Jeffrey McCormick

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

The objective of the present study was to investigate live weight (LW) gain, urinary nitrogen (UN) excretion and urination behaviour of dairy heifers grazing pasture, chicory and plantain in autumn and spring. The study comprised a 35-day autumn trial (with a 7-day acclimation period) and a 28-days spring trial (with a 7-day acclimation period). For each trial, 56 Friesian × Jersey heifers were blocked into five dietary treatments balanced for their LW and breeding worth (i.e. genetic merit of a cow for production and reproduction): 1·00 perennial ryegrass–white clover pasture (PA); 1·00 chicory (CH); 1·00 plantain (PL); 0·50 pasture + 0·50 chicory (PA + CH); and 0·50 pasture + 0·50 plantain (PA + PL). A fresh allocation of the herbage was offered every 3 days with allowance calculated according to feed requirement for maintenance plus gain of 1·0 kg LW/day. In both trials, LW gain was lower on CH than other treatments. In the spring trial, UN concentration and UN excretion were lower in CH and PL than other treatments. In autumn, a higher urination frequency was observed over the first 6 h after forage allocation in CH and PA + CH than other treatments. Data from the present study indicate that feeding CH alone limited heifer LW gain. However, heifers grazing swards containing chicory (CH and PA + CH) and plantain (PL and PA + PL) had the potential to lower nitrous oxide emissions and nitrate leaching from soil compared with heifers grazing PA, by reducing N loading in urine patches.

Live weight gain, animal behaviour and urinary nitrogen excretion of dairy heifers grazing ryegrass–white clover pasture, chicory or plantain

ABSTRACT The objective of this study was to assess live weight gain, animal behaviour and N excretion in the urine of dairy heifers fed herbs during autumn and spring. Sixty heifers were allocated into five dietary treatments: 100% ryegrass–white clove pasture (100RG/WC); 50% RG/WCu2009+u200950% chicory (50CH); 75% RG/WCu2009+u200925% chicory (25CH); 75% RG/WCu2009+u200925% plantain (25PL); and 50% RG/WCu2009+u200950% plantain (50PL). The 100RG/WC had the highest (5.0 times/6u2005h) and lowest (2.5 times/6u2005h) urination frequency compared with other treatments in autumn (averaged 3.5 times/6u2005h) and spring (averaged 4.5 times/6u2005h), respectively. The heifer LWG in spring was higher in 25CH (1.36u2005kg/day) than other treatments (averaged 1.10u2005kg/day). Urinary N concentration was 0.18% and 0.23% in autumn and spring, respectively, across treatments, with no difference between treatments. The study demonstrated inconsistent results of use of chicory and plantain as a mitigation tool to reduce the environmental impact of heifer rearing systems in autumn and spring.

Addressing biophysical constraints for Australian farmers applying low rates of composted dairy waste to soil

This study examined the response of forage crops to composted dairy waste (compost) applied at low rates and investigated effects on soil health. The evenness of spreading compost by commercial machinery was also assessed. An experiment was established on a commercial dairy farm with target rates of compost up to 5 t ha −1 applied to a field containing millet [ Echinochloa esculenta (A. Braun) H. Scholz] and Pasja leafy turnip ( Brassica hybrid). A pot experiment was also conducted to monitor the response of a legume forage crop (vetch; Vicia sativa L.) on three soils with equivalent rates of compost up to 20 t ha −1 with and without ‘additive blends’ comprising gypsum, lime or other soil treatments. Few significant increases in forage biomass were observed with the application of low rates of compost in either the field or pot experiment. In the field experiment, compost had little impact on crop herbage mineral composition, soil chemical attributes or soil fungal and bacterial biomass. However, small but significant increases were observed in gravimetric water content resulting in up to 22.4 mm of additional plant available water calculated in the surface 0.45 m of soil, 2 years after compost was applied in the field at 6 t ha −1 dried (7.2 t ha −1 undried), compared with the nil control. In the pot experiment, where the soil was homogenized and compost incorporated into the soil prior to sowing, there were significant differences in mineral composition in herbage and in soil. A response in biomass yield to compost was only observed on the sandier and lower fertility soil type, and yields only exceeded that of the conventional fertilizer treatment where rates equivalent to 20 t ha −1 were applied. With few yield responses observed, the justification for applying low rates of compost to forage crops and pastures seems uncertain. Our collective experience from the field and the glasshouse suggests that farmers might increase the response to compost by: (i) increasing compost application rates; (ii) applying it prior to sowing a crop; (iii) incorporating the compost into the soil; (iv) applying only to responsive soil types; (v) growing only responsive crops; and (vi) reducing weed burdens in crops following application. Commercial machinery incorporating a centrifugal twin disc mechanism was shown to deliver double the quantity of compost in the area immediately behind the spreader compared with the edges of the spreading swathe. Spatial variability in the delivery of compost could be reduced but not eliminated by increased overlapping, but this might represent a potential 20% increase in spreading costs.