Do forage legumes have a role in modern dairy farming systems?

peer-reviewedIntensification in New Zealand dairy farming systems has placed greater pressure on clover performance and fitness and has highlighted the need to develop clover cultivars that are better adapted to intensive grazing systems. Increased stocking rates and increased use of nitrogen fertiliser have put enormous pressure on the contribution of clover to modern dairy systems. Future innovations such as semi-hybrid cultivars offer the potential to improve the competitiveness of legumes with nitrogen-fertilised forage grasses. Similarly, advances in condensed tannin research suggest that significant animal performance gains can be achieved in conjunction with reduced environmental impact. In order to capture these benefits, dairy farmers will need to reassess their grazing management to ensure that legumes can be maintained at economically useful levels. Novel grazing management systems that optimise the benefits provided by the grass and legume components need to be used in future dairy farming systems. Forage legumes, and especially white clover, have an important role to play in modern dairy systems

Tocilizumab in patients admitted to hospital with COVID-19 (RECOVERY): a randomised, controlled, open-label, platform trial

Background: In this study, we aimed to evaluate the effects of tocilizumab in adult patients admitted to hospital with COVID-19 with both hypoxia and systemic inflammation. Methods: This randomised, controlled, open-label, platform trial (Randomised Evaluation of COVID-19 Therapy [RECOVERY]), is assessing several possible treatments in patients hospitalised with COVID-19 in the UK. Those trial participants with hypoxia (oxygen saturation <92% on air or requiring oxygen therapy) and evidence of systemic inflammation (C-reactive protein ≥75 mg/L) were eligible for random assignment in a 1:1 ratio to usual standard of care alone versus usual standard of care plus tocilizumab at a dose of 400 mg–800 mg (depending on weight) given intravenously. A second dose could be given 12–24 h later if the patient's condition had not improved. The primary outcome was 28-day mortality, assessed in the intention-to-treat population. The trial is registered with ISRCTN (50189673) and ClinicalTrials.gov (NCT04381936). Findings: Between April 23, 2020, and Jan 24, 2021, 4116 adults of 21 550 patients enrolled into the RECOVERY trial were included in the assessment of tocilizumab, including 3385 (82%) patients receiving systemic corticosteroids. Overall, 621 (31%) of the 2022 patients allocated tocilizumab and 729 (35%) of the 2094 patients allocated to usual care died within 28 days (rate ratio 0·85; 95% CI 0·76–0·94; p=0·0028). Consistent results were seen in all prespecified subgroups of patients, including those receiving systemic corticosteroids. Patients allocated to tocilizumab were more likely to be discharged from hospital within 28 days (57% vs 50%; rate ratio 1·22; 1·12–1·33; p<0·0001). Among those not receiving invasive mechanical ventilation at baseline, patients allocated tocilizumab were less likely to reach the composite endpoint of invasive mechanical ventilation or death (35% vs 42%; risk ratio 0·84; 95% CI 0·77–0·92; p<0·0001). Interpretation: In hospitalised COVID-19 patients with hypoxia and systemic inflammation, tocilizumab improved survival and other clinical outcomes. These benefits were seen regardless of the amount of respiratory support and were additional to the benefits of systemic corticosteroids. Funding: UK Research and Innovation (Medical Research Council) and National Institute of Health Research

Convalescent plasma in patients admitted to hospital with COVID-19 (RECOVERY): a randomised controlled, open-label, platform trial

Background: Many patients with COVID-19 have been treated with plasma containing anti-SARS-CoV-2 antibodies. We aimed to evaluate the safety and efficacy of convalescent plasma therapy in patients admitted to hospital with COVID-19. Methods: This randomised, controlled, open-label, platform trial (Randomised Evaluation of COVID-19 Therapy [RECOVERY]) is assessing several possible treatments in patients hospitalised with COVID-19 in the UK. The trial is underway at 177 NHS hospitals from across the UK. Eligible and consenting patients were randomly assigned (1:1) to receive either usual care alone (usual care group) or usual care plus high-titre convalescent plasma (convalescent plasma group). The primary outcome was 28-day mortality, analysed on an intention-to-treat basis. The trial is registered with ISRCTN, 50189673, and ClinicalTrials.gov, NCT04381936. Findings: Between May 28, 2020, and Jan 15, 2021, 11558 (71%) of 16287 patients enrolled in RECOVERY were eligible to receive convalescent plasma and were assigned to either the convalescent plasma group or the usual care group. There was no significant difference in 28-day mortality between the two groups: 1399 (24%) of 5795 patients in the convalescent plasma group and 1408 (24%) of 5763 patients in the usual care group died within 28 days (rate ratio 1·00, 95% CI 0·93–1·07; p=0·95). The 28-day mortality rate ratio was similar in all prespecified subgroups of patients, including in those patients without detectable SARS-CoV-2 antibodies at randomisation. Allocation to convalescent plasma had no significant effect on the proportion of patients discharged from hospital within 28 days (3832 [66%] patients in the convalescent plasma group vs 3822 [66%] patients in the usual care group; rate ratio 0·99, 95% CI 0·94–1·03; p=0·57). Among those not on invasive mechanical ventilation at randomisation, there was no significant difference in the proportion of patients meeting the composite endpoint of progression to invasive mechanical ventilation or death (1568 [29%] of 5493 patients in the convalescent plasma group vs 1568 [29%] of 5448 patients in the usual care group; rate ratio 0·99, 95% CI 0·93–1·05; p=0·79). Interpretation: In patients hospitalised with COVID-19, high-titre convalescent plasma did not improve survival or other prespecified clinical outcomes. Funding: UK Research and Innovation (Medical Research Council) and National Institute of Health Research

Genetic improvements in New Zealand forage cultivars

Substantial genetic gains have been achieved across a range of temperate forage grass and legume species in New Zealand during the past 60 years. The genetic gains reported here compare favourably with those achieved in cereals and with those achieved for similar species internationally. Substantial improvements in grain yield of cereal crops have been achieved through changes in harvest index; however, increases in yield of forage grasses and legumes reflect increases in total above ground biomass. Rates of genetic gain have been lower in lucerne (Medicago sativa L.) than in red clover (Trifolium pratense L.) and white clover (Trifolium repens L.) and lower in perennial ryegrass (Lolium perenne L.) than in annual ryegrass (Lolium multiflorum Lam.) and tall fescue (Festuca arundinacea Schreb.). Gains in forage yield and quality have often exceeded 1% per year and have led to significant (0.3 to 1.3% per year) increases in animal performance. Keywords: animal performance, forages, genetic improvement, quality, symbiotic associations, yield</jats:p

NZ Grassland Association: Over 50 years of communication in grassland farming

The New Zealand Grassland Association (NZGA) was formed in 1931 and since then has held 50 annual conferences and provided a forum for the discussion of agricultural problems and the latest research findings A membership of almost 1500 makes it one of the largest organisations of its kind in the world and the annual proceedings is distributed to members in over 40 countries. This paper reviews the history of the NZGA its achievements, goals and possible future directions. Keywords: New Zealand, communication, grassland farming</jats:p

A SURVEY OF ROOT KNOT AND CLOVER CYST NEMATODES IN DRY HILL COUNTRY

Clover cyst nematode (Heterodera trifolii Goffart, 1932) and root knot nematode (Meloidogyne spp.) were found throughout summer-dry hill country in the North Island. Clover cyst nematode was found at 50% of sites in the corresponding South Island hill country regions sampled but no root knot nematode was found at South Island sites. The implication for white clover breeding programmes is discussed. Keywords: Pasture, dry hill country, clover cyst nematode, root knot nematode, Heterodera trifolii, Meloidogyne sp., white clover, Trifolium repens.</jats:p

Breeding strategies for developing transgenic white clover cultivars

The introduction of foreign genes into elite white clover (Trifolium repens L.) genotypes has resulted in the first field test of genetically modified white clover. We now require breeding strategies which efficiently deploy transgenes into commercial cultivars. Current white clover cultivars are synthetics, produced by randomly intermating selected parents or seed lines for up to 6 generations. Unfortunately, the uncontrolled nature of transgene insertion means each transformant has a different site of insertion and frequently has a variable number of inserts. This complicates breeding strategies because populations produced by intercrossing these transformants will contain multiple insertion sites, variable dosage at each insertion site, and be highly heterogeneous for expression level. A modified synthetic breeding method is proposed for crosspollinated crops such as white clover which overcomes these difficulties by identifying F2 progeny homozygous for a defined number of transgenes. These homozygotes are used as the parents to develop a synthetic with a specific genetic composition and high expression levels of the transgene in all progeny. The advantages of backcrossing into existing cultivars or directly transforming inbreds are also discussed. The initiation of new crossing programmes in successive years can be utilised to offset the initial lagphase until strategies which reduce the number of generations required to obtain commercial quantities are developed. Keywords: backcrossing, breeding methods, cross-pollinated, hybrids, inbreeding, plant breeding, transgenic plants, Trifolium repens L.</jats:p

ADAPTATION OF WHITE CLOVER TO MOISTURE STRESS

In a series of four experiments, the w-seeding ability and shoot and root characteristics of dryland white clover populations (Trifolium repens L.), and the effect of selection for root characteristics within white clover were examined. There was little evidence that dryland populations were better at re-seeding than Huia, but dryland populations were more taprooted than populations collected from moister environments. Root morphologies of dryland populations were similar to that of Huia but were smaller leaved, although not as small leaved as Tahora. Evidence that selection for more taprooted, smaller-leaved types of white clover would be successful is also presented. Keywords: root type, drought, re-seeding, plant breeding, survival</jats:p

Factors affecting white clover persistence in New Zealand pastures

Better persistence and reliability of white clover (Trifolium repens L.) is critical in achieving a more competitive New Zealand farming industry. To persist, white clover must establish well and withstand the accumulated stresses of competition from associated grasses, grazing, variable soil fertility, drought, plus pest and disease pressure. These factors vary markedly with environment and farming system, making the choice of appropriate grazing management, plant nutrition, companion species and cultivar difficult. White clover is particularly vulnerable to mismanagement and environmental stresses during spring when plant size is at its smallest. This vulnerability is further compounded by the current trend in dairying to apply high rates of nitrogen (N) which favours grass growth more than clover growth. A faster grazing rotation and/or higher stocking rates can offset the adverse effects of N on white clover by utilising the additional grass produced and reducing competition for light. Irrespective of N inputs, frequent defoliation during spring favours white clover persistence by increasing grass tiller density, resulting in better ground cover and in lower soil surface temperatures in summer. There is a threshold above which the density of associated grass suppresses clover growth. This is most prevalent in swards containing browntop, cocksfoot and kikuyu, which are more competitive against white clover than tall fescue, timothy and perennial ryegrass. Plant breeding efforts to improve persistence concentrate on increasing the rate of stolon formation and decreasing the rate of stolon death. These efforts include selecting genotypes that have better spread and persistence in association with different grasses, and genotypes that continue to grow with lower inputs of phosphate. Changes in root morphology have enhanced persistence under moderate drought stress, while significant improvements in resistance to clover cyst nematode, root-knot nematode and clover flea offer real hope in reducing the impact of these pests. Developing cultivars with higher stolon growing point densities at a particular leaf size should improve persistence while maintaining the greater yield potential. Keywords: climatic stresses, competition, diseases, grazing management, pests, plant breeding, plant nutrition, Trifolium repens L.</jats:p

Do forage legumes have a role in modern dairy farming systems?

Intensification in New Zealand dairy farming systems has placed greater pressure on clover performance and fitness and has highlighted the need to develop clover cultivars that are better adapted to intensive grazing systems. Increased stocking rates and increased use of nitrogen fertiliser have put enormous pressure on the contribution of clover to modern dairy systems. Future innovations such as semi-hybrid cultivars offer the potential to improve the competitiveness of legumes with nitrogen-fertilised forage grasses. Similarly, advances in condensed tannin research suggest that significant animal performance gains can be achieved in conjunction with reduced environmental impact. In order to capture these benefits, dairy farmers will need to reassess their grazing management to ensure that legumes can be maintained at economically useful levels. Novel grazing management systems that optimise the benefits provided by the grass and legume components need to be used in future dairy farming systems. Forage legumes, and especially white clover, have an important role to play in modern dairy systems