Enhancement of daily gain and feed efficiency of growing heifers by dietary supplementation of β-mannanase in Hanwoo (Bos taurus coreanae)

• Supplementation of β-mannanase increased growth rate of Hanwoo growing heifers.
• The β-mannanase supplementation tended to improve feed efficiency.
• The positive effects of β-mannanase were observed regardless of the basal diets.

β-mannanase is an enzyme that breaks down mannan which is complex biopolymers commonly found in plant cell walls. It has been reported that supplementation of β-mannanase in a diet that composed of high mannan containing feedstuffs (e.g. palm kernel meal, copra meal, soy hull; HMCF) improves digestibility and utilization of livestock feeds. In ruminants, β-mannanase supplementation also increased growth rate of goats and Holstein calves. No study, however, has been conducted to evaluate the effect of β-mannanase supplementation in growing heifers. Moreover, little is known whether β-mannanase supplementation will have beneficial effects in conventional corn-soy based diets (CS). The objective of this study was thus to investigate the effect of supplementation of β-mannanase in Hanwoo growing heifers fed a diet composed of either a CS or HMCF based concentrate mix. For this purpose, a feeding trial was conducted for 12 weeks using a total of 40 Hanwoo growing heifers (BW: 236.2 kg±1.1 kg, 11 month of age). Total mixed rations (250 g/kg of ryegrass and 750 g/kg of concentrate mix) were offered ad libitum. The experimental design was 2×2 factorial approach with two different concentrate mixes (CS or HMCF based) and with or without a commercial feed β-mannanase (800,000 U/kg DM) product (CTCZYME®, CTC Bio Inc., Seoul, Korea) at a level of 1 g/kg in concentrate mixes. In both diets, supplementation of β-mannanase significantly increased ADG of Hanwoo heifers by 95 g/d on average (111 g/d or 90 g/d for CS and HMCF, respectively). No significant difference was observed in DMI among treatments, but β-mannanase supplementation tended to decrease feed conversion ratio (DMI/ADG) by 1.3 on average. The ADG of CS (943 g/d) was significantly greater than that of HMCF (854 g/d). These results indicated that supplementation of β-mannanase enhanced growth rate and feed efficiency of Hanwoo heifers regardless of the basal diets. Therefore, we conclude that supplementation of β-mannanase can be beneficial to improve the feed utilization in Hanwoo growing heifers.