An observational study on the effects of dam breed and individual Belgian Blue sire on carcase traits and retail cut yields in beef × dairy crossbred heifers produced in mountain farms

Beef-on-dairy production enables the combination of high milk yield with the production of high-value crossbred calves. As a consequence, this practice may be particularly relevant for improving the sustainability of low-input mountain farms. However, the influence of the dam breed remains poorly understood. This study evaluates the effects of specialised dairy and dualpurpose dam breeds crossed with Belgian Blue (BB) sires on growth performance, carcass weight, and yield of individual retail cuts in 3,443 crossbred heifers born in 441 dairy farms, weaned in 7 specialised weaner farms, and fattened in the same intensive farm. The heifers were sired by BB bulls on Holstein Friesian, Brown Swiss, Simmental, Alpine Grey, Rendena, and dairy Crossbred dams. Compared with the individual sire effect, dam breed exerted a stronger influence on most carcase traits, particularly first-quality retail cuts (p<0.001). Heifers from dualpurpose dams, especially Simmental, showed heavier carcase and individual retail cuts than specialised dairy dams (p<0.01), which instead produced earlier maturing crossbreds (p<0.001). Conversely, heifers from local Alpine dual-purpose dams (Alpine Grey and Rendena) displayed higher percentage of first- and second-quality cuts on arcase weight and reduced trimming losses (p<0.01). Selection criteria for BB sires should therefore consider traits supporting the carcase weight, to enhance carcase performance and overall market value in crossbred heifers within each dam-breed context. The results reinforce the growing interest in beef dairy crossbreeding and highlight the importance of local breeds in supporting the economic resilience of mountain dairy systems.