Can cattle learn to eat weeds in the field?
Cattle can in some situations learn to eat weeds directly in the field using a relatively simple method of adaptation.
A pilot study on “Interactions between animals and plants – focusing on the weed dock (Rumex crispus & Rumex obtusifolius),” has shown that cattle can learn to eat docks directly in the field by means of a relatively simple method of adaptation. From nature’s side, cattle are rigid when it comes to feed preferences; however, by means of this method, they can expand their feed preference to include weeds like docks.
Docks are hard to control
Controlling docks in grassland areas is hard, and it includes both control of the mature plant and avoidance of seed setting and new sprouting. The most often used methods when trying to control docks are to use herbicides or to do a complete reseeding of the affected area.
Need for alternative methods
There is a need for alternative methods for how to control docks. This applies especially to organic farmers who are not allowed to use herbicides, but also to farmers using grazing cattle for nature management in areas where they are not allowed to use herbicides or to reseed the areas.
Test of method of adaptation using beef cattle
Originally, the American Kathy Voth invented the method, which was adopted to the conditions and limitations in this pilot study, conducted during two summer periods in 10 beef cattle herds. The method of adaptation was running for seven days, of which feed will be provided twice daily during the first three days in troughs placed in the field. During the last four days, feed will be provided once daily in the field. During the seven days, various feed topics were introduced as a snack to expand the animals’ choice of feed. Along the way, the type of weed that is intended to learn the animals to graze was also introduced, to accustom the animals to the taste and texture of the weed.
The experiment defined three general criteria for success:
1st criterion for success: Can the cattle learn to eat the docks provided in feed troughs?
2nd criterion for success: Can the cattle learn to eat the docks directly from the field?
3rd criterion for success: Do cattle, who have learned to graze docks, still include docks in their feed preference after a period of stay in the stables or in other fields without docks?
The method of adaptation was implemented with success
It turned out that in all herds cattle learned to eat docks in the trough, while in two of the cases, cattle learned to eat docks directly in the field. The herds where cattle learned to eat docks in 2019 were visited again in 2021, and it turned out that in one of the herds the cattle still grazed docks thus having docks as part of their feed preference after two periods with indoor feeding.
It seems that the greatest success is achieved if the amount of docks in the field is relatively high. In the successful cases, the proportion of docks accounts for around 20% of the area of the field. Furthermore, the best results were achieved if the leader of the herd, e.g. an older cow or bull, shows interest in the docks fed in the troughs and in the end is one of the animals that learn to eat docks directly from the field.
Docks have a relatively high content of oxalic acid. If grass or other feed topics are also available together with the grazing of the docks, the intake of oxalic acid does not pose a problem according to the literature.
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Type of study
The study is elaborated as a finishing master project from the master education in agrobiology from Aarhus University.
The project is partly funded by Velas and Landboforeningen Kronjylland.
The project has been written in cooperation with Velas.
Troels Kristensen, Department of Agroecology, Aarhus University, and Martin Riis Weisbjerg, Department of Animal Science, Aarhus University, have been supervisors on the project.
Marianne Sjuve Seekjær
Troels Kristensen, Institut for Agroøkologi, Aarhus Universitet