Cow Size and Reproductive Efficiency_ A Western Ranch Perspective

Cow Size and Reproductive Efficiency: A Western Ranch Perspective David Secrist, USU Extension Beef Cattle Specialist

Introduction Production costs and reproductive efficiency are critical elements to the survival of cow-calf operations in the West. A cow’s ability to produce a healthy calf at a marketable weight is closely tied to her maintenance requirements and management’s ability to fulfill those needs from ranch resources at a low cost. The very traits that produce a heavier calf may also hurt her ability to function efficiently in a Western range environment with minimal inputs.

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The West is typified by high elevation, cold winters, and generally dry conditions. The range and pastures are dominated by cool-season grasses that are high in quality and low in quantity. Most grass growth occurs over a 60-day period. Fortunately, much of the dormant grass maintains a reasonable quality as compared to warm-season grasses.

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The western landscapes are vast and are often discussed in sections rather than acres. Cattle are normally moved on and off public grazing lands that are often shared with other ranchers and are always shared with abundant wildlife and the general public. Public lands grazing permits are relatively inexpensive, but operational cost, limited control, and uncertainty of government policy make this advantage debatable.

Public Land Grazing The Intermountain West region encompasses approximately 294 million acres. About 198 million acres are publicly owned (67%), while approximately 1

Western ranches face high costs and challenging environments, making cow efficiency critical for profitability. Average beef cow size has increased by 450 pounds since 1965, raising maintenance costs and reducing pasture capacity. Smaller cows can be more efficient, supporting higher stocking rates and greater total calf weaning weight per acre. Reproductive efficiency—timely breeding and calving—directly impacts ranch productivity and economic sustainability. Selecting for both genetic progress and environmental fit is essential; crossbreeding strategies and careful management boost longterm success.

185 million acres are managed by the Bureau of Land Management and U.S. Forest Service for multiple uses, including livestock grazing. National Parks and National Monuments account for approximately 8–9 million acres, or about 3% of the region's total land area and roughly 4%–5% of its public lands. Approximately 2.8 million beef cows and 1.0 million sheep graze public lands in the West (National Agricultural Statistics Service [NASS], 2024; author's calculations). This accounts for roughly 10% of the U.S. beef cow inventory. The beef cattle industry generates roughly $25–30 billion in direct annual cattle and calf sales across the West, before accounting for multiplier effects through feed, labor, trucking, veterinary services, processing, equipment, and rural business activity (Economic Research Service, 2026). Rugged and remote mountains and high deserts characterize grazing land in the West. Motorized vehicle access is limited, with much of the area accessible only on horseback. This limited access makes management practices common in many parts of the country very difficult. Livestock water is also scarce. While some mountain areas have abundant surface water, most water is obtained from developed springs or wells. The Bureau of Land Management (BLM) and U.S. Forest Service (USFS) have regulatory authority over any water development. Grazing permit holders are responsible for developing and maintaining water infrastructure. Water developments are critical for livestock to use available forage; however, wildlife also benefits from increased access to water. Similarly, the BLM and USFS regulate and approve range improvements after thorough environmental impact studies and input from other stakeholders. Typically, ranchers assume at least a portion of the financial responsibility for range improvements. Ranchers often share public lands grazing allotments. While this practice can help pool labor required for cattle movements and gathering, it can be challenging to coordinate differing management practices, leading to suboptimal compromises in management philosophy. Cooperative grazing can make it harder to manage the resource for the longterm good if permittees focus on getting what they can before their neighbor does. Achieving agreement on key management decisions, including grazing strategies, bull turnout timing and selection, and stocking rate adjustments, can be problematic. There are, however, examples of like-minded ranchers working with federal agencies for the good of the whole and making this system work very effectively. Additionally, land managed by the BLM and USFS is subject to a multiple-use mandate. Alongside livestock grazing, these lands support a variety of commercial activities, including mining, oil and gas development, and commercial outfitting. They also provide public access for recreational pursuits such as hunting, fishing, camping, hiking, and off-highway vehicle use. While these diverse uses can and often do coexist successfully, conflicts may arise when management objectives and user interests are not aligned.

Cow Efficiency The beef industry produced slightly more beef in 2025 than it did in 1975. However, this was accomplished in 2025 with 61% of the cowherd that existed in 1975 (NASS, n.d.). This amazing feat was achieved through genetic advancement, new technology, and improved nutrition and animal health. However, since 1965, the average cow's mature body weight 2

has increased by 450 pounds (Lalman & Beck, 2019). Larger cows require more maintenance energy, reduce pasture carrying capacity, and increase input costs. It is also important to note that 71% of the total dietary energy consumed in beef production supports cattle maintenance. Of that maintenance energy, 70% is used to maintain the cow (Johnson, 1984). Therefore, the cow consumes 50% of the maintenance energy required for beef production. Smaller cows have been shown to be more efficient. Nebraska researchers demonstrated that smaller cows wean a higher percentage of their body weight (Ziegler et al., 2020). Additionally, small cows can be more efficient at converting body weight to the hot carcass weight of their offspring. The steer calf from a 1,200-pound cow entering the feedlot as a yearling will produce 85.7 pounds of hot carcass weight per 100 pounds of the dam’s weight. Conversely, the offspring of a 1,500-pound cow going on feed as a calf will produce 68.6 pounds of hot carcass weight per 100 pounds of cow body weight (Beck et al., 2026). This study highlights how management (calf-fed versus yearling-fed) affects carcass weight and how efficiently a smaller cow can produce offspring with a greater ability to convert cow body weight to hot carcass weight.

Cow Size Efficiency Example Using NRC and data obtained from the cowherd at the University of Nebraska, Gudmundsen Sandhills lab (National Academies of Sciences, Engineering, and Medicine [NASEM], 2016; Ziegler et al., 2020), a model was created to demonstrate the productive and economic efficiency of a 1,100-pound cow versus a 1,200-pound cow (Table 1). A 1,200-pound cow consumes 2.0 pounds more forage per day (9.1% increase). A 1,200-pound cow consumes 18 pounds more protein supplement annually. If we assume a ranch with forage production to support 500 head of 1,200-pound cows, the same ranch will produce enough forage to support 545 head of 1,100-pound cows, an increase in stocking rate of 9.1%. • •

Table 1. Comparing Expected Revenue Generated by 500 1,200-lb Cows Versus 545 1,100-lb Cows Occupying Equivalent Forage Resources Item Headcount Calf weaning weight, lb Sale price, $/lba Revenue per calf, $ Gross revenue (90% weaning rate), $ Additional protein cost, $ Net benefit, $ a

1,200-lb cow 500 479 $5.04 $2,414 $1,086,372 ($2,250) —

1,100-lb cow 545 460 $5.17 $2,378 $1,166,507 — $82,385

Sale prices are based on market values reported by CattleFax, Western U.S., October–November 2025.

Although the weaning weight per cow was lower, the total pounds weaned off the ranch increased by 4.7% in the 1,100pound cow scenario. This observation raises an important question: What is the most appropriate key performance indicator for evaluating ranch productivity and profitability?

Key Performance Indicators A key performance indicator (KPI) is a measurable metric used to evaluate how effectively a production system converts resources into desired outputs and achieves the ranch objectives. For this discussion, the ranch objective is long-term

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profitability. It is best to narrow KPIs to three to six metrics that can be consistently and objectively obtained year over year. Individual ranch KPIs may be different, but consider the following: Pregnancy rate: the number of pregnancies per exposed female. A manager may want to track different age groups separately, especially first-calf replacement heifers and females coming pregnant with their second and third calf. That will help narrow down areas of opportunity. • Calving rate: the number of calves born per bred female. Once again, cow age can be a factor and may warrant tracking. Calving rate can identify problems with misdiagnosed pregnancies, abortions, and losses at calving. • Weaning rate: the number of calves weaned per bred female. This KPI includes the calving rate but also accounts for losses after calving. • Weaning weight per bred female: the total pounds of calf weaned divided by the number of bred females. It is inclusive of calving rate and weaning rate but adds the element of calf weight. • Weaning weight per acre: the total pounds of calf weaned divided by the number of acres used for cattle production. The advantage of looking at production on a per-acre basis is that it measures actual ranch productivity rather than individual cow productivity. Ranch management should focus on optimizing forage production now and in the future. o This KPI is best to evaluate ranch productivity over time and not a means to compare one ranch to another. o Differing resources on each ranch make this comparison difficult and can lead to erroneous conclusions. Ultimately, all KPIs should be combined with economic metrics to gain their full value. The cost required to achieve the desired objectives will determine whether these objectives are sustainable in the long term. Without accurate cost accounting, production indicators become trivial points discussed without context and with limited value. •

The Value of Reproductive Efficiency The efficiency with which cows are bred, calve, and wean healthy calves is the central focus of ranch management. Economic sustainability is dependent on the efficiency of this process. As noted earlier, approximately 70% of a cow's total energy intake is devoted to maintenance. The priority of energy use is as follows (NASEM, 2016): 1. Basal metabolism (maintenance). 2. Activity (includes grazing activities and travel to water). 3. Growth (primarily young cows up to 4 years old). 4. Body reserves (fat deposition). 5. Maintaining pregnancy (fetal growth and development). 6. Lactation. 7. Reproduction (estrus and conception). A cow will not cycle and conceive if her body stores are low and other higher-priority functions are not satisfied. Body condition score (BCS) has long been used to assess cows’ nutritional status (Herd & Sprott, 1986). Cows with a BCS of 4 or lower at calving will rebreed at a lower rate than those with a higher BCS. This is further magnified in young cows (Richards et al., 1986; Spitzer et al., 1995). Lower BCS at calving will result not only in more open cows at the end of the breeding season but also in a greater number of cows bred late in the breeding season.

Reproductive Efficiency Example Table 2 shows results from a model using a 90-day calving season, comparing steer calves born on the first versus the last day of the season. Assuming a steer gains 2.2 pounds per day of age (Cundiff et al., 1998), missing one heat cycle (21 days) will reduce weaning weight by 46 pounds.

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Table 2. Comparison of expected net revenue from steers born early (April 1) versus late (June 30) in the calving season. Item Birthweight, lb Age at weaning, days Weaning weight, lb Sale price, $/lba Gross revenue, $ Annual cow cost, $ Net revenue/cow, $ a

April 1 calving 90 210 552 $4.47 $2,467 $1,500 $967

June 30 calving 90 120 354 $5.50 $1,947 $1,500 $457

Sale prices are based on market values reported by Cattle Fax, Western U.S., October-November 2025

This model assumes that all calves are sold 210 days after the start of the calving season. Although a manager may choose a different option for lighter/younger calves, these calves are most often sold with their herd mates, resulting in a reduced average weaning weight for the herd. It is a good practice to monitor calving interval by tracking the percentage of calves born in each 21-day period during the calving season. Although overall breeding rates may be acceptable, a drift in the calving interval can be very costly and difficult to recover from. Close attention to cow BCS at calving, resulting in a greater proportion of calves born during the first 21-day period, will increase weaning weights for calves born early and the total weight of calves weaned for the herd. Although good genetics are also critical for growth, the top 1% of bulls in the Angus breed will only add 32 pounds of weaning weight to average Angus cows, while gaining one heat cycle will increase weaning weight by 46 pounds. Obviously, the benefits of good genetics and good management are additive.

Summary Genetic and nutritional improvements, advancements in technology, and ever-adapting management have dramatically increased the productive capacity of the beef cow. Breakthroughs will continue well into the future. However, the beef industry possesses two significant competitive advantages that competing protein sources cannot replicate: 1. Beef offers a unique combination of taste, palatability, and nutritional value that is highly sought after by consumers worldwide. 2. The beef cow has the remarkable ability to convert low-quality forage into high-quality protein for human consumption. Ranching operations throughout the Intermountain West rely primarily on native rangelands and forages that occur on landscapes largely unsuitable for conventional crop production. In essence, the beef cow transforms grasses and other fibrous plant materials that humans cannot consume into nutrient-dense products such as ribeye steak and hamburger, creating food from resources that would otherwise have little direct value in the human food chain. Selection for growth and milk production increases costs and decreases stocking rates, which may not be offset by increased calf revenue at weaning. These effects are magnified in the extensive and often harsh environments of Western ranches. The foundation of the beef industry is the cow-calf sector. Over the long term, the industry cannot remain viable if cowcalf producers are not profitable. Profitability depends largely on a producer's ability to control costs while efficiently 5

using available natural resources to produce a healthy calf prepared for the next phase of production. This principle holds true regardless of whether calves are marketed at weaning or ownership is retained through subsequent production stages. Continued genetic progress aimed at The foundation of the beef industry is the cow-calf improving product consistency, quality, and growth sector. Over the long term, the industry cannot performance is essential; however, these advancements must remain viable if cow-calf producers not come at the expense of the rancher's ability to produce are not profitable. calves in a cost-effective and sustainable manner.

Solutions Ideally, the beef industry needs to capture the advantages of accelerated growth enabled by modern genetic technology while keeping the ranch at a profitable break-even. The knowledge to address these solutions has been in place for many decades. The advantage of heterosis need not be set aside to capture the genetic progress demonstrated by one breed or another. Income derived from a cross-bred female is 22% higher over her lifetime than that of a straight-bred cow (Kuehn & Freetly, 2024). Crossbreeding advantages are additive to careful genetic selection (Weaber, 2015). The National Cattlemen’s Beef Association reported that black-hided cattle have increased from 45.1% in 2000 to 62.3% in 2022 (Borders et al., 2025). The success of Angus-based marketing programs has been dramatic, and premiums are paid in all stages of production for black-hided cattle. However, repeated use of any breed within a single herd will reduce heterosis and its associated production advantages. Composite breeding maintains heterosis while keeping a simple breeding program. Bulls thoughtfully engineered from complementary breeds have been successfully used to maintain uniformity in color and animal type while preserving some of the advantages of crossbreeding. Terminal breeding allows focus on maternal traits important for maintaining reproductive efficiency in a specific ranch environment while capturing the advantages of heterosis and selection for growth and carcass traits. Although there is sentiment that purchased heifers have difficulty adapting to a new environment, this potential problem should be weighed against the advantages. If heifers are purchased bred, there is no need to maintain heifer bulls. Terminal breeding significantly improves weaning weights and subsequent feedyard and carcass performance. Additional costs may be incurred at the time of the original purchase of the bred heifer, and she may require additional feed to help her adapt. However, that same heifer will produce a heavier calf for her entire lifetime. Implementing a management system to maintain environmental fit for the female while improving her individual productivity will require additional effort. Nevertheless, the potential gains can far offset the implementation cost and management intensity.

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Acknowledgments The author did not use generative AI in creating this content; it is solely the author’s work.

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Ziegler, R. L., Musgrave, J. A., Meyer, T. L., Funston, R. N., Dennis, E. J., Hanford, K. J., MacDonald, J. C., & Mulliniks, J. T. (2020). The impact of cow size on cow-calf and postweaning progeny performance in the Nebraska Sandhills. Translational Animal Science, 4(4), txaa194. https://doi.org/10.1093/tas/txaa194 In its programs and activities, including in admissions and employment, Utah State University does not discriminate or tolerate discrimination, including In its programs and activities, including in admissions and employment, Utah State University does not discriminate or tolerate discrimination, including harassment, based on race, color, religion, sex, national origin, age, genetic information, sexual orientation, gender identity or expression, disability, status as a protected veteran, or any other status protected by University policy, Title IX, or any other federal, state, or local law. Utah State University is an equal opportunity employer and does not discriminate or tolerate discrimination including harassment in employment including in hiring, promotion, transfer, or termination based on race, color, religion, sex, national origin, age, genetic information, sexual orientation, gender identity or expression, disability, status as a protected veteran, or any other status protected by University policy or any other federal, state, or local law. Utah State University does not discriminate in its housing offerings and will treat all persons fairly and equally without regard to race, color, religion, sex, familial status, disability, national origin, source of income, sexual orientation, or gender identity. Additionally, the University endeavors to provide reasonable accommodations when necessary and to ensure equal access to qualified persons with disabilities. The following office has been designated to handle inquiries regarding the application of Title IX and its implementing regulations and/or USU’s non-discrimination policies: The Office of Equity in Distance Education, Room 400, Logan, Utah, titleix@usu.edu, 435-797-1266. For further information regarding non-discrimination, please visit equity.usu.edu, or contact: U.S. Department of Education, Office of Assistant Secretary for Civil Rights, 800421-3481, ocr@ed.gov or U.S. Department of Education, Denver Regional Office, 303-844-5695 ocr.denver@ed.gov. Issued in furtherance of Cooperative Extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Justen Smith, Vice President for Extension, Utah State University.

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