Extension

The most common method to regulate intake of self-fed supplements is the use of salt since it is readily available, generally safe, and the salt level can be modified to achieve desired levels of intake.¹ However, research has demonstrated that the daily individual intake of salt-limited supplements can be highly variable which can reduce animal performance and/or decrease profit margins for the producers.^{2, 3} Little is known about the effects of high salt levels on subsequent intake and digestion of low-quality roughages. Recent Montana State University research evaluated the impacts of increasing supplemental salt levels on forage intake, water intake, digestibility, and rumen fermentation of beef cattle consuming high-fiber, low-quality forages.

 

In this study, six ruminally cannulated Angus crossbred heifers (14 months of age; 831 lb body weight [BW]) were housed in individual pens, and randomly assigned to 3 supplemental treatments in a dual 3 x 3 Latin square design. Two animals were assigned to each treatment per period. Prior to the initiation of each period of the Latin square, all heifers were weighed following a 16 hour shrink. Salt treatments were mixed into a protein supplement of 50% cracked corn and 50% soybean meal and fed at 0.3% of shrunk BW. The salt treatments consisted of 1) control, no salt (CON), 2) 0.05% of BW salt (LOW), and 3) 0.1% of BW salt (HIGH). Chopped, low-quality grass hay (7.4% crude protein and 64.2% NDF) was used as the base ration and was provided daily at 120% of the average daily intake of the previous 3 days. The supplement/salt treatments were fed at 8:00 AM and then after total consumption of supplement, the basal hay diet was offered. The diets were formulated to meet or exceed nutritional requirements for yearling heifers gaining 1.10 lb/day. Before the start of the experiment, heifers were adapted to a salt-limited (25% salt) supplement for 14 days prior to the initiation of the trial. Each 22-day period included 14 days of diet adaptation, 6 days of sample collection (feed, orts, and feces), 1 day collection of rumen fluid samples for ruminal fermentation characteristics, and 1 day of complete ruminal evacuations.

 

The influence of salt level on intake and digestibility is shown in in Table 1. Supplemental salt did not influence forage intake (P = 0.19) or total intake (P = 0.20) expressed as lb/day. However, both forage and total intake expressed as grams/lb BW tended to decrease linearly (P = 0.06) with increasing levels of salt in the supplement. In contrast, water intake increased linearly (P < 0.01) by ~18.8% with increasing salt levels ranging from 13.43 to 15.95 gallons/day.

 

¹ Salt levels include 1) CON, no salt, 2) LOW, 0.05% of BW, and 3) HIGH, 0.1% of BW.
² Treatment main effect.
³ Linear preplanned contrast.
⁴ Quadratic pre planned contrast.

 

Adapted from White et al., 2024.

 

These researchers also reported that ruminal pH and ammonia levels both decreased linearly with increasing salt (P < 0.01). Acetate concentration and acetate: propionate ratio increased linearly with increasing levels of salt (P < 0.01). In contrast, isobutyrate and butyrate concentrations decreased linearly with increasing levels of salt (P < 0.01).

 

They concluded that these “results demonstrate that high salt diets alter rumen function by impacting digesta kinetics and ruminal fermentation. While salt may be a tool to assist in supplement intake regulation, the addition of dietary salt may also result in lower intakes and less efficient rumen fermentation of beef cattle consuming low-quality forages.”

 

¹ W. E. Kunkle, J. T. Johns, M. H. Poore, and D. B. Herd. 2000. Designing supplementation programs for beef cattle fed forage-based diets. J. Anim. Sci. 77 (E-Suppl.):1–11.
² Williams, G. D., M. R. Beck, L. R. Thompson, G. W. Horn, and R. R. Reuter. 2018. Variability in supplement intake affects performance of beef steers grazing dormant tallgrass prairie. Prof. Anim. Sci. 34:364–371.
³ Wyffels, S. A., J. M. Dafoe, C. T. Parsons, D. L. Boss, T. DelCurto, and J. G. P. Bowman. 2020. The influence of age and environmental conditions on supplement intake by beef cattle winter grazing northern mixed-grass rangelands. J. Anim. Sci. 98:1–8.
⁴ White, H. C., N. G. Davis, M. L. Van Emon, H. M. DelCurto-Wyffels, S. A. Wyffels, and T. DelCurto. 2024. Impacts of increasing levels of salt on intake, digestion, and rumen fermentation with beef cattle consuming low-quality forages. J. Anim. Sci. 102. Available at: https://doi.org/10.1093/jas/skae284