Subacute Ruminal Acidosis (SARA) in Dutch Dairy Herds -
Results of a Field Study
J. L. Kleen, G. A. Hooijer, J. Rehage, J. P. T. M. Noordhuizen
J. L. Kleen, Dr med vet, MRCVS, Division of Animal Production and Public
Health, University of Glasgow, Veterinary Faculty, Bearsden Road, Glasgow,
G61 1QH
G.A. Hooijer, DVM, PhD, Dipl. ECBHM, Veterinary Practice Mid-Fryslân, NL-
8491 BK Akkrum, The Netherlands
J. Rehage, Dr med vet, Dipl. ECBHM, Clinic for Cattle, University of
Veterinary Medicine, Bischofsholer Damm, D-30175 Hanover, Germany
J.P.T.M. Noordhuizen, DVM, PhD, Dipl. ECBHM, Department of Farm Animal
Health & Public Health, Ecole Nationale Vétérinaire de Nantes, Route
Gachet, F - 44300 Nantes, France & Department of Reproduction,
Obstetrics & Herd Health, Faculty of Veterinary Medicine, Ghent University,
Salisburylaan 133, B - 9820 Merelbeke, Belgium
Corresponding author: Joachim Lübbo Kleen, Email:
[email protected]
Abstract
In this field study, the prevalence of subacute ruminal acidosis (SARA) in
dairy herds in the Dutch province of Friesland was determined in a field
study. One hundred and ninety seven cows from 18 dairy herds were sampled
for ruminal fluid by means of rumenocentesis and the pH-value of the
samples determined. Between five and 19 animals were sampled per farm. Body
condition was scored on 139 cows about three weeks pre-partum and post-
partum at the time of ruminal pH measuring.
The overall prevalence in all animals sampled was 13.8%, while the farm
prevalence was pending between 0% on seven farms and 38% on a single farm.
The stage of lactation did not influence the occurrence of SARA. An
influence of the presence of SARA on body condition loss could be
determined.
Subacute ruminal acidosis is present in dairy herds in the region of
Friesland, which largely resembles conditions found in broader parts of the
E.U. The role of SARA in the transition period should be investigated
further.
Key words: SARA, ruminal acidosis, negative energy balance, dairy cow
Abbreviation Key: MFD= Milk fat depression, NEB= Negative energy balance,
SARA = Subacute ruminal acidosis, DMI= Dry Matter Intake
Introduction
Subacute Ruminal Acidosis (SARA) is a condition which has been thoroughly
described in the literature in recent years (Kleen and others 2003, Enemark
2008, Plaizier and others 2008). The feeding of a large proportion of
concentrate feed or a diet relatively deficient in long fibre may lead to
this form of acidosis mainly described in dairy cattle. Maladaptation of
the ruminal environment or mistakes in feeding management and preparation
of the ration may then lead to the increase of short-chain fatty acids
which are poorly absorbed by the ruminal mucosa (Goff 2006). SARA has been
linked to loss of body condition, milk fat depression (MFD) and lameness
(Garrett 1996, Oetzel 2000, Livesey and others 2003). It has been pointed
out recently that the pathogenic mechanism of SARA might consist of
activation of systemic inflammatory responses due to lysis of gram-negative
bacteria (Gozho and others 2006, Gozho and others 2007).
SARA can be defined as an intermittent fall of ruminal pH at or below 5.5
some hours after concentrate feeding (Garrett and others 1999, Oetzel
2000), although the accuracy of this definition is subject to debate
(Plaizier and others 2008). A ruminal pH between 5.6 and 5.7 is viewed as
being a marginal area for SARA by some authors (Garrett et al. 1999,
Morgante and others, 2007). SARA has been reported to occur predominantly
in two situations. Firstly, in the freshly lactating animal that has not
yet developed a ruminal environment capable of metabolising the lactating
cow diet; second, the high-producing dairy cow, which is confronted with a
ration insufficient in structure and a larger proportion of concentrate,
respectively (Nordlund and others 1995).
The prevalence of SARA is not well researched. So far, a study from the
U.S. showed a prevalence of 19% in early lactating cows and 26% in cows
further into lactation. Single herds with SARA-prevalence up to 40% had
been observed in this field study (Garrett and others 1997). An Italian
study (Morgante and others 2007) investigated the prevalence of SARA in ten
intensive dairy herds. They identified 3 herds experiencing SARA, having
found >33% of cows tested with rumen pH 5.5 in those herds.
The objective of this study was to determine the proportion of SARA-
affected cows in dairy herds of the type which is found in that region and
determine whether stage of lactation has an influence on the occurrence of
SARA. Furthermore, possible influence of SARA on the dynamics of body
condition around calving was to be detected.
Material and Methods
Herds and Husbandry
In order to investigate SARA-prevalence, 18 dairy farms in the Dutch
province of Friesland were included in a field study. All farms receive
herd-health service by one private veterinary practice, from which herd-
data including insemination dates, prospective calving dates and milk
production data were available using an electronic herd management system.
Farms were selected on basis of production, expected compliance and
management standard. All farms were typical for this area in terms of herd
size, production level and management.
All farms cooperating in this study are dairy farms with Holstein Friesian
cattle. The mean milk yield was 8600 kg milk (305 d) with a mean of 4.4 %
fat and 3.46 % of protein. The mean herd size was 87 dairy cows, with a
range from 55 to 250 animals. The basic winter feeding consisted of grass
silage and maize silage, delivered by a mixer-wagon on most of the farms.
An additional component of concentrate was given between three and five
times a day by automatic feeding and during milking time. With the
exception of one farm, all had a loose housing system with a pasture period
between May and November. The study described here was done in the housing
period from November 2002 to March 2003.
Animals and Sampling
In total, 197 cows had been selected for the study on the basis of their
expected calving dates and stage of lactation with the objective to have
animals at different stages of lactation available throughout the study,
irrespective of individual milk production level. Additionally, the animals
were divided in two groups. Group 1 consisted of animals up to 25 days in
lactation at time of examination (early lactation group; 117 cows); group 2
included animals 25 - 182 days in lactation (mid-lactation group; 80 cows).
Between five and 19 cows in both groups were included per farm. The 25 day
threshold was chosen as involution processes of the post-partum period have
ceased by this point of time (Leslie 1983). Table 2 gives an overview of
herd and sample size.
Before ruminal fluid sampling was undertaken, all cows were examined
clinically with auscultation of the digestive tract and scored for their
body condition. Here, a 0.25-point system on a 17- point scale, ranging
from 0 to 5 was used. Of the 197 cows in the study, 139, (71% group 1, 29%
from group 2) were scored for body condition three weeks before the
expected calving date by the same person. This was done in order to monitor
changes in body condition.
Ruminal fluid was collected three hours after intake of concentrate in the
usual ration, by means of rumenocentesis (Nordlund and Garrett 1994). The
puncture site was located on the left-hand side approximately 20 cm caudal
to the last rib at the level of the stifle joint. A needle (2.1 x 80 mm)
was thrust into the ventral ruminal sack. A sample of ruminal fluid (10-15
ml) was then aspirated. The ruminal pH was measured with a portable pH-
meter (Hanna Instruments, Italy; HI 9025/1230) immediately after sampling.
The pH meter was calibrated before each examination according to the
manufacturer's instructions. A cow was considered to be experiencing SARA
with a ruminal pH of 5.5. In order to assess the quality of ruminal
fluid, a 5-point scoring system for the parameters colour, smell,
consistency, biological activity and presence of ruminal protozoa was
developed by the authors. Table 1 gives an overview of the parameters and
the scoring for the ruminal fluid ranging from 1 (acidotic) to 5
(physiological). Furthermore, a faecal consistency score (FCS) and an
Undigested Faecal Fraction Score (UFFS) were done on cow side based on a
five-point scale according to Zaaijer and others (2001). The scores are
also described in table 1.
Statistical analysis
In the statistical analysis the SPSS computer program (SPSS Inc,. Chicago,
USA) was used.
All findings from ruminal pH measuring were analysed for both study
population and per herd. Here, herd prevalence of animals currently
experiencing SARA were calculated as well as proportion of animals within
the marginal range of pH 5.6 and 5.7
Possible influences of body condition score on ruminal pH were analysed by
a general linear model with 'BCS' as outcome variable and ruminal pH as
fixed factor.
To determine differences in SARA prevalence between study groups, Chi
Square testing was used to evaluate differences in SARA prevalence between
early and mid-lactation animals. In order to evaluate an influence of day
post partum on SARA prevalence, a general linear model with "days post
partum" as a fixed effect to account for the clustering of cows within
farms was constructed.
In order to evaluate the influence of SARA on body condition change, a
general linear model was constructed to analyse the data, with the 'BCS
difference' as the outcome variable and the 'SARA classification' (Animal
at or below cut off point pH 5.5) of each animal as the factor of interest.
'Farm' was included as a random effect in all calculation models.
The data from faecal consistency scoring and scoring of undigested faecal
fraction were analysed by a one-way ANOVA where faecal scores as outcome
variable were plotted against ruminal pH.
Correlation of ruminal fluid characteristics and pH were examined. Results
from the ruminal fluid scoring were compared to the ruminal pH using
Spearman rank correlation.
In all cases the p value for statistical significance was set to 0.1), all other ruminal fluid scores were highly correlated with
ruminal pH (rs= 0.4 – 0.47, p
