Effects of Ambient Temperature and Glycerol Supplementation on Growth Performance in Korean Cattle Steers

Glycerol may be used as a glucogenic source for glucose synthesis in the liver to provide increased requirement of energy due to heat stress. This study was performed to evaluate whether ambient temperature and dietary glycerol supplementation affect growth performance in beef cattle. In experiment 1 (Exp1), fourteen Korean steers (average 23.5 months of age and 466.9 kg of BW) were divided into a control diet group (n = 7) and a 3% glycerol supplementation group (n = 7). Steers were allowed to receive daily a concentrate of middle fattening stage (1.5% of BW) and rice straw (0.3% of BW). Feeding trial was performed at barn with roof for three months [(two months of hot temperature (July and August) and one month of temperate climate (September)] in 2016. Climate data were analyzed by ANOVA, and growth performance data were analyzed by repeated-measured two-way (month, diet) ANOVA. Maximum temperature-humidity index (THI) were higher (P < 0.01) in July (88.5) and August (90.5) than those in September (83.1). No month x diet interaction was detected for all parameters. Neither month nor diet affected both concentrate and roughage intake. Month did not affect both average daily gain (ADG) and feed efficiency (FE: gain/feed). Glycerol supplementation increased (P < 0.05) both ADG and FE. In experiment 2 (Exp2), six Korean steers (average 23.5 months of age and 478.2 kg of BW) were raised on metabolic cages in a temperature-controlled room. Animals were divided into a control diet group (n = 3) and a 3 % glycerol supplementation group (n = 3). Steers were allowed to receive the same amount of concentrate and roughage as that of Exp1. Feeding trial was performed for each 20 days at normal- (mean 21℃) and hot- ambient temperature (mean 30℃). Statistical analyses were performed using the same method as Exp1. Maximum THI values of hot temperature period (88.2) were higher (P < 0.01) than those of normal temperature period (73.6). Hot temperature decreased (P < 0.05) both concentrate and roughage intake, and it tended to decrease (P = 0.07) ADG. Glycerol supplementation increased roughage intake without affecting concentrate intake and ADG and FE. In conclusion, hot temperature month did not affect growth performance, but glycerol supplementation improved growth performance in a barn trial. In feeding trial on metabolic cages with a temperature-controlled room, hot temperature decreased growth performance, but glycerol supplementation did not affect it.