Integrating Grazing Management and Behavioral Responses to Optimize Pasture Utilization

By James Lawhead, DVM and Leoni F. Martins, PhD., The Pennsylvania State University

Numerous factors influence decisions in grazing systems. Cattle number, land availability, soil types, weather conditions, and animal productivity are some of the key variables directly affecting pasture management for dairy cows. In grazing systems, the decision of when to graze and how much to harvest often considers the economic trade-offs between maximizing milk production per animal and per acre. For instance, increasing the stocking density (number of cows/area) and the grazing intensity may contribute to maximizing the total amount of forage harvested; however, it could also limit the productivity of individual cows due to decreased forage quality.

Data collection in grazing systems has long relied on manual, intensive, and time-consuming activities. With the rapid ascension of precision technologies, farmers now have the potential to generate information and improve grazing management more efficiently. In this article, we discuss novel grazing strategies with the potential to improve cow and land productivity, with a focus on grazing intensity and cow behavior. Additionally, we discuss the variability in forage mass yield across different grazing systems in Pennsylvania, and how this variation needs to be considered when evaluating pastures.

Sward Height and Grazing Management

Sward height, defined as the length of the plants from the ground to the top of the leaf canopy, is a measure commonly used for pasture evaluation. Sward height can be easily determined with a pasture (i.e., grazing) stick by holding the stick vertically in the pasture vegetation. The height is not determined at the tallest leaves reach, but at the height of the densest part of the vegetation (Figure 1). In the example below, pasture height reading should be 9.5” rather than over 11” (the height of the tallest leaves).

The sward height is a direct measure of light interception, which is correlated with forage production (lbs/acre). Light interception refers to the amount of solar radiation that is intercepted by the forage canopy, with research showing that optimum forage production is achieved when 95% of the light is intercepted. Exceeding 95% light interception at pre-grazing does not promote net gains in forage production but substantially decreases forage quality due to greater accumulation of aging material, reproductive structures (e.g., blooms and blossoms), and lignification (i.e., decreased digestibility) of basal plant structures. Sward height corresponding to 95% light interception has been extensively studied, and general recommendations for different forage species are available in the literature.

For long-term pasture productivity and persistency of cool season grasses, a practical goal is to aim for post-grazing height of 1.6 to 2.0” because most of the water-soluble carbohydrates needed for plant regrowth are stored below this point. In rotational (intermittent) systems, post-grazing heights could be managed around 50% of the pre-grazing height. For example, for many tall-growing cool season grasses, such as orchardgrass, pre- and post-grazing heights would be 8–10 and 4–5”, respectively. This practice would likely decrease grazing interval and may improve forage quality.

Post-grazing Heights for Dairy Cows: What Does the Research Show?

Recent research (Menegazzi et al., 2025; https://doi.org/10.3168/jds.2025-26767) has evaluated the effects of two post-grazing heights on forage production and lactational performance in dairy cows maintained in a strip-grazing system of tall fescue (Lolium arundinaceum) across nearly an entire lactation. Pre-grazing height was 9.3 and 8.7” whereas post-grazing heights were 3 and 6” for conventional (control) and moderate grazing (treatment), respectively. Sward height depletion was 66 and 35% of pre-grazing height, period of stay was 2.9 and 3.9 days/strip, and number of grazing cycles was 3.3 and 8.3 for control and treatment strategies, respectively. Area used was lower (2.9 and 4.0 acres) and stocking rate (1.4 and 1.0 cow/ac) was greater in conventional than moderate grazing systems.

Overall, cows managed in a moderate grazing system (highest sward height) had increased milk production (72.8 vs. 67.2 lbs/d energy-corrected milk; ECM) and earlier recovery of body condition score in the lactation compared with cows managed in a conventional grazing system. Additionally, higher post-grazing sward reduced feed use per unit of milk produced. The drawback was that the stocking rate was 29% lower for the higher sward height group, leading to decreased milk and ECM yields/acre compared with the lower post-grazing sward height. Despite a numerical difference ($1,245 vs. $1,092/acre per 215 days), income over feed costs did not statistically differ between treatments in that study. Clearly, moderate grazing positively affected individual cow performance, but these benefits were offset by lower land productivity.

The mechanisms underlying the improved individual cow performance observed at the taller post-grazing height reported by Menegazzi et al. (2025) were further investigated in a follow-up study (Menegazzi et al., 2026; https://doi.org/10.1016/j.animal.2026.101850). The authors demonstrated that cows managed under a 6” post-grazing height exhibited shorter but more frequent meals and sampled feeding stations at a faster rate than cows managed under a 3” post-grazing height. The taller post-grazing height resulted in fewer but larger bites per feeding station, increasing nutrient intake rate without extending daily grazing time. These findings suggest that differences in post-grazing sward height primarily influence grazing behavior, with taller post-grazing heights promoting greater selection of higher-quality forage by dairy cows.

Forage Mass, Between- and Within-Farm Variation in Forage Yield

In addition to height, density or volume (estimated as the forage mass lbs/ft2 or lbs/ft3, respectively) also affect the availability of forage and grazing behavior. Cows grazing pastures with high versus low forage density show marked differences in biting activity and number of feeding stations—both representative of short-term grazing behavior. It is important to note that cows have preference and motivation during grazing, and forage quality and availability are key determinants for optimum feed intake in grazing systems. Low quality swards are expected to reduce grazing efficiency as cows waste time sorting for the most nutritive plant structures (leaves versus stems and aging material). In this sense, grazing intensity plays a role in forage quality and intake, which can be easily determined by post-grazing height.

Forage mass can be measured using the quadrat technique, which consists of harvesting forage within a frame of known area (Figure 2). A quadrat can be constructed using four PVC pipes measuring 1.64 ft in length, resulting in an area of 2.69 ft2. The quadrat should be placed randomly throughout the paddock, and all forage within the frame should be harvested and collected in a bag or bucket. Be sure to record both the initial and final sward heights. The final height should represent the target post-grazing residual height defined by your grazing system. Weigh the harvested forage and collect a subsample for dry matter determination using your preferred method (e.g., microwave, Koster tester, or air fryer). Multiply the harvested forage mass by the dry matter concentration to calculate forage dry matter yield within the quadrat. This value can then be converted to forage mass on an area basis and expressed as either lb/ac or lb/in/ac. When estimating the amount of forage available to grazing cows, it is important to account for grazing efficiency, as not all forage present in the paddock will be consumed. Depending on pasture conditions and grazing management, grazing efficiency typically ranges from 30 to 50%.

Figure 2. Quadrat with an area of 2.69 ft2 used for forage mass determination in pasture systems.

Alternatively, forage mass may be determined using a rising plate meter. The plate meter estimates total forage mass (lb/ac = kg of dry matter/ha × 0.89) based on compressed height of the sward. This represents an easier and efficient way to determine forage mass and sward height, although frequent calibrations may be required. Compressed height determined by the plate meter is used in a model to estimate total forage mass, and several studies have reported the limitations of these models to accurately predict forage mass across different forage species, seasons, and sward structure (e.g., grazing architecture and sward height).

Data collected by our team from April to June 2026 on organic and regenerative dairy farms across Pennsylvania illustrate the variability between forage mass estimates obtained using a rising plate meter and the quadrat technique (Table 1). Notably, substantial discrepancies were observed between the two methods, with the rising plate meter overestimating forage mass on a dry matter basis by approximately 3- to 13-fold relative to the quadrat method. These findings highlight the importance of calibrating plate meter equations to local pasture conditions to ensure accurate estimates of forage yield and, consequently, more reliable assessments of forage intake by grazing cows.

Table 1. Characterization of height and forage mass estimated using the rising plate meter or quadrat techniques across farms between April and June 2026 in Pennsylvania

Datapoint	Height	Rising Plate Meter			Quadrat		Ratio2
		lb/ac1	lb/in/ac1		lb/ac1	lb/in/ac1
1	4.50	3,249	728		331	74	9.8
2	4.22	3,057	750		375	89	8.2
3	3.70	2,744	756		605	163	4.5
4	4.65	3,326	724		1,025	221	3.2
5	4.82	3,445	729		1,150	238	3.0
6	4.82	3,450	730		1,303	270	2.6
7	4.51	3,251	737		413	92	7.9
8	7.05	4,860	711		677	96	7.2
9	7.24	4,968	690		2,182	301	2.3
10	2.01	1,670	854		130	64	12.9
11	8.45	5,753	685		3,317	393	1.7
12	7.76	5,317	732		1,768	228	3.0
13	4.65	3,330	732		932	201	3.6
14	6.32	4,402	702		1,177	186	3.7
15	3.75	2,763	747		852	227	3.2
16	5.92	4,146	706		1,446	244	2.9
Average	5.27	3,733	732		1,105	193	3.4
SD3	1.71	1,083	38		806	92	1.3
CV3, %	32.4	29.0	5.2		73.0	47.8	-

1 Forage mass is expressed on a dry matter basis.

2 Ratio was calculated as rising plate meter forage mass ÷ quadrat forage mass.

3 Standard deviation and coefficient of variation (SD ÷ Average).

The choice of calibration equation can substantially influence the relationship between forage mass estimates obtained from the two methods. In our dataset, the best fit was achieved using a linear regression with the intercept constrained to zero. Based on this model, each 1 lb/ac increase in forage mass measured by the rising plate meter corresponded to 0.32 lb/ac measured by the quadrat. Therefore, rising plate meter values can be converted to quadrat-equivalent forage mass estimates by applying the corresponding calibration equation. It is noted, however, that these values may only be accurate for the dataset used to generate the equations.

Summary

Different grazing intensities and management are expected to modulate cow behavior and productivity. Farms with limited acreage may choose to be more aggressive with the stocking density and utilize lower sward heights to maximize production per acre. Other farms may have the opportunity to utilize lower stocking densities and higher post-grazing sward heights, taking advantage of faster regrowth and higher-quality forage to increase individual cow production. Alternatively, some farms may choose to group cows based on production merit and manage these groups using different grazing approaches.

As for many biological responses, the optimum balance between individual cow and land productivity may fall somewhere in the middle. It is important to note, however, that these decisions can only be made on farms that have adequate record keeping and data collection. “Measure to manage” is key for dairy farms that want to remain profitable and improve their performance in grazing systems.

The grazing stick and quadrat are accurate methods for determining sward height and forage mass, respectively. However, these methods can be time-consuming. Alternatively, a rising plate meter can provide a more efficient means of estimating forage mass, although calibration is required to improve the accuracy of forage mass predictions.

Dr. Leoni Martins, PhD., Asst. Clinical Professor of Precision Dairy Nutrition, Dept. of Animal Science, Penn State University, leonimartins@psu.edu, 814-863-1690, and Dr. James Lawhead, DVM, Extension Associate, Dairy Science, Penn State University, jbl5606@psu.edu, will be presenting at the 26th Annual NODPA Field Days in Leesport PA on September 24 & 25, 2026.

Posted: to Organic Production on Sat, Jul 4, 2026
Updated: Sun, Jul 5, 2026