Irrigated farming systemsNutrition and animal health considerations

D Squibb and C WestwoodPGG Wrightson Seeds

27 July 2018

Irrigation and paradigm shifts

• Irrigation = opportunities

• Increased dry matter (DM)/ha and stocking rates

• Pasture persistence

• Novel forages and enhanced feed value

• Too good to be true?

Irrigation planning and implementation

• financing / investment / infrastructure / agronomics / stock class changes

• Presumption new forage = productivity/profit• Sometimes…

– reduced feed conversion efficiency (FCE)– increased health issues (on ‘knife edge’)

Issues are manageable!

Planning to manage new forages

• Novel forage types — new grazing management

• Forage types grasses, legumes, herbs, annual crops– Higher digestibility and energy

(MJME/kg DM and MJME/ha)– Lower neutral detergent fibre

(NDF) and less effective? – Higher crude protein

More digestible, lower NDF

• Inherent forage attributes• Changed management —

rotational grazing, lower pre-graze mass

• More digestible, higher energy = fewer kgDM/g or kg liveweightgain, increased efficiency

BUT1. Less peNDF (cattle)2. Faster rumen outflow rate (ROR)

Less peNDF

• Less NDF and lower peNDF• NDF:

– cattle 35%– lambs 28–30%

• Cattle anissue, less so lambs• SARA rare, questionable clinical

consequence?• Susceptibility to ruminal bloat? • Manage grazing rotation length,

high peNDF supplementary feed

Rapidly rumen fermentable — irrigation

• Fast breakdown, plant cells• More VFA production (SARA??) not lactic acid• Grasses less issue• Legumes (red/white clovers/lucerne) BLOAT

– bloat oils– supplementary fibre– wilting– cattle not hungry– shift later in day

Faster rumen outflow rate (ROR)–irrigation • Young stock• More fermentable carbs to intestines1. Clostridial disease (vaccinate) lambs, calves2. Redgut lambs lucerne (red clover?) small rumen capacity Fibre supply on-off graze grass, baleage3. ‘Academically’ – lower MJME/kgDM as less fermented rumen, more hindgut

High crude protein (CP)

Depends on• Soil mineralisable nitrogen (N)• Nitrogen fertiliser• Pasture or crop species• Management • Typically greater crude protein

concentration vs dryland

High crude protein (CP)

Usually = GOOD thing• Prime lambs, heavily in lamb and lactating ewes,

yearling cattle 14–18% CP• Too much of a good thing? • Rumen and liver adaptation – up to six weeks +• Less issue, always on irrigated pasture• Greater issue, change dryland quality to irrigated

Other possible challenges

SUDDEN CHANGE TO HIGH QUALITY

PASTURES

Low peNDF

Rapid Rumen outflow rate

High crude protein

Internal parasite larval challenge

Vitamin B1 deficiency (Polioencephalomalacia’

‘PEM’ or ‘PE’ )

Bloat

Tryptophan toxicity

High faecal moisture (fleece staining)

Footrot fine wool breeds

Pulpy kidney

So, irrigated pastures are different? Often yes, vs. dryland • Poor feed conversion efficiency and/or health

challenges • Dryland stock to irrigation for finishing esp late

spring/summer months• Set stocking for lambing / calving

Think irrigated pastures as ‘crop’• May need ‘transition’ rumen and liver adaptation

dryland to irrigated new pasture species• Better if stock remain on irrigated pastures

SUMMING UP

Top three take home messages

Challenges are manageable! Think of irrigated pasture as a ‘crop’ changing

from lesser quality drylandGradual adaptation from dryland to irrigated

pastures — especially during late spring and summer if not closed systemClostridial vaccination for young stock

Tools, resources and training• Pasture Principles – Macquarie Franklin• https://www.evergraze.com.au/library-content/feedbase-

planning-and-budgeting-tool/

• https://www.mla.com.au/extension-training-and-tools/tools-calculators/health-cost-benefit-calculator/

• https://www.mla.com.au/extension-training-and-tools/tools-calculators/stocking-rate-calculator/

• Facebook groups1. The Rumen Room2. The Forage Forum

Thank you

David SquibbPGG Wrightson Seeds Aust

Mobile 0425790222Email dsquibb@pggwrightsonseeds.com.au

Charlotte WestwoodPGG Wrightson Seeds NZ

Mobile +64275544541Email cwestwood@pggwrightsonseeds.co.nz