Influence of Different Levels of a Rubber Seed Kernel Pellet Supplement on Feed Efficiency, Blood Chemistry, and Growth Performance in Beef Cattle.

The rubber seed kernel is a byproduct of rubber plantations and has potential as a source of protein and lipids. The aim of the current study was to evaluate the effect of rubber seed kernel pellet (RUSKEP) supplementation on feed intake, nutrient digestibility, blood chemistry, and growth performance. Twelve crossbred (Brahman × Thai native) bulls with a body weight (BW) of 285 ± 17 kg were randomly assigned to three treatments for 60 days in a completely randomized design (CRD). RUSKEP was supplemented at 0, 200, and 400 g/animal/day. Animals were fed a total mixed ration (TMR) at 2.3% BW. The dry matter (DM) intake was similar among treatments (p > 0.05). The addition of RUSKEP did not influence nutrient intake (p > 0.05), whereas ether extract (EE) intake increased with the increasing levels of RUSKEP (p < 0.001). The digestibility of crude protein (CP) and EE increased with increasing levels of RUSKEP (p ≤ 0.03). Supplementation of RUSKEP had no effect on blood metabolites (p > 0.05), except for cholesterol, which increased with adding RUSKEP (p ≤ 0.005). Average daily gain (ADG) increased with the RUSKEP supplementation (p = 0.03). ADG was highest at 200 g/animal/day, suggesting a potential optimal level for cattle. The feed conversion ratio (FCR) decreased with the RUSKEP supplementation (p = 0.04). Supplementation with 200 g/animal/day of RUSKEP improves ADG and feed efficiency in tropical beef cattle.