Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School

Animal Science


Heifers comprise 30 to 40% or- the feed cattle slaughtered annually. The ratio of steers to heifers will vary depending on the numbers saved for breeding herds. Numbers needed for this purpose may vary somewhat depending on the rate or culling in cow herds and changes in the cattle population. It is apparent, however, that a large percentage of the cattle available for feedlots will be heifers. Heifers gain at a slower rate and utilize feed less efficiently than steers under similar feeding systems. Heifer carcasses have also been shown to contain more fat trim than steer carcasses when fed to the same market grade. These facts affect the value of heifers for the feedlot and for the slaughter market. While they are priced lower in both instances than steers, more experimental data is needed to aid in determining appropriate price differentials under various market conditions and at various weights and degrees of finish. The lower and more costly production of feed1ot heifers with less desirable-carcasses presents a challenge to the researchers. While it is important to know the comparative performance and carcass value in-relation to ·steers, of more basic concern are ways by which these may be improved for heifers. Types of rations and feeding systems need to be investigated more thoroughly for heifers. Other methods available whereby feedlot performance and carcass merit may be improved are the use of chemicals, drugs and hormones as feed additives and implants. Several compounds have already been shown to be beneficial for these purposes and others are being investigated. Diethylstilbestrol (DES), an estrogen-like compound, has been shown to be a nonnutrient-growth stimulant for heifers but to a smaller degree than for steers. More recently a synthetic progestin, melengestrol acetate (MGA), has been shown to be effective in suppressing heat periods in heifers when fed at very low levels. These low levels have also been reported to result in improved weight gains and feed efficiency.

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South Dakota State University