Search

Simple Summary: We observed a forage allowance by forage type effect on improvements in the daily milk yield of dairy cows grazing swards sown with perennial ryegrass, white clover and plantain relative to those sown to perennial ryegrass only. Improvements in milk yield were evident at lower forage allowances of 14 to 20 kg of dry matter/cow per day (inclusive), diminishing at the highest allowance of 25 kg of dry matter/cow per day. At the lower forage allowances, energy intake would have been a limiting factor for milk production, potentially highlighting the nutritive advantages of plantain and white clover. Increasing species diversity is a possible strategy for overcoming seasonal nutritive challenges present in perennial ryegrass monocultures. We tested for a forage allowance effect on the milk yield of early lactation dairy cow herds grazing swards sown with perennial ryegrass (Lolium perenne L.), white clover (Trifolium repens L.) and plantain (Plantago lanceolata L.) relative to perennial ryegrass alone. The examined allowances consisted of offering 12, 14, 16, 18, 20 or 25 kg of dry matter (DM)/cow per day of grazeable herbage, with diverse swards sown as mixtures and spatially adjacent monocultures. After adapting cows to their assigned forage type for 8 days, treatment effects on milk yield and composition, blood metabolites (beta-hydroxybutyrate, non-esterified fatty acids and urea concentrations), body weight change, forage intake and selection differentials for forage species and certain nutrients were monitored over 7 days. We confirmed a forage allowance effect on milk yield improvements in dairy cows grazing diverse swards relative to perennial ryegrass monocultures. Improvements in milk yield were evident at forage allowances of 14 to 20 kg of DM/cow per day, diminishing at the highest allowance of 25 kg of DM/cow per day. Improvements in milk yield for the mixture and spatially adjacent monocultures peaked at forage allowances of 18 and 16 kg of DM/cow per day, equalling increases of 1.3 and 1.2 kg of milk/cow per day, respectively. [ABSTRACT FROM AUTHOR]

The profitability of dairying in south-eastern Australia can be improved by increasing pasture production during summer–autumn, when growth rates for the existing perennial ryegrass (Lolium perenne L.) feedbase are low. A study undertaken in cool-temperate north-west Tasmania examined the effect of stubble height and irrigation management on swards of perennial ryegrass, continental (summer-active) tall fescue (Festuca arundinacea Schreb.) and chicory (Cichorium intybus L.). Irrigation treatments included full irrigation (~20 mm applied at every 20 mm precipitation deficit), deficit irrigation (~20 mm applied at alternate full-irrigation events) and rainfed (no irrigation). All species achieved greater summer–autumn yields when repeatedly defoliated to stubble heights of 35 or 55 mm than when defoliated to 115 mm, irrespective of irrigation treatment. Swards were managed under a common defoliation schedule of nine defoliation events in 12 months. Under full irrigation, second-year tall fescue achieved a greater summer–autumn yield than perennial ryegrass (by 10%, or 0.7 t DM ha–1), highlighting the potential role of tall fescue in north-west Tasmania. This was further demonstrated by the high marginal irrigation water-use index values (1.6–2.7 t DM ML–1) of tall fescue. By contrast, summer–autumn growth achieved by chicory was less than or equal to perennial ryegrass. The profitability of dairying in south-eastern Australia can be improved by increasing summer–autumn pasture production. In a study in cool-temperate north-west Tasmania, perennial ryegrass, tall fescue and chicory achieved higher summer–autumn yields when repeatedly defoliated to stubble heights of 35 or 55 mm cf. 115 mm. When regularly irrigated to correct precipitation deficits, tall fescue showed potential to increase summer-autumn yields beyond that of perennial ryegrass. [ABSTRACT FROM AUTHOR]

In many south-eastern Australian dairying regions, supraoptimal ambient temperatures (Ta > 30°C) often challenge the perennial ryegrass (Lolium perenne L.)-dominated feed-base during the summer months. A glasshouse experiment was undertaken to identify alternative summer-active temperate (C3) perennial forages more tolerant of supraoptimal temperature stress (day/night Ta of 38/25°C) than perennial ryegrass. Supraoptimal temperature stress was mposed both with and without irrigation. Chicory (Cichorium intybus L.) was the only species to survive 18 days of combined supraoptimal temperature stress and non-irrigation. Lucerne (Medicago sativa L.), plantain (Plantago lanceolata L.), and tall fescue (Festuca arundinacea Schreb.) survived 12 days of this treatment. Twelve days of exposure to these conditions caused death of perennial ryegrass, prairie grass (Bromus catharticus Vahl.), cocksfoot (Dactylis glomerata L.), birdsfoot trefoil (Lotus corniculatus L.), and red clover (Trifolium pratense L.). Irrigation (daily to through drainage) mitigated detrimental effects of imposed supraoptimal temperature stress on the growth and survival of all species. Chicory and to a lesser extent lucerne, plantain, and tall fescue may have a role to play in south-eastern Australian dairying regions, where supraoptimal temperature stress is a frequent and ongoing issue. [ABSTRACT FROM AUTHOR]

• Benefits of irrigating perennial ryegrass more frequently during heat waves tested. • Novel outdoor heater system designed for evaluating heat wave mitigation options. • Irrigating more frequently suppressed crown temperature elevation under heaters. • Simulated heat wave conditions reduced perennial ryegrass growth by 23%. • Heat wave effects on growth were independent of irrigation frequency. Heat waves are problematic for grazing livestock systems in regions dependant on temperate (cool-season) pasture species, owing to the often minimal heat tolerance (thermotolerance) of these pastures. A field experiment in north-west Tasmania, Australia, tested the hypothesis irrigating more frequently reduces detrimental heat wave effects on perennial ryegrass (Lolium perenne L.) above-ground growth and short-term persistence (measured via basal frequency). Heat wave conditions were imposed using freestanding infrared heater arrays fitted with a novel control system designed for evaluating heat wave mitigation options. The control system enabled the extent of warming to be regulated, whilst applying an equal infrared flux (heating) to all heated plots. Increasing the frequency of irrigation events suppressed crown temperature (plant-soil interface) elevation under heaters. When irrigation was applied every 2, 5 or 10 days, median crown temperature elevation under heaters equalled 5.5 °C, 6.5 °C and 7.0 °C, respectively. However, detrimental effects of imposed heat wave conditions on perennial ryegrass growth were not mitigated by more frequent irrigation events. This resulted from the small differences in crown temperature elevation between irrigation frequency treatments, combined with supraoptimal crown temperatures occurring <10% of the time during the simulated 10-day heat wave events. The infrequent occurrence of supraoptimal crown temperatures: (i) resulted from mild ambient conditions (mean ambient air temperature, 17.2 °C); and (ii) explains why applied heating only reduced perennial ryegrass growth by 13 kg DM ha−1 day−1 (23%) when heaters were operated, with no residual effect in the accompanying recovery regrowth cycle. Applied heating also had no appreciable effect on perennial ryegrass basal frequency. Under more extreme heat wave conditions, irrigation frequency may have a larger effect on perennial ryegrass tissue temperature and subsequent growth, especially in environments characterised by higher crown temperatures. [ABSTRACT FROM AUTHOR]