Two autoctonous beef cattle breeds with different body size were managed in two different hill vegetation covers. The principal species in the vegetation community were Agrostis-Festuca-Nardus and Calluna vulgaris. Seventy four Asturiana de los Valles (AV) beef cows (56 suckling and 18 dry) and other seventy four Asturiana de la Montaña (AM) beef cows (46 suckling and 28 dry) were al located in two plots with different C. vulgaris cover 30% of the total area (C₃) or 70% of the total area (C₇).
There were not significant differences between breeds in live weight changes, milk production and calves live weight gains. However vegetation cover affected significantly (p<0.001) in either cow live weight and body condition changes as on calves live weight gains. Significant (p<0.01) interaction between breed and vegetation cover on live weight changes during the second half of the grazing season (August to September: period 2) were observed, and also between breed and physiological status (p<0.05). In that less favoured condition (treatment C₇ period 2) cows of AM breed had better live weight changes than AV cows, however on treatment C₃ in either period 1 or 2 AV cows had slightly better total body weight changes than AM cows.
In conclusion, cattle breed must be chosen considering vegetation availability and enviroment and market conditions, being in general the breed with smaller body size the most apropiated for those less favoured conditions, but not when pasture availability is high.