Massey Dairy Day ticks sustainability

01-08-2010 | Jackie Harrigan

Nitrate reduction through duration-controlled grazing:

The dairy industry's strategy is to reduce nitrate leaching by 50% by 2020. Year-round duration-controlled grazing trials at Massey are looking at how excluding cows from pastures for part of the day affects their milk production and reduces nitrate excreted on to pastures, particularly through urine.

Cows are grazed for four hours each grazing, then removed, simulating a return to a feedpad/animal shelter to receive supplement. This grazing area is compared with a standard grazing area, where cows are grazed for seven hours during the day or 12 hours at night. Pasture accumulation is measured, along with estimated cow intake, N, P, and E coli concentrations in the drainage and run-off water.

Results in the first year show a 42% reduction in nitrate leaching into drainage water, while similar pasture accumulation and cow-intake rates were recorded from the duration controlled and standard grazing regimes. With a 60% reduction in cow grazing time and a 46% reduction in dung/urine returned to the paddock, the researchers say the results are significant and further trial results will prove whether the method is a feasible and practicable strategy to decrease environmental impacts, particularly on heavy soils.

More? Christine Christensen, James Hanly, Mike Hedley and Dave Horne. Email C.L.Christensen@massey.ac.nz

Use of reflectance sensors to optimise nutrient and grazing management:

Light reflectance sensors operating in the visible spectrum (VIS) and near infrared (NIR) spectrums are able to give measurements of pasture mass and pasture quality in terms of metabolisable energy (ME) and crude protein (CP) content. The sensors can be mounted on the front of a quad bike as a pasture meter is trailed behind.

A map can then be produced for each paddock showing the pasture mass, ME and crude protein content, and used to plan feeding and supplementation of the herd. Combining kgDM/ha with crude protein and metabolisable energy would mean there is potential to start talking about the energy value/ha of a pasture.

If the N losses to the environment (excreted in dung and urine) are a result of the differences between the crude protein content of the pasture and the amount of protein in the milk, then rationing of feed may be possible to ensure similar milk production but with lower N loss by feeding lower crude protein pastures. On the other hand, knowledge of a protein deficient pasture at certain times of the year would mean silage or soy meal high in protein could be added, thus improving the efficiency of feeding the cows on grass and supplements.

More? Reddy Pullangari, Ian Yule, Mike Tuohy, Mike Hedley and Peter Hutton. Email I.J.Yule@massey.ac.nz

New cultivars an opportunity to increase productivity:

Many dairy farmers are reaching production levels of 400+ kgMS/cow and1100-1200kgMS/ha, considerably above the national averages of 325 and 930 respectively.

Agronomist Cory Matthew says farmers are achieving these levels with comparatively high feed conversion efficiency, driven by focusing on high dietary ME levels by targeting pre- and post-grazing herbage mass targets and supplying adequate quantities of quality forage.

New Zealand farmers are well served by the progress made by seed companies, producing cultivars with increased yields and innovations like Italian hybrid, tetraploid and late-flowering varieties, AR37 novel endophyte, meadow fescue germplasm introgression and high sugar varieties.

Farmers can choose new grass varieties to meet specific needs of their farming system, he says, adding that it is a good idea to sow a test paddock of a new variety first.

Peter Kemp outlined to farmers the advantages legumes and herbs have for dairy pastures, providing pasture of higher nutritive value than ryegrass in summer. Modern white clover varieties with high stolon density and medium to large leaves are world-leading, but can be challenged by clover root weevil, more competitive ryegrass cultivars, and poor establishment practices. Chicory has a higher nutritive value than higher forage-producing plantain but the latter out-yields chicory in the summer and is more compatible with a ryegrass pasture mix. Chicory provides high feeding value forage in summer and autumn but under typical grazing management usually persists for only one or two years.

Kemp advises caution when grazing newly established ryegrass chicory pastures, saying the herbs do not persist after being grazed into the crown so they should not have their first grazing until the chicory has grown six leaves.

This might sacrifice some of the early tillering of the ryegrass but will increase the chicory establishment and improve persistence, he says.

Plantain will out-yield chicory except in the summer and with improved digestibility and high milk production off the two forages, the necessary grazing management adjustments are worth adapting to.

More? Cory Matthew and Peter Kemp. Email C.Matthew@massey.ac.nz

Increasing dairy sustainability - nutrition and management:

Jean Margerison outlined Massey's research work on optimising heifer production and potential in dairy herds to maximise profitability through lifetime productivity.

Optimising potential includes low calf mortality by use of the three Qs of colostrum:"quickly, quality and quantity". Growth targets from birth to calving need to be met, pushing high growth rates in 0-3 months, but avoiding mammary fat deposition in the critical 12 months to puberty while still ensuring the heifers have met the target of 60% of mature body weight by breeding at 13 months. By calving at 22-24 months they need to be at 90% of mature weight so they use energy for milk production rather than for growing and are able to maximise conception rates at rebreeding.

Heifers need to enter the herd with good liveweights to minimise competition with the older cows, Margerison says. Minimising stress at this time would include being introduced to the shed before calving and teat sealing to reduce mastitis infection. Lameness is a common source of stress - Margerison says heifers have lower foot fat levels and making them stand on concrete for long periods, low drymatter feeds and sudden diet changes can all exacerbate the problem.

Lameness research is ongoing at Massey, where researchers have discovered lameness in NZ herds is different to overseas. A different area of the cow claw is susceptible to damage and it tends to last longer in Kiwi herds.

More? Jean K Margerison. Email j.margerison@massey.ac.nz

Reproduction and sustainability:

Effective reproductive manage­ment is the key to a sustainable dairy herd as empty cows are lost to the herd, needing to be replaced and thus preventing the replacement of other less efficient producers (lame, older or high cell count cows).

As inductions are phased out in the medium term, the importance of effective reproductive management will only increase, Richard Laven says.

The two factors crucial for successful reproduction are accurate and effective heat detection (easier to solve with personnel training) and a higher conception rate (requiring longer term action).

Solving these two problems has the potential to achieve a six-week in-calf rate of greater than 75%, he says.

More? Richard Laven. Email R.Laven@massey.ac.nz

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