Characterization of topcross progenies from Hereford, Limousin, and Piedmontese sires

Breeds of larger mature size tend to grow more rapidly and be older when at taining a given level of fatness. Hereford, Limousin, and Piedmontese are o f approximately equal mature size and yet may vary in body composition at a given degree of maturity. However, direct comparisons among these three br eeds were not found. Therefore, the objective of this research was to compa re Hereford, Limousin, and Piedmontese progenies for economically important traits. Crossbred cows were bred to Hereford (n = 23), Limousin (n = 24), or Piedmontese (n = 24) sires. Male calves were either left intact or castr ated at approximately 2 mo of age. Calves remained with their dams until we aning at an average age of 179 d. Male calves were then individually fed a growing ration until they reached 386 kg and then fed a finishing ration ei ther 90 or 132 d. They were then slaughtered at a commercial abattoir and c arcass data were collected, Female calves were group-fed and used to examin e nutritional effects on age at puberty. Data were analyzed using REML and linear contrasts among the breed-of-sire effects evaluated. Hereford-sired calves had shorter gestation periods and weighed less at birth than either Limousin- or Piedmontese-sired calves. Calving difficulty of Hereford- and Limousin-sired calves was less than that of Piedmontese-sired calves. Limou sin-sired calves tended to grow more rapidly than Hereford-sired calves. By the finishing phase, Limousin- and Hereford-sired calves had greater avera ge daily gains than Piedmontese-sired calves. Differences in dry matter int ake among breeds of sire were relatively small. Differences in carcass weig ht, longissimus muscle area, fat depth, and percentage kidney, pelvic, and heart fat resulted in a clear stratification of USDA yield grade between br eeds of sire. Differences in percentage primal cuts were similar to those f or USDA yield grade. Hereford-sired calves had more marbling than progeny o f Limousin or Piedmontese sires. However, the force necessary to shear core s from steaks of Piedmontese-sired calves was less than for progeny of Limo usin or Hereford sires. Hereford- and Piedmontese-sired heifers were younge r at puberty than Limousin-sired heifers. Within breeds of similar mature s ize and growth rate, ample variation exists in age at puberty and body comp osition at an approximately equal degree of maturity.