Choosy grazers: Why plants are tasty to cattle and why Highland cattle eat almost everything

Caren M. Pauler, Johannes Isselstein, Matthias Suter, Joel Berard, Thomas Braunbeck, Manuel K. Schneider

On pastures, cattle choose what they eat: they prefer some plants and avoid others. This has consequences for the pasture itself: tasty plants are regularly consumed and may be overgrown by those which are avoided.

Our study, conducted in the Swiss Alps, analysed characteristics of plants that make them tasty or not. Three contrasting breeds of cattle grazed alpine pastures with more than 150 different plant species. We measured their choices and found surprising differences in plant selection among cattle breeds.

Cattle require nutrients, especially phosphorus and nitrogen, to produce milk and meat. Therefore, they select nutrient-rich plants and avoid those with low nutrient content such as mat grass or sedges. However, Highland cattle, an undemanding and low-productive breed originating from the Scottish Highlands, behaved differently from the two more production-oriented breeds: Original Braunvieh and Angus-Holstein crossbreed. Highland cattle ate more nutrient-poor plants. The reason is that they grow slower and produce less milk, and therefore, have less need to select plants of the highest forage quality.

Plants with thin and soft leaves (e.g., dandelion and many grasses) are easier to graze and to digest than those with thick and tough leaves (e.g., shrubs). Thus, cattle prefer soft plants. Cattle also avoid plants that contain toxins (e.g., crowfoot or aconite) or protect themselves from being eaten by thorns or spines (e.g., thistles). Again, Highland cattle cared much less about these constraints and foraged them anyway. One Highland cow ate a whole aconite – one of the most toxic plants in Europe, of which a few grams can kill a man.

Low-productive, traditional breeds like Highland cattle select their forage less strictly than production-oriented, modern breeds. Thereby they prevent the dominance of plant species that are not tasty. Therefore, a higher number of different plant species can survive on their pastures.

Read the paper in full here.


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