Oklahoma State University Extension

The most common method to regulate beef cattle 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 (Kunkle et al., 2000).

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 producers (Williams et al., 2018; Wyffels et al., 2020). 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. of bodyweight) were housed in individual pens and randomly assigned to three 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.

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Salt treatments were mixed into a protein supplement of 50% cracked corn and 50% soybean meal and fed at 0.3% of shrunk bodyweight. The salt treatments consisted of: 1) control, no salt (CON); 2) 0.05% of bodyweight salt (LOW), and 3) 0.1% of bodyweight salt (HIGH). Chopped, low-quality grass hay (7.4% crude protein and 64.2% neutral detergent fiber) was used as the base ration and was provided daily at 120% of the average daily intake of the previous three days. The supplement/salt treatments were fed at 8 a.m., 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, six days of sample collection (feed, orts and feces), one day for collection of rumen fluid samples for ruminal fermentation characteristics, and one day of complete ruminal evacuations.

The influence of salt level on intake and digestibility is shown in the Table. Supplemental salt did not influence forage intake (P = 0.19) or total intake (P = 0.20) expressed as pounds per day. However, both forage and total intake expressed as grams per pound of bodyweight 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 approximately 18.8%, with increasing salt levels ranging from 13.43 to 15.95 gal./day.

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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.”

References

¹Kunkle, W.E., 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.

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²Williams, 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.

³Wyffels, 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.

⁴White, 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