Two hundred forty Holstein steers (343 lb)
were stratified by weight and allotted to one of
eight treatment combinations in a 2 × 4 factorial
arrangement. Main effects were implant
(Synovex-S (S) or Synovex-S + Finaplix-S (SF)
on day 0, 87, 168, and 238 and level of rumen
escape amino acids (Smartamine-ML (SML) at
0, 5, 10, or 15 grams/head/day). These levels of
SML supplied 0, 2.75, 5.5, and 8.25 g/day of Llysine
and 0, .75, 1.5, and 2.25 g/day of DL-methionine.
Steers implanted with SF gained
4% faster, had a 4% improvement in feed:gain,
a lower dressing percentage, 12% less backfat,
3.4% more rib-eye area, a lower yield grade,
less marbling, and fewer Choice grades (P<.05)
compared to S-implanted steers. Overall feed
intake and carcass weights were similar between
S- and SF-implanted steers. Use of SML resulted
in a linear decline in hot carcass weight
(P<.10) and KPH (P<.05), with other carcass
traits unaffected. Increasing the level of SML
tended to increase feed intake (P<.15), and
quadratically degraded feed:gain (P<.10).
Repeated implants of SF did not improve carcass
worth and the use of rumen escape amino
acids did not improve performance, suggesting
that the basal diet was not first-limiting in lysine
and(or) methionine.
