Managing the dairy herd this autumn

After a summer of record high temperatures and low rainfall, many dairy farmers are now entering the autumn/winter period with lower than normal grass covers and depleted winter feed stocks. Brendan Horan, Michael O'Donovan and Laurence Shalloo from Teagasc Moorepark outline the strategy that farmers must adopt to meet requirements

Grass Budgeting and Feed Supplementation

Grass is in short supply on many farms this autumn, with farm covers of 600-700kg DM/ha common compared to a target of 1,150kg DM/ha for this time of year (Table 1). Given current poor grass growth rates and winter feed shortages, short-term plans with the objective of maximizing grass supply and minimizing feed cost for the winter period need to be implemented.

In order to describe the grass budget targets and supplementary feed usage for the remainder of the year, we will take the case of the Curtin farm, Teagasc Moorepark and discuss the feed plan for the remainder of the season. The farm details as of Monday, 28 August are outlined in Table 2. Herd performance is similar to previous years, however, the concentrate supplementation level is much higher this year with overall grass availability and winter feed stocks much lower than previous years.

The basis for the feed budget for the remainder of the season must be a relatively accurate prediction of growth rates. The growth rates for the 2006 season thus far and the predictions for growth for the remainder of the 2006 season are shown in Figure 1.

The Feed Strategy

Due to the increased rainfall during the past week, grass growth rates can be expected to reach normal figures for the remainder of the grazing season (Figure 1). On that basis, the feed budget for Curtin's farm for the remainder of the season is shown in Table 3 below.

There are five clear components to the budget:

Maximize grass growth. While greater than normal growth rates can be expected, we base the budget on the annual average figures. Unlike in spring, autumn growth rates are mainly governed by daylight hours with soil temperature and rainfall levels less important.

Growth rate on the farm can be maximized by lengthening the rotation to 40 days now to take advantage of the remaining number of long days. Putting more grass on the farm is critical for those short on winter feed.

Supplement now. Supplement the herd with 4-6kg of concentrate until late September to reduce herd demand for grass, maintain rotation length at 40 days and therefore maximize the amount of grass on the farm for the month of September. Using lower levels of supplements for longer will reduce the grass growth potential of the farm and therefore more supplements will need to be fed overall to make up the shortfall in grass supply.

Secondly, high supplementation rates during the final rotation may make the critical cleaning out of paddocks more difficult to achieve.

Achieve the target residual during the last rotation. Paddocks must be fully cleaned out during the last round to ensure good quality spring regrowth and taking advantage of winter tillering. Target grazing residuals of 150 to 200kg DM/ha during the final round.

Achieve the target closing cover. Commence the last rotation on 15 October and ensure that a cover of 500kg DM/ha (200kg DM/cow) remains on the farm at closing in late November.

Be flexible. The entire budget for the autumn is based on predicted growth rates therefore measure each week and adjust the budget. Higher than anticipated growth rates should be matched by reductions in supplement levels.

Autumn Nitrogen Application Strategy

Grass growth rates have returned to normal or slightly above with most parts of the country receiving decent rainfall amounts in the last 10 days. The final component necessary to ensure grass supply is maximized on the farm for the remainder of the season is an efficient nitrogen fertilizer application regime.

As part of the Statutory Instrument No. 378 of 2006, the last day for nitrogen application is 15 September for all counties in the Irish Republic. It would have been a tradition in some parts of the country (especially the south) to apply nitrogen up to the end of September. However, latest research from Moorepark has shown that a blanket dressing in early to mid September rather than continuing to apply after each grazing up until the end of September will result in similar grass DM production in the autumn.

The level of N required will depend on overall stocking rate (demand for grass) and the quantity of N used in the last six weeks. If N was applied as normal over the last six weeks, then there is no requirement for increased levels in the final blanket application.

Generally, in these situations there is a build up in N reserves in the soil as a result of the below normal grass growth rates during the summer.

In situations were an N application was missed in previous rotations, then increased N application rates maybe required. Therefore to get the benefit of good autumn growth rates a bulk application rate of between 30 and 40 units per acre is recommended.

With current conditions, the optimum form of N (both economically and environmentally) is in the form of urea.

Farms with a high grass demand in October/November, who have their nitrogen applications up-to-date, should now consider applying a blanket application (0.75 bag of Urea /acre OR 1 bag CAN/ acre) across the entire farm.

Farms that do not have their nitrogen up-to-date may consider applying slightly more than this (one bag urea or 1.5 bags CAN/acre) across the farm.

Winter Feed Purchase Options

Farmers should now assess winter feed stocks and if in deficit consider the most economic purchase options based on current feed prices. Six feeds were evaluated using the net energy system with each unit of energy within that system called a UFL.

When all feeds are given a common platform (the UFL) they can then be compared based on their relative energy value.

Grass silage, maize silage, citrus pulp, barley and a 16.5% crude protein ration were compared when purchased in tonnes of DM, while round bales of hay, straw and grass silage were also analysed. Table 4 shows the relationship between feed purchase costs of various feeds in €/ tonne DM and €/ round bale relative to energy per 1,000 UFL.

The dairy cows diet must be made up of at least 40% forage

Table 4 shows the relative values of different feeds in €/1,000 UFL with different purchase costs in €/tonne of DM and €/round bale. For example, if grass silage was purchased for €130 per tonne of DM, this equates to a cost of €187/1,000 UFL while baled silage purchased at €26/bale also equates to €187/ 1,000 UFL

Maize silage purchased at €130/tonne DM equates to a cost of €181/1,000 UFL. If maize silage was purchased for €600/acre with a yield of 6t DM/ acre the relative cost would be €152/1,000 UFL while €800/acre equates to a cost of €204/1,000 UFL.

Select from the table the most likely purchase costs of the various feeds to determine the relative cost of each feed.

When deciding which feed to purchase, Table 4 should be consulted. Feeds that are cheaper per tonne of DM may not turn out to be the cheapest feed overall as their feed value is not considered.

The purchase cost of the feed (per tonne, per acre or per bale) will determine the relative energy costs of that feed.

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