In the past 75 to 100 years, we have seen cow size go from belt-buckle cattle to hat-brim cattle. Much of this was done in efforts to increase income, and cow-calf producers have placed heavy selection pressure on growth traits to increase weaning and yearling weights. Since growth traits are highly heritable, retaining replacement females with increased growth potential has caused the cow size in herds in the U.S. to increase. Between 1975 and 2005, the average cow weight in the U.S. at slaughter increased from 1,050 to 1,350 pounds. Since 2005, cow size in the U.S. has probably pushed into the 1,400- to 1,500-pound range.
The increasing trend of larger cattle has implications for forage consumption, stocking rates and overall ranch profitability. This increase in cow size has led cow-calf producers to commonly comment, “I run fewer cows today than I used to on the same range,” or, “My grazing days have decreased over the years,” or, “We have had to increase feeding harvested feedstuffs.” Some of these situations can stem from yearly changes in precipitation; however, due to increased selection for growth traits, today’s cow herd has crept up to larger sizes, resulting in changes that need to be made at the ranch to carrying capacity and stocking rates.
Forage demand
Determining the correct carrying capacity is one of the most critical factors in ranch management. It determines the stocking rate a ranch can support sustainably without long-term degradation of forage resources. While factors such as climate (inter- and intra-annual precipitation), soil quality, grazing and pasture management play significant roles in carrying capacity, one often overlooked factor is cow size.
Larger cows have greater maintenance energy requirements and consume more forage than smaller cows. For instance, an 1,100-pound cow consuming 2.5% (on a dry matter basis) of her bodyweight would consume 27.5 pounds per day; whereas a 1,200-pound cow consuming the same 2.5% would consume 30 pounds of forage per day. Over the course of a year, this 100-pound difference would equate to 912.5 additional pounds of forage needed to support the increase in cow weight. As cow size increases, the number of cows a ranch can support on the same acreage decreases. Studies from the Southern Plains show that increasing cow size by 100 pounds increases feed cost by approximately $42 per cow to support the added forage intake or increased harvested forage feeding associated with larger cows.
Stocking rates
Stocking rate – the number of cows per acre over a period of time – is directly influenced by cow size. Stocking pastures with the right number of animals is one of the cornerstones of proper grazing management. Proper stocking depends on two factors: animal intake and pasture productivity. As discussed above, animal intake and weight go hand in hand. Methods such as animal unit (AU) that allow for a standardized unit for calculating forage demand and forage supply can help provide recommendations on stocking rate; however, an accurate adjustment in cow size is needed for proper grazing management. Ranchers managing larger cows must reduce their stocking rates to avoid overgrazing or increase pounds of harvested feeds to offset the decreased grazing capacity. If a ranch’s carrying capacity is based on 1,100-pound cows and the herd size shifts to 1,400-pound cows, stocking rates must be adjusted downward, often leading to fewer total cows on the land.
Calf weaning weights
Larger cows generally produce larger calves, which can be advantageous in terms of weaning weights. Data from the Sandhills of Nebraska has shown that increasing cow size by 100 pounds increases calf weaning weight by 14 pounds. The ratio of calf weaning weight to cow weight has previously been used as a measure of the efficiency of cow size. Bigger cows do not always wean heavier calves proportionate to their body size. Calf weaning weight to cow weight ratio significantly declines as cow size increases. The smaller cow, therefore, produces a greater percentage of her bodyweight in calf, potentially leading to better efficiency while maintaining an ability to run more cows. To offset the increased forage intake and decreased carrying capacity in larger cows, larger cows must have the ability to pay for the bigger feed bill. Studies from the Southern Plains and Nebraska Sandhills have illustrated that smaller cows (around 1,000 pounds) weaning smaller calves are still more profitable than larger cows.
Drought and forage availability considerations
In drought conditions, larger cows are riskier because of their higher forage intake needs and increased nutrient requirements, which puts more pressure on limited forage resources. Larger cows require more feed to maintain body condition, support reproduction and sustain milk production. During drought or feed shortages, these increased demands can strain forage resources and raise production costs.
Economic considerations
Ranchers must balance the tradeoffs between larger cows and carrying capacity. While larger cows may produce heavier calves, the additional feed and lower stocking rates might reduce overall profitability. A smaller, more efficient cow herd may allow for more total weaned weight per acre, even if individual calves are lighter. Even in retained ownership enterprises, smaller cows have an advantage. Our data shows that progeny from smaller cows perform and grade relatively better than progeny from larger cows. Regardless of grid or cash liveweight pricing, cow-calf producers maximize the highest amount of profit by selecting smaller cows.
Finding the right balance
Optimizing cow size for a specific ranch requires a balance between cow efficiency, forage availability and economic returns. A driver of cow size at the ranch is the energetic inefficiency of beef production due to the high cost of body maintenance requirements. With that in mind, of the entire beef production system, the beef cow or cow herd is the most energetically demanding segment. For instance, 71% of the total dietary energy expenditure in beef production is used for maintenance, and 70% of that maintenance energy is required for the cow herd. Therefore, an overwhelming 50% of the total energy expended in producing beef is used for the maintenance of the cow. However, with genetic trends and selection for output traits, maintenance costs for the cow herd may have increased over time.
What are the criteria for the right cow size? Is it calf weaning weight and eventual slaughter weight, marketing endpoint, optimal ranch forage utilization, optimizing net returns for the cow-calf operation or a lower-risk production system? The answer is “yes” to all of the above, as they are all interrelated. Every decision we make on the ranch has a downstream impact. Therefore, as we make or have previously adjusted genetics, we need to consider the ramifications to all aspects of the ranch as an integrated approach.
Conclusion
Cow size plays a significant role in determining the carrying capacity of a ranch. While larger cows can produce heavier calves, their increased forage demand may reduce overall stocking rates and profitability. Ranchers must carefully evaluate the tradeoffs and select cow sizes that optimize forage use, reproductive efficiency, marketing endpoint and economic returns. By finding the right balance, producers can improve the sustainability and profitability of their operations.
