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Management of Reproduction of Beef Cattle, Sheep and Pigs¹

University of Illinois, Urbana 61801 and Livestock and Range Research Station, Miles City, MT 59301

Abstract

Productivity depends on reproductive efficiency and is often measured by the number of offspring per breeding animal per unit of time. Reproductive management, in turn, relies on using the resources available to best advantage. Genetic selection of those individuals that will fit best into present production plans is helpful in enhancing productivity. Manipulating the environment or adjusting to it are also helpful. The components of the diet and the level are very important environmental factors in maximizing reproductive rates. In general, extremes in diet are detrimental to long-term productivity with low caloric intake as the least desirable. Other environmental factors such as light, temperature, social contacts, gases and toxins must be considered in managing reproduction. What conditions should we provide to maximize reproductive efficiency? We may be on the threshold of being able to switch gradually from serving primarily in a husbandry role to one of directing events. Currently, nature dictates. We must serve her every whim of season of mating, day and hour of estrus, ovulation and birth. Control of the time and season, of ovulation would facilitate planning of activities associated with inseminations, gestation and parturition. With application of developments now possible and those probable, perhaps we can control the genetic makeup of our domestic animals by incorporating genetic information into gametes and embryos by unconventional means. The season and hour of ovulation and birth may be controlled. Animals may be transported as embryos with relatively little expense or risk of disease transfer. The reproductive status of an animal may be determined to aid in decisions of reproductive management. How many ovulations will this prepuberal animal have as an adult? How fertile will this male be? Is the female pregnant and what is the potential number of offspring? Are there simple tests and procedures that can be applied that will provide the manager with information to make decisions? Progress towards these ends has been dramatic in the past 50 yr and is increasing at an ever increasing rate. Reproductive management may truly become that of deciding, planning and execution in the foreseeable future.

Key Words: Beef Cattle Management • Reproductive Performance • Future • Control of Reproduction

¹ USDA-ARS and Montana Agr. Exp. Sta. cooperating. Paper approved by the Director of Montana Agr. Exp. Sta. Journal Series No. 1357.

² Dept. of Anim. Sci., Univ. of Illinois.

³ Livestock and Range Res. Sta., USDA, SEA-AR.