Nutrition
Mid to Late Summer Supplementation for Fall-
Born Replacement Heifers
By Glenn Selk, Oklahoma State University
Fall born replacement heifers
have been (or soon will be)
weaned and will be at a very
critical growing period. It is
important that they grow at
about 1.5 pounds per day from
weaning until the start of the
breeding season. Currently
summer pastures are green,
growing, and adequate in
protein content. However, warm
season pastures such as native
grass or bermudagrass can
be expected to be declining
in forage quality in the hot,
dry days of July, August,
and September. Also these
grasses will be reaching plant
maturity which accelerates the
decline in protein content.
To expect a very high
percentage (greater than
90%) to be cycling at the start
of the breeding season, the
heifers need to be at least
60% of their mature weight.
Therefore, the young heifers
must receive supplemental
protein to continue to grow
at the necessary pace of 1.5
pounds per head per day going
into their first breeding season.
An economical solution would
be to give these heifers 1.5 to
2 pounds per head per day of
the protein supplement called
Oklahoma Gold. This is an OSU-
developed protein supplement
scheme that consists of a
high protein (38% - 45%)
pellet that contains the label-
recommended dosage of one
of the ionophores. Ionophores
are feed additives (monensin
or lasalocid) that improve feed
utilization, inhibit coccidiosis,
and enhance the onset of
puberty in growing heifers.
Research from Texas A&M in
the 1970’s indicated that heifers
receiving an ionophore reached
puberty about 2 weeks earlier
than counterparts that did not
receive an ionophore. Inclusion
of the ionophore in the growing
program should cause a few
more heifers to be cycling
early in the breeding season.
The protein supplement will
allow microbial digestion of the
average quality late summer
forage which in turn provides
the energy needed to support
the desired amount of gain. If
forage quantity is very limited,
160 | JUNE/JULY 2018