Utilisation of reactive lysine from meat and bone meals of different ash content by growing-finishing pigs

Abstract

A growth experiment was conducted using 50 pigs (25-100 kg) to evaluate the use of meat and bone meals of different ash content as a substitute for soyabean meal (SBM) for growing pigs and the potential of 1-fluoro-2,4-dinitrobenzene (FDNB) reactive lysine in diet formulation. The control diet consisted of barley and SBM. For test diets, either 33 or 67% of SBM was replaced with meat and bone meal of low (ML, 205 g ash/kg) or high (MH, 349 g ash/kg) ash content. SBM, ML33, ML67, MH33 and MH67 diets contained 7.8, 7.8, 8.2, 7.8 and 7.9 g FDNB-reactive lysine/feed unit (feed unit is equivalent to 9.3 MJ NE), respectively. For these diets, average daily live weight gains (ADG) were 859, 830, 805, 854 and 813 g/d with feed conversion ratios of 2.25, 2.40, 2.41, 2.31 and 2.44 feed units/kg, respectively. Pigs fed the SBM diet grew faster (P<0.01) and utilised feed more efficiently (P<0.001) than those offered ML and MH diets. The ADG decreased (P<0.001) with increasing meat and bone meal dietary inclusion. These results indicate that FDNB-reactive lysine is unsuitable for diet formulation as it may be incompletely absorbed. Faecal digestibilities of nutrients in the experimental diets were determined at live weights of 30, 44, 64 and 85 kg, respectively. Mean digestibility of crude protein (CP) was 74, 74, 68, 75 and 72%, while that of crude fat (CF) was 44, 55, 51, 48 and 41%, for SBM, ML33, ML67, MH33 and MH67 diets, respectively. Faecal digestibilities of CP and CF increased with live weight, with the largest increase being observed between 44 and 65 kg. Increased replacement of SBM with ML or MH increased back fat oleic acid content (P<0.01), decreased back fat firmness (P<0.05) but had little influence on palatability.