Asparagopsis taxiformis concentrates halogenated compounds that are known to inhibit cobamide-dependent methanogenesis in vitro and, therefore, has potential to mitigate enteric methane production. The present study investigated the effect of Asparagopsis on methane (CH4) production from sheep offered a high-fibre pelleted diet (offered at 1.2 × maintenance) at five inclusion levels of Asparagopsis for 72 days (0% (control), 0.5%, 1%, 2% and 3% organic matter basis as offered). Individual animal CH4 measurements were conducted at 21-day intervals using open-circuit respiration chambers. Asparagopsis inclusion resulted in a consistent and dose-dependent reduction in enteric CH4 production over time, with up to 80% CH4 mitigation at the 3% offered rate compared with the group fed no Asparagopsis (P < 0.05). Sheep fed Asparagopsis had a significantly lower concentration of total volatile fatty acids and acetate, but a higher propionate concentration. No changes in liveweight gain were identified. Supplementing Asparagopsis in a high-fibre diet (<2% organic matter) resulted in significant and persistent decreases in enteric methanogenesis over a 72-day period. Granulomatous and keratotic ruminal mucosa changes were identified in several sheep with Asparagopsis supplementation. While the outcomes of the present study may be extrapolated to feedlot to achieve the antimethanogenic effect associated with Asparagopsis, further work is required to define the long-term effects on productivity and animal health.

Salinity is a problem facing many crop and livestock producers in southern Australia. One management option is to revegetate with salt-tolerant plants suitable for animal production. These plants are often halophytic shrubs containing up to 30% ash, predominantly as sodium, potassium, or chloride. This experiment examines the consequences of a high intake of sodium and potassium separately or together on feed intake, digestibility, liveweight change, and wool growth. Twelve groups of 6 weaner wethers were allocated to treatments according to a balanced 3 × 4 factorial design with 3 levels of added potassium (0, 0.38, and 0.77 mol/kg DM equivalent to 0, 15, and 30 g/kg DM) and 4 levels of added sodium (0, 0.87, 2.18, and 3.48 mol/kg DM, equivalent to 0, 20, 50, and 80 g/kg DM) as the chloride salts. The treatment diets were fed to sheep for 6 weeks. Increasing sodium in the diet significantly decreased feed intake, digestibility, liveweight gain, and wool growth either as a main effect or through an interaction with potassium. Organic matter intake was reduced from 1.35 kg at the lowest levels of sodium and potassium to 0.67 kg at the highest levels. Comparing the same 2 groups, liveweight gain was reduced from 144 to 0 g/day, organic matter digestibility from 59.1% to 57.3%, and wool growth from 1.21 to 1.04 mg/cm2.day. The response surfaces indicate that production was depressed even at the lower levels of sodium, whereas high potassium depressed intake, digestibility, and liveweight gain at high levels of sodium only. The interaction between sodium and potassium was always negative at high levels of sodium, indicating that manipulation of the proportions of the 2 elements is unlikely to provide benefits for animal production when total salt levels are high. Although wool growth was depressed at high sodium and potassium, the efficiency of wool growth increased from 10.0 to 15.4 g/kg organic matter intake when the lowest and highest levels of the sodium and potassium were compared. This result may present significant opportunities for the use of saline land to grow fine wool.

Annual legumes rely on hardseededness, a form of seed dormancy, to spread the risk of mortality associated with germination and to encourage germination at the optimal time in a season. This paper examines seed softening strategies of a number of clover ( Trifolium ) species collected over a range of environments. Three hypotheses are tested. The first is that within species, long-term hardseededness increases with aridity due to the greater chance of failure to reproduce in dry environments. It is tested by comparing seed softening patterns of populations of a number of clover species collected from a range of environments. The second hypothesis, that annual legumes from dry environments have a smaller subset of seed softening strategies than legumes from wetter environments, is tested by comparing the range of seed softening patterns from all species found at collection sites. The third hypothesis is that within-year patterns of seed softening that prevent germination after summer rainfall may partially substitute for long-term hardseededness. It is tested by examining the relationship between within-year hardseededness and between-year hardseededness. Accessions of the same species from different collection sites differed in both within-year pattern of seed softening and long-term hardseededness but there was little evidence that these differences were between ecotypes. Different species from the same collection site did not have similar seed softening strategies, and seed softening strategies of clovers from dry sites were as variable as those from wetter environments. Within-year pattern of seed softening does not appear to substitute for between-year hardseededness as a dormancy strategy.