Pasture brome (Bromus valdivianus Phil.) has the potential to increase current levels of herbage production and pasture persistence in New Zealand dryland, well-drained soils. However, there is little literature on the effect of defoliation management on growth of this grass under contrasting soil-water restriction levels. The growth physiology and performance of pasture brome were evaluated in pots in a glasshouse. Defoliation frequency (DF) treatments were applied based on three different accumulated growing degree-days (AGDD): 250, 500 and 1000 AGDD (high, medium, and low DF). At end of the first growing cycle (1000 AGDD), water availability was restricted to 20–25% of field capacity (FC) in half of the pots, while the other pots were maintained between 80–85% FC. Total accumulated herbage mass was positively related with the low DF and well-watered conditions (p < 0.05). At the final harvest, plants subjected to low DF had greater root mass than high and medium DF (p < 0.05). At each harvest, the leaf regrowth stage (LS) for low DF was 3.5, while for high and medium DF, the LS was 1.5 and 2.0; respectively. Tiller water-soluble carbohydrates were highest at the low DF and under 20–25% FC. Regardless of soil-water conditions, defoliation at 3.5 LS supports production, enhancing survival during a drought.

The present study aimed to determine the impact of ewe body condition score (BCS) (over a range of 2.0 to 3.0) and nutritional treatments (consisting of differing herbage masses) during very late pregnancy and lactation and their potential interaction on the performance of twin-bearing ewes and their lambs to weaning. On day 142 of pregnancy, twin-bearing ewes with a BCS of 2.0, 2.5, or 3.0 were allocated to a "Moderate' or 'Unrestricted' nutritional treatment until day 95 of lactation (weaning). The nutritional treatments aimed to achieve average herbage masses of 1,200 to 1,300 kg dry matter (DM)/ha (Moderate) and 1,500 to 1,800 kg DM/ha (Unrestricted). There were no three-way interactions between ewe BCS group, nutritional treatment and time for any ewe or lamb parameter. The nutritional treatments had no effect (p>0.05) on lamb birth or weaning weight. Lambs born to Moderate ewes had greater survival and total litter weight at weaning (p<0.05). Regardless of BCS group, Unrestricted treatment ewes had greater body condition and back-fat depth at weaning than Moderate treatment ewes (p<0.05). Ewes of BCS 2.0 group reared lighter lambs to weaning (p1,200 kg DM/ha during very late pregnancy and lactation.

This article reviews the literature on nitrate leaching under sheep grazing systems and focuses on identifying future research needs. Urinary nitrogen (N) is an important source of the nitrate leached from pastoral agriculture. Urinary N excretion can be measured or simulated using models and has been well characterised for dairy systems. It is difficult to continuously monitor the urinary N excretion of sheep under field conditions; consequently, measurements of N excretion in sheep urine are limited. Urination events by sheep vary greatly in volume (0.5 L to 6.9 L), concentration (3 to 13.7 g N/L), and frequency (8 to 23 events/day); this variation results in a corresponding variation in N loading rates in urine patches. The amount of nitrate leached under pastures grazed by sheep has typically varied between 1 and 50 kg N/ha/year, but rates as high as 300 kg N/ha/year have been reported. The quantity of nitrate leached under sheep depends on the season, climate, quantity and timing of drainage, the interaction between forage production and stocking rate, fertiliser applied, N fixation by legumes, forage type, and grazing management. The majority of studies examining nitrate leaching under sheep grazing systems are more than 20 years old; so, there is little recent information on nitrate leaching under modern pasture-based sheep production systems. Further research is required to quantify nitrate leaching levels under current sheep farming practices, to understand the impacts of this leaching on water quality, and to help identify effective strategies to reduce the transfer of N from grazed paddocks to receiving water bodies. This additional information will help provide information for decision support tools, including models and management practices, to help sheep farmers minimise their impact on the aquatic environment.

Bromus valdivianus Phil. (Bv) is a water stress-tolerant species, but its competitiveness in a diverse pasture may depend on defoliation management and soil moisture levels. This glasshouse study examined the effect of three defoliation frequencies, based on accumulated growing degree days (AGDD) (250, 500, and 1000 AGDD), and two soil water levels (80–85% of field capacity (FC) and 20–25% FC) on Bv growth as monoculture and as a mixture with Lolium perenne L. (Lp). The treatments were applied in a completely randomised block design with four blocks. The above-ground biomass of Bv was lower in the mixture than in the monoculture (p ≤ 0.001). The Bv plants in the mixture defoliated more infrequently (1000 AGDD) showed an increase in root biomass under 20–25% FC compared to 80–85% FC, with no differences measured between soil water levels in the monoculture. Total root length was highest in the mixture with the combination of infrequent defoliation and 20–25% FC. Conversely, frequent defoliation treatments resulted in reduced water-soluble carbohydrate reserves in the tiller bases of plants (p ≤ 0.001), as they allocated assimilates mainly to foliage growth. These results provide evidence that B. valdivianus can increase its competitiveness relative to Lp through the enhancement of the root growth and the energy reserve in the tiller base under drought conditions and infrequent defoliation in a mixture.

The use of alternative herbage types such as herb‐clover mixes and lucerne can improve the weaning weight of twin and triplet lambs born to mature ewes and single lambs born to ewe hoggets. The aim of this study was to compare the live weights of twin bearing ewe hoggets and their progeny grazed on either ad libitum permanent pasture (ryegrass white clover), lucerne or plantain‐clover during lactation over two years. In both years of the study, twin bearing hoggets and their lambs grazed on lucerne or plantain‐clover were heavier at weaning than those on pasture. Lambs grazed on lucerne had greater live weights at weaning than plantain‐clover, however, among ewe hoggets differences were seen only in the first year of the study. In conclusion, both lucerne and the plantain‐clover resulted in increased mean live weights of ewe hoggets and their lambs at weaning compared with those on pasture.