Grass and dairy nutrition in the late 2018 spring
The last few weeks have brought many difficulties for managing grass and herd nutrition on dairy farms. Persistent cold wet weather has severely impacted on growth rates. Many farmers report very low covers of only 300-400kg per ha on first areas grazed in February, instead of the target 500-600kg. On heavier land, less than 10% of area grazed at this stage is reported, with fertiliser N applications falling well behind target also. A further complication is an emerging scarcity of silage in some areas, on top of the longer term shortage endured in the North West. Collectively, these factors place increased pressure on herd management at a busy time of year. Every farm faces its individual challenges. Typical scenarios reported can be summarised as: Low grass covers (under 600kg per ha and slow recovery), but with adequate silage stocks available. Low grass covers and shortage of silage in the yard. High grass covers (but low percentage grazed), poor ground conditions, adequate silage.
High covers (but low percentage grazed), shortage of silage in the yard.
The main objectives to be met in the short term are to: Feed milking cows well to maintain good milk production, body condition and rumen health.
Ensure youngstock and remaining dry cows are correctly fed.
Manage grazing to protect ground conditions while utilising available grass. Maintain adequate grass cover on the farm by managing rotation length. Promote new grass growth by grazing winter covers and applying fertiliser. The following are tips and guidelines to meet these aims for scenarios outlined above.
Average farm covers
Mean growth rates around the country were 5-7kg per ha last week, however 12-18kg per day was reported in Ballyhaise, Moorepark and Johnstown, and commercial farms with early N applied indicated some potential pick-up in growth rates. However, for many farms corrective action will still be required in the short term:
Holding average farm cover above 500kg per ha in early April is very important to allow the farm respond quickly to improving growth conditions.
Farms with large areas grazed and/or little to no grass need to get daily demand below growth rate to prevent covers from falling too much. If covers are dropping rapidly, now is the time to reduce demand by reducing the daily area grazed and introducing supplementary feed. Cows must be adequately fed. Housing a proportion of the herd can work well, if cubicles and feed space are under pressure.
The aim is to have at least 1100kg of DM per ha (enough grass for 80 cows for 24 hours on 1ha) back on the first paddock in the second round. With only a 300-400kg recovery by March 22, a further 700-800kg of total growth is needed before the next grazing. It is difficult to project growth over the next few weeks, but at a reasonable estimate of 30kg per day on average, adequate cover to start the second rotation will take until April 13-15.
The plan now should be to stretch the end of the first rotation to that point (plus or minus 3-4 days). Review at the end of the first week of April, and adjust if needed. Ground conditions are slowly improving so farms with a low percentage grazed, and good grass covers, can get area grazed now. This must be a priority, especially where silage is running tight. Graze some lower covers to settle cows into grazing and then remove the heaviest covers (if dry overhead).
These paddocks will lie dor- mant until new growth is stimulated by grazing. Use on-off grazing if conditions are marginal and aim for two grazing bouts per day. Bring the evening milking time forward to reduce labour impact. Fertiliser N needs to be applied as a priority now. Aim is to have 87kg of N per ha (70 units per acre) out by the end of March. Some farmers on heavier land have brought in contractors with low impact machinery (such as ATV spreaders). Explore all options. Apply P fertiliser after grazing heavy covers, to aid root recovery.
Silage stocks, feed options
Assess available silage and feed demand immediately. Early action on feed deficits makes them easier to solve. As a guideline for intake of fresh silage (22-24% DM), use 380-400kg per week for mature animals (dry/milking cows, bulls, in-calf heifers); 150170kg per week for youngstock (yearling heifers). These are based on full-time housing; reduce by 40-50% if cows are grazed by day. Compare total demand for the next four weeks, net of available grass, to silage stocks in the yard.
Aim to have at least 1.5 weeks of silage reserve on hand by late April. If this is unlikely, take action now to stretch supplies. A 30% silage deficit can be managed by feeding extra concentrates. Bigger deficits will increase digestive problem risks due to fibre shortages, so forage purchase may be needed. Straight ingredients like hulls, beet pulp, and palm ker-