed price. James Cullen, Florence Viard, Gillian Gardiner and Peadar Lawlor explain more.
One reason for this is that microbial growth in the liquid mix can reduce the energy and amino acid content in the liquid feed. Microbes also grow on internal surfaces of mixing tanks and pipes and poor hygiene of the system likely contributes to the poorer feed efficiency.
As part of the WetFeed2 project, we recently developed and trialled a sanitisation programme for liquid feeding systems to improve the hygiene of the feeding system. The cleaning of the system was performed between batches and included physical cleaning, and an alkali and acid wash. The new batch of pigs (~35 kg) were fed from the clean system for 10 weeks during which nightly (maintenance) acid rinses of the system were performed. We collected feed samples and swabs from the system before and after cleaning for microbiological analysis. The results showed that the hygiene of the mixing tank and feed pipe improved dramatically after cleaning (Figure 1).
Figure 1: Hygiene of the feeding system before (baseline) and after cleaning
The red line on the graphs in Figure 1 show the ATP levels which measure surface hygiene. These readings were highest before cleaning and decreased immediately after cleaning. ATP levels remained low up to 10 weeks after cleaning in the feed pipe but started increasing after ~4 weeks in the mixing tank. Of particular note in the feed pipe, high levels of moulds were found before cleaning, but they were eliminated after cleaning for the duration of the trial.
We also saw this after using scanning electron microscopy (SEM) on sections of the feed pipe that we removed from the system (Figure 2). Moulds and bacteria were widespread in the pipe before cleaning but one day after cleaning, these moulds were damaged and were not found for the duration of the trial, which indicated that they were killed off completely. Despite the improved hygiene of the system, there was little impact on the microbiology of the liquid feed itself.
Figure 2. Scanning electron microscopy (SEM) images of the internal feed pipe surface before and after cleaning
Based on the improved hygiene of the feeding system, we estimated a return from implementing our sanitisation protocol (Table 1). We assumed a very conservative improvement in FCE of 0.05 between 30 and 115kg LW, based on four batches of pigs per year. Taking into account the costs associated with implementing the sanitisation programme, there is a potential financial return of up to €1.20 per pig, depending on the size of the unit.
Table 1: Estimated financial return from implementing the sanitisation programme
From this work we can conclude that implementing our sanitisation programme between batches improves the hygiene of the system. We believe that we can improve this protocol further by ensuring that the upper surfaces inside the mixing tank are thoroughly rinsed down with acid during nightly acid rinses. However, in order to improve the quality of the liquid feed itself, other strategies such as the use of dietary acidification should be combined with cleaning.
This article first appeared in the May Pigs newsletter, access the entire newsletter here.
Acknowledgements
The WetFeed2 project is funded by Teagasc Core funding. Thanks to Interchem Ltd. (Colum Killeen and Lisa Hopkins), Irish Dairy Services (Gerard Kellett and David Mulhall), Annona (Hans Jensema), Big Dutchman (Dennis Engelking) for their invaluable input. Thanks to Antonio Lourenco and Laura Gómez-Mascaraque for performing the SEM work. James Cullen is funded by the Irish Research Council GOIPG Scholarship and WIT PhD Scholarship. Florence Viard is in receipt of a Teagasc Walsh Scholarship.