| Three experiments were conducted to evaluate the performance of dairy and beef heifers. In Experiment 1 the effects of Jose tall wheatgrass ( Agropyrum elongatun) and kleingrass (Panicum coloratum L.) grazed alone or in combination with alfalfa (Medicago sativa) were evaluated. Ninety-four heifers grazed from April 15 through Oct. 28, 1998 and from April 8 through Nov. 25, 1999 one of four replicated pastures: (1) Jose tall wheatgrass (JTW), (2) 50% JTW + 50% alfalfa (JTWA), (3) kleingrass (KG), or (4) 50% KG + 50% alfalfa (KGA). In both years, herbage mass availability of JTW was greater (P < 0.03) than JTWA, KG or KGA. Average daily gain did not differ (P > 0.05) among treatments in Year 2. In Experiment 2, the effects of dietary protein level to ME on growth, puberty, and mammary development were evaluated in Holstein heifers. Twenty-four Holstein heifers (initial BW = 143 +/- 13 kg) were individually fed a 52:48 concentrate:roughage diet with increasing CP:ME (46, 53, 61 and 68:l; g CP/Mcal ME) until they reached puberty.{09}Final BW was greater (P = 0.02) in heifers consuming 61:1 CP:ME compared with 46, 53, or 68:1 CP:ME (376 > 346, 366 and 352 +/- 13). Average daily gain was not influenced (P > 0.05) by increasing CP:ME, but it was influenced by time (P < 0.01).; In Experiment 3 the relationships of metabolic hormones and serum glucose to growth and reproductive performance were evaluated in Angus, Brangus and Brahman heifers fed ad libitum for maximal performance. Twenty-four heifers (n = 8 per breed) were fed an alfalfa corn-based diet. Initial and final BW for Angus, Brangus and Brahman, heifers was 313, 287, 247, +/-9, and 421, 392, 332, +/-9 kg. In parallel, serum concentrations of the adipose derived hormone leptin were greater (P ≤ 0.05) In Angus (4.4 +/- 0.2) than In Brangus and Brahman heifers (3.1 and 2.9 +/- 0.2) throughout the study. Conversely, serum concentrations of GH (P < 0.13) and glucose. (P < 0.05) tended to be greater in Brahman heifers relative to Angus and Brangus whereas serum concentrations of IGF were greater (p < 0.05) in Brangus and Brahman compared to Angus heifers. Puberty was observed in 75% of the Angus 75% of the Brangus and none 0% of Brahman heifers during the study. |
