PSVI-18 Water intake analysis of high-risk beef calves.

Abstract Water is a critical factor in livestock health and performance. While water intake (WI) models exist for most beef cattle categories, limited research has focused on newly received calves at an individual level. This study analyzed WI, dry matter intake (DMI), average daily gain (ADG), and mortality status in 160 high-risk heifers (205 ± 17 kg of body weight) purchased from different sale barns. Heifers were randomly assigned to four pens (270 m² each), with six Vytelle Sense bunks per pen. Two bunks were filled with water daily, and WI was recorded gravimetrically. Water was collected weekly using a measuring cylinder and weighed on an electronic scale to determine density. Gravimetric WI data were converted to L using average bunk water density. The remaining four bunks in each pen contained a diet with 16% CP and 1.05 Mcal of NEg/kg diet DM to measure DMI. Heifers were weighed on d 0, 30, and 60. A multiple regression analysis using general linear models assessed WI predictors, including DMI, coat type (proxy for breed), and mortality. Variance Inflation Factor (VIF) checks confirmed collinearity was not an issue. Some environmental factors were excluded due non-significance, probably due to shade and fans mitigating their effects in these facilities, except for the Temperature-Humidity Index (THI). Body weight, ADG and antibiotic treatment history (number of pulls) were removed from the model via stepwise selection due to non-significance. The model (R² = 0.38) identified DMI (P < 0.01), coat type (P < 0.01), and mortality (P = 0.04) as significant WI predictors. Each 1 kg increase in DMI corresponded to a 2.32 L increase in WI. Black and black white-faced heifers had greater WI than white-coated heifers (7.0 L difference at a given DMI). When grouping heifers by health status, heifers that died had a different intercept and slope, with DMI explaining 52.6% of WI variability, whereas in the healthy group, DMI explained 17% of the WI. In deceased animals, the WI intercept was 2.39 L (P < 0.01), and WI increased by 3.3 L per kg DMI. In healthy animals, the intercept was 9.3 L (P < 0.01), and WI increased by 2.2 L per kg DMI. These findings highlight DMI as a key driver of WI in high-risk calves and suggest morbid animals may have increased WI requirements but systemic limitations in consumption. The lower intercept in deceased animals suggests a different baseline WI pattern but a greater slope compared to healthy animals, possibly due to differences in hydration status, metabolic demands, or systemic limitations in water intake. Understanding these patterns can inform management strategies to optimize health and performance in newly received calves.