Transcript Slide 1

Production Research Priorities
and PRG Endophyte Toxicity
By
R A Leng
Emeritus Professor
UNE
An animal nutritionist interest in
endophyte toxicity?
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Prior to 1996 –As a nutrition researcher never considered
possibility of endophyte ill thrift—Puzzled by low
productivity of experimental animals particularly in New
Zealand grazing PRG.
Since 1996 ---increasing awareness of ill thrift and sudden
death of livestock in many different grazing areas I visited
on lecture tours
Led me to research literature on ill thrift which ultimately
convinced me of major insidious problems associated with
endophytic fungus [Leng 2000]
Few if any nutrition or production researchers consider
endophytes. e g team at Lincoln NZ working on effects of
parasites/nutrition interaction. Blaxter’s energy
requirements team [Autumn PRG vs Spring PRG]
Endophyte Toxicosis Goes Largely
Unrecognised
•Producers who are not looking for a fescue toxicity
problem [and PRG toxicity] are much less likely to
detect one than someone who is - so endophyte effects
may go unnoticed [Ball 1997].
•The effects of endophytes on annual gains and
reproduction are much greater than is generally
realized. [Ball 1997]
•Research fund providers in Australia have not
recognised the economic losses from endophyte toxicosis
[Leng 2000]
Australia’s research contribution
has been miniscule and has not
even attempted a survey of the
economic losses
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Most research has been done on endophyte
toxicosis in
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Southern states of USA with Tall Fescue pastures
growing in hot conditions
New Zealand with perennial rye grass under cool
conditions
Research in Australia has been minimal.
Considerable production research has been done
on PRG without knowing alkaloid content.
Rye Grass Pastures Are Normally
Heavily Infected [60-80%] With N.Lolli
in Australia
Endophyte
[Neotyphodium Lolli]
in the stem of PRG.
Neotyphodium spp are not
restricted to PRG
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A number of grasses
contain Endophytes
Including Australian
native Echinopogan
Ovatus that is found in
all States and contains a
Neotyphodium sp that
caused staggers and
death of sheep in the
Tenterfield area as far
back as 1890
Anecdotal evidence of
production losses in cattle
and sheep in Australia
% lambs with fly strike
PRG staggers is common in
Victoria and Tasmania on the
spring PRG shoot
80
70
60
50
40
30
20
10
0
0
20
40
60
80
100
Dry weigtht of dags[g/lamb]
120
140
160
Diarrhea in lambs on
PRG, appears to be
associated with
Endophyte toxicosis.
The amounts of dags
and fly strike are
highly correlated.
Diarrhea and
endogenous protein
loss are associated
Heat stress has been associated with consumption of
endophyte PRG. Death rates from crowding into dams
with subsequent drowning have been recorded on PRG
pastures in hot weather
Sheep and cattle even on relatively
cool days will get into water or
seek shade for no apparent
reason
When you go looking for endophyte toxicity
symptoms they are apparent through out the country
Evidence of likely production losses
from NZ [cool climate] and
Southern USA [warm climate]
research
Growth rates of lambs on rye grass
and cattle on fescue pastures
Plus endophyte
No endophyte
0.9
0.8
0.7
0.6
Live weight
0.5
change
0.4
[kg/d]
0.3
0.2
0.1
0
Cattle on fescue in
Southern USA
Ala.
Miss.
Geo.
Virg.
Tenn.
90
80
70
60
Live weight
50
change of
40
lambs[g/d]
30
20
10
0
Lambs on rye grass in NZ
0
25
50
75
% PRG pasture as endophyte infected
100
Heat stress associated with lowered feed
intake, is an important factor in ill-thrift on
endophyte infected pastures
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Cattle generally are poor thermo-regulators.
[Their capacity to sweat is about 0.2 of humans]
Breeds with higher capacity to regulate body
temperature [greater ability to sweat] are less
effected.
The major measured effects
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Depressed cow and calf live weight
Reduced fertility particularly in lactating dairy and
beef cows
Reduced milk production in dairy and beef cattle
25
Sheep decrease feed intake a
environmental temperature rises
[kg/day]
20
15
10
5
0
-18
-12
-9
0
10
20
25
27.5
30
40
Friesians reduce feed intake
and milk yield as environmental
Heat stress increases
Reduction in milk yield
[kg/day]
Environmental temperature [oC]
5
4
3
2
1
0
70
72
74
76
78
80
82
35
40
Grazing Friesian cows change
their feeding behavior as
temperature rises
% total grazing in the
daytime
Thermal humidity index
70
60
50
40
30
20
10
0
10
15
20
25
30
Maximum daily temperature[oC]
Ergovaline and lolitrem are both
implicated in heat stress in
ruminants
Ergovaline decreases blood flow to skin reducing heat dissipation but
lolitrem has a heating effect. High body temperatures are associated with
low feed intake and often assumed to be the main cause of ill thrift.
38.4
38.2
38
37.8
37.6
37.4
37.2
37
36.8
36.6
36.4
200
180
160
140
120
100
80
60
40
20
0
-1
0
1
2
3
4
5
6
7
Hours from injection of lolitrem
Body temp.
Respiration rate
8
Respiration rate
Body temperature and respiration rate in sheep given a dose of lolitrem
B[75ug/kg LW] under cool conditions [McLaey 1999]
Body temperature oC
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Australia Is the Sun Burnt Country
and THI Is Often Very High
One January day in Australia
Research Priorities-1. Monitoring
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Pasture monitoring
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To provide information on variations in endophyte
alkaloids
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levels of toxins in PRG and how they are effected by soil, soil
fertility climate and grazing management
level of toxin effects intake or selection of pasture by cattle,
sheep or other herbivores
To provide information on economic losses deaths,
body weight, milk, wool, reproductive efficiency
To provide information where research is being
undertaken on other management factor e g
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Parasite control and production
Supplementary feeding strategies etc
Research Priorities 2.Thermal stress
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Establish the production responses to endophyte
alkaloids in relation to thermal stress [THI].
Potential for early warning of risk problems and
for establishing heat ameliorating management
practices.
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Shade
Yard work
Supplementary feeding [e g substitute feeding or
alternative pastures]
Research Priorities 3 –other
economic effects
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Diarrhoea
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Incidence
Effects in animals under thermo-neutral and
hot conditions
Cost
Dagging
 Fly strike
 Production losses
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Implication of diarrhoea
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Ill-thrift has many causes either single or
multiple and interactive
The symptoms are simply reduced production
[which is often clear to the producer] associated
with reduced feed intake [which is not apparent
to the producer]
Reduced feed intake is very often associated
with inflammatory cytokines and leptin secretion
The persistent diarrhoea may implicate
inflammation of the gut wall and indirectly the
immune system
Research Priorities 4 Interactions
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Seems safe to suggest that if there are animals
dying from heat stress or misadventure caused
by heat stress then most animals will be subject
to reduced feed intake and some form of illthrift.
Grazing animal production is complex and there
are potentially many interacting factors as is
clear from recent studies on the interaction of
protein requirements with parasites, immuno
nutrition and physiological state
Research Priorities 5. Protein
nutrition, parasite/disease
challenge/climate
The highest levels of alkaloids in PRG occur
in mature pasture on fertilised land.
3000
120
2500
100
2000
80
1500
60
1000
40
500
20
5
0
0
0
25
20
Concen 15
tration
[ppm] 10
Winter
Autumn
Pasture availability
Green Pasture
Spring
Peramine
Rainfall [mm]
Summer
Lolitrem
Autumn
Ergovaline
3.5
Crude protein in pasture [%]
30
3
25
2.5
20
Ergovaline 2
[ppm] 1.5
Dry pasture
15
10
5
0
Green
pasture
1
0.5
0
Oct.
Nov.
Dec.
Plus N fertilizer
Jan.
No fertizer
Feb.
Deficiencies of Growth Factors Alter the Flow of
Fermentation Intermediates Into Absorbed Nutrients
Deficient
medium
Well balance
growth medium
Digestible
forage
Digestible
forage
1.0
1.0
Fermentation
intermediates
0.17
Microbial
cells
0.83
Short chain
organic acids
+
methane
+
heat
Fermentation
intermediates
0.66
0.34
Microbial
cells
Short chain
organic acids
+
methane
+
heat
Priorities for Research—6
Implications of the immune system
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Environments where the sum of environmental
and immunological stressors is high divert
nutrients away from accretion in muscle, milk
and wool to liver anabolism and host defence
mechanisms [Husband 1995]
Physical and psychological stressors can activate
the acute phase response with potential [Colditz
2002] [calves on slippery floors]
Immune activation then is a primary factor in
reduced feed intake and reduced production
Parasites of the small intestine
progressively reduce feed intake
Steele 1996
Feed
intake[g/
day]
1400
1200
1000
800
600
400
200
0
30
60
90
Normal diet
Faecal egg count
Essential amino acids, in late
pregnancy and early lactation
are prioritised for lamb and milk
production. Lowering immune
function
Donaldson 1999
Control
Infected
120
Plus bypass protein
3000
2500
2000
1500
1000
500
0
-10
-7
-3
0
3
7
10
14
17
21
Days prior to and after lambing
Both the immune competence and
the feed intake effects are overcome
by increasing in metabolisable protein
intake
Van Houtert et al 1996
16
14
12
Cumulative 10
Live Weight 8
[kg]
6
4
2
0
-36 -18
0
18
36
44
62
80
98 114 130 148
Days of infection
100g fish meal
100g FM infected
0g FM
0g FM infected
Effects of parasitism on the nutrient economy
of small ruminants
Epithelia cell
turnover
tissue repair
Gut
Plasma
protein
leakage
Albumin
/globulins
from liver
Local inflammatory
response
Peripheral
Inflammatory
response
Muscle
Microbe &
diet protein
Muscle
protein
breakdown
increase
increase
decrease
VFA Energy
Skeletal
Wool or
Hair
Growth
of foetus
Milk
Endophyte toxicosis is likely to interact with
climate, physiological state and demand for
nutrients and disease incidence
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Ruminants on imbalanced feeds[ dry forages] reduce feed intake
and increase wasteful metabolism and therefore are more prone to
heat stress[ the need for a balanced rumen vs imbalanced]
Metabolisable protein requirements are increased
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in late preg. early lactation and at weaning
when the immune system is stimulated by foreign bodies, stress and
deficiencies of key nutrients
by the need to repair damaged areas of the gut
by increased secretion of mucous in the intestines
by increased drain of endogenous and microbial protein to the lower
gut
The metabolisable protein requirements to prevent the
periparturient rise in parasite egg production in ewes is
about 350g protein or 30% greater then book requirements
Research Priorities- 7 Discipline
oriented
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Study metabolism in the rumen and the site of
absorption of the alkaloids--- using labelled alkaloids and
cannulated animal [Hill 2005]
Study potential of a range of chemicals to adsorb the
alkaloids
Examine the effects of alkaloids on the immune system
Understand the effects on the gut
Understand transfer to foetus and milk[?].
Measure their effects on the immune system, illeum wall
and protein flow to the caecum large intestine[ site of
provitamin B12 absorption]
Radiolabelled Peptide Ergot Alkaloids. 83.Mitteilung über MutterkornalkaloideEmil
SchreierBiopharmaceutical Department, Division of Pharmaceutical Research and Development,
Sandoz Ltd., CH-4002 BaselHerrn Dr. Albert Hofmann zum 70. Geburtstag gewidmet
A number of binders including bentonite
prevent absorption of aflatoxins
60
50
40
Aflatoxin
Reduction in 30
Milk [%]
20
10
0
Bentonite-Na Bentonite-Ca
Bentonite increases wool growth [Fenn and
Leng 1985] in sheep by increasing microbial
protein supply [Klieve 2002]
Mycosorb
Activated
Charcoal
40
35
30
Relative
25
wool
20
growth
15
[g/patch/d]
10
5
0
0
Bentonite clays strongly bind ergot alkaloids between ph 2-8
but dissociate at Ph 8.5
Site of absorption of lysergic acid is from the rumen [Hill 2005]
5
10
15
20
Bentonite given[g/day]
Grazier observation. Under field conditions wool growth is increased by
feeding bentonite and scouring is eliminated or reduced in sheep .
25
Recombinant DNA ?
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Is their a role for recombinant RNA to
metabolise endophyte alkaloids.
Soil organisms will degrade alkaloids
Recent work inducing Fluroacetate
detoxification by rumen organisms
suggests any thing is possible[ Greig et al
2004]
It is likely that the industry will have to live
with endophyte infected pastures for a long
time, therefore remedial strategies must be
developed.
Wild card could be climate change in the long term
The 3 hottest years of the past century have occurred
since 2000
The Aussie Cow is just as susceptible to
endophyte toxicosis as overseas cows
The End