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Context: In most pasture-based herds in Australia, supplementation with concentrates is normally a flat rate, with quantities determined by average cow requirements, rather than individual-cow requirements. Comparisons between flat rate and individual feeding rarely show advantages such as milk yield benefits for either. However, in pasture-based systems little is understood regarding milk production responses or levels of pasture substitution, when different groups of cows within the herd are fed concentrates at higher supplementation levels. Aims: To investigate the effect on milk yield, feeding time, and ruminating time, of two flat-rate supplementation levels of concentrate, fed over 8 months to 180 cows selected for one of three different parameters. Methods: Cohorts of cows were selected on contrasting differences for either milk production at the start of lactation, bodyweight, or genotype. Each cohort was divided into two balanced groups receiving either 2 or 6 kg DM/cow.day of concentrate, from approximately 12 days in milk onward. All cows remained part of the main milking herd (total herd size 320 spring-calving cows), with a similar opportunity for all cows to graze pasture or feed on supplemented grass silage during periods of pasture shortage. Milk yield was recorded at each milking and feeding behaviour continuously recorded by MooMonitor+ collars. Results were analysed for three seasonal periods of 10, 12 and 10 weeks (P1, P2 and P3 respectively) commencing in spring. Key results: Mean marginal milk response (L milk per 1 kg DM extra of concentrate) over the trial period was 0.88 L, increasing from 0.71 L in P1, to 0.92 L in P2 and 1.03 L in P3. The high-concentrate cohorts recorded reduced feeding time per day of 37 min overall (46, 35 and 29 min for P1, P2 and P3 respectively). Significant differences were found for milk yield and feeding time between several contrasting cohorts. The lowest marginal milk response was for cross-breed cows in P1 with 0.18 L and feeding reduced by 65 min/cow.day, with the contrasting cohort of Friesian cows at a larger marginal response of 0.94 L and smaller feeding time reduction of 32 min/cow.day. Conclusions: The differences among cohorts demonstrated potential for targeted concentrate feeding to specific groups of cows that respond differently in marginal milk yield and grazing behaviour. Implications: When a significant change is made in strategic amounts of concentrate feeding, the impact not only on marginal milk response should be considered, but also on pasture intake. In pasture-based dairy systems little is understood regarding production responses or pasture substitution with different amounts of concentrates fed. Cohorts of cows were selected on contrasting differences for three parameters and fed concentrate at two flat-rate levels, while milk yield and feeding time were monitored. Contrasting responses were found between cross-breed and Friesian cows. Differences between cohorts demonstrated potential for targeted concentrate feeding to contrasting cohorts of cows, and the need to consider both marginal milk response and pasture intake. This article belongs to the Collection ADSS 2022: A Changing Climate for Dairy Science. [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]

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]

One possible approach for improving the nitrogen (N)‐use efficiency of perennial ryegrass (Lolium perenne L.) pastures and reducing environmental N losses is to select cultivars or incorporate alternative pasture species with lower shoot N concentrations. Viability of this strategy depends on herbage production not being unduly compromised. A pot experiment compared the shoot N concentration requirements of a diverse range of perennial ryegrass cultivars to achieve 90% and 99% of the herbage yield maxima achievable within a 20 day regrowth cycle. This research was undertaken to quantify if and what effect Australasian breeding programs have had on the N nutrition of perennial ryegrass. Our experiment found minimal genetic variation in the shoot N concentration requirements for vegetative perennial ryegrass swards to achieve near‐maximum herbage yields of living biomass. Across evaluated cultivars, swards achieving 90% and 99% of herbage yield maxima required minimum shoot N concentrations (on a dry matter basis) of 2.56% and 2.87%, respectively. Our experiment also evaluated the shoot N concentration requirements of modern summer‐active cocksfoot (syn. orchardgrass; Dactylis glomerata L.) and tall fescue (Festuca arundinacea Schreb.) ecotypes. We found their shoot N concentration requirements to achieve optimal herbage growth to be similar to those of perennial ryegrass. Taken together, our results suggest that within the perennial ryegrass genome, and among similar high yielding temperate perennial grasses, there may be limited scope for selecting plants with lower shoot N concentration requirements. [ABSTRACT FROM AUTHOR]

If the production of forage for dairy cattle is to become less reliant on synthetic nitrogen (N) fertilizers, there is need to better understand and account for the N contributed by on‐farm and imported organic amendments. A 254‐day aerobic soil incubation study (typical length of a growing season in many temperate dairying regions) quantified the inorganic (mineral) N supply from a commercial compost and dried bovine dung (i.e., on‐farm effluent solids). Amendments were incubated in soils with contrasting synthetic N fertilization histories (i.e., 70–100 vs. 350–400 kg N/ha per year) to evaluate if higher synthetic N fertilization histories would reduce the lag time that often exists between organic amendment application and significant release of inorganic N for plant uptake. This proposition was based on previous research, which showed greater soil inorganic N availability accelerating organic amendment decomposition. Our experiment did find that the release of inorganic N from evaluated organic amendments was greater in soils with higher synthetic N fertilization histories, but that this effect was not apparent until after the first 6‐months of this 9‐month experiment. Despite this finding, soils with contrasting synthetic N fertilization histories were not found to differ in their initial inorganic N content, nor microbial activity or other physiochemical properties known to affect N mineralization. Our study highlighted the long‐term vision needed when transitioning from synthetic N fertilizers to organic amendments, with most of the N present in the compost and dried dung remaining unavailable for forage production (i.e., remained bound in organic carbon‐based molecules). [ABSTRACT FROM AUTHOR]

Virtual fencing is promoted as the next advancement for rotational grazing systems. This experiment compared the capacity of conventional temporary electric versus virtual fencing to contain a herd of 30 lactating dairy cows within the boundaries of their daily pasture allocation (inclusion zone). Cows were moved each day to a new rectangular paddock that was divided crosswise into an inclusion and exclusion zone by a single linear electric (first 10 d) or virtual (second 10 d) front-fence. A 3-d virtual fence training period separated the 2 treatments. Virtual fences were imposed using a pre-commercial prototype of the eShepherd virtual fencing system (Agersens Pty Ltd.). Neckband-mounted devices replaced the visual cue of an electric fence with benign audio cues, which if ignored were accompanied by an aversive electrical stimulus. Cows learned to respond to the audio cues to avoid receiving electrical stimuli, with the daily ratio of electrical to audio signals for individual cows averaging (± standard deviation) 0.18 ± 0.27 over the 10 d of virtual fence deployment. Unlike the electric fence, the virtual fence did not fully eliminate cow entry into the exclusion zone, but individual cows were generally contained within the inclusion zone ≥99% of the time. Pasture depletion within the inclusion zone reduced the efficacy of the virtual fence in preventing cows from entering the exclusion zone, but the magnitude of this effect was insignificant in practical terms (i.e., increased time spent in the exclusion zone by ≤28 s/h per cow). This highlights the potential for virtual fences to control grazing dairy cow movement even when pasture availability is limited (i.e., 1 kg of dry matter/cow above a target residual of 1,500 kg of dry matter/ha), but requires confirmation under longer and more complex virtual fencing applications. Within each treatment period, uniform daily pasture utilization (% of pasture consumed above a target residual of 1,500 kg of dry matter/ha) within inclusion zones indicates that cows did not avoid grazing near electric or virtual front-fences. Overall, this study demonstrated a successful simple application of this virtual fencing system to contain a herd of grazing lactating dairy cows within the boundaries of their daily pasture allocation. [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]