Effects of rumen-protected lysine supplement on growth and carcass traits in a traditional finishing scheme with crossbred beef steers

Abstract

The effects of rumen protected amino acids on feedlot performance and carcass characteristics are inconsistent in the literature. Therefore, the purpose of this experiment was to study the effects of rumen-protected lysine supplementation on feedlot performance and carcass characteristics on light weight steers. This 198-d experiment used 192 crossbred steers (BW 266 kg ± 11.2) in a completely randomized block design, which blocked steers by initial body weight (BW) and by arrival source (Bos indicus crossbreds were blocked separately from the Bos taurus). The experiment included 4 treatments; negative control (1,940 g of ground corn; NCTRL) supplemental bloodmeal (Perdue Ag Solutions; Salisbury, MD [1940 g of bloodmeal; BLDM]), 2 g of supplemental rumen-protected lysine (Smartamine ML; Adisseo, Atony, France [1,655 g of ground corn and 285 g of Smartamine ML; 2GSM]), and 4 g of rumen-protected lysine (Smartamine ML; Adisseo [1370 g of ground corn and 570 g of Smartamine; 4GSM]). There was no difference in final BW or average daily gain (P ≥ 0.20). Dry matter intake (DMI) showed a difference between BLDM and 2GSM of 0.27 kg with BLDM consuming more, additionally BLDM and NCTRL were both different from 4GSM with 4GSM consuming the least by 0.23 kg or more (P < 0.01). For gain to feed ratio (G:F) there was a difference between 2GSM and all other treatments with 2GSM being 0.003 less efficient than the next closest treatment (P < 0.01). For carcass characteristics, there was no difference in marbling score, loin muscle area (LMA), 12th rib back fat, yield grade (YG), percent of liver abscesses, or dressing percentage (P ≥ 0.28). There was a difference in hot carcass weight (HCW), but this was likely unrelated to treatment (P = 0.05). Ultimately, there was no significant advantage in supplementation of rumen protected lysine in this subset of cattle. However, based off observations made during the last 35 days of this trial there is a need for further research into how beta-adrenergic agonist effect amino acid requirements. Key words: feedlot steers, rumen protected lysine