The effect of including plantain in a perennial ryegrass-white clover forage on dry matter intake, milk production, and urine nitrogen concentration of dairy cows

Pressure is increasing on Irish dairy farmers to reduce nitrogen (N) losses to the environment. Research has shown that plantain (Plantago lanceolata L.; PL) can reduce urine N excretion and concentration in cows. Hence, this study investigated the effect of PL inclusion in a perennial ryegrass (Lolium perenne L.; PRG)-white clover (Trifolium repens L.; WC) forage for dairy cows on dry matter intake (DMI), milk production, and urine N concentration. Eight mid-lactation multiparous dairy cows were utilised in a complete 2 × 2 crossover design (n = 8). Cows were offered one of two cut forages ad libitum: PRG-WC (GrC) or PRG-WC-PL (GCP) plus 2.75 kg DM concentrate feed/cow per day. Each period consisted of 16 days of dietary acclimatisation followed by five days of measurements with cows in individual tie stalls. Individual DMI and milk production were measured daily, and urine samples were collected from cows at 00:00, 04:00, 08:00, 12:00, 16:00, and 20:00 h daily. Total DMI was greater for cows offered the GCP treatment (22.9 vs. 21.4 kg/day). Cows consuming the GCP treatment had a lower free water intake but greater feed water intake. Cows offered the GCP treatment tended to produce greater milk and milk protein yields but a lower milk fat concentration. For cows offered the GCP treatment, daily urine N concentration was 20 % lower. This reduction was consistent throughout the day for cows offered the GCP treatment, with urine N concentration significantly lower at 00:00, 08:00, 12:00, and 16:00 h. This study demonstrates the potential of including PL in a GrC forage to increase DMI, reduce urine N concentration, and maintain milk production of cows in Irish dairy systems.