DairyNZ Autumn Winter Feed Plan

April 2011

Countering the effects of the colder seasons with a good feed plan

Dr. Dawn Dalley has been working with four commercial farms plus the Southland demonstration dairy farm for the past four years looking at what happens to rainfall, soil temperature, pasture covers and stock condition through autumn and using that information to work out the amount of feed they can get from pasture and how much needs to be brought in as supplements. Her presentation at the field day will show the value of collecting this data and using them as a predictive management tool.

There is great value in regular monitoring of growing conditions on farms. Data collected over a number of seasons can identify how much variability there is in pasture growth through the autumn and that will determine how much supplement farmers might need to have on hand for the winter. Once they know that, they can put plans in place and identify trigger points they can use to make decisions around feeding supplements, culling animals or maybe putting animals onto once-a-day milking to reduce feed demand.

Pasture covers are assessed during a weekly farm walk over an established route that covers all of the paddocks. This can be done using a rising plate meter, a Cedax rapid pasture meter or just visually. The amount of dry matter in each paddock is put into a spreadsheet program. Paddocks are ranked from highest to lowest and this creates a feed wedge and is used in autumn/winter feed decision making.

At the end of the season you can look back over the whole year and gauge the variation in production on each of the paddocks and use that information to identify paddocks that may need renovation or drainage or have other constraints, and then plan a strategy to bring some or all of these paddocks up closer to the average.

Recording soil temperature helps to forecast growth rate, especially going into autumn when soil temperature starts dropping and can very quickly have an impact on potential pasture growth. Soil temperature will also determine the level of response from nitrogen fertiliser.

A suitable soil temperature probe costs about $40. Readings should be taken at the same time of the day each time – say, at 10am – so do a couple of measurements at 10cm around that time.

Ideally, condition scoring should be done on monitor cows each month but otherwise there are four critical times of the year when body condition of the whole herd should be measured:

• Early autumn, to allow farmers to make decisions about drying-off animals and planning feed for autumn;

• At drying-off or just before they go to winter grazing, so that farmers know what the situation is;

• At the start of calving so they can see how successful wintering has been – have target condition scores been reached, and how much variation is there in the herd?

• Prior to mating.

By looking at autumn conditions over previous years says Dawn, farmers can get an idea of what the coming winter going to be like.

“If conditions are usually settled then that gives a bit more confidence to putting plans in place, but there is great variation from year to year so farmers need to be more vigilant in doing farm walks and looking to see how the situation compares with previous seasons and how the season is tracking in terms of pasture cover,” she says.

“The soil temperature gives an indication of potential growth especially around autumn when growth is usually more driven by soil temperature than moisture because usually soil moisture is not limiting at that time. Temperature also will indicate what sorts of responses there are likely to be to nitrogen fertiliser applications, so if the farm is short of feed and soil temperatures were still in the right range then you could look at using nitrogen to push grass growth forward.”

In terms of body condition scores in autumn, the range is important. Does most of the herd have a condition score of 4.0 to 4.5, or is there a tail of cows that may be below 4.0? That identifies the number of animals that are at risk, and so they will need more time to get them to the pre-calving target of 5.0 for cows and 5.5 for heifers.

It is also valuable to look at the range of scores in relation to animal age – are all the lighter cows younger ones? If so, once-a-day milking in the autumn for those animals might be needed to take a bit of pressure off them and allow them to get more condition on before drying off. Alternatively, milking them twice a day could continue but allocate them more feed for winter.

“This shows the possible synergies between planning for autumn and how that is going to impact on winter management”, says Dawn.

“In autumn we also need to be monitoring pastures, particularly on farms in Southland that are wintering on forage crops. We also need to be monitoring the forage crop yields so we can estimate whether or not we are going to have enough feed for winter and if we are going to be short, then we will have to change our plan for autumn and maybe dry cows off earlier because feed will be tight in winter and we won’t have enough to put condition on them,” she says.

“A lot of farmers make their own decisions, but in Southland we also have the SIDC website and we post the information each week for each of the farms. We put the average pasture cover and growth rate and any supplements that are being fed, and we’ve got the historical growth and soil temperature figures for each of the regions.”

“Trigger points – usually these involve average pasture cover”, says Dawn.

“Working backwards, we know what the average pasture cover needs to be at calving, and we know what the growth rate is through the winter period too. So we know that we can’t dry our cows off with any less than a certain amount of cover which is only slightly less than the amount needed at calving because there is not much growth during the winter.”

“Ideally we would hit that target cover at the end of May but if we had a cold, wet autumn we might actually decide on a trigger point slightly higher than the drying-off cover target. For example, if on 30th April we’re just 100 above the target, that could be a trigger point where we need to think about buying more supplement in or dropping the stocking rate, getting rid of culls, or whatever.”

For farmers who are not doing regular monitoring there are websites for each of their local demonstration farms. They can go to that site, look at the farm walk notes and see what is happening and what decisions are being made on those farms. There is also a series of discussion groups in various areas and DairyNZ consulting officers have access to demonstration farm data so they can be raising what is happening on these farms as part of a discussion on autumn planning.