Month: October 2024

Phillip Lancaster, MS, PhD Ruminant nutritionist Beef Cattle Institute Kansas State University palancaster@vet.k-state.edu

Pasture management is a key component to cow-calf production systems by affecting the carrying capacity of grasslands but also the ability of forage to meet the nutritional requirements of cattle. A lot of focus has been on management intensive grazing (e.g., rotational grazing, adaptive multi-paddock grazing, etc.) and its ability to maintain or increase the ecosystem function and productivity of rangelands. However, another important component of rangelands is fire.

A recent study evaluated the effects of patch-burning on forage nutritive value, animal grazing distribution, and animal performance. Patch-burning is a practice where only a section of the pasture is burned every 3-5 years rather than burning the entire pasture at once. This creates an array in grazing pressure across the pasture, adds heterogeneity to the landscape for different wildlife species, helps control undesirable plants, and leaves plant residue to increase organic carbon back into the soil. In the study, continuous grazing management was used with patch burning treatment and was compared with continuous and rotational grazing management systems without fire in mixed grass rangeland. Each of the 3 treatments had 4 pastures and Angus cow-calf pairs were used to graze the pastures over a 4-year period. The rotational grazing system was a seasonal rest-rotation within a twice-over rotational system.

In the year of burning, patch-burned sites had improved crude protein, acid detergent fiber, and neutral detergent fiber digestibility of forage than continuous and rotational grazing systems without fire. Patch-burned sites that were burned 1 to 3 years prior also had improved forage nutritive values compared with continuous and rotational grazing systems without fire. Only the unburned site in the patch-burned treatment had lower forage nutritive value than the continuous and rotational grazing systems without fire. The rotational grazing system had improved forage nutritive value than the continuous grazing system.

In the patch-burned treatment, cattle spent more time in the most recently burned section of the pasture most likely due to the increase forage nutritive value. Additionally, the most recently burned section had the greatest proportion of forage samples that met or exceeded the nutrient requirements of cows (Figure 1). This resulted in cows in the patch-burn treatment gaining > 0.4 lb/d compared with < 0.2 lb/d for cows in the continuous and rotational grazing treatments without fire. Thus, the need for protein supplementation of cow-calf pairs may be decreased when patch-burn grazing is used.

In conclusion, patch-burning can be used to improve forage nutritive value for grazing cattle in continuous grazing systems compared with rotational grazing systems. Patch-burning can also be used to concentrate grazing on different sections of the rangeland over time because cattle will preferentially increase time spent in the most recently burned section of the rangeland. Additionally, patch-burning is a good management practice to blend cattle production with wildlife conservation goals.

Figure 1. The proportion of forage samples meeting or exceeding nutrient requirements for protein and energy of 1250-lb cow producing 18 lb/d at peak milk. Adapted from Wanchuk et al., (2024; https://doi.org/10.1016/j.agee.2024.109004)