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Diet Quality and Performance of Heifers in the Subtropics


This article in AJ

  1. Vol. 94 No. 1, p. 88-95
    Received: May 30, 2000

    * Corresponding author(s): mjwi@mail.ifas.ufl.edu
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  1. Mimi J. Williams *a,
  2. Chadwick C. Chasea and
  3. Andrew C. Hammondb
  1. a USDA-ARS, Subtropical Agric. Res. Stn., 22271 Chinsegut Hill Rd., Brooksville, FL 34601-4672
    b Usda-Ars, Saa, Athens, Ga 30604


The effects of continuous vs. rotational stocking of bahiagrass (Paspalum notatum Flugge), previous winter nutritional regimen {corn (Zea mays L.) + soybean [Glycine max (L.) Merr.] meal (CS) vs. soybean meal (SBM)}, and breed [Angus, Hereford, and Senepol (Bos taurus) and Brahman (B. indicus)] were determined in 1990 to 1992. Forage mass [kg ha−1 dry matter (DM)], forage nutritive value [crude protein (CP) and in vitro organic matter digestibility (IVOMD)], average daily gain (ADG), body weight (BW), body condition score (BCS), and plasma urea N (PUN) and glucose (PGLU) were measured. There was a consistent carryover effect (P < 0.05) of winter supplementation for initial BW and BCS, with CS > SBM while for PUN, SBM > CS. Breed affected most animal variables, with the general ranking of Angus ≤ Hereford ≤ Brahman and Senepol. Forage mass varied from an average of 1000 kg ha−1 in 1990 to 2000 kg ha−1 in 1992 because of rainfall distribution. Grazing treatment did not affect forage DM, CP, or IVOMD, but heifers that were continuously grazed had higher (P = 0.0001) PUN levels than heifers that were rotationally grazed. Only during 1990, when dry weather restricted forage growth, did this translate into a trend for improved ADG and final BW. Because grazing management did not affect heifer performance in most years, the effects noted in this study resulted from: (i) the change in forage nutritive value during the grazing season; (ii) the carryover effect of previous winter supplementation; and (iii) breed differences, particularly temperate vs. tropical breeds.

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Copyright © 2002. American Society of AgronomyPublished in Agron. J.94:88–95.