Different levels of macadamia oil cake meal, and wood ash vs. feed lime as dietary sources of calcium on bone characteristics of slow-growing chickens
A study was conducted to evaluate the potential of macadamia oil cake meal (MOCM) and wood ash as feed ingredients for poultry under subsistence farming conditions. In this article, the effect of these ingredients on bone characteristics is reported. Two hundred and eighty eight day-old New Hampshire chickens were used in the study. The research was conducted as a 3 x 2 factorial design, and 48 chicks were randomly allocated per treatment. Three basic diets were formulated: one without MOCM and the other two containing 10% and 50% MOCM. The MOCM contained 132 g/kg of crude protein, 228 g/kg crude fat and 365 g/kg crude fibre on an ‘as-fed’ basis. Each of these three treatments was split into two: one receiving feed lime (CaCO3) as the main source of calcium; and the other wood ash, which contained 257 g Ca/kg. All diets contained a Ca level of ca. 10 g/kg. The chickens received the experimental diets from 2 to 15 weeks of age. After week 15, eight chickens per treatment were killed and their right legs removed at the femorotibial articulation and frozen for later evaluation. Between Ca sources there were no significant differences in tibia weight, diameter, volume, density and breaking strength. The ash content and Ca, P and Mg concentrations in bone ash between Ca sources were similar. However, in the two Ca diets containing 50% MOCM the Ca and P concentrations of the tibiae were significantly lower than in the diets containing lower levels of MOCM. It was concluded that wood ash was as effective as feed lime in supplying Ca to chickens. However, some practical problems in the feeding of wood ash became apparent, such as that wood ash is a fine powder and does not mix well with other ingredients, except when the oil content of the diet is high, as with the treatments containing MOCM.
Keywords: Bone ash, bone strength, feed lime, subsistence farming, tibia