Plantain (Plantago lanceolata) reduces the environmental impact of farmed red deer (Cervus elaphus)

The objective of this study was to evaluate the effect of plantain ( Plantago lanceolata L.) on water dynamics and balance, as well as nitrogen (N) excretion by red deer (Cervus elaphus L.) as a potential forage tool to reduce negative environmental impacts. This experiment used a crossover design with red deer (n = 8) in metabolism crates to determine how fresh-cut herbage diets of either plantain or ryegrass (Lolium perenne L.) compared in terms of dry matter intake (DMI), diet digestibility, water dynamics, and N dynamics. Deer consuming plantain had greater water intake from herbage (P < 0.01) compared with ryegrass. Additionally, when fed plantain, deer had greater water excretion from urine (P < 0.01; 69.4%) and feces (P < 0.01; 29.4%) and, thus, total water excretion (P < 0.01; 61.7%) than when fed ryegrass. When consuming plantain, deer had greater DMI (P = 0.02; +11.2%) and fecal output (P < 0.01; +36.8%) and lower apparent dry matter digestibility (P = 0.03; -8.3%) compared with ryegrass. Plantain (15.9%) contained 30% less crude protein than ryegrass (22.8%) so that even with the greater DMI of plantain, plantain had lower (P < 0.01; -23%) N intake (g/d). Deer consuming plantain had lower urine N concentration (P < 0.01) than when consuming ryegrass. Additionally, deer consuming plantain had much less daily urine N (P < 0.01; -34.9%) excretions. Our results indicate deer fed plantain had greater DMI, ingested more water, and excreted more water than those consuming ryegrass, with lower urinary N (UN) concentration and lesser daily urine N excretion. Thus, we conclude that offering red deer plantain may reduce the environmental impact associated with UN output, such as nitrate leaching or N2O emissions to the atmosphere.