Abstract

SKENJANA, A; VAN RYSSEN, J.B.J.  and  VAN NIEKERK, W.A.. In vitro digestibility and in situ degradability of avocado meal and macadamia waste products in sheep. S. Afr. j. anim. sci. [online]. 2006, vol.36, n.5, pp.78-81. ISSN 2221-4062.

Waste products from the avocado (avocado meal, AM) and macadamia (macadamia oilcake, MOC and macadamia chips, MCH) processing industries have the potential to be included in animal diets, depending on their nutritive value. Avocado meal consisted of oil-extracted avocados unsuitable for the fruit market; MOC consisted of oil-extracted remnants of macadamia nuts, while MCH was a mixture of pieces of macadamia nuts and hull chips. The aim of this study was to determine the in vitro organic matter digestibility (IVOMD) and the in situ dry matter (DM) and crude protein (CP) degradability of these products. These waste products were also analysed for components that could influence their digestibility, viz. fibre components, acid detergent lignin (ADL), acid detergent insoluble nitrogen (ADIN) and condensed tannin. To determine in situ DM and CP degradability the products were incubated for 0, 2, 5, 8, 16, 24 and 48 h in the rumens of lucerne-fed sheep. The IVOMD of AM was 54.3%, that of MOC 79.2% and that of MCH 29.2%. The rate and extent of DM and CP degradation in MOC were significantly higher than those of AM. However, degradability of MCH was very low, suggesting that it contains a high proportion of indigestible components. The NDF concentrations ranged from 404.4 g/kg DM in MOC to 558.3 g/kg DM in MCH. The ADL concentrations of AM, MOC and MCH were 258.0, 117.5 and 254.6 g/kg DM, respectively, which could explain some of the differences in digestibility and degradability between the products. It was concluded that AM and MOC could be used as ingredients in the diets of ruminants, but that MCH is not suitable as a feedstuff for ruminants.

Keywords : Tropical fruit waste; acid detergent lignin; acid detergent insoluble nitrogen; condensed tannin; digestibility.

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