ABSTRACT Inadequate dietary energy intake and poor body condition can negatively affect reproductive function. Supplemental lipids have been used to increase energy density of the diet and may also have direct positive effects on reproduction in beef cattle. Several fatty acid sources have been studied as they relate to reproductive function. Common sources include sunflower, safflower, cottonseed, rice bran, soybeans, fishmeal, animal tallow, and calcium salts of fatty acids. Fats have been fed before and after calving, during the breeding season, and during heifer development. Response to fat has been investigated through measuring body weight and body condition score, age at puberty, postpartum interval, first-service conception rates, pregnancy rates, calving interval, calving difficulty, and calf birth and weaning weight. Animal response seems to depend on body condition score, age (parity), nutrients available in the diet, and type of fat supplemented. To elucidate potential mechanisms of action, scientists have investigated changes in follicular and uterine development, hormonal profiles, brain function, and embryonic development. Feeding supplemental fat has resulted in varied and inconsistent effects on reproductive function. Elucidating how supplemental fat can influence reproductive function has been a difficult process. The complexity of the reproductive system and makeup of fat supplements are often confounded by management conditions and forage quality both in research and commercial feeding situations.
Key Words: Beef Cattle, Fat Supplementation, Reproduction
© 2004, by the American Society of Animal Science. All rights reserved.
J. Anim. Sci. 2004. 82(E. Suppl.):E154-E161
Implications
Improvements in reproduction reported in some studies may be a result of added energy in the diet or direct effects of specific fatty acids on reproductive processes. As is the case for any technology or management strategy that improves specific aspects of ovarian physiology and cyclic activity, actual improvements in pregnancy rates, weaned calf crop, or total weight of calf produced depend on an array of interactive management practices and environmental conditions. Until these interrelationships are better understood, producers are advised to strive for low cost and balanced rations. If a source of supplemental fat can be added with little or no change in the ration cost, producers would be advised to do so. Research investigating the role of fat supplementation on reproductive responses has been variable. Therefore, adding fat when significantly increasing ration cost would be advised when the risk of low reproduction is greatest.
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