Efficient utilization of Macadamia oil cake based diets in ruminants

Abstract

Ruminants and rumen bacteria form a symbiotic relationship. However, because of nitrogen (N) inefficiency, this interdependent relationship loses energy and protein. Strategic feeding of ruminants with diets containing non-conventional feedstuffs appears to be a promising way to enhance proficiency of protein and energy utilization in ruminants. Macadamia Oil Cake (MOC) can be classified among the non-conventional ingredients that can be included in animal diets, without resulting in any negative effects. The present study evaluated the utilization of MOC-based diets in ruminants. Eight Boer and eight Pedi bucks initially weighing an average of 34 ± 8.39 kg and aged 18 to 24 months were housed individually in metabolic cages (1.8 m × 0.58 m × 1.33 m) to measure nutrient intake, apparent digestibility, nitrogen (N) retention and microbial protein yield. The goats were balanced for breed and allocated in a completely randomized design (CRD) to four dietary treatments containing 0, 10, 15, and 20% MOC inclusion. Microbial protein yield was assessed using the urinary excretion of purine derivative (PD) allantoin method to estimate the efficient utilization of nitrogen in the MOC-based diets. The study was carried out for 21 days, beginning with 14 days for acclimatization and seven days for sample collection. MOC inclusion significantly affected (P˂0.05) the intake of ether extract (EE), neutral detergent fibre (NDF) and acid detergent fibre (ADF). However, the intake of dry matter (DM) , organic matter (OM) and crude protein (CP) were not significantly affected (P˃0.05) by MOC supplementation. Significant differences (P˂0.05) were observed for OM and EE apparent digestibility of MOC-based diets by goats. However, No significant differences (P>0.05) were found in the apparent digestibilities of DM, CP, NDF and ADF. Nitrogen (N) retention was not significantly affected (P>0.05). All goats had positive N-retention values. Urinary allantoin excretion differed significantly (P<0.05) within treatments and affected (P<0.05) microbial protein yield. To conclude, the results attained in this study imply that MOC does not affect apparent digestibility of DM, CP and N-retention but enhanced microbial protein yield. Therefore, MOC showed to be a promising protein source to be utilized in goat diets without significantly causing any adverse effects.NRF