Topcross performance of 36 different sire breeds has been evaluated in the ongoing Germplasm Evaluation Program at the U.S. Meat Animal Research Center. Results have provided the basis for classifying the breeds into biological types (Table 1). In the table, increasing Xs indicate relatively greater growth rate and mature size, lean-to-fat ratios, marbling, beef tenderness, age at puberty of females, milk production, and tropical adaptation.
In the 1970s Continental breeds (breeds that originated in Continental Europe; e.g., Charolais, Simmental, Braunvieh, Gelbvieh, Maine Anjou, Chianina) had significantly greater growth rates and heavier body weights at weaning, yearling, and mature ages than British breeds (originating in the British Isles, e.g., Angus, Hereford, Shorthorn, Red Poll). However, recent results indicate that British breeds are comparable to Continental breeds in growth rate. The advantage of Continental breeds over British breeds in retail product yield is about the same today as in the early 1970s. British breeds, especially Angus, Red Angus, and Shorthorn, still excel in marbling, relative to Continental breeds. Bos taurus breeds have advantages over Bos indicus breeds or Bos indicus-influenced breeds (Brangus, Beefmaster) in tenderness of longissimus steaks.
Females sired by breeds with large mature size and relatively high lean-to-fat ratios (e.g., Chianina, Charolais) have tended to be older at puberty than those sired by breeds of smaller mature size and greater propensity to fatten. However, the relationships between mature size and age at puberty can be offset by increased genetic potential for milk production. Breeds that have been selected for milk production reach puberty earlier than breeds that have not been selected for milk production. Bos indicus breeds (Brahman, Nellore, Sahiwal, Boran) reach puberty at older ages than Bos taurus breeds.
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