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Monday 5 December 2016

Completing your feed budget

Mary Kinston

Published 31/08/2010 | 10:29

LAST WEEK I explained the importance of an autumn feed budget, understanding the simple balance of feed supply against feed demand and its effect on pasture cover.

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Again, for example if you are working forwards and your opening cover on September 1 is 700kgDM/ha, if pasture growth is 45kgDM/ha/day and pasture demand is 35kgDM/ha/day (2.5 cows/ha x 14kgDM/cow), this will result in a daily pasture cover increase of plus 10kg DM/ha (45kgDM/ha growth – 35kgDM/ha demand).

Therefore over a two-week period this would increase pasture cover by 140kgDM/ha (+10kgDM/ha/day x 14days) from 700kgDM/ha to 840kg DM/ha by September 15. An increase in pasture cover is desirable at this time of year.

So when completing your autumn feed budget:

- Assess pasture cover atSeptember 1 on milking area;

- Determine grazing milking cow and dry-cow numbers, with your drying off/culling strategy;

- Consider other stock grazing on the milking area and when they will be removed;

- Consider what level of supplement you plan to feed during feed-budget period and intake of pasture by all stock classes.

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Once a feed budget is completed, you should assess the change in pasture cover and whether this is suitable. Most farms will need to close the milking area at a pasture cover of between 450-550kgDM/ha to provide enough grass for grazing in early spring (550-650kgDM/ha). It is also imperative that pasture covers do not decrease below 300kgDM/ha but are no more than 500kg DM/ha by magic day in order to maintain pasture quality from April onwards. The variance in these figures is due to differences in stocking rate and calving rate. If your budget pasture covers are substantially below or above these targets, then changes to your feed budget and management will have to be made.

Tricky

For those farming high stocking rates this can be a tricky balancing act and such an example is shown below. This budget assumes that there are 140 cows on 40ha, with an overall stocking rate of 3.5 cows per hectare. Heifers and February calvers with poor condition score are dried off by October 1 (eg 40 cows) and removed from 40ha. All other cows are dried off by November 15 (eg 100 cows) and removed from 40ha. Cows are fed 2kgDM/day of ration throughout the budget. No other stock are grazed on the 40ha. Pasture cover on September 1 is 700kgDM/ha and is worked forwards (ie closing cover becomes next period’s opening cover). The target is 550kgDM/ha for February 1. Demand and growth are considered on a per hectare basis.

With a high stocking rate of 3.5cows/ha up until October 1 and only 2kg ration being fed per cow throughout, overall demand is 3tDM per hectare during the autumn budget period. As grass growth is only contributing 2.3tDM per hectare, this results in a 715kg/ha deficit. This level of demand is clearly too high and the management strategy must be adjusted. The target cover for February 1 is 550kgDM/ha, and if wintergrowth hopefully provides around 100kgDM/ha, the closing cover at December 1 must not decrease below 450kgDM/ha.

With an opening cover of 700kgDM/ha, there is 250kg DM/ha (700-450) of extended cover available for grazing. With a demand of 3tDM/ha, minus growth of 2.3 tDM/ha and minus 0.25tDM/ha of extended cover, there is still a clear shortfall of around 0.45tDM/ha. So how can this deficit be filled? Pasture eaten must be decreased by around 464.5kg/ ha (-714.5kg + 250kg extended cover) over the 91 days (5.1kgDM/ha/day). Options are:

- Reduce the stocking rate by drying off/culling extra cows earlier;

- Increase the level of supplementary feeding (ration/silage);

- Increase the land area available, or apply more nitrogen up to September 15.

As light-conditioned cows are already being dealt with in this scenario, a simple option is to increase the level of feeding by 1.5kgDM/cow (5.1kgDM/ha ÷ 3.5 cows/ha) to 3.5kgDM/cow (2kg + 1.5kg) during September and 2kgDM/cow (5.1kgDM/ ha ÷ 2.5cows/ha) to 4kgDM/cow (2kg + 2kg) for October and November.

Options must suit the farm’s circumstances. Whatever your decision, the body condition score of cows and the closing pasture cover of the milking area must not be compromised.