Influence of sire and maternal grandsire breed on functional and production traits in organic dairy cows.

This study evaluated the effects of sire and maternal grandsire (MGS) breed on functional and production traits of 3,623 lactating dairy cows across 14 certified organic US herds and examined phenotypic associations between these traits and test-day milk performance. Data were analyzed using linear mixed models to compare Holstein (HO), Jersey (JE), Montbéliarde (MO), Red Dairy Cattle (RDC), and other (OT) breed. The HO-sired cows and HO-MGS cows had the greatest milk yield but only marginal advantages in fat and protein yields compared with other breeds. The HO and OT-sired cows exhibited higher fly scores and fly counts. Also, the HO-sired cows had the poorest hygiene among the breeds studied. The MO, and RDC-sired cows had greater BCS and JE cows were shorter and had udder floors closer to their hock. The MGS effects followed similar but weaker trends as the sire breed, with MO and RDC associated with higher BCS and improved hygiene. Regression coefficients show that reduced milk, protein and fat yield were linked to higher BCS, poorer locomotion, and shallow udders, whereas cows with a taller stature had increased yields. The results of this study reveal breed-based differences for production and functional traits in a population of dairy cows housed in an organic and pasture-based production system. This study emphasizes the potential for utilizing genetic differences between breeds to optimize production and functional traits of organic dairy cows and to enhance the sustainability of organic dairy farming.