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 percent) to be cycling at the start of the breeding season, the heifers need to be at least 60 percent 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 pound 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 percent to 45 percent) 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 1970s indicated that heifers receiving an ionophore reached puberty about two 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 Oklahoma Gold program for stocker cattle is used in conjunction with growth-promoting implants. However, do not implant weaned heifers intended for replacements.
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, the protein supplement alone will not produce adequate gains. In this scenario, a rancher first needs to decide if keeping more replacement heifers is really in his or her best interest.
Lightweight or young, weaned heifers that need an added boost while still on late summer pasture may benefit more from the Oklahoma Super Gold supplementation program. Super Gold consists of feeding 2.5 pounds per head per day of a 25 percent crude protein pellet. Once again, an ionophore is included at the proper dosage and will be beneficial to these young growing heifers. Supplements such as Oklahoma Super Gold can be purchased or manufactured to include antibiotics such as aureomycin. These supplements must be prescribed by a veterinarian and have an accompanying veterinary feed directive in order to be mixed and fed. Plan ahead for late summer supplementation of fall-born replacement heifers. — Glenn Selk, Oklahoma State University Emeritus Extension animal scientist