Live weight gain and urinary nitrogen excretion of dairy heifers grazing pasture, chicory and plantain

Abstract

The objective of this study was to determine the effect of feeding plantain and chicory at different proportions in the diet with perennial ryegrass-white clover pasture on the live weight (LW) gain, urinary nitrogen (N) excretion, and urination behaviour of dairy heifers grazing in autumn. The study was completed at Lincoln University’s Ashley Dene Pastoral Systems Research Farm, Canterbury, New Zealand and had a duration of 32 d in autumn. A total of 60 Friesian x Jersey dairy heifers aged 8-9 months, were blocked into five dietary treatments balanced for their LW and breeding worth; 100% perennial ryegrass-white clover pasture (R; n = 12); 50% pasture + 50% chicory (50%C; n = 10); 75% pasture + 25% chicory (25%C; n=12); 50% pasture + 50% plantain (50%P; n = 12); and 75% pasture + 25% plantain (25%P; n=12). A fresh allocation of the herbage was offered every 3 d with herbage allowance calculated according to feed requirement for maintenance plus gain of 1.0 kg LW/d. The results showed no significant difference in LW gain between treatments (mean = 0.70 kg/d/hf; P = 0.11). There was no significant difference in urine N, NH3, BUN, glucose, urea, faecal DM and microbial protein synthesis between all treatments (P>0.05). Allantoin was significantly lower in R and 25%P (2.45mmol/L and 2.43mmol/L respectively) and higher in 25%C (4.17mmol/L) (P=0.029). Uric acid was significantly lower in R and 25%P (0.17mmol/L and 0.16mmolL respectively) and higher in 25%C (0.28mmol/L) (P =0.033). A small difference was apparent in creatinine, where R and 25%P were lower (0.75mmol/L and 0.78mmo/L) and 25%C was higher (1.18mmol/L) (P=0.07). A significantly higher urination frequency was observed in R and a significantly lower urination frequency in 50%C (5.91 urination/hf/6h and 2.33 urinations/hf/6h respectively; p-value <0.001) than 25%C, 50%P and 25%P (mean = 3.92 urination/hf/6h). 25%C & 25%P both had smaller urine patch areas when compared to other treatments (P=0.071) therefore indicating a lower volume per urination event. Data from this study indicates that there is a benefit to feeding chicory and plantain at 50% and 25% of pasture area on N loss to the environment through urination frequency and volume and that feeding chicory and plantain at these percentages has no negative effect on LW gain.