The Digestive Tract
Early spring forage dynamics and their effect on postpartum nutrition.
February 24, 2025
As calving season kicks off for many spring-calving herds across the United States, we need to start thinking about setting up cows for a successful breeding season. That starts with nutrition management decisions made months ahead of bull turnout. Building a nutrition program for a cow-calf system requires understanding nutritional requirements and knowing the quality and quantity of your forage resources.
The greatest need
Late gestation and early lactation have the greatest nutrient requirements for a beef cow. For instance, moving from mid- to late gestation increases a cow’s energy requirement 25% and her protein requirement 10%. However, the period postcalving has the greatest nutrient demand a cow will experience during her entire production cycle.
Table 1 illustrates the increased protein and energy intake difference between late gestation and early lactation for a 1,200-pound (lb.) mature beef cow with 25 lb. of milk production at peak lactation (approximately 60 days postcalving). Due to the difference in nutrient requirements, the last chance to economically increase body condition score on a cow during late gestation is the last 90 days prior to calving.
Table 1: Maintenance requirements (DM basis) for a 1,200-lb. mature beef cow with 25 lb. of milk production
The last chance to economically increase body condition score on a cow during late gestation is the last 90 days prior to calving.
After that 90-day window, it is difficult for a thin cow to gain condition — even while consuming large quantities of high-quality feeds — due to her increased nutrient demand during lactation. To overcome some of these hurdles, supplementation is generally recommended if forage protein and energy are inadequate.
Spring forage dynamics
Knowledge of the nutritive value and availability of forage selected by cattle (along with cow nutrient requirements) is critical for understanding supplementation programs and how to meet your production goals.
For instance, the start of the forage growing season will be here soon. However, for many spring-calving herds, cows may be several weeks into lactation prior to forage green-up or having sufficient grass growth. This delay in sufficient grass growth could present problems for many spring-calving producers.
After winter and when cool-season forages start greening up, cows will start chasing the green forage. In these early forage green-up periods, we sometimes believe we have more high-quality forage available than there truly is. This can be deceiving on two ends: The overall forage quality is lower-quality than what we perceive it is with green grass, and the subsequent forage intake is lower than what we think it will be due to the lower forage quality.
Following these general rules of thumb can help us estimate daily feed intake of cows on a dry-matter basis consuming forage:
- When forage quality is low [52% total digestible nutrients (TDN) or less] and cows are not lactating, they will consume 1.8% and lactating cows will consume about 2.0% of body weight on a dry-matter basis.
- If the forage is average (TDN between 52% and 59%), non-lactating cows will consume about 2.0%-2.2% and lactating cows will consume 2.3%-2.5% of their body weight on a dry-matter basis.
If intake of high-quality forage is limited, additional supplementation will be needed to offset the overall decrease in energy intake. In this situation, providing a supplement that is high in protein and energy without limiting forage intake would be ideal. Increasing the energy content of the diet postcalving will help decrease the postpartum interval and increase the reproductive success during the breeding season.
Another aspect with grazing early green-up to consider are the long-term effects on forage production. Grazing before pastures are ready causes the plants to use additional nutrients from already low root stores to recover. If there are not enough nutrients stored in the roots, the plant may go dormant and stop growing, reducing the total annual production.
If grazing before pastures are ready is unavoidable, the negative effects can be spread lightly across multiple pastures by only grazing each pasture for a few days before moving.
The key is to not stay too long and to only lightly graze the fresh growth. Grazing will stress the vulnerable plants; however, effects can be limited if the plant is not grazed repeatedly and sufficient recovery time is allowed before being grazed again. As always, avoid grazing a pasture at the same time of year multiple years in a row. As a last resort, a sacrifice pasture can be designated to limit damage to a single pasture; however, the negative effects may last for many years.
Takeaway
During these early spring grazing periods, management may have to look at stocking pastures at lower rates and/or cattle may need to receive supplementation to meet a desired level of nutrient intake.
Under these circumstances, nutritional requirements may not be met and cows can go into a negative energy balance postcalving, which can cause cows to have delayed resumption of estrus postcalving and may result in a greater percentage of open or late-breeding cows.
To combat this negative energy balance issue, management decisions around supplementation during early lactation can better prepare cows for breeding.
Editor’s note: “The Digestive Tract” is a regular column focused on nutrition for the beef cattle life cycle. Travis Mulliniks is the Glenn & Mildred Harvey Professor of Beef Cattle Management, as well as the associate head of the Department of Animal and Rangeland Sciences, at Oregon State University.
Featured in the 2025 Angus Beef Bulletin
Topics: Nutrition , Reproduction , Pasture and Forage , Feedstuffs
Publication: Angus Beef Bulletin
Issue: March 2025
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