Grazing Trials

Stocking density is a term used in the animal agriculture industry to define the number of pounds of animal mass present on a single acre of land (expressed as lbs./ac). A higher stocking density means that there are more animals present per available acre of land. Some forms of intensive grazing management utilize a higher stocking density on a smaller area of land to get more uniform grazing. The key to this type of grazing system is determining the time period that results in half of the plant material being consumed by the cattle, while the other half is left standing or trampled into the ground. The trample effect of the leftover plant biomass, plays a large role in soil health by putting nutrients back into the soil supporting future growth.

            Here on Grant Ranch, we have recently conducted a trial using 670 head of yearling steers to determine the optimal time of adequate grazing and trampling effect. The objective of this trial was to have a very high stocking density, of over 300,000 lbs./acre, to observe the grazing patterns and trample effect. Photographs were taken of the grass before cattle entry and again after the allotted time of grazing, using a knife as reference for plant height. Sections were separated using electric fence and cross fences were picked up when cattle were moved to the next paddock. Back fences, to prevent the cattle from going back to the previous paddock, were not used in this trial as water access would have been cut off with the use of back fences. Majority of the paddock were an acre and a half sections and cattle were left on that section for forty-five minute to an hour and a half depending on the biomass of the paddock prior to entry.

            From observation and photographic sampling prior and post grazing, we have determined that the expected more uniform graze from less headspace was not seen with this stocking density. Cattle were still able to move around for more palatable feed and consume more than half of those plants compared to the less palatable. It was also observed that the trampling effect was not seen in majority of the paddocks. However, paddocks that contained lower areas with swamp type grass were laid in more often than other areas of the paddocks, resulting in more trampling effect on those areas of land. Observation will continue as regrowth occurs to determine the effect of the increased stocking density on total biomass and regrowth that occurs.

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