Utilization of piggery waste II. The chemical composition and in vitro organic matter digestibility of fractions of pig faeces separated by sieving and by centrifuging

Abstract

Samples of pig faeces with an in vitro organic matter digestibility (IVOMD) of 31.0% were fractionated by wet sieving through four sieves of mesh sizes 2.34, 1.19, 0.11 and 0.05 mm, and by centrifuging with a force of 2,500 g for 20 min. The fraction passing through the smallest sieve (calculated by difference) represented 35% of the dry matter and had appreciably higher concentrations of nitrogen, true protein, ether extract, ash and copper, and lower concentrations of gross energy, neutral detergent fibre, acid detergent fibre and lignin than the other sieved fractions. However, the IVOMD values were similar for all five fractions. Centrifuging produced three distinct fractions: the supernatant, a layer of ‘fine slimy particles’, and ’coarse fibrous particles’. The supernatant represented an insignificant proportion of the faecal dry matter. The fine slimy particles had higher concentrations of nitrogen, true protein, ether extract, ash and copper and lower concentrations of fibre components than the coarse fibrous particles. The IVOMD values of the fine and coarse fractions were 42.6 and 30.2%, respectively, but because the fine slimy particles accounted for only 10% of the faecal dry matter the separation was considered to be of no practical importance. It was concluded that fractionation of pig faeces by these methods, and without any other processing, did not provide a means of achieving improved utilization by microbial digestion.