Journal of Animal Science

Effects of sodium chloride and fat supplementation on finishing steers exposed to hot and cold conditions

J. B. Gaughan * and T. L. Mader **

Abstarc :

Three studies were conducted to evaluate the effects of supplementalfat and salt (sodium chloride) on DMI, daily water intake (DWI),body temperature, and respiration rate (RR) in Bos taurus beefcattle. In Exp. 1 and 2, whole soybeans (SB) were used as thesupplemental fat source. In Exp. 3, palm kernel meal and tallowwere used. Experiment 1 (winter) and Exp. 2 (summer) were undertakenin an outside feedlot. Experiment 3 was conducted in a climate-controlledfacility (mean ambient temperature = 29.9°C). In Exp. 1,three diets, 1) control; 2) salt (control + 1% sodium chloride);and 3) salt-SB (control + 5% SB + 1% sodium chloride), werefed to 144 cattle (BW = 327.7 kg), using a replicated 3 x 3Latin square design. In Exp. 2, 168 steers (BW = 334.1 kg) wereused. In Exp. 2, the same dietary treatments were used as inExp. 1, and a 5% SB dietary treatment was included in an incomplete3 x 4 Latin square design. In Exp. 3, three diets, 1) control;2) salt (control + 0.92% NaCl); and 3) salt-fat (control + 3.2%added fat + 0.92% NaCl) were fed to 12 steers (BW = 602 kg)in a replicated Latin square design. In Exp. 1, cattle fed thesalt-SB diet had elevated (P < 0.05) tympanic temperature(TT; 38.83°C) compared with cattle fed the control (38.56°C)or salt (38.50°C) diet. In Exp. 2, cattle fed the salt andsalt-SB diets had less (P < 0.05) DMI and greater (P <0.05) DWI than cattle in the control and SB treatments. Cattlefed the salt-SB diet had the greatest (P < 0.05) TT (38.89°C).Those fed only the salt diet or only the SB diet had the least(P < 0.05) TT, at 38.72 and 38.78°C, respectively. Underhot conditions (Exp. 3), DMI of steers fed the salt and salt-fatdiets declined by approximately 40% compared with only 24% forthe control cattle. During hot conditions, DWI was greatest(P < 0.05) for steers on the salt-fat diet. These steersalso had the greatest (P < 0.05) mean rectal temperature(40.03 ± 0.1°C) and RR (112.7 ± 1.7 breaths/min).The RR of steers on the control diet was the least (P < 0.05;98.3 ± 1.7 breaths/min). Although added salt plus fatdecreased DMI under hot conditions, these data suggest thatswitching to diets containing the combination of added saltand fat can elevate body temperature, which would be a detrimentin the summer but a benefit to the animal during winter. Nevertheless,adding salt plus fat to diets resulted in increased DWI underhot conditions. Diet ingredients or the combination of ingredientsthat can be used to regulate DMI may be useful to limit largeincreases in DMI during adverse weather events.

Key Word :
beef cattle, environmental stress, fat, salt

Volume 87, Number 2, February 2009