Managing replacement stock within the environment of the south--plant, soil, and animal interactions: a review

The South extends from the Atlantic Coast and the Gulf of Mexico north through Virginia and Kentucky and west to the 100th meridian, which extends through Texas and Oklahoma. The soils, environment, and range of adapted forage species offer many and varied opportunities for designing forage-livestock systems for rearing replacement stock. Anti-quality factors of concern when using forages for replacement stock include the presence of Acremonium coenophialum (Morgan-Jones and Gams) in tall fescue (Festuca arundinacea Schreb.), phytoestrogens potentially in several species of Trifolium and Medicago, toxins in some species of brush that contribute to infertility, and imbalances of several minerals including Ca, P, K, Fe, I, Zn, Na, Cu, and Se. Systems should be designed to provide appropriate quality and quantity of forage to produce reproductively active female animals of the desired weight and condition for breeding at the target age, usually 15 mo for beef and dairy heifers and 8 to 9 mo for ewe lambs. Systems generally require sequence grazing of two or more forage species or mixtures to provide extended or year-round grazing opportunities. Stockpiling of tall fescue in the Upper South and use of cool-season annuals in the Lower South extend grazing in autumn, winter, and early spring. Successful systems coordinate plant growth potential with changing animal forage requirements for both quantity and quality of forage to achieve optimum growth rates for replacement stock.