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.