Effect of forage plantain integration into a grazing dairy system on urination behaviour and urinary nitrogen concentration in late-lactation cows

Abstract

As part of a farm-system study, this sub-study aimed to contribute to existing evidence on the effects of varying dietary levels of plantain (Plantago lanceolata L.) on urinary N (UN) concentration and urination behaviour in cows managed under typical farming practices. In late July 2021, 108 dairy cows were blocked into nine herds of 12 cows. The herds were randomly allocated into one of three replicated pasture treatments sown with an increasing plantain seed rate: (i) RGWC with nil plantain (PL0); (ii) RGWC+3 kg/ha plantain (PL3) or (iii) RGWC+6 kg/ha plantain (PL6). Over a 10-day sub-study period in late March-early April 2022, UN concentration was measured in morning and afternoon spot samples collected from 18 monitor cows (n=6; three cows each from two of the three farmlets per treatment) on two occasions. Urination behaviour (daily urine volume and urination frequency) was measured using a Lincoln University PEETER V.1.0 sensor attached to the monitor cows for 24-48 hours. During the sub-study period, the dietary levels of plantain leaves in dry matter were nil in PL0, 31.7% in PL3 and 47.5% in PL6. Pasture silage fed (kg/cow/day) to maintain regrowth interval was higher in PL3 (1.7 kg) than PL0 (0.7 kg) and PL6 (nil), resulting in 7-8% lower N intake (g/d) in PL3 (402) compared to PL0 (438) and PL6 (430). Urine N concentration tended (P=0.07) to be lower in PL3 and PL6 than PL0. Urine volume (P=0.005) and urination frequency (P=0.007) were higher in cows in PL6 than in those in PL0 and PL3, but similar between PL0 and PL3. While these results showed a tendency for plantain to reduce UN concentration, they highlight the opportunity to explore stacking strategies that combine plantain with low-N supplements for additional environmental benefits.