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j.compag.2018.08.011

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Computers and Electronics in Agriculture 153 (2018) 54–61
Contents lists available at ScienceDirect
Computers and Electronics in Agriculture
journal homepage: www.elsevier.com/locate/compag
Original papers
The influence of different milking settings on the measured teat load caused
by a collapsing liner
T
⁎
Susanne Dembaa, , Christian Ammona, Sandra Rose-Meierhöferb
a
b
Leibniz Institute for Agricultural Engineering and Bioeconomy, Department of Engineering for Livestock Management, Max-Eyth-Allee 100, 14469 Potsdam, Germany
Hochschule Neubrandenburg, University of Applied Sciences, Department of Agricultural Machinery, Brodaer Str. 2, 17033 Neubrandenburg, Germany
A R T I C LE I N FO
A B S T R A C T
Keywords:
Machine milking
Milking settings
Teat-liner interface
Pressure
Load
Milking machine settings such as the machine vacuum, pulsation rate, and pulsation ratio influence teat tissue
and teat condition, but there remains a lack of knowledge about the teat-liner interface and the pressure applied
to the teat tissue by the teat cup liner during milking. The aim of the present study was to determine the
influence of different milking settings on the teat-liner interface with the help of a pressure-indicating film. The
Extreme Low Prescale film by Fujifilm and a hollow artificial teat made of silicone were used to measure the
influence of different machine vacuum levels (30 kPa, 40 kPa, 50 kPa), different pulsation rates (40 cycles min−1, 60 cycles min−1, 80 cycles min−1), and different pulsation ratios (60:40, 65:35, 70:30) on the teat
load caused by the collapsing liner. The response surface methodology with a central composite design was used
to plan the experiment. The experiment was performed with a conventional milking cluster equipped with round
silicone liners. The average pressure (AP), the maximum pressure (MP), and the load (L) were used to analyse the
influence of different milking settings. Analysis of covariance was used to estimate the differences between
measuring areas, machine vacuum levels, pulsation rates, and pulsation ratios. Machine vacuum levels, pulsation
rates, and pulsation ratios had a significant influence on the measured teat load caused by liner collapse; the
higher the machine vacuum and the pulsation rate, the higher the measured values of AP, MP, and L. MP values
decreased with an increase of the pulsation ratio. The pulsation ratio affected L significantly depending on the
machine vacuum. The liner applied more pressure to the end of the teat compared with the whole teat barrel. In
conclusion, the results of the present investigation show that different adjustments to the machine vacuum, the
pulsation rate, and the pulsation ratio can significantly influence the pressure applied to the whole teat by a
collapsing liner.
1. Introduction
Machine milking significantly affects teat tissue parameters
(Gleeson et al., 2002) and can worsen teat condition (Mein et al., 2001;
Mir et al., 2015). Several methods, such as teat scoring (Neijenhuis
et al., 2000; Mein et al., 2001; Rose-Meierhöfer et al., 2014), ultrasound
measurements (Neijenhuis et al., 2001; Gleeson et al., 2004; Parilova
et al., 2011), calculating the Touch Point (TP), the Over-Pressure (OP),
and the Liner Compression (LC) (Mein and Reinemann, 2009), and direct pressure measurements (Davis et al., 2001; Tol et al., 2010;
Leonardi et al., 2015), are available to assess the influence of machine
milking on teat tissue and teat condition directly after milking as well as
over a longer period of time.
The settings of machine vacuum, pulsation rate, and pulsation ratio
affect teat tissue and teat condition. Excessive machine vacuum leads to
⁎
cracks in the epithelium of the teat tissue (Williams and Mein, 1985).
Hamann and Mein (1988) investigated the thickness of the teat end in
response to different vacuum settings (30 kPa, 50 kPa, and 70 kPa) and
found that the teat-end thickness increased as the vacuum level increased; tissue stiffness increased as well (Hamann and Mein, 1988).
The comparison between a machine vacuum at 30 kPa, 40 kPa, and
50 kPa showed significant differences in teat thickness (Hamann et al.,
1993), and a comparison of two different vacuum settings showed that
milking at a lower level resulted in less colour changes of the teat and
less cornification of the teat orifice (Ebendorff and Ziesack, 1991).
According to Ryšánek et al. (2001), a high vacuum correlated significantly (correlation coefficient of 0.50) with the formation of teatend hyperkeratosis, and reducing the machine vacuum decreased the
risk of hyperkeratosis (Neijenhuis et al., 2005). Reinemann et al. (2001)
did not find a significant correlation between machine vacuum level
Corresponding author.
E-mail address: sdemba@atb-potsdam.de (S. Demba).
https://doi.org/10.1016/j.compag.2018.08.011
Received 12 January 2017; Received in revised form 12 March 2018; Accepted 4 August 2018
0168-1699/ © 2018 Elsevier B.V. All rights reserved.
Computers and Electronics in Agriculture 153 (2018) 54–61
S. Demba et al.
and teat-end callosity, but they found a tendency towards more teats
with worse scores and fewer teats with improving conditions with a
vacuum of 50 kPa compared to 42 kPa. Parilova et al. (2011) tested the
influence of two different vacuum levels (39 kPa and 45 kPa) on the
traits teat length, teat diameter at the base, teat diameter at the middle,
teat canal length, teat end width, teat wall thickness, and teat cistern
width. The authors found a longer teat and teat canal, a narrower teat
diameter at the base and at the middle, a wider teat and teat cistern,
and a thicker teat wall with a higher machine vacuum. A machine vacuum level of 42 kPa resulted in increased teat wall thickness and a
decrease in teat cistern diameter compared with a machine vacuum of
50 kPa (Besier and Bruckmaier, 2016). In contrast, a low machine vacuum level extended the milking duration and worsened the teat end
condition (Reid and Johnson, 2003).
Different pulsation settings can influence both teat condition and
teat tissue condition. Grindal (1988) found that extending the suction
phase led to an increase in teat lesions and subcutaneous bleedings.
Hansen et al. (2006) investigated the influence of different pulsation
rates and pulsation ratios on teat thickness and found significant differences between ‘fast’ (22–55 cycles min−1, 66–81% suction phase)
and ‘slow’ (47 cycles min−1, 43% suction phase) treatments; the ‘fast’
treatment resulted in an increase in teat thickness. A comparison of
seven d-phase duration levels (50 ms, 100 ms, 150 ms, 175 ms, 225 ms,
250 ms, and 300 ms) resulted in a significant reduction in the estimated
cross-sectional area of the teat canal at d-phase durations of 50 and
100 ms (Upton et al., 2016). Bluemel et al. (2016) found that an extended c-phase during the pulsation cycle decreased the total vacuum
per cycle by 1 kPa and increased the opening and closing duration of
the liner, so the authors concluded that an extended c-phase indicated
gentler milking. In contrast, Gleeson et al. (2004) observed no negative
effect on teat tissue by widening the pulsation ratio, and Ferneborg and
Svennersten-Sjaunja (2015) detected no negative effects of different
pulsation ratios on teat-end hyperkeratosis or teat tissue thickness as
well. A quarter individual milking system for conventional milking
parlours (MultiLactor®) with a machine vacuum of 37 kPa, a sequential
pulsation at a rate of 60 min−1 and a pulsation ratio of 65:35 resulted in
better teat colour scores after milking compared with a conventional
milking system with a machine vacuum of 40 kPa, a pulsation rate of
60 min−1, and a pulsation ratio of 60:40 (Rose-Meierhöfer et al., 2014).
Machine vacuum and pulsation settings influence TP, OP, and LC
values as well. TP was found to increase with a higher machine vacuum
(Spencer et al., 2007), and according to Mein et al. (2003), OP increased with increasing liner vacuum. These authors found a slight
increase in OP as the pulsation c-phase was shortened as well, so adjusting the pulsation settings to a ratio of 65:35 and a rate of 60 cycles
min−1 might reduce the effects of OP. A higher claw vacuum was found
to create a larger difference in pressure across the wall of the collapsed
liner and result in a higher LC (Mein and Reinemann, 2009). Both OP
and LC were found to increase as the vacuum level of the individual
liners increased (Reinemann and Mein, 2011).
The aim of the present investigation was to determine the influence
of different milking settings on the pressure applied to the whole teat by
a collapsing liner using a pressure-indicating film and a hollow artificial
teat made of silicone.
Table 1
Coded and uncoded levels for the independent variables used in the response
surface methodology.
Independent variable
Coded level
Milking system vacuum (kPa)
Pulsation rate (cycles min−1)
Pulsation ratio
−1
0
+1
30
40
60:40
40
60
65:35
50
80
70:30
Table 2
The 15 combinations of machine vacuum, pulsation rate, and pulsation ratio
detected with the central composite design.
Machine vacuum (kPa)
Pulsation rate (cycles/min−1)
Pulsation ratio
30
30
30
30
30
40
40
40
40
40
50
50
50
50
50
40
40
60
80
80
40
60
60
60
80
40
40
60
80
80
60:40
70:30
65:35
60:40
70:30
65:35
60:40
65:35
70:30
65:35
60:40
70:30
65:35
60:40
70:30
different levels of each variable were coded to conform with the CCD
(Table 1).
The CCD design resulted in 15 unique combinations (Table 2) of
machine vacuum, pulsation rate, and pulsation ratio. The central point
(40 kPa, 60 cycles min−1, 65:35) was repeated ten times, and five replicates were performed for each of the other combinations for a total of
80 measurements.
2.2. Data collection
Data were collected using an experimental setup similar to Demba
et al. (2016). The Extreme Low film type (Prescale by Fujifilm; KAGER
Industrieprodukte GmbH, Dietzenbach, Germany) and an artificial teat
made of silicone were used to investigate the influence of different
milking settings on the teat load caused by a collapsing liner. The
pressure range of the film was 0.05–0.2 MPa. The teat had a length and
a mean diameter of 56 mm and 21 mm, respectively and was hollow
with a teat wall thickness of 4.5 mm. According to the manufacturer,
the silicone rubber had a Shore A hardness of 25, a density of
1.16 g cm−3 at a temperature of 23 °C, a tensile strength of
5.00 N mm−2, an ultimate elongation of 350%, a tear resistance of more
than 20 N mm−1, and a linear shrinkage of 0.5%. The experiment was
carried out in the experimental milking parlour of the Leibniz Institute
for Agricultural Engineering and Bioeconomy e.V. (ATB). A conventional milking cluster (Surge, GEA Group AG, Düsseldorf, Germany)
equipped with round silicone liners (IQPro, GEA Group AG, Düsseldorf,
Germany) was used, and each liner had a shaft diameter of 24 mm, a
mouthpiece diameter of 21 mm, and a head diameter of 58 mm. All
measurements were performed using the same teat cup; the other teat
cups were closed with plugs (Fig. 1). The pressure-indicating film was
cut into pieces (35 mm × 45 mm), all of which were attached with tape
to the same position on the teat. The artificial teat was then inserted in
the teat cup so that the collapsed liner and the sides of the pressureindicating film were pressed together, and milking was simulated for
1 min. The pieces of film were then analysed with FDP-8010E software
by Fujifilm (Prescale by Fujifilm; KAGER Industrieprodukte GmbH,
2. Materials and methods
2.1. Study design
Following Bade et al. (2009), the response surface methodology
(RSM) with the central composite design (CCD) was used to design the
experiment. Machine vacuum, pulsation rate, and pulsation ratio were
chosen as independent variables, and the three levels of each variable
were as follows: the machine vacuum was adjusted at 30 kPa, 40 kPa,
and 50 kPa; the pulsation rates were 40 min−1, 60 min−1, and
80 min−1; and the pulsation ratios were 60:40, 65:35, and 70:30. The
55
Computers and Electronics in Agriculture 153 (2018) 54–61
S. Demba et al.
(AV)i * x is the regression coefficient for the interaction between the
measuring area and machine vacuum; and εik is the residual.
The influence of different milking settings on MP was calculated
using the following model:
yik = μ + Ai + V∗x + V2∗x 2 + PL∗z + PR∗w + (VPL) ∗x∗z + εik
(2)
where yik is the observed values of the i-th measuring area (i = WHOLE,
END), and the k-th measurement (k = 1, …, 80) for MP; μ is the overall
mean; Ai is the fixed effect of the measuring area (i = WHOLE, END); V
is the regression factor of the machine vacuum x; V2 is the regression
factor of the squared machine vacuum x2; PL is the regression factor of
the pulsation rate z; PR is the regression factor for the pulsation ratio w;
(VPL)i * x * z is the regression factor of the interaction between the
machine vacuum and the pulsation rate; and εik is the residual.
The following model was used to calculate the influence of the
different milking settings on L:
yik = μ + Ai + V∗x + V2∗x 2 + PL∗z + PR∗w + (AV)i ∗w + (VPR) ∗x∗w
+ εik
where yik is the observed values of the i-th measuring area (i = WHOLE,
END), and the k-th measurement (k = 1, …, 80) for L; μ is the overall
mean; Ai is the fixed effect of the measuring area (i = WHOLE, END); V
is the regression factor of the machine vacuum x; PL is the regression
factor of the pulsation rate z; PR is the regression factor of the pulsation
ratio w; (AV)i * w is the regression factor of the interaction between the
measuring area and the machine vacuum; (VPR) * x * w is the regression factor of the interaction between the machine vacuum and the
pulsation ratio; V2 is the regression factor of the squared machine vacuum x2; and εik is the residual.
All tests were performed at a significance level of 0.05 and all estimated values are given with the standard error of the mean. As a
measure of accuracy for the predictions the root mean square error
(RMSE) is given.
Fig. 1. The experimental setup to measure the teat load caused by liner collapse.
Dietzenbach, Germany). The average and maximum pressure on the
area of the teat where colour is generated (AP and MP in MPa, respectively) and the load, which is the product of the pressurised surface
area and the average pressure (L in N), were used to analyse the influence of the different milking settings. AP, MP, and L were calculated
for the whole area covered by the film (WHOLE), as well as the area of
the teat end (END), which was defined as the area of the lower third of
the barrel of the artificial teat, so WHOLE included END.
3. Results
Fig. 2 shows pressure-indicating film scans of the tested levels of
machine vacuum, pulsation rate, and pulsation ratio.
The results of the ANCOVA showed a significant influence of the
machine vacuum (P < 0.0001), the squared values of the machine
vacuum (P < 0.0275), the pulsation rate (P < 0.0012), and the interaction of measuring area and machine vacuum (P = 0.0008) on AP
(Fig. 3). The pulsation ratio did not affect AP (P = 0.111) and therefore
was omitted from the regression equations for AP below. The mean AP
values differed significantly between both measuring areas
(P < 0.0001); AP was higher for END compared with WHOLE.
The regression equation for AP and WHOLE derived from the results
for the effect estimates of the ANCOVA model for AP (R2 = 0.730) is
the following:
2.3. Statistical analysis
Data were analysed using the SAS 9.4 software package (SAS
Institute Inc., Cary, NC, USA). Analysis of covariance (ANCOVA) was
used to estimate the differences between measuring areas and the
slopes of the influence of machine vacuum levels, pulsation rates, and
pulsation ratios on the response variables using the MIXED procedure.
The null hypotheses for AP, MP, and L were that the regression coefficients were zero, and it was assumed that there were no differences
between the measuring areas of the tested traits. First, the influence of
all factors and all twofold interactions were tested. Then all interactions
without significant influences were deleted from the model and the new
model was calculated again. The models were compared and the Akaike
information criterion (AIC) was used to choose the optimal model. The
following model was used to calculate the influence of the different
milking settings on AP:
yik = μ + Ai + V∗x + V2∗x 2 + PL∗z + PR∗w + (AV)i ∗x + εik
(3)
V −40
V −40 2
PL−60
⎞ + 0.0031 ⎛
⎞−0.0034 ⎛
⎞
AP = 0.09537 + 0.0124 ⎛
⎝ 20 ⎠
⎝ 10 ⎠
⎝ 10 ⎠
(4)
where AP is the average pressure in MPa; V is the machine vacuum; and
PL is the pulsation rate.
The regression equation for AP and END derived from the results for
the effect estimates of the ANCOVA model for AP (R2 = 0.730,
RMSE = 0.009) is as follows:
(1)
V −40
V −40 2
PL−60
⎞ + 0.0031 ⎛
⎞−0.0034 ⎛
⎞
AP = 0.11062 + 0.0188 ⎛
⎝ 20 ⎠
⎝ 10 ⎠
⎝ 10 ⎠
where yik is the observed values of the i-th measuring area (i = WHOLE,
END), and the k-th measurement (k = 1, …, 80) for AP; μ is the overall
mean; Ai is the fixed effect of the measuring area (i = WHOLE, END); V
is the regression factor of the machine vacuum x; V2 is the regression
factor of the squared machine vacuum x2; PL is the regression factor of
the pulsation rate z; PR is the regression factor of the pulsation ratio w;
(5)
where AP is the average pressure in MPa; V is the machine vacuum; and
PL is the pulsation rate.
According to the results of the ANCOVA, the machine vacuum
56
Computers and Electronics in Agriculture 153 (2018) 54–61
S. Demba et al.
Fig. 2. Pressure-indicating film scans, with the teat end at the bottom, of the tested levels of machine vacuum, pulsation rate, and pulsation ratio.
(P < 0.0001), the squared values of the machine vacuum
(P < 0.0001), pulsation rate (P = 0.0058), pulsation ratio (P = 0.01),
and the interaction of machine vacuum and pulsation rate (P = 0.0077)
influenced the MP values significantly (Fig. 4). The mean MP values did
not differ between WHOLE and END, and no significant influence of the
interaction between machine vacuum and area was found.
The regression equation for MP and WHOLE derived from the results for the effect estimates of the ANCOVA model for MP (R2 = 0.360,
RMSE = 0.01) is the following:
the pulsation ratio.
The regression equation for MP and END derived from the results
for the effect estimates of the ANCOVA model for MP (R2 = 0.360,
RMSE = 0.01) is as follows:
V −40
V −40 2
PL−60
⎞ + 0.0029⎛
⎞−0.00697⎛
⎞
MP = 0.2031 + 0.0071⎛
⎝ 20 ⎠
⎝ 10 ⎠
⎝ 10 ⎠
SPR−65
⎞−0.00313VPL
−0.0027⎛
(6)
5
⎝
⎠
where MP is the maximum pressure in MPa; V is the machine vacuum;
PL is the pulsation rate; and SPR is the amount of the suction phase of
the pulsation ratio.
The results of the ANCOVA showed that the machine vacuum
(P < 0.0001), the squared values of the machine vacuum
(P < 0.0001), and pulsation rate (P = 0.0009) as well as the interactions of machine vacuum and measuring area (P < 0.0001) and
V −40
V −40 2
PL−60
⎞ + 0.0029⎛
⎞−0.00697⎛
⎞
MP = 0.20222 + 0.0071⎛
⎝ 20 ⎠
⎝ 10 ⎠
⎝ 10 ⎠
SPR−65
⎞−0.00313VPL
−0.0027⎛
(7)
5
⎝
⎠
where MP is the maximum pressure in MPa; V is the machine vacuum;
PL is the pulsation rate; and SPR is the amount of the suction phase of
57
Computers and Electronics in Agriculture 153 (2018) 54–61
S. Demba et al.
Fig. 3. The measured values of the average pressure (AP in MPa) depending on the machine vacuum level in kPa and the pulsation rate in cycles min−1 for the
measuring area of the whole teat (left) as well as the teat end area (right) with pulsation ratios of (a) 60:40, (b) 65:35, and (c) 70:30. Different grey intensities show
intervals of 0.005 MPa.
V −40
V −40 2
PL−60
⎞ + 4.77 ⎛
⎞−7.7033 ⎛
⎞
L = 44.4125 + 9.96 ⎛
10
⎝ 20 ⎠
⎠
⎝ 10 ⎠
⎝
PR−65
⎞−3.1375VPR
−2.37 ⎛
⎝ 5 ⎠
machine vacuum and pulsation ratio (P = 0.0477) influenced L significantly (Fig. 5). The L values were significantly higher (P < 0.0001)
for WHOLE compared with END.
The regression equation for L and WHOLE derived from the results
for the effect estimates of the ANCOVA model for L (R2 = 0.865,
RMSE = 14.058) is the following:
V −40
V −40 2
PL−60
⎞ + 4.77 ⎛
⎞−7.7033 ⎛
⎞
L = 105.8 + 24.82 ⎛
⎝ 20 ⎠
⎝ 10 ⎠
⎝ 10 ⎠
PR−65
⎞−3.1375VPR
−2.37 ⎛
⎝ 5 ⎠
(9)
where L is the load in N; V is the machine vacuum; PL is the pulsation
rate; and PR is the amount of the suction phase of the pulsation ratio.
4. Discussion
The machine vacuum significantly influenced AP, MP, and L; the
values of all three traits increased as the machine vacuum increased.
This agrees with Tol et al. (2010), who found an increasing pressure
difference over the liner wall during the d-phase of pulsation with increasing vacuum level. The results of the present investigation led to
the assumption that a higher machine vacuum resulted in a higher teat
load during milking, and the results of Hamann and Mein (1988) and
Hamann et al. (1993) confirmed this assumption. The authors found a
(8)
where L is the load in N; V is the machine vacuum; PL is the pulsation
rate; and PR is the amount of the suction phase of the pulsation ratio.
The regression equation for L and END derived from the results for
the effect estimates of the ANCOVA model for L (R2 = 0.865,
RMSE = 14.058) is as follows:
58
Computers and Electronics in Agriculture 153 (2018) 54–61
S. Demba et al.
Fig. 4. The measured values of the maximum pressure (MP in MPa) depending on the machine vacuum level in kPa and the pulsation rate in cycles min−1 for the
measuring area of the whole teat (left) as well as the teat end area (right) with pulsation ratios of (a) 60:40, (b) 65:35, and (c) 70:30. Different grey intensities show
intervals of 0.005 MPa.
and L, so the values of the three traits were lowest at a machine vacuum
of 30 kPa. It should be noted that a certain pressure of the teat cup liner
is necessary to massage the teat during the c and d pulsation phases, so
both Reid and Johnson (2003) and Besier and Bruckmaier (2016) advised a machine vacuum of no less than 30 kPa.
In the present study, the pulsation rate influenced the values of AP,
MP, and L; the three traits increased with an increase in pulsation rate.
A higher pulsation rate resulted in a higher teat load due to the teat cup
liner, and this could explain the results of Hansen et al. (2006), who
found a better teat tissue condition and thus a less stressed teat with a
lower pulsation rate.
The pulsation ratio significantly influenced the values of MP; the
values decreased with an extension of 5 percentage points to the suction
phase. Hansen et al. (2006) found significant differences between a
large and a small pulsation ratio as well, and short c and d pulsation
phases resulted in increased teat thickness and higher stress on the teat.
negative influence of the vacuum level on the condition of the teat
tissue in both studies; i.e., the condition of the teat tissue worsened as
the machine vacuum level increased. Parilova et al. (2011) found that
teat tissue condition worsened with increasing machine vacuum as
well. Besier and Bruckmaier (2016) compared three milking vacuum
treatments (treatment 1: 42 kPa system vacuum, 33 kPa min claw vacuum during milk flow; treatment 2: 50 kPa system vacuum, 34 kPa
claw vacuum during milk flow; treatment 3: 42 kPa system vacuum,
during milking claw vacuum drop down to 24 kPa) and found increased
teat wall thickness and decreased teat cistern diameter with treatment
2. Teat condition, which indicates the stress on the teat tissue during
milking, is influenced by the machine vacuum. The colour changes of
the teat after milking were lower at a lower machine vacuum level
(Ebendorff and Ziesack, 1991), and a reduced machine vacuum resulted
in less teat-end hyperkeratosis (Ryšánek et al., 2001; Neijenhuis et al.,
2005). The lower the machine vacuum, the lower the values of AP, MP,
59
Computers and Electronics in Agriculture 153 (2018) 54–61
S. Demba et al.
Fig. 5. The measured values of the load (L in N) depending on the machine vacuum level in kPa and the pulsation rate in cycles min−1 for the measuring area of the
whole teat (left) as well as the teat end area (right) with pulsation ratios of (a) 60:40, (b) 65:35, and (c) 70:30. Different grey intensities show intervals of 20 N.
The calculated values of TP, OP, and LC, which are used to estimate
the pressure caused by a collapsing liner, were affected by the adjustment of the milking settings as well; TP, OP, and LC increased with
increasing machine vacuum (Mein et al., 2003; Spencer et al., 2007;
Reinemann and Mein, 2011). Mein et al. (2003) suggested a pulsation
rate of 60 cycles min−1 to reduce the effects of the calculated OP values, which could help to reduce the formation of machine-related teatend hyperkeratosis and is consistent with the results of the present investigation. In terms of the pulsation ratio, Mein et al. (2003) confirmed
the results of the present study, because they found a slight increase in
the calculated OP values with a shortened c pulsation phase. However,
the calculated values of TP, OP, and LC were much lower compared
with the measured pressure values of the present study. The average OP
ranged from < 5 to > 20 kPa (Mein et al., 2003; Mein and Reinemann,
2009) and 9.8–18.2 kPa (Leonardi et al., 2015) depending on liner type.
Spencer et al. (2007) found TP values between 25.73 and 33.52 kPa
The comparison of different d-phase durations indicated a significant
reduction in the estimated cross-sectional area of the teat canal with
shorter durations (Upton et al., 2016). The results of the present study
regarding MP disagree with the results of Gleeson et al. (2004), who did
not find a negative influence of different pulsation ratios on teat load
(tissue and teat-end hyperkeratosis).
However, the results of the present research could not yet be
transferred directly to the live animal because a teat of a dairy cow is
much more flexible and reacts differently to the teat load due to liner
collapse than an artificial teat. Tol et al. (2010) found 2.5 times smaller
pressure values on a live cow teat compared with the pressure values of
an artificial teat.
The AP values were higher for END compared with WHOLE, which
confirms the results of Tol et al. (2010) and Muthukumarappan et al.
(1994). The authors of both studies found that the teat cup liner applied
more pressure to the teat end than to the whole teat.
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Computers and Electronics in Agriculture 153 (2018) 54–61
S. Demba et al.
depending on the operating hours of a liner. While the estimation of TP,
OP, and LC is based on the calculation of pressure differences across the
liner walls, the pressure values of the present research were directly
measured and resulted from a force applied to an area. This could be an
explanation for the big differences between the pressure values. According to Reinemann and Mein (2011), LC is the most biologically
relevant way to measure the pressure applied to the teat by a liner, but
it is not the same as direct pressure measurements with a pressure
sensitive film and an artificial teat.
The pressure values measured in the present investigation are much
higher than those found in earlier studies. Muthukumarappan et al.
(1994) measured a pressure of 18–35 kPa, Davis et al. (2001) found
pressure values between 20 kPa and 41 kPa, Tol et al. (2010) measured
pressure values of 99–180 kPa at the teat end, and Leonardi et al.
(2015) detected pressures of 20–34 kPa. The used artificial teats could
be the reason for these findings because they differ in their dimensions
and the liner could have applied a different amount of pressure to the
teat. The artificial teat used by Tol et al. (2010) was 20 mm longer, had
a tapered shape, and a 2.5 mm-thinner teat wall compared to the artificial teat used in the present investigation. Differences in the material
of the artificial teats offer an additional explanation.
Muthukumarappan et al. (1994) used a liquid-filled, flexible, not extensible artificial teat made of a plastic teat cup plug, a surgical glove
finger, and a cloth glove finger. The artificial teat of Davis et al. (2001)
was made of natural gum rubber or a gel-like material. The artificial
teat of Leonardi et al. (2015) was covered by a silicone rubber with a
Shore A hardness of 10. In the present investigation, an artificial teat
made of silicone rubber with a Shore A hardness of 25 was used. The
functionality of the pressure-indicating film could be another reason for
the higher pressure values of the present investigation. The pressureindicating film used in the present investigation does not support shear
stress (Rodríguez-Martínez et al., 2012), and shear stress can alter the
colour intensity measured by the film (Patterson et al., 1997). On the
other side neither negative pressure nor bending the sensor around the
artificial teat influenced the measuring results (Demba et al., 2016).
The studies of Henak et al. (2014) and Mutlu et al. (2014) showed that
the Prescale pressure-indicating film measures a higher maximum
pressure compared with other pressure-measurement methods.
In conclusion, the results of the present investigation showed that
different adjustments of the machine vacuum, the pulsation rate, and
the pulsation ratio result in different teat loads caused by a collapsing
liner as measured with Prescale pressure-indicating film. The higher the
machine vacuum and the pulsation rate, the higher the measured values
of AP, MP, and L. MP values decreased with an increase of the pulsation
ratio. The pulsation ratio affected L significantly depending on the
machine vacuum.
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5. Conflict of interest
The authors declare that they have no conflicts of interest.
6. Funding
This research did not receive any specific grant from funding
agencies in the public, commercial, or not-for-profit sectors.
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