2. Friday - Ruminant Sessions dr finbar mulligan university college, dublin - ruminal acidosis & sara

Subacute ruminal acidosis and low rumen
pH in grazing dairy cattle
Feedworks Conference
Twin Water Resort, Queensland
September 19th to 21st 2018
Assoc Prof Finbar Mulligan
School of Veterinary Medicine
University College Dublin
Ireland

UCD: Lyons Research Farm
200 Dairy cows, 7500 kg of milk, 1.5tonnes of concentrate feed, (600) kg of milk fat and
protein per cow per lactation, Spring and Autumn calving herds

Dairy Herd Health at University College Dublin

Subacute ruminal acidosis and low rumen pH in
grazing dairy cattle
• Subacute ruminal acidosis (SARA)
• Low rumen pH
• A. Causative factors / grazing diets
• B. Discussion of consequences in grazing cows
– Milk Production
– Fibre digestion
Steel et al Acta Veterinaria Scandinavica2009

Subacute ruminal acidosis and low
rumen pH in grazing dairy cattle
• Important to note: rumen pH and all uses of rumen pH data
• Unlikely to describe or at least describe fully the changes in
rumen fermentation which are important in the consequences
of this symbiotic relationship that we encounter
• Bramley et al., 2008
• Calsamiglia et al., 2012
• Plaizier et al., 2008
• Lean et al., 2016

• Subacute ruminal acidosis (SARA)
• Rumen pH < 5.5 in 3 out of 12 animals by rumenocentesis
• Present in 20 to 40% of cows in confined high production
systems (Garrett et al., 1997)
• Present in 10-15% of grazing cows
• (O’Grady, 2008)

• Dietary causative factors
• Ingestion of excessive amounts of rapidly
fermentable carbohydrate
• Starches (wheat starch especially problematic)
• Sugars?

• Ingestion of excessive amounts of rapidly
fermentable carbohydrate
• UCD Dairy Herd Health Group working standard:
• 35% or more starch + sugar in a TMR type diet is
a risk for SARA

• The more rapidly fermentable the diet is the
greater the challenge to maintain rumen pH
within a desired range
• In acute acidosis fermentation is reduced
• (Bramley et al., 2005)

5.4
5.6
5.8
6
6.2
6.4
6.6
6.8
0 2 4 6 8 10 12 14 16 18 20 22
RumenpH
Time of day
GS MS
80
90
100
110
120
130
0 2 4 6 8 10 12 14 16 18 20 22
RumenVFA(mmoll-1)
Time of day (h)
GS MS
Whelan et al 2012: Animal Feed Science and Technology: UCD Lyons Farm

• Physically effective NDF should be 22% of ration DM
(Mertens, 1997)
• Cattle require a diet that is adequate in fibre.
• Deficient fibre increased risk of ruminal acidosis and other
related disorders.
• EFSA: Report on Dairy Cow Welfare
The EFSA Journal 2009 1143:1-38

• In research at UCD Lyons Farm
• Simultaneously breaking advocated thresholds for
maximum starch and sugar and minimum NDF from
forage has produced SARA in dairy cows

4.50
5.00
5.50
6.00
6.50
7.00
9:00:00
AM
10:40:00
AM
12:20:00
PM
2:00:00
PM
3:40:00
PM
5:20:00
PM
7:00:00
PM
8:40:00
PM
10:20:00
PM
12:00:00
AM
1:40:00
AM
3:20:00
AM
5:00:00
AM
6:40:00
AM
pH
Time (h)
Rumen pH determined with an indwelling pH probe held in the region
between the dorsal and ventral caudal rumen for a diet containing 38.2 %
starch and sugar ; 23% NDF from forage; Dry matter intake 18 kg/d; Milk
production 25 litres/d (n=4)
Not SARA
Molloy et al 2015 ADSA: UCD Lyons Farm
25% of time less than pH 5.5
SARA

• The transition period
• SARA may be more prevalent at peak feed
intake than it is during dietary transition from
dry to lactating diets (Oetzel, 2005)

Krause and Oetzel, 2006

• Transition period
Source Dairy Australia: Lean and DeGaris 2010

• High quality grazed pasture and rumen pH
• Low DM concentration
• High digestibility
• High DM intakes from pasture eg.,
• 18kg of Grass DM per day = 2.3 kg of sugar
(especially for high yielding dairy cows)
• Sward management
– Low sward heights presented to grazing cows
– Pastures managed to maintain high digestibility
– Swards not permitted to become long or fibrous

• High quality grazed pasture and rumen pH
• NDF content of grazed grass in Spring 35 – 40%
• Effective NDF content 14 – 20%
• Effective NDF Requirement at grass 17%
• Kolver 1998
• eNDF of perennial ryegrass 40-50% of total NDF
Some perennial ryegrass pastures in Ireland and New Zealand
NDF less than 35%!

• Pasture-based diets:
• A common source of energy supplementation is cereal grains with
wheat being used by some
• Most practice abrupt introduction to pasture post-calving
• Often huge variation in diet where cows are housed again for 1 day, 2
days or 1 week due to poor weather or poor soil conditions in spring
• Little opportunity introduce supplements eg forages or buffers
• Rumen fill is often lacking

• SARA: Dietary causative factors: Pasture –based diets

 Rumen pH samples in 12 dairy herds
 Average yield 8114kg (sd 733kg)
 Average herd size 95 (sd 38 cows)
 Average concentrate fed 3.3kg/d (sd 1.5kg/d)
 Cows sampled were 80 to 150 DIM
 Pasture NDF > 50% (sampling period mid summer)
 Results
 3 out of 12 herds had a significant diagnosis of SARA
 11% of cows had a rumen pH < 5.5
O’Grady et al, 2008, UCD

• Gibbs et al., 2005 New Zealand Data
• 80% of time rumen pH less than 6.0
• Most cows experienced a trough in the range
5.0 to 5.5 each day

• Lewis et al., 2010 Ireland (unpublished)
• Grazing cows 40% of day under rumen pH 5.8
• TMR cows 10% of day under rumen pH 5.8

• Bramley et al., 2008
• 100 dairy herds selected from 5 regions in Australia
• 10.2% of cows were considered to be acidotic

• Transition to Pasture V Transition to TMR
• In relation to the development of metabolic and
reproductive disorders, the risk assessment showed that an
inadequate transition feeding is the hazard with the highest
risk estimates in all indoor farming systems (Note:
transition to fresh pasture with low fibre content can also
cause problems). EFSA 2009

• Group Grazing: Grazing immediately after calving
• Abrupt turnout to pasture (allowance 20kg DM/cow/day) from day of
calving + 3.5 kg of concentrate
• Group Indoor: Indoors for first 3 weeks only
• From day of calving fed balanced TMR until day 21 (grass silage, maize
silage and concentrate, allowance was 23kg of DM per day of which 53%
concentrate).
• Introduced to grass gradually between day 21-28 when critical first few
weeks had passed
• Alibrahim et al., 2013 UCD
University College Dublin: Experiment
Transition to Perennial Ryegrass Pasture V Transition to TMR

5.5
5.7
5.9
6.1
6.3
6.5
0 2 4 6 8 10 12 14 16 18 20 22
PH
Hours of the day
Effect of Feeding Method on Rumen pH in
Fistualted Cows at days 8-10 post-partum
Alibrahim et al. 2012
Grazing
TMR

Effect of abrupt turnout to pasture on rumen fermentation in
grazing dairy cows days 8 – 10 in lactation
AP: abrupt pasture introduction
GP: gradual pasture introduction

• Pasture-based diets
• Assessments with pH recording devices likely to be
located in the reticulum indicate that the reticulo-
rumen of grazing cows can become quite acidic
• Duffield 2004
• Subtract 0.3 to 0.4 units from reticulum pH to compare
with rumenocentesis pH

UCD Lyons Farm Data
Rafferty et al., 2013. Cow 462 15 July 2012
Drinking
Feeding line
pH decline after
feeding
pH Temp

• Does low rumen pH in grazing cows have a
detrimental effect on:
Production???
Fibre digestion??

• Does low rumen pH in grazing cows have a
detrimental effect on:
Production???

• Dietary causative factors: Pasture –based diets

 Rumen pH samples in 12 dairy herds
 Average yield 8114kg (sd 733kg)
 Average herd size 95 (sd 38 cows)
 Average concentrate fed 3.3kg/d (sd 1.5kg/d)
 Cows sampled were 80 to 150 DIM
 Pasture NDF > 50% (sampling period mid summer)
 Results
 3 out of 12 herds had a significant diagnosis of SARA

SARA High Risk Normal
Milk yield kg/d 31.54 29.98 29.28
Milk fat% 3.22 3.37 3.68
Milk protein% 3.19 3.05 3.15
Rumen pH 5.81a 5.82a 6.19b
Rumen acetate mmol/l 89.64 96.88 78.51
Rumen propionate mmol/l 29.85 26.64 21.34
A:P ratio 3.13 3.68 3.72
Iso butyrate mmol/l 0.95 1.14 0.59
N butyrate mmol/l 18.30 17.00 12.92
Iso valerate mmol/l 1.97 2.38 1.45
N valerate mmol/l 2.91 3.03 1.66
TVFA mmol/l 143.6 147.1 116.5
O’Grady et al 2008: SARA and low rumen pH in grazing Irish dairy herds

Effect of SARA on production
100 dairy herds
Australia Bramley et al., 2005
Acidotic Suboptimal Non Acidotic
milk volume (L/d) 33.0a 27.0ab 29.1b
Milk fat% 3.3a 3.9ab 3.7b
Milk protein% 3.2a 3.2a 3.1b
Fat:protein ratio 1.1a 1.2b 1.2b
Milk fat yield (kg/d) 1.1 1.0 1.0
Milk protein yield (kg/d) 1.0a 0.9b 0.9b

• In grazing research very little data on ‘increasing of rumen
pH’ and associated rumen changes and how it impacts
performance (Rafferty et al 2018 ‘in-press’)
• UCD Research Grazing cows
• Access to 13 kg DM of Perennial ryegrass based pasture
• 8 kg of high starch concentrate (65% cereal, 48% wheat)
• Fed 70 g (Buf 1) or 140 g (Buf 2) of rumen buffer
• Grass 14 to 24% WSC; approximately 40-45% NDF
• Based on Calcified Seaweed and Marine Magnesium

Influence of rumen buffer products on reticulo-rumen pH in grazing dairy cows (n=8)

a
b
P < 0.01

Control Buffer 1 Buffer 2
Milk kg/day 27.54a 28.74b 28.61b
ECM 29.20a 30.23ab 30.74b
Milk fat and protein kg/d 1.97a 2.02ab 2.06b
FCM (3.5%) 28.33a 29.52ab 30.20b
FCM (4.0%) 26.20a 27.31ab 27.93b
Fat yield kg/day 1.01a 1.05ab 1.09b
Protein yield kg/day 0.96 0.98 0.97
Lactose yield kg/d 1.27a 1.33b 1.33b
Milk fat g/kg 36.50 36.37 37.60
Milk protein g/kg 34.67a 33.84b 33.83b
Milk lactose g/kg 45.55 45.74 45.77
Influence of rumen buffer products on milk production of grazing dairy cows (n=24)

Proportion of Herds with bulk tank milk fat < 3.3% 2004 to 2014
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
2004 13.54% 12.21% 11.70% 25.03% 30.19% 17.74% 15.95% 9.14% 4.14% 1.64% 2.90% 7.18%
2005 10.81% 9.17% 10.85% 17.49% 23.86% 19.07% 13.51% 8.75% 3.03% 1.67% 2.26% 6.57%
2006 10.12% 10.46% 10.23% 21.28% 20.65% 22.32% 18.30% 8.46% 3.67% 2.41% 2.49% 4.41%
2007 7.93% 7.69% 9.74% 24.65% 20.75% 15.83% 11.98% 7.45% 4.43% 1.74% 1.67% 4.41%
2008 6.92% 7.09% 6.71% 11.36% 17.48% 12.11% 9.20% 4.62% 1.94% 1.49% 1.74% 3.89%
2009 6.30% 7.81% 8.14% 12.01% 12.04% 10.68% 8.24% 4.62% 2.50% 1.34% 2.22% 4.55%
2010 4.36% 3.96% 5.05% 18.10% 21.16% 12.44% 7.94% 5.34% 2.69% 1.36% 1.41% 2.17%
2011 6.69% 6.51% 7.35% 13.03% 11.57% 10.71% 8.55% 3.92% 1.97% 0.85% 1.66% 2.92%
2012 5.09% 4.72% 6.22% 8.10% 12.54% 7.67% 5.13% 3.39% 1.30% 0.78% 0.88% 3.54%
2013 4.99% 4.50% 5.62% 8.58% 13.58% 8.29% 8.39% 4.14% 1.70% 0.70% 0.87% 4.09%
2014 5.09% 5.24% 5.47% 9.80% 11.79% 10.77% 6.98% 3.47% 2.10% 0.42% 0.63% 1.40%
Carty et al 2017: Irish Veterinary Journal

Proportion of herds with low milk fat% within milk recorded Spring and
Autumn Calving Irish Herds (Data for 2004 to 2014)
Spring calving
Autumn calving
Carty et al 2017: Irish Veterinary Journal

• Low milk fat% in grazing dairy herds
• PUFAs and biohydrogenation
• Low rumen pH (6.2 to 5.8) also a factor

• Controlled studies would indicate that we can
alter rumen conditions in grazing cows by using
discrete buffer supplements
• This may increase milk production

• What are the consequences of low rumen pH
• Fibre digestion

• What are the consequences of low rumen pH
• Reduced fibre digestion
– Is the reduced fibre digestion pH or substrate
induced
– Is reduced fibre digestion only an issue in starch or
rapidly fermentable carbohydrate induced SARA
– ‘The carbohydrate effect’
Calsamiglia et al 2012; Mould and Orskov 1984

• Reduced fibre digestion also happens when
there is no starch in the diet
• This has been proven in UCD research using a
soya hulls and grass silage in-sacco for diets
with zero starch

GED = - 0.738 + 0.216 × (pH 6h); R2 = 0.69; P < .001
Relationship with high rumen pH values
Diets contain only perennial ryegrass silage and soya hulls
Mulligan et al., 2002
NDFD = -0.89 + 0.239 (pH 6h), R2 = 0.50, P<0.01

Diets composed only of soya hulls and
grass silage
1.5
1.7
1.9
2.1
2.3
2.5
2.7
2.9
3.1
Rate of digestion
%/hr
SH DM* SH NDF GS DM GS NDF
50% SH
85% SH
Effect of diet soya hulls % (50 v 85%) on rate of digestion in-sacco
Diet composed only of grass silage and soya hulls
Mean pH 6.72 v 6.59 (P<0.001)
Mulligan et al., 2002

Ruminal pH and rate of NDF digestion
Closed: 32% starch
Open: 21% starch
Circle: HMC
Triangle: DRY
R = 0.58, P < 0.001
51
Oba and Allen 2003 J Dairy Sci
86:184

Other consequences of SARA and low
rumen pH??
• Inflammation!!
• On our University farm cows walk 4 km per day
• Many farms up to 6 km per day or more for
twice daily milking!
• Is SARA and rumen fermentation important for
lameness

• Take home messages
• Highly fermentable diets (>35% starch and sugar)
with low levels of fibre consistently produce low
rumen pH (with Northern European forage types)
• Pasture-based diets
– Low DM%, low fibre, high sugar, short sward length
– Consistently produce low rumen pH

• Take home messages
• Ryegrass fibre digestion is higher at higher
rumen pH values
• Grazing dairy cows supplemented with a high
wheat concentrate have demonstrated
increased milk output following interventions
to increase rumen pH

Thank you for your attention!!

2. Friday - Ruminant Sessions dr finbar mulligan university college, dublin - ruminal acidosis & sara

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