Case for sup­ple­ments

South Waikato News - - RURUAL DELIVERY -

Many Waikato dairy farm­ers want to know why they need to feed sup­ple­ments, when in the past grass was enough. Waikato Far­mWise con­sul­tant Brid­get Ray ad­dresses this.

Of­ten on a farm the dis­cus­sion: ‘‘What is go­ing on? We used t o do i t j ust on grass, we never had to buy sup­ple­ments,’’ comes up.

Prob­a­bly the biggest cont ri but­ing f ac­tor as t o why now, grass alone i s not enough, is that for the past t hree years we have had sea­sons with poor grow­ing con­di­tions. Put sim­ply, we are not grow­ing grass as we used to.

Al­though it is hard to put an ex­act fig­ure on how much less grass we are grow­ing there are some re­ports that we are pro­duc­ing be­tween two and four tonnes a hect are a year l ess i n some ar­eas in the Waikato.

There are a num­ber of rea­sons why t his is hap­pen­ing.

Ob­vi­ously, l ack of rain means less growth but it is also the three hard sea­sons in a row, hav­ing an ac­cu­mu­la­tive ef­fect.

Farm­ers look­ing at their pas­ture sward will, I am sure, no­tice a change in com­po­si­tion. The death of de­sir­able pas­ture species has left gaps for weeds and un­de­sir­able grasses such as poa to come into swards.

With long dry spells the ni­tro­gen cy­cle slows or stops al­to­gether mak­ing less ni­tro­gen avail­able f or plant growth. Stressed plants are more prone to in­sect dam­age.

DairyNZ f i gures show a 450kg cow pro­duc­ing 350kg of milk solids (MS), eat­ing 11 mega joules of metabolis­able en­ergy (MJME) feed, be­ing milked f or 250 days and us­ing 80 per cent of pas­ture grown needs 5.1 t onne of f eed an­nu­ally.

A 500kg cow do­ing 400kgMS needs 5.8 tonne.

A dairy f arm stocked at three cows/ ha would, there­fore need to grow 15.3 tonne grass/ha to meet feed de­mands for a grass only, fully fed cow.

This raises the ques­tion, ‘ ‘ how many peo­ple have grown t his much on t heir f arms in t he l ast t hree years?’’

Prob­a­bly not very many in the Waikato. What can be done? Farm­ers have t hree op­tions:

1) Ac­cept less pro­duc­tion per cow and main­tain stock­ing rate.

2) De­crease the stock­ing rate but main­tain cow pro­duc­tion.

3) Buy in sup­ple­ment. It is im­por­tant to note the sce­nario, grass growth drops by 1 tonne a hectare, a year.

To main­tain t he same stock­ing rate and ac­cept a drop in per cow pro­duc­tion farm­ers can ex­pect a drop in kgMS/ ha by about 10 per cent. On a 300 cow f arm do­ing 1000kg MS/ha, milk pro­duc­tion would drop to 900kg MS/ha. All other costs would stay sim­i­lar so at a pay­out of $6/kg MS loss in in­come would be $600/ha.

If there is less feed avail­able on farm, in or­der to meet cow body con­di­tion score and pas­ture cover t ar­gets cows would have t o be dried off ear­lier t han be­fore. If t his was not done, pro­duc­tion and mat­ing perf or­mance t he f ol­low­ing sea­son would be com­pro­mised.

The other op­tion to feed the cows at the same lev­els with less grass grown is to de­crease the stock­ing rate.

Farm­ers would need t o drop stock­ing rates about 7 per cent to achieve this.

On the av­er­age farm, as de­scribed above, this means drop­ping the stock­ing rate from 3 cows/ha to 2.8 cows/ ha. The cost is about 60kg MS/ ha or at a $ 6 pay­out $360/ha.

Brid­get Ray

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