Strategies to improve the microbial quality of liquid feed and optimise growth of liquid-fed grow-finisher pigs

Fiona O'Meara

    Research output: Types of ThesisDoctoral Thesis


    The objectives of this thesis were to (1) characterise the microbiological quality of liquid feed on Irish pig units; (2) control spontaneous fermentation during liquid feeding using controlled fermentation and dietary acidification; (3) compare feed form and delivery in grow-finisher pigs; (4) determine the optimum water-to-feed ratio for grow-finisher pigs. A survey of eight commercial pig production units was conducted, in which spontaneous fermentation and amino acid degradation were found in liquid feed. Controlled whole diet fermentation and cereal-only fermentation were then compared to fresh liquid and wet/dry feeding of the same diet. Feeding a fermented whole diet reduced pig growth and caused feed conversion efficiency (FCE) to deteriorate. As no benefits were found for fermentation, feed form (meal, pellets) and delivery methods (dry, wet/dry, liquid) were compared. The conclusion was that wet/dry feeding of a pelleted diet to growfinisher pigs optimises growth and FCE. In an attempt to improve FCE in liquid-fed pigs, four commercially used water-to-feed ratios (2.4:1, 3:1, 3.5:1 and 4.1:1, dry matter basis) were compared. The 3.5:1 ratio optimised FCE without reducing killout percentage. Lastly, diets supplemented with benzoic acid (BA) at 0, 2.5, 5 and 10kg/t were liquid-fed to grow-finisher pigs. While BA inclusion stabilised liquid feed pH and controlled lactic acid bacteria (LAB) growth in troughs, no improvements in growth or FCE were observed; however, FCE was excellent for the control and hence a response to BA was unlikely. In conclusion, wet/dry feeding of a pelleted diet optimised growth and FCE in grow-finisher pigs. Spontaneous fermentation occurs during fresh liquid feeding and even controlled whole diet fermentation leads to amino acid degradation. To optimise FCE, a 3.5:1 water-tofeed ratio is optimal for short-trough liquid feeding of grow-finisher pigs. Benzoic acid stabilised liquid feed pH and controlled LAB growth but did not improve pig growth.
    Original languageEnglish
    Awarding Institution
    • Gardiner, Gillian E., Supervisor
    • Lawlor, Peadar G., Supervisor, External person
    • O’Doherty, John V., Supervisor, External person
    Publication statusUnpublished - 2020


    • Liquid feed, Pigs


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