ASAS Public Policy Newsletter

Cow Size: Implications for Grazing Rangelands and the Beef Industry

Dr. John ‘Derek’ Scasta, University of Wyoming, jscasta@uwyo.edu

Beef cows have been getting larger over the past 4 to 5 decades which can create problems for many different segments of the beef industry (Scasta, et al. 2019).  According to the United States Beef Improvement Federation and National Cattle Slaughter Summary, in 1975 the average U.S. beef cow weighed ~1,050 pounds and by 2009 weighed ~1,350 pounds, and today it is thought they weigh ~1,400 pounds but potentially stabilizing (Wiseman et al. 2018).  However, it seems that calf weaning weights may not have kept up with the increase in cow size and plateaued in most regions according to various data sources (Lalman et al. 2019).  This calf weaning weight plateau is problematic because as cows get larger their nutrient requirements increase but may not yield increasing returns in terms of larger calves.  Moreover, in rangeland environments forage production is constrained by weather and soils, and the forage available likely has not increased over time but the forage demand has increased creating a potential mismatch between forage supply and forage demand.  Similar increases in sheep size have also been noted over the last 5 decades (Burton et al. 2015).

This trend of increasingly larger cows has been attributed to the selection for animals that are growthier through genetic selection information such as Expected Progeny Differences (EPDs) (Johnson et al. 2010; Kuehn and Thallman 2016).  EPDs provide values for traits such as Calving Ease Direct (CED), Birth Weight (BW), Weaning Weight (WW), Yearling Weight (YW), and more.  Many cow-calf producers select sires based on such “production” EPDs including low CED and BW but high WW and YW values.  In other words, they want a bull that does not create any calving issues but produces calves that will grow rapidly and large.  If the heifer calves out of such bulls are retained as replacements, then they are likely to be growthier cattle that can continue the proliferation of such growth genetics and increases in size.  

Producers should therefore think about different sires in terms of producing terminal calves or replacement heifers and consider the implications of their genetic potential and the heritability of size-associated traits.  If the desire is to produce replacement heifers, then producers may want to pay additional attention to “maternal” EPDs such as Maternal Milk (MM) and Maternal Height (MH) because those tailor expectations as to what the bull’s daughters will be like.  Also, increases in maternal milk often coincide with increases in size and increased nutrient requirements.  

There are a number of important consequences of the increasing size of the U.S. beef cows from rangeland grazing, profitability, and industry infrastructure perspectives.  First, the number of cows a ranch can accommodate today may be different than what it was for previous generations because the cows may be 1.4x larger with a higher demand for forage due to their greater size.  Second, if the number of cows has not been adjusted down accordingly then, there may be a greater risk of overgrazing and greater difficulty for those cows to maintain adequate body condition.  Third, if the issue of overgrazing and lower body condition do occur then a ranch may experience lower reproductive efficiency in terms of increased post-partum intervals, lower breeding success, and lower pregnancy rates.  Fourth, larger cows may have reduced longevity as it has been reported that a 1,400 pound cow will wean one fewer calves in her lifetime than a 1,100 pound cow (Doye and Lalman 2011; Stewart and Martin 1981).  Fifth, larger cows may be less efficient in producing calves when you consider an efficiency ratio of calf weight to cow weight where large cows are unable to wean a calf that is 50% of more of their body weight (or a target efficiency ratio of 0.5; Scasta et al. 2015).  This is also a function of a larger cow having to eat more forage to wean a calf of similar size as a smaller cow in the herd.  Sixth, this relative inefficiency can affect profitability where modeling using production data from Wyoming suggested that a herd comprised of more small cows yielded greater per cow profits and lower unit costs of production than a herd comprised of fewer larger cows (Scasta et al. 2019).  Seventh and finally, the transportation and slaughter infrastructure may not be able to accommodate these larger cattle.  It has been reported that finished cattle have outgrown the trailers that transport them with ~68% of carcasses having bruising, particularly in the strip loin area, from bumping their backs when they go down the ramp into the lower deck (Henderson 2020).  These bruises require trimming of 5 to 6 pounds of meat from one of the most valuable cuts on the carcass leading to a loss of profit.  Similarly, some slaughter facilities have rails that are too low to accommodate some of these larger carcasses. 

References

Burton, D. J., Ludden, P. A., Stobart, R. H., & Alexander, B. M. (2015). 50 years of the Wyoming ram test: How sheep have changed. Journal of Animal Science, 93(3), 1327-1331.

Doye, D., & Lalman, D.L. (2011). Moderate versus big cows: Do big cows carry their weight on the ranch? Proc. South. Ag. Econ. Assoc. pp. 1–20.

Henderson, G. (2020). Cattle’s $35 Million Bruise. Drovers. https://www.drovers.com/news/cattles-35-million-bruise 

Johnson, J.J., Dunn, B.H., & Radakovich, J.D. (2010). Understanding cow size and efficiency. In: Proc. Beef Improvement Fed. pp. 62–70.

Kuehn, L. A., & Thallman, R. M. (2016). Across-breed EPD tables for the year 2016 adjusted to breed differences for birth year of 2014. Proc. Beef Improvement Fed. pp. 114-141.

Lalman, D. L., Andresen, C. E., Goad, C. L., Kriese-Anderson, L., King, M. E., & Odde, K. G. (2019). Weaning weight trends in the US beef cattle industry. Applied Animal Science, 35(1), 57-65.

Scasta, J. D., Henderson, L., & Smith, T. (2015). Drought effect on weaning weight and efficiency relative to cow size in semiarid rangeland. Journal of animal science, 93(12), 5829-5839.

Scasta, J.D., Mount, D., Hauptman, B., & Jorns, T. (2019). B-1343 Beef Cow Size: Industry Trends, Economics, and Implications for Grazing Wyoming Rangelands. University of Wyoming. https://www.wyoextension.org/agpubs/pubs/B-1343_beef-cow-size_web.pdf 

Stewart, T. S., & Martin, T. G. (1981). Mature weight, maturation rate, maternal performance and their interrelationships in purebred and crossbred cows of Angus and Milking Shorthorn parentage. Journal of Animal Science, 52(1), 51-56.

Wiseman, A., Lalman, D., & DeVuyst, E. (2018). ANSI-3301 Mature Cow Size Considerations. Oklahoma State University. https://extension.okstate.edu/fact-sheets/print-publications/afs/mature-cow-size-considerations-afs-3301.pdf