PSXIV-2 Influences of glycerol and bypass fat supplementation on performance of early fattening Hanwoo steers under heat stress

Abstract

Abstract This study was conducted to determine the influence of glycerol and bypass fat supplementation on growth performance of early fattening Hanwoo steers under heat stress. Thirty-six Hanwoo steers were randomly allocated into 4 treatments based on BW and age for 112 days from the beginning of July to the end of October 2020. Experimental treatments were divided into four by the type of energy supplements: Control (CP, 14%; TDN 71.9), glycerol addition (GL; CP, 14%; TDN 74.9), bypass fat addition (BF; CP, 14%; TDN 74.9), and glycerol plus bypass fat additive (GL+BF; CP, 14%; TDN 74.9). During the experimental period, automatic temperature-humidity recorders were used for measuring every 10 minutes in the pen. The temperature-humidity index (THI) range of the 1st and 2nd periods was recorded above the threshold (THI 75~77) level based on the Korean beef heat stress index, and the average THI of the 2nd period was 79.91, being the mild-moderate (THI 78~81) level. The dry matter intake (DMI) and average daily gain (ADG) did not show significant differences in all treatments during the whole period. The feed conversion ratio (FCR) during 1st and 2nd periods showed the same pattern because FCR is related to DMI and ADG. Additionally, the rectal temperature showed no significant difference in all treatments, but a significant difference in each period (P < 0.05). The results demonstrated that early fattening Hanwoo steers under mild-moderate stress did not affect DMI and productivity but 9.8% of GL or 1.9% BF in a concentrate only could be included in Hanwoo steers diets without decreasing palatability. In addition, increasing the energy content in the feed by 5% did not lead to a difference in productivity. Further studies would be needed on the effect of increasing the energy density on productivity under more severe thermal stress conditions.