Effects of dietary addition of wormwood (Artemisia montana Pampan) silage on growth performance, carcass characteristics, and muscle fatty acid profiles of beef cattle

Abstract

This study aimed to determine the effect of substituting rice straw with wormwood (Artemisia montana) silage on growth performance, carcass quality, and muscle fatty acid profiles of Hanwoo steers during the fattening period. Twenty steers (326±23kg body weight) were blocked by body weight and assigned randomly to one of four treatments in which 0, 50, 100 or 150g/kg of rice straw (dry matter (DM) basis) was substituted with wormwood silage. Concentrate feed mixtures containing crude protein and metabolizable energy values of 120g/kg DM and 6.5MJ/kg DM and 122g/kg DM and 9.6MJ/kg DM were used for the early and late fattening periods, respectively. The forages and concentrate feed mixtures were fed separately for 390d and the forage to concentrate feed mixture ratio was changed from 7:3 (DM basis) initially to 1:9 at the end by increasing the concentrate proportion monthly. Wormwood silage had greater crude protein and ether extract concentrations, but lesser neutral detergent fiber concentration than rice straw. The C18:2 n-6 and C18:3 n-3 concentrations in rice straw were lesser than in wormwood silage (15 vs. 29g/100g fatty acid; 3 vs. 21g/100g fatty acid, respectively). Increasing the level of addition of wormwood silage linearly (P<0.001) increased concentrate and total DM intake, and quadratically increased final body weight (P<0.01) and average daily gain (P<0.001), consequently, feed conversion ratio (DMI/BW gain) decreased (P<0.01) concomitantly. Backfat thickness decreased quadratically (P<0.01) as dietary wormwood silage addition increased, whereas carcass weight (P=0.002), longissimus muscle area (P=0.002), and marbling score (P=0.014) increased. Meat color was not affected by treatment. Concentrations of C18:0 (P<0.05), C18:1 n-9 (P<0.05) and monounsaturated fatty acid in the longissimus muscle decreased linearly (P<0.01) with increasing wormwood silage addition but cis-9 trans-11 conjugated liloneic acid (P<0.001), C18:3 n-3 (P<0.01), C22:0 (P<0.001), C24:1 n-9 (P<0.001) and polyunsaturated fatty acid (P<0.001) concentrations increased. Replacing rice straw with up to 100g/kg of wormwood silage improved the growth performance, carcass quality, and muscle fatty acid profile of Hanwoo steers during the fattening period.