pH: a promising indicator of feed waste in piggery effluent?

Abstract

Feed waste in pork production sheds can amount to substantial economic losses. No simple methods exist to quantify this waste, which commonly ends up in the effluent stream. Monitoring piggery effluent might offer producers a practical alert solution for feed waste losses. We investigated piggery effluent pH as a potential marker of feed waste, given that most feed substrates and breakdown products are acidic whereas effluent is alkaline. To explore this prospective relationship, we constructed simulated effluent streams comprising faeces, urine and feed. These waste components were acquired from a commercial batch grower shed, at four different times over the 12-week growth cycle. In laboratory settings (25°C) we used the collected wastes to simulate the two stages of typical flushing piggery effluent systems: (1) Faeces + urine + feed waste accumulation in flushing channels, and (2) flush water mixing with these wastes in an effluent collection sump. We repeated the exercise for a one-off sampling event at a sow facility. For all events, at the grower and sow facility, the pH of the simulated effluents yielded exponentially decreasing relationships with increasing feed waste level (P < 0.05). For the grower facility we applied each of the four laboratory-derived relationships to the farm’s sump effluent pH, which was measured during each of these sampling events. The predicted feed waste levels were commensurate with estimates of feed waste for the same facility derived from alternative, time intensive approaches reported in other studies. Further work is needed to transition the promising results uncovered here into an alert system to help farmers improve profitability and minimise waste.