Nutritional Limitations of Free-Ranging Cattle: The Importance of Habitat Quality

The nutritional limitations of free-ranging cattle were examined in relation to variations in habitat quality. Twenty steers were allocated to four different treatments over 2 years: year-round grazing on heathland with low soil fertility; year-round grazing on riverine grassland with high soil fertility; summer grazing on riverine grassland (April-November) and winter grazing on heathland (December-March) (control); and year-round grazing in an area with heathland and riverine grassland combined. 2. The nutritional budget for nitrogen (N), sodium (Na), phosphorus (P) and calcium (Ca) was calculated by quantifying forage intake and quality. Energy intake was estimated from digestible organic matter intake. Animal condition was measured by live weight change, condition score, saliva samples, fat reserve estimation with the deuterium oxide method and rib bone analysis after slaughter. 3. Forage intake and quality showed significant monthly variation. Dry matter intake was lower for the steers of the combination treatment than for other treatments. Forage quality was significantly higher in riverine grassland than on heathland. 4. Metabolizable energy-intake per unit gain was higher on heathland than for the other treatments. The implied reduction in energy retention suggests an impaired digestive efficiency. The nutrient balance was poorest on heathland, intermediate, but always positive in the control and combination treatments, and best in the Riverine treatment. 5. Requirements for the heathland animals were approximately met for N and Ca, but not for Na and P. As a consequence, heathland animals showed various signs of malnutrition: lower weight gain in summer and higher weight loss in winter, apparent deficiencies of Na and P, lower condition scores and fat reserves, and pica behaviour (geophagia, osteophagia and carnivory). 6. The significance of differences in soil fertility is discussed with respect to the performance and survival of large herbivores in homogeneous or heterogeneous habitats.