COMPARISONS AMONG TULI-SIRED, BRAHMAN-SIRED, AND ANGUS-SIRED HEIFERS - INTAKE, DIGESTA KINETICS, AND GRAZING BEHAVIOR

As part of an evaluation of Tuli crossbred cattle, forage intake, dige sta kinetics, and grazing behavior were estimated in two Texas environ ments. In humid east Texas, Tuli x Brahman heifers were compared with purebred Angus and Brahman and Angus x Brahman heifers. Fecal output, forage intake, compartmental mass, and compartmental residence time di d not differ among breeds. Angus and Brahman heifers had different (P < .02) gastrointestinal residence times (51.1 +/- 1.56 vs 43.1 +/- 1.5 6 h, respectively), but values for the purebreds did not differ from t hose for Tuli x Brahman or Angus x Brahman heifers. Angus heifers had shorter (P < .05) 24-h grazing times (398 +/- 15.4 min/d) and fewer (P < .05) grazing periods (7 +/- .4) than Tuli x Brahman (552 +/- 16.8 m in/d and 10 +/- .4), Angus x Brahman (507 +/- 18.4 min/d and 9 +/- .5) , and Brahman (560 +/- 16.8 min/d and 9 +/- .4, respectively) heifers. In semiarid southwest Texas, Tuli x Angus heifers were compared with purebred Angus and Brahman and Brahman x Angus heifers. Fecal output a nd forage intake were similar in Tuli x Angus and Brahman x Angus heif ers (14.2 +/- .69 and 14.9 +/- .91 g fecal DM/[d.kg BW] and 24.5 +/- 1 .33 and 25.6 +/- 1.75 g/d of forage DMI, respectively) but higher (P < .05) than those of purebred Brahman heifers (12.2 +/- .64 and 20.3 +/ - 1.23 g/[d.kg BW] of fecal DM and forage DMI, respectively). Grazing times did not differ among breeds. We conclude that Tuli-sired heifers are likely to be as productive as Brahman crossbred heifers in Texas, based on the similarities in intake, digesta dynamics, and grazing be havior.