EFFECTS OF SOURCE AND CONTENT OF ASH IN POULTRY LITTER USED IN DIETS FOR BEEF-CATTLE

Two experiments were carried out in order to study the effect of the a sh content of poultry litter (PL) on its nutritional value. In Expt 1, broiler PL was incorporated in the proportions of 30 and 45 % into di ets based on wheat straw supplemented with 20% maize grain. The PL was either fresh (containing 19% ash) or had been heated in a stack (givi ng 26% ash). There were also two additional diets containing 45% fresh PL to which either ground limestone or wood ash had been added to pro vide the same ash content as the diets containing 45 % stored, high as h FL. An in vivo digestibility and nitrogen balance trial was carried out. Storing the FL, which resulted in heating and an increase in ash content, reduced dry matter intake significantly. The largest and most significant effect on the digestibility of dry matter, organic matter and crude protein can be ascribed to the freshness of the FL. Stored, heated PL had a highly negative effect on crude protein digestibility and on nitrogen retention. No negative effect of adding extrinsic ash was recorded. In Expt 2, the nutritional value of layer PL (LPL), com pared with that of broiler PL (BPL), was examined using ten beef cows before and after calving. The diet was composed of 45% FL, 35% wheat s traw (WS) and 20% maize grain. Daily dry matter intakes were 12.7 and 16.2 g/kg liveweight (LW) before calving and 15.5 and 22.8 g/kg LW aft er calving, for cows fed LPL and BPL, respectively. Owing to the combi ned effect of the lower dry matter intake, lower gross energy content and lower digestibility of LPL, the digestible energy intake of BPL di ets was almost three-fold, and nitrogen absorption (g/kg LW0.75) on th e BPL was 2.4-fold higher than on the LPL diets. Because the ash intak e of both diets was similar, it is suggested that the main inhibiting factor of intake after calving was the rumen's ability to mobilize the large amounts of ash-rich complexes of ash and organic matter to the reticular omasal orifice and, consequently, out of the rumen.