By Alfredo DiCostanzo
It is not a surprise to anyone that carcass weights are increasing. Fewer feeder cattle from the U.S. supply and the U.S.-Mexican border closed to feeder cattle imported from Mexico since November of 2024 because of screwworm detection in the southern Mexican state of Chiapas are contributing to a shortage of feeders. Incidentally, the border reopened recently, under a heavily controlled importation process (Importing Live Cattle and Bison from Mexico to the United States | Animal and Plant Health Inspection Service).
Other factors such as the economic incentive to add pounds to the existing feedyard inventory are contributing to heavier finishing weights. Yet, finishing cattle to heavier weights is not without financial risk: heavier cattle may get sick, resulting in condemnation or a realizer animal, or die. This risk is difficult to assess because it is heavily dependent on each feedlot’s individual situation.
Owners and managers of feedlots should conduct their own assessment of late-term death risk for cattle they might consider feeding longer. Some ideas are presented at the end of this article.
Likely because of economic conditions and continuously fewer cows in the US cattle inventory, feeding cattle to heavier endpoints is a long-term trend. A review of data maintained by Kansas State University (Focus on Feedlots) since 1993 revealed that cattle finished in 2023, although weighing the same at feedlot entry (750 lb), finished heavier because of 40 days longer on feed. At a modest rate of gain of 2.5 lb daily, an extra 100 lb of weight is added on 40 days on feed.
Taking into consideration what we know about carcass weight gain relative to live weight gain in the final days on feed leads to an interesting consideration. As cattle mature, they are known to deposit more weight of carcass than non-carcass components. It is not uncommon to observe a 75-dressing percentage on the last 100 to 200 lb of live gain. But, if a heavy steer deposits 75% of the gain in the carcass component, then it deposits only 25% of the gain in the non-carcass component (head, legs, hide, and organs).
This situation leads to increasingly smaller vital organ mass (relatively speaking) to deal with increasingly larger nutrient supply. Cattle that consume 26 to 30 lb of dry matter during this period are presented with 12% more energy to partition into maintenance and gain. This extra energy load results in greater metabolic loads on all organs.
In other words, the metabolic load on a steer gaining weight from 1,500 to 1,600 lb is 12% greater than that on a steer gaining weight from 1,400 to 1,500 lb. Relatively speaking, the heavier steer must accomplish this with heart, lung, liver and digestive tract of the same size as the lighter steer.
This is why risk of late-term death increases with weight in feedlot cattle.
Contributing factors to digestive, respiratory, cardiac and structural (leg and feet) conditions are exaggerated by this relative insufficiency in metabolic capacity. Acid loads in the small intestine, resulting from intake fluctuations, for example, may lead to greater bacterial and toxin loads reaching the blood stream.
Greater ash content in fermented whole plant silages should be monitored as they may indicate greater soil contamination of these feed sources. Certain clostridial strains are harbored in soil. Concentrations of ash in fermented feeds greater than 5% would be a source of concern.
As the beef industry works towards meeting beef demand by feeding cattle for longer days on feed, an individual or pen score that takes into consideration cattle thriftiness and background may be warranted.
- Manage cattle so that respiratory disease is prevented at the appropriate time
- Identify cattle that have recovered from respiratory or digestive disease (including an identified bout with acidosis) while in the grow or finish yard
- At 40 to 60 days prior to harvest of the lot, visual inspection of the lot accompanied by review of individual data should be used to market cattle deemed “in need of marketing” for various reasons (previous issues with respiratory, digestive or foot and leg problems)
- If using a Beta-agonist, “cattle in need of marketing” should be marketed prior to the remaining cattle in the pen or lot begin receiving a metabolically enhancing agonist or agonist/antagonist
- Consideration should be given to feeding feed additives that show promise to reduce morbidity and mortality during the late-term finishing period
Hopefully, this science-driven discussion will inspire additional strategies to manage cattle fed to heavier weights.
Source : unl.edu