Nutrition Impacts Feedlot Health, Part 4: Finishing Phase By: Dr. Jeremy Martin and Dr. Dan Larson, Great Plains Livestock Consulting, Inc.
Nutritional management of calves in utero through receiving and effects of nutrition on health in the feedlot have been the focus of the previous articles in this series. Once the receiving period is over and the cattle are well-started on feed, we tend to experience fewer health challenges as an industry. From this point on though, a high percentage of pulls are either related to feeding management or nutrition in some way. Nutritional disorders that impact cattle during the finishing phase can have serious consequences in terms of performance and conversion; three of the more common issues are acidosis, liver abscesses, and polioencephalomalacia (PEM). The three are distinct but interrelated conditions. The goal of feedyards and their nutritionists for finishing cattle is generally to achieve maximum performance and feed conversion while minimizing digestive disorders. In ruminant animals adjusted to high starch rations, we can expect cattle to experience acidosis of varying degrees at some point during the feeding period. In general, acidosis is simply low rumen pH due to an imbalance between volatile fatty acid (VFA) production in the rumen and the ability of cattle to absorb and utilize VFAs. Since cattle convert energy in feeds to VFAs in the rumen, VFA production increases as cattle are stepped up to rations with more grain and less roughage, or due to increasing intakes. Managing the risk of acidosis is the very reason for the step-up process. Since acidosis is a continuum of rumen pH, rather than a disease, it can be classified as acute or subacute. Acute acidosis occurs when rumen pH drops below 5.2 and produces noticeable symptoms including reduced intake, cattle panting in an effort to maintain acid-base balance in the blood, bloat, loose stools that contain bubbles and a white appearance when dried, and pen deads. Unseen results of acute acidosis include founder which becomes apparent 45-60 days further into the feeding period, damage to the gut lining which reduces ability of cattle to absorb nutrients, and liver abscesses. All of these result in reduced feed efficiency and performance at the least. Additionally, there is a link between acidosis and polioencephalomalacia (PEM) – more on that later. University of Nebraska-Lincoln data also associate risk of PEM with pacdvms.com 27
