Nutrient evaluation and ruminal degradation of dry matter and protein from amarula (Sclerocarya birrea), macadamia (integrifolia) and baobab (Adansonia digitata L.) oilcakes as dietary supplements for ruminants.

Abstract

Inadequate availability of feed ingredients significantly contributes to reduced animal production. Nutritional evaluation of feed ingredients for potential use in feed ration is key. Triplicate samples of oil extraction by-products viz.: amarula (Sclerocarya birrea), macadamia (integrifolia) and baobab (Adansonia digitata L.) oilcakes were analysed for proximate, mineral and amino acids content. To determine the in situ rumen degradability of dry matter (DM) and crude protein (CP) from the oilcakes, polyester bags were used to incubate triplicate subsamples of each oilcake in the ventral rumen of each of the three cannulated mid-lactating Holstein cows for 2, 4, 8, 16, 24, or 48h. Amarula oilcake (AOC) had higher (P < 0.05) CP, ether extract and essential amino acid content than macadamia (MOC) and baobab (BOC) oilcakes. Fibre fractions were higher (P < 0.05) in MOC and BOC than in AOC. While calcium (Ca) and potassium (K) concentrations were high (P < 0.05) in MOC and BOC, phosphorus (P) concentration was high (P < 0.05) in AOC. The effective degradability of DM and water-soluble, rapidly degradable fractions of DM and CP were high (P < 0.05) in AOC. Insoluble but degradable fraction of CP was high (P < 0.00) in BOC and effective degradation of CP was high (P < 0.05) in AOC and BOC. The AOC with its high CP, EE and essential AA can be used as both protein and energy source for ruminants. Seemingly, MOC and BOC can be used as supplements for fibre as well as Ca and K in ruminant diets. Hence, these non-conventional oilcakes have the potential to partially replace conventional oilcakes in ruminant diets. Evaluation of growth performance, nitrogen digestion and carcass characteristics in ruminants fed diets containing the AOC, BOC and MOC are recommended.