The effects of feeding cut plantain and perennial ryegrass-white clover pasture on dairy heifer feed and water intake, apparent nutrient digestibility and nitrogen excretion in urine

Urinary nitrogen concentration (UNcc) and urinary N excretion (UN) are directly associated with the nitrogen (N) leaching potential of soil and greenhouse gas emissions from grazing ruminants' urine patches. This study was carried out to examine the effects of feeding cut plantain (PL) and perennial ryegrass-white clover pasture (PW) on dairy heifer feed and water intake, apparent nutrient digestibility and N excretion in urine. Twelve Jersey-Friesian heifers aged 9-10 months with an average body weight of 200 ± 18.8 kg (mean ± standard deviation (SD)) and breeding worth of NZ$162 ± 16.9 (mean ± SD) were randomly allocated to one of two treatments (six heifers per treatment): PW and PL. No difference was observed in dry matter intake (P = 0.117) and N intake (P = 0.370) between PW- and PL-fed heifers. The dry matter digestibility and digestible organic matter in the dry matter were similar between PL- and PW-fed heifers (P > 0.05). Heifers consuming PL had lower UNcc and UN than those consuming PW (P < 0.01). Estimated urine volume and total water intake were higher for PL-fed heifers than those fed PW (P < 0.01). Further, in comparison with PW-fed heifers, PL-fed heifers had lower plasma urea N (P < 0.001) and tended to have lower plasma δ15N - feed δ15N (P = 0.086). The findings suggest that feeding PL to dairy heifers may reduce UNcc and UN in comparison with those on conventional pastures; therefore it provides an opportunity to mitigate on-farm N pollution.