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Heifers as beef animals traditionally have been discriminated against in the marketplace. This discrimination is the result of ovarian secretions acting on performance and nutrient partitioning, as well as the possibility of pregnancies. The actions of ovarian secretions can be through their differentiational effects, permanent effects on the development and physiology of the individual, and through activational effects, temporary effects expressed only when the activating agent is present. Expression of heat or estrual activity is an example of an activational effect. The fatter carcasses which heifers generally produce is an example of a differentiational effect. Not only do heifers produce a fatter carcass, they are generally considered to be less efficient in conversion of feed to gain. This is often attributed to the estrous cycles and accompanying behaviors, riding and reduced feed intake. Periodically ovariectomy or spaying has been proposed as a means to prevent heifers from exhibiting estrous cycles (Wilson and Curtis, 1896; Dinusson et aI., 1950; Kercher et aI., 1960; Horstman et aI., 1982; Hamernik et aI., 1985). Ovariectomy does certainly stop estrous behavior in heifers. However, it also removes the estrogens and other steroids produced by the ovary. Ovarian steroids, particularly estrogens, are well known to have positive actions on growth. A proposed solution to this problem has been to surgically remove the ovaries and transplant a portion of one ovary to the rumen wall or to simply drop one ovary into the abdominal cavity. This process is referred to as ovarian autotransplantation or autografting. Ovaries removed from their normal connections to the uterus do not support normal estrous cycles but do still produce and secrete many of their steroids.
The objective of this study was to determine whether ovariectomy alone or ovariectomy with ovarian autografting would improve the growth performance or carcass quality of heifers in the feedlot. Ovaries were surgically removed, and one ovary was transplanted to the muscles of the flank in the autograft group. This site was chosen in the hope that retrieval of the ovary for determination of its functional status would be possible at slaughter.