Apparent Digestibility, Nitrogen Retention, and Microbial Protein Yield in Goats Fed a Diet Based on Macadamia Oil Cake

The study assessed the apparent digestibility, nitrogen retention, and microbial protein production in goats fed a Macadamia oil cake-based diet. Sixteen mixed breed bucks about 34 kg and age ranging from18 to 24 months old, were randomly allocated to four dietary treatments of 0, 100, 150, and 200 g/kg macadamia oil cake in a complete randomised design and each goat was considered an experimental unit. Faecal digestibility and nitrogen balance were assessed through total faecal and urine collection. Microbial protein production was estimated using urinary purine derivatives allantoin method. The study lasted 21 days, with 14 days for acclimatization and 7 days for sample collection. Data were analysed using one way analysis of variance, through General Linear Models procedures. Treatment means were compared using Tukey's post-hoc test. Macadamia oil cake inclusion did not affect dry matter, organic matter, or crude protein intake. There were no differences in nitrogen retention and the apparent digestibility of dry matter, crude protein, neutral detergent fibre, and acid detergent fibre. Positive nitrogen retention was observed across treatments. Microbial protein yield increased with more than 10% macadamia oil cake supplementation. The findings supported its use as an alternative protein source in goat diets. Further research is recommended to determine the optimal dietary inclusion.