Microbiological assessment of liquid feed for finisher pigs on commercial pig units

Abstract

Aims To investigate the microbiological and nutritional quality of liquid finisher pig feed on commercial production units and the factors influencing this. Methods and results Microbiological and physio‐chemical analyses were performed on liquid feed sampled from the mixing tank and troughs of the finisher section of eight commercial pig units. Lactic acid bacteria, yeast and Escherichia coli counts, as well as lactic acid, ethanol and acetate concentrations were higher in residual feed sampled from the troughs compared with mixing tank samples (P < 0·001). Feed pH, as well as lysine, methionine and threonine concentrations and gross energy were all lower in the residual trough samples (P < 0·001). Liquid co‐products reduced E. coli counts in the residual trough samples (P < 0·05), pH in the mixing tank (P < 0·01) and fresh trough samples (P < 0·05) and mould counts at all three sampling locations (P < 0·01) but sanitation practices had no impact. Conclusions Even when considered unfermented, a considerable degree of spontaneous fermentation occurs in liquid feed, with resultant negative effects on nutritional quality. Significance and Impact of the Study This is one of the first studies showing that uncontrolled fermentation of fresh liquid pig feed is commonplace on commercial units, highlighting the need for implementation of suitable control strategies.

Microbial Quality of Liquid Feed for Pigs and Its Impact on the Porcine Gut Microbiome

“…Additionally, E. coli counts were reduced in residual LF remaining in troughs just prior to the next feed-out on the units that used liquid co-products. Dietary co-product inclusion also reduced mould counts in the mixing tanks, as well as in fresh and residual LF in troughs, while also reducing the pH of the feed in the mixing tanks and of the fresh feed in the troughs [12].…”

“…This may have a negative impact on the microbial quality of the feed as a result of malfermentation. This occurs due to the selection for, and proliferation of, undesirable microbes and subsequent microbial degradation of crystalline amino acids in the diet, leading to the production of undesirable metabolites such as biogenic amines [2,[11][12][13]. On the other hand, FLF is deliberately fermented, either with/without the use of a microbial inoculant.…”

“…The resultant lactic acid, and to a lesser extent acetic acid, are known to exhibit antimicrobial activity against pathogenic and spoilage microorganisms [9,14]. In a survey of liquid feeding practices in the finisher section of commercial Irish pig units, O'Meara et al [12] found that 3 of the 8 units surveyed included either pot-ale syrup and/or liquid whey in their diets. The study found that on these pig units, Enterobacteriaceae counts in LF delivered freshly to troughs tended to be lower compared to units that did not use coproducts.…”

“…However, due to the occurrence of unintentional spontaneous fermentation, it is likely that many farmers intending to feed fresh LF are in practice feeding a diet in which some degree of fermentation has occurred along the feed circuit. This is particularly the case with short trough ad libitum feeding, where feed remaining in troughs continues to ferment and acts as an inoculum for freshly delivered feed [12,16,50]. The degree of fermentation occurring in fresh LF is exemplified in a study by O'Meara et al [12] which sampled finisher feed on commercial pig units feeding 'fresh' LF.…”

“…This is particularly the case with short trough ad libitum feeding, where feed remaining in troughs continues to ferment and acts as an inoculum for freshly delivered feed [12,16,50]. The degree of fermentation occurring in fresh LF is exemplified in a study by O'Meara et al [12] which sampled finisher feed on commercial pig units feeding 'fresh' LF. They found that LAB, yeast and E. coli counts increased from the mixing tank to the residual feed remaining in the troughs, resulting in reduced pH, indicating the occurrence of spontaneous fermentation (Figure 2).…”