Diet quality affects water and feed utilisation in beef heifers drinking high-sulfate water

Context Consumption of water with high sulfate concentrations can negatively affect on feed intake in beef cattle. However, limited information is available on how water quality interacts with diets differing in digestibility. Aim This study evaluated the interaction between a broad range of diet quality (DQ) and water quality (WQ) on feed and water intake (WI), total tract digestibility, nitrogen (N) metabolism, and ruminal hydrogen sulfide (H2S) production in beef heifers. Method Eight Braford-crossbred heifers (326 ± 34 kg BW) were used in an eight-treatment crossover design combining two types of WQ, namely, low-sulfate water (LSW; 333 mg/L sulfate, SO4) and high-sulfate water (HSW; 3286 mg/L, SO4) with four DQ of low (LQ), medium–low (MLQ), medium–high (MHQ), and high (HQ). Key results A significant DQ × WQ interaction was observed for WI (P = 0.04), digestible organic matter (OM) intake (DOMI; P = 0.01), and digestible neutral detergent fiber (NDF) intake (DNDFI; P 0.01). Diet quality had a quadratic effect on both water (P = 0.02) and feed intake (P 0.01), with the highest values occurring at intermediate levels of digestibility. High-sulfate water reduced WI (P 0.01), OM intake (OMI; P 0.01), and NDF intake (NDFI; P 0.01). In heifers consuming HSW, DOMI tended to be lower at the highest DQ (HQ; P = 0.07), with lower values also observed at intermediate DQ levels (MLQ and MHQ; P 0.01). Water quality improved and tended to enhance total tract NDF (P = 0.03) and OM digestibility (P = 0.06) respectively. High-sulfate water also increased ruminal H2S concentrations (P 0.01). Conclusions The results of this study demonstrated an interaction between diet and water quality affecting feed intake in beef heifers. Implications Improving diet quality may help mitigate the negative effects of high sulfate-containing water on feed intake. Additionally, incorporating highly digestible NDF into the diet appears to be a viable strategy to maintain ruminal H2S concentrations below toxic thresholds.