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]

Forage management underpins the viability of pastoral dairy systems. This review investigated recent developments in forage research and their potential to enable pastoral dairy systems to meet the challenges that will be faced over the next 10 years. Grazing management, complementary forages, pasture diversity, fertiliser use, chemical restriction, irrigation management and pasture breeding are considered. None of these areas of research are looking to increase production directly through increased inputs, but, rather, they aim to lift maximum potential production, defend against production decline or improve the efficiency of the resource base and inputs. Technology approaches consistently focus on improving efficiency, while genetic improvement or the use of complementary forages and species diversity aim to lift production. These approaches do not require additional labour to implement, but many will require an increase in skill level. Only a few areas will help address animal welfare (e.g. the use of selected complementary forages and novel endophytes) and only complementary forages will help address increased competition from non-dairy alternatives, by positively influencing the properties of milk. Overall, the diversity of activity and potential effects will provide managers of pastoral dairy systems with the best tools to respond to the production and environmental challenges they face over the next 10 years. Forage management underpins the success of pastoral dairy industries. Recent dairy forage research was reviewed through a production and input loss frontier framework along with their potential impacts on competition from non-dairy alternatives, labour and animal welfare challenges. The diversity of approaches to modifying both the production and input loss frontiers will provide the tools for pasture managers to meet future production and environmental challenges. [ABSTRACT FROM AUTHOR]

There is interest in the reincorporation of legumes and forbs into pasture-based dairy production systems as a means of increasing milk production through addressing the nutritive value limitations of grass pastures. The experiments reported in this paper were undertaken to evaluate milk production, blood metabolite concentrations, and forage intake levels of cows grazing either pasture mixtures or spatially adjacent monocultures containing perennial ryegrass (Lolium perenne), white clover (Trifolium repens), and plantain (Plantago lanceolata) compared with cows grazing monocultures of perennial ryegrass. Four replicate herds, each containing 4 spring-calving, cross-bred dairy cows, grazed 4 different forage treatments over the periods of early, mid, and late lactation. Forage treatments were perennial ryegrass monoculture (PRG), a mixture of white clover and plantain (CPM), a mixture of perennial ryegrass, white clover, and plantain (RCPM), and spatially adjacent monocultures (SAM) of perennial ryegrass, white clover, and plantain. Milk volume, milk composition, blood fatty acids, blood β-hydroxybutyrate, blood urea N concentrations, live weight change, and estimated forage intake were monitored over a 5-d response period occurring after acclimation to each of the forage treatments. The acclimation period for the early, mid, and late lactation experiments were 13, 13, and 10 d, respectively. Milk yield (volume and milk protein) increased for cows grazing the RCPM and SAM in the early lactation experiment compared with cows grazing the PRG, whereas in the mid lactation experiment, milk fat increased for the cows grazing the RCPM and SAM when compared with the PRG treatments. Improvements in milk production from grazing the RCPM and SAM treatments are attributed to improved nutritive value (particularly lower neutral detergent fiber concentrations) and a potential increase in forage intake. Pasture mixtures or SAM containing plantain and white clover could be a strategy for alleviating the nutritive limitations of perennial ryegrass monocultures, leading to an increase in milk production for spring calving dairy cows during early and mid lactation. [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]