Take Half and Leave Half: Pasture Management for Sustained Productivity

"Take half and leave half" is a grazing expression used to define a particular grazing management strategy. It is a broad declaration but can be utilized as an excellent starting point for an effective pasture management strategy.

Grazing management encompasses both animal and plant management. By leaving approximately half of the plant material after a grazing pass, ample green leaf remains for photosynthesis to occur and grow more leaves and roots. Leaves capture sunlight, while roots capture moisture and nutrients that are in the soil water. The ability of a plant to maintain high production levels through adequate photosynthesis is very important to growth efficiency.

In a recent study from Argentina, it was suggested that cattle bite into the top half of the canopy that exists in the pasture - whether it is tall or very short. Half of a tall plant will certainly be much greater than half of a short plant. This suggests that when plants are left tall, even when cattle graze half of the plant, plenty remains for regrowth. On the contrary, when half of a short plant is grazed, cattle are consuming much less forage and in addition, the plant will suffer the effects of over-grazing (low productivity).

Beef cow eating on pasture

Figure 1. Cattle take 25,000 to 30,000 bites per day.

Animal intake is largely influenced by bite size and bite rate. Efficient feed intake can be optimized by controlling these factors. Animal performance relies on adequate intake. On average, cattle bite about 25,000-30,000 times per day, and in ideal situations, it has been shown that they will spend about 6.5-7 hours per day at a feed bunk in order to meet their intake requirements. Animals that need to search for food will graze considerably longer, but usually no more than 10 hours per day. This negatively affects the animal's ability to rest. They need to rest and ruminate to digest the feed that they have ingested throughout the day. Longer rest times correlate to more efficient animal productivity.

With a set number of animal bites per day, the pasture manager needs to ensure each bite is as big as possible. If the bites are small, the animal will require more bites per day to meet intake demands and will experience decreased rest times. Offering grass or forage that allows for a big bite size will optimize animal intake, resulting in more optimum performance

Herd of beef cattle on pasture

Figure 2. Thick, vegetative pasture will provide optimum intake for cattle.

As mentioned, the "take half and leave half" concept is not always accurate or complete, but it provides an excellent reference for developing a successful management system. Once you are able to manage your pastures in this fashion, you will be able to successfully tweak the system to meet specific challenges that you are presented with.

For example, in situations where the pasture is very thick and vegetative, there is an opportunity to take more than half of the available forage. In this circumstance, when more than half of the forage is removed, there would still be a large amount of green leaves remaining to support continued plant growth and provide ground cover in order to help prevent the soil from drying out or becoming heated. When the ground is not adequately covered and bare soil is exposed, sunlight is able to reach it and heat the ground, accelerating evaporation of moisture from the soil. The cool season grass species that predominate in Ontario pastures have reduced growth rate when soil temperatures are too warm.

On the other hand, in pastures that are sparse and thin, taking half may compromise the ability of the remaining plant life to rebound, especially when challenging soil conditions or climate are a factor. In these conditions, you want to leave as much material as possible to regrow, providing ground cover and litter to protect the soil.

Essentially, the most important factor to consider is the amount of green leaf area left relative to total production. In difficult growing conditions, leaving more forage will put less stress on the desirable plant species and aid in their recovery from grazing. In this type of situation, the pasture manager should do everything possible to assist growth and improvement of the pasture, which means reducing the stocking rate.

In conclusion, "take half and leave half" is an excellent guideline and a great starting point. From this starting point however, the pasture manager must adjust for individual conditions of the pasture and growing environment. To develop and maintain a healthy productive pasture, the pasture manager must focus on the plant requirements first and adjust the animal numbers to the available forage.

The Grazing Index from Agriculture and Agri-Food Canada is a good reference.

Although this link is focused on western range management it provides some good information that is applicable to all pasture scenarios.

For more information:
Toll Free: 1-877-424-1300
E-mail: ag.info.omafra@ontario.ca