Impact of increasing levels of NaCl in drinking water on the intake and utilization of low-quality forages by beef cattle hand-fed a protein supplement or protein supplement containing 25 percent salt

Water is one of the most important nutrients for livestock production (Petersen et al., 2015), but often overlooked in western range settings. Water is required for digestion, rumen fermentation, body temperature regulation, and reproduction (National Academies of Science, E., and Medicine [NASEM], 2016). Many factors influence water requirements including size, lactation status, forage base, activity, external temperature, and water quality (NASEM, 2016). Water sources, such as streams/rivers, ponds/reservoirs, springs, and tanks, can vary greatly in quantity and quality (Petersen et al., 2015). In addition, this variation of water quality can also be affected by geographical location, year, precipitation, season, recharge site, and soil composition (Anderson and Woosley, 2005; Petersen et al., 2015). High concentrations of salts in water are most common in arid and semi-arid regions (Beke and Hironaka, 1991). In Montana, high sodium chloride (NaCl) is common in livestock water, especially during drought years (Petersen et al., 2015). In a survey of livestock water sources, Petersen et al. (2015) reported 42% of samples exceeded the maximum upper limit for sodium in livestock. In addition, total dissolved solids (TDS) in water during drought years were increased. It is generally accepted that total soluble salt levels at or below 3,000 mg/L may be refused but are tolerable; however, levels above 7,000 mg/L could potentially be toxic (Beke and Hironaka, 1991; NASEM, 2016). Still, little research has been done to establish these levels and examine the impacts increasing NaCl levels in water have on cattle performance (Tomlinson et al., 2003; NASEM, 2016). In addition, forage is also low quality in arid and semi-arid regions. Self-fed supplements are common to provide minerals, vitamins, and protein for grazing cattle. Furthermore, NaCl is the most common supplement limiter (Cardon et al., 1951; Meyer et al., 1955; Berger and Cunha, 1993) with 25% salt being common. However, salt limited supplement intake can be highly variable (among animals and across days) with daily intakes often exceeding 5 kg of supplement (Wyffels et al., 2020). Thus, self-fed delivery systems utilizing salt as an intake limiter can result in high salt intake that may impact the use of low-quality forages (White et al., 2019). Previous research suggests that NaCl in small amounts within the diet does not alter protein, cellulose, and/or gross energy digestibility, but amounts > 1% can decrease forage intake and weight gain (Weeth et al., 1960). However, little to no research exists on the impacts of NaCl from supplements and water on low-quality forage intake and use. Therefore, the objectives of this study were to evaluate how increasing levels of NaCl in water and supplement delivery impacts forage intake, water intake, digestibility, and rumen fermentation of beef cattle consuming high-fiber, low-quality forages. We hypothesized that increasing levels of NaCl alters forage and water intake, as well as rumen fermentation.

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