Milk Yield and Quality in Cows Sired by Different Beef Breeds12

Breed differences in milk production and milk quality are related to differences in calf preweaning growth, differences in cow maintenance requirements, and differences in efficiency of production. Cows from Brangus dams and sired by 12 Bonsmara, 12 Brangus, 15 Charolais, 18 Gelbvieh, 13 Hereford, and 13 Romosinuano sires were sampled in 2005 (n = 45), 2006 (n = 50), 2007 (n = 53), and 2008 (n = 50) to evaluate sire breed differences in milk yield and quality. There was little evidence of daily milk yield differences among cows sired by Bonsmara, Brangus, Charolais, Gelbvieh, or Hereford sires, but Romosinuano-sired cows produced less milk (P < 0.05) than the other breed groups. Gelbvieh-sired cows had less milk fat than Bonsmara-, Charolais-, Hereford-, and Romosinuano- sired cows (P < 0.05) but not Brangus-sired cows. Percentage of milk protein was greater in Romosinuanosired cows than in Brangus-, Charolais-, Gelbvieh-, and Hereford-sired cows (P < 0.05), whereas percentage of milk protein was greater in Bonsmara-sired cows than in Charolais- and Gelbvieh-sired cows (P < 0.05). Percentage of milk lactose was similar for Bonsmara- and Romosinuano-sired cows, which both had greater percentages of milk lactose than Hereford-sired cows (P < 0.05). Somatic cell counts for Romosinuano-sired cows were less than those of Bonsmara-, Charolais-, Gelbvieh-, and Herefordsired cows (P < 0.05) but not Brangussired cows. The lack of differences in milk yield among the sire breeds, with the exception of Romosinuano, suggests possible nutritional limitations on native rangeland that prevent expression of the full genetic potential for milk yield. The lower milk yields and SCC in the Romosinuano suggest possible advantages for this breed in efficiency of production and mastitis resistance.