Selection for beef traits and calving performance in Piemontese cattle

Beef cattle selection programmes are usually focused on the improvement of production traits. However, also functional traits play an important role for the efficiency of animal production. Among these traits calving performance, affecting stillbirth of calves, fertility of cows, animal welfare and consumers' perception of products is particularly relevant for specialized beef cattle breeds.<span style='mso-spacerun:yes'> </span>The aim of this thesis was the development of a programme for the improvement of calving performance and beef traits through selection in the Italian Piemontese cattle population. The breeding goal has been defined using both economic and biological approaches. The effect of production circumstances on the estimated economic and biological values has been discussed. Genetic parameters for calving performance have been estimated using animal models including direct and maternal additive genetic effects. Estimated heritabilities ranged from 0.05 for maternal effect in cows to 0.19 for direct effect in heifers. Direct and maternal effects showed strong negative genetic correlations. Estimated genetic relationships between calving performance and beef production traits were generally unfavourable, requiring the development of a specific selection strategy.<span style='mso-spacerun:yes'> </span>Alternative breeding programmes have been implemented and compared in term of response to selection. Genetic improvement of beef traits and direct calving performance was obtained while maintaining the current genetic level of the population for maternal calving performance. The improvement of phenotypic expression of calving performance could only be achieved by including direct and maternal effects both in the breeding goal and in the index. Strategies allowing a reduction of generation interval proved to be crucial to allow genetic gain for beef traits. The selection of specialized paternal and maternal lines to be crossed increased the overall economic response of 20%. This scheme was the recommended strategy to select beef traits and calving performance, when allowed by the social structure of farms