Forage Production and Ecosystem Services in Silvopasture-Based Beef Cattle Systems

Sep 29

4 min read

Funded by the Rangeland Sustainability Program (Government of Alberta)

Introduction

The intentional combination of trees, forage, and animals into a single unit has the potential of providing ecosystem services (i.e., forage yield, soil health benefits) and improving the conditions and performance of cows. The silvopastoral project was established on-farm to compare the effects of three grazing systems: open system (i.e., without tree canopy), semi-closed system (i.e., with about 50% tree canopy), and closed system (i.e., with full canopy) on forage dry matter (DM) yield and nutritional value, animal performance (body condition score, weight, temperament), and soil health.

What We Did

This is the second year of a 3-year field project, taking place in the High Prairie area.
Three systems are being investigated (open, semi-closed and closed).
The systems were sub-divided into three paddock strips averaging 14 acres each and fenced.
The closed and semi-closed systems were dominated by Aspen trees.
Water was made available within the paddocks through pipes connected to a dugout source regulated by a pump. The pipelines were fitted with pressure gauges to monitor periodic water flow into the system.
Body condition scores of five selected cows were noted before their introduction into various paddocks.
Before stocking each paddock, weekly forage clippings were taken with 1m x 1m quadrat to aid in estimating the dry matter (DM) yield and nutritive value.
Subsequently, soil infiltration and normalized difference vegetation index (NDVI) were measured before stocking, using the single-ring method and a Trimble Greenseeker handheld crop sensor, respectively.
Cows were introduced into the paddocks for each system with 110, 75, and 40 cows in open, semi-closed, and closed systems, respectively.
The grazing period lasted for 3 weeks, starting from 25 May to 11 June 2025.
During each grazing week, soil moisture and temperature were measured twice using Time Domain Reflectometry - TDR 350, as well as the temperament of five selected cows monitored and scored 0-2 (i.e., 0 is good, 1 is compromised condition, and 2 is poor condition) (Welfare quality, 2009).
Additionally, weekly water consumption within each paddock was recorded. The gauge attached to the watering system records the daily volumes of water. The remaining quantity of water in the trough at the end of the week is subtracted from the total volumes that was captured by the system and divided by the number of cows in the paddock to obtain weekly water consumed.
Final BCS was taken at the end of the 3-week grazing period.
Raw data collected during the 2025 season was analyzed with R statistical software (version 4.2.3) using the Analysis of Variance (ANOVA) program in a mixed-effect model.

Open system during grazing

Cows grazing on a hot day (27.1oC)

What We Found

The three systems differed widely in DM yield and nutritive values (Table 1).

Forage DM yield ranged between 666 lb per ac for the closed system and 3,066 lb per ac for the open system. The trend of DM yield within systems was open>semi-closed>closed (Table 1). Overall, the open system produced 1,568 and 2,400 lbs per ac more of DM over semi-closed and closed systems, respectively. Comparatively, high crude protein (CP) was found in forage from the open system (17.1%), followed by semi-closed (16.9%), and closed systems (11.2%). Forage detergent fiber showed lower acid (31.8-31.9%) and neutral (46.6-46.9%) detergent fiber in closed and semi-closed systems, respectively. In terms of energy, the highest TDN (total digestible nutrients) was found in forages from semi-closed system (68.9%) and the lowest from closed system (62.5%). The NDFD-48h ranged between 56.7 – 63.4. The highest was recorded for forages from the semi-closed system (63.4%) while the lowest was found in the open system (56.7%). Forage from the semi-closed and closed systems showed greater RFV (relative feed value) over forages from the open system. However, no difference was found between semi-closed (129) and closed system (127).

There was variation in potassium, but no significant differences in phosphorus and calcium concentrations were found in forage across the three grazing systems (Table 2). Forages from both semi-closed and closed grazing systems had the highest and similar potassium content, whereas those of open systems had the lowest.

The soil infiltration rates showed the highest rate for closed system compared to both semi-closed and open systems. The open system recorded the lowest infiltration rate (Figure 1). This indicates that when all systems receive the same amount of water, the closed system infiltrates the water better than the open and semi-closed systems. Overall, the infiltration rates under all three systems are within the ideal ranges for a loam soil (0.2 – 0.4 inches per hr).

Figure 1: Soil infiltration rate (inches per hour) under the three grazing systems (OP, open system; SC, semi-closed system; CD, closed system). — **Figure 1:** Soil infiltration rate (inches per hour) under the three grazing systems (OP, open system; SC, semi-closed system; CD, closed system).

Figure 2: Weekly water consumption by cows within grazing systems — **Figure 2:** Weekly water consumption by cows within grazing systems

More water was consumed under the open system of grazing compared to semi-closed and closed systems (Figure 2). Cows within the open system consumed 6 and 15 gallons of water per week more than those from semi-closed and closed systems, respectively.

Conclusion and Implications

Open grazing systems produced high forage dry matter yield, while nutritive values were consistently superior in forages from both semi-closed and closed systems. This can be attributed to differences in the botanical composition of each grazing system (data not shown here). Additionally, high yields in open systems were influenced by effective photosynthesis under sunlight compared to closed systems, which had limited penetration of sunlight due to tree canopies.

In open systems, cows had no protection from direct sunlight, hence consumed more water during hot days as opposed to the closed and semi-closed systems. Shades from trees provide comfort zones for cows, which encourages more forage consumption, affecting their overall performance.

Soil infiltration improvement under a closed system has important implications for soil management in forage grazing systems. This indicates that when the system receives an amount of rainfall, it infiltrates better compared to open and semi-closed systems. This is crucial for reducing soil loss through erosion.