Grass man­age­ment is a pow­er­ful but un­der­val­ued tool in sheep farm­ing

Irish Independent - Farming - - FARM OUR - TOMMY BOLAND

CON­DI­TIONS have im­proved some­what at Lyons since my last ar­ti­cle. We had re­ceived our to­tal av­er­age April rain­fall by April 12, but ex­pe­ri­enced more nor­mal rain­fall for the fi­nal two weeks of the month.

Tem­per­a­tures were around av­er­age for the re­main­der of April and soil tem­per­a­ture also im­proved as the month pro­gressed.

Up to the time of writ­ing, May has been favourable for grass growth. Grass growth in the week to May 10th was av­er­ag­ing 104 kg of DM per ha per day.

For a farm stocked at 12 ewes per ha with each ewe rear­ing 1.75 lambs daily herbage de­mand is in the re­gion of 50 kg DM per ha, so there is am­ple op­por­tu­nity to close up area for silage where these types of growth rates are be­ing achieved. It is im­por­tant to note that not all fields will grow grass at the same rate.

At the sim­plest level, the most re­cently grazed fields/ pad­docks will grow at a slower rate than those with a higher cover of grass, but where an av­er­age growth rate of 80 to 100 kg DM per ha per day is be­ing achieved am­ple op­por­tu­nity to close ground for silage ex­ists.

From talk­ing to farm­ers who are car­ry­ing out grass mea­sure­ment and grass bud­get­ing on sheep farms, they have seen big sur­pluses de­velop in the last 10 days and have re­sponded by clos­ing ground for silage.

This is im­por­tant for a num­ber of rea­sons, firstly it al­lows ro­ta­tion length to be short­ened which pre­vents pre graz­ing herbage mass from be­com­ing ex­ces­sive and thus re­duc­ing the qual­ity of grass con­sumed by ewes and lambs and fi­nally it pro­vides im­por­tant winter fod­der stocks on farms.

The as­sump­tion un­der­pin­ning the above ad­vice is that grass mea­sure­ment and bud­get­ing is tak­ing place. The up­take of the grass mea­sure­ment and bud­get­ing tech­nolo­gies has been dis­ap­point­ingly low amongst live­stock farm­ers in gen­eral and sheep farm­ers in par­tic­u­lar are no ex­cep­tion.

One of the key mes­sages com­ing from the Tea­gasc Bet­ter Sheep Farms pro­gram is the ben­e­fit that is achieved by a stronger fo­cus on grass­land man­age­ment. This fo­cus in­cludes cor­rect­ing soil pH and fer­til­ity, im­prov­ing graz­ing infrastructure (ie smaller and more nu­mer­ous pad­docks), grass mea­sure­ment and bud­get­ing and fi­nally re­seed­ing.

A com­mon mis­take is that re­seed­ing is the first step taken in an at­tempt to im­prove grass­land man­age­ment, how­ever if the other pieces of the puz­zle are not in place then the ben­e­fits of re­seed­ing will soon be lost, if ever achieved at all.

So what are some of the key tar­gets or fo­cus points in man­ag­ing grass at this time of the year?

This year has proved, as if any proof was re­quired, that man­ag­ing an­i­mals at grass is ex­tremely chal­leng­ing. The months of May and June are the tra­di­tional months for mak­ing first cut silage on farms. The pri­mary piece of in­for­ma­tion re­quired in this process is how much silage is re­quired. This is par­tic­u­larly ap­pro­pri­ate this year as most for­age re­serves have been ex­hausted.

To cal­cu­late your silage re­quire­ment you must know how many sheep you will over winter, how many days they will be housed for and how much silage they re­quire per day. Each farm must then build in their own safety net to al­low for ex­treme cir­cum­stances.

So let’s as­sume a daily re­quire­ment of 1.3 kg DM per ewe per day (al­low­ing for some moder­ate wastage) at the av­er­age flock size of 108 ewes for a four month winter. This gives a to­tal silage re­quire­ment of ap­prox. 17 tonnes of DM. So if you are us­ing pit silage this is 68 tonnes of fresh pit silage at a DM con­tent of 25% or 87 bales of silage.

By clos­ing silage ground, ro­ta­tion length also be­comes short­ened, as is sen­si­ble with higher growth rates. Data from Pas­ture­base would show that av­er­age growth rate dur­ing the four main grass grow­ing months av­er­ages around 65kg DM per ha per day.

If your tar­get pre graz­ing herbage mass is 1200 kg DM per ha then at a growth rate of 65 kg DM per day it will take ap­prox­i­mately 18 days for a field to re­grow this amount of grass af­ter graz­ing.

Ro­ta­tions

As the sea­son pro­gresses and growth rates be­gin to de­cline, ro­ta­tion length will need to be ex­tended to al­low for suf­fi­cient grass build up. It is also im­por­tant to main­tain grass qual­ity by achiev­ing low post graz­ing sward heights, though the graz­ing sever­ity should not be as hard as that achieved in the first and sec­ond ro­ta­tion.

For the av­er­age mid-sea­son flock at this time of year, the con­tri­bu­tion of milk yield to lamb re­quire­ments and in­take is de­clin­ing rapidly.

In sit­u­a­tions where grass still re­mains scarce there is lit­tle ben­e­fit to sup­ple­ment­ing ewes with con­cen­trates in week 8 of lac­ta­tion or later. It is bet­ter to pri­ori­tise the lambs in this sit­u­a­tion.

This can be achieved by for­ward creep graz­ing of the lambs where infrastructure al­lows, or even ad­vanc­ing the wean­ing date to re­serve the avail­able grass for the weaned lambs.

One of the keys to good and suc­cess­ful grass­land man­age­ment is mak­ing de­ci­sions early, whether it is in times of deficit or sur­plus, and this is greatly helped where mea­sure­ment and bud­get­ing is tak­ing place.

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