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The Influence of Premilking Teat Preparation and Attachment Delay on Milk Yield and Milking Performance
The Influence of Premilking Teat Preparation and Attachment Delay on Milk Yield and Milking Performance M. D.
RASMUSSEN and E. S. FRIMER
National Institute of Animal Science Department of Research in Cattle and Sheep Foulum, PO Box 39 DK-8830 Tjele, Denmark
D.
M. GALTON and L. G. PETERSSON Department of Animal Science Cornell University Ithaca, NY 14853
ABSTRACT
Premilking teat preparation and attachment delay were varied in four experiments conducted with American Holstein, Danish Holstein, and Danish Jersey cows. Premilking teat preparation varied from 10 to 30 s and consisted of wiping teats for 6 to 20 s and stripping one to five squirts of milk from each teat. Attachment delay from beginning of premilking teat preparation until machine attachment varied from .5 to 3.0 min. Longer preparation significantly increased milk yield for Danish Jersey cows, but not for American or Danish Holstein cows. Older Danish Jersey cows were more sensitive to premilking teat preparation than first lactation cows. Attachment delay influenced the milk yield in Danish Jersey cows, amount of residual fat in American Holsteins, and fat percentage in the residual milk of American and Danish Holstein cows. A 1.3-min delay can be generally recommended for the whole herd with only small or no milk loss for cows in early stage of lactation. Milk yield decreased for Danish Jersey cows and tended to decrease for American Holstein cows when machine attachment was delayed to 3.0 min, regardless of stage of lactation. The lack of treatment effects for Danish Holstein cows may be due to a lack of conditioned stimulation for cows
Received June 28, 1991. Accepted January 13, 1992. 1992 J Dairy Sci 75:2131-2141
milked in their tie stalls compared with the response of cows moved to milking parlors for milking. Added duration of teat wiping, vigorousness of teat stripping, and delay of machine attachment hastened steady milk flow. Conversely, advanced days in lactation delayed steady milk flow. The high fat content of Danish Jerseys did not delay the start of steady milk flow compared with the American and Danish Holsteins. In late stage of lactation, 30 s of teat preparation and 1.3 min of machine attachment delay minimized time until steady milk flow as well as 10 s of teat preparation and 3.0 min of attachment delay. (Key words: premilking teat preparation, milk yield, milking performance)
Abbreviation key: AH = American Holstein, DH = Danish Holstein, DJ = Danish Jersey. INTRODUCTION
The relative importance of stimulation obtained through premilking teat preparation, dynamic movement of the liner, emptying of the udder, and local intramammary regulatory mechanisms needs evaluation with respect to differences in breed, selection improvement, stage of lactation, milking management, and milking equipment. Through intensive selection and technology advancement, these factors have become dynamic and require periodic reevaluation. Phillips (9) demonstrated that Jersey cows required more stimuli for maximal milking management than did Holstein cows. More2131
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RASMUSSEN ET AL.
over, Phillips (9) proposed that selection against cows with high requirements for udder stimulus by applying little or no premilking teat preparation has, over time, reduced the threshold value for triggering the milk ejection reflex. In contrast, once oxytocin is released from the pituitary into the blood stream, transport time to the myoepithelial cells probably does not differ much between breeds and stages of lactation. The timing of oxytocin release might be of greater importance to milk removal than absolute concentrations of oxytocin released during milking (11, 12). In this context, both premilking teat preparation and machine attachment delay (defined as interval between start of preparation and attachment) need to be varied in order to check for interactions. Gorewit and Gassman (2) varied teat preparation from 0 to 120 s and attached the milking unit immediately after termination of preparation and thereby, according to the definition just given, confounded duration of teat preparation and attachment delay. Therefore, the influence on milking dynamics cannot be sorted into effects of preparation, attachment delay, or interactions between those factors. A time delay of 5 min, from preparation until attachment of the milking machine, increased residual milk and fat and decreased milk yield (l), although results from different studies are equivocal (7, 8, 10, 11). Finally, the existence in the udder of local regulatory mechanisms related to milk yield has been demonstrated (13). Previous stimulation studies (1, 2, 6, 7, 8, 9, 10, 11) focused on milk yield and composition, and this study is no exception. However, machine-on time decreases, and milk flow rate increases, with duration of premilking teat preparation (2, 6). These parameters and the time until steady milk flow might be more important for udder health and the practicability of a milking routine than recognized earlier. Machine milking of empty teats results in a higher compressive load applied from the liner on the teat surface ( 5 ) and in discomfort to the cow, which may result in cows kicking the milking unit. Moreover, automatic removers with a present neutral phase (phase at the beginning of the milking in which the unit does not detach, normally 1 to 2 min) detach the milking unit when milk flow fails to reach detachment flow rate within this phase; that is, milk ejection must occur Journal of Dairy Science Vol. 75, No. 8, 1992
within 1 to 2 min. Teat end erosions occur more often in herds with the milking unit attached immediately after preparation than with attachment 1 to 2 min after preparation (14). The objective of these studies was to evaluate the effects of premilking teat preparation and time delay until machine attachment on the time until steady milk flow, machine-on time, milk yield, and milk composition. MATERIALS AND METHODS
Four experiments were conducted in 1989. Cows used in Experiment 1 were American Holsteins (AH-I), as were cows in Experiment 2 (AH-2).Experiment 3 included Danish Holstein cows (DH),and Danish Jerseys (DJ) were used in Experiment 4. Experiment 1
Twelve AH cows from the Cornel1 University herd were used. Seven cows were in their second lactation, 2 cows were in their third lactation, and 3 cows were in their fourth lactation. Selection criteria were four functional quarters and no clinical signs of disease. Six cows were in early stage of lactation, 69 f 24 DIM, with an average daily milk yield of 36.0 f 4.5 kg, and 6 cows were in late stage of lactation, 266 f 17 DIM, with an average daily milk yield of 14.9 f 3.6 kg. Cows were subjected to six treatments in a Latin square design within stage of lactation. Duration of the experiment was 6 wk, and cows received a given treatment for nine consecutive milkings; the first milking started with an evening milking. Five milkings elapsed before cows were rotated to the next treatment. Treatments of premilking teat preparation (stimulation) were short (10 s) or long (30 s) and were combined with one of three attachment delays, .5, 1.3, or 3.0 min, measured from beginning of teat preparation until attachment of the milking machine. Short preparation included wiping of each teat twice with a nearly dry cotton towel and prestripping of one squirt of milk from each teat. Long preparation included wiping of each teat five times, scrubbing of each teat end with a nearly dry cotton towel, and powerful prestripping (full streams of milk entered the strip cup) of five to six squirts of milk from each teat.
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Residual milk was obtained immediately after the first and the ninth milkings by injection of 20 IU of oxytocin (Butler Co., Rochester, NY) into the milk vein and attachment of the milking unit 1 min thereafter. If present, stripping yield was included in the amount of residual milk. Milk samples were analyzed for milk fat and protein percentages at Northeast DHI Laboratory (Ithaca, NY).Milk yield was recorded at every milking. Time until steady milk flow (visual estimation of milk flow through the long milk hose) and machine-on time were recorded at two morning and two evening milkings between residual milk collections. Average flow rate was calculated by milk yield divided by machine-on time. Electronic milk flow recording was not possible in every study without interfering with the milking routine. Therefore, visual estimation of the milk flow was chosen. Milk was defined to flow steadily as soon as milk flowed continuously in every pulsation cycle. Cows were milked at 0600 and 1700 h in a double-five herringbone milking parlor. Cows entered the milking parlor one at a time to synchronize possible conditioned stimuli with the onset of a treatment. Cows were milked with an IBA Quarter Milker with IBA liners (S-6OO0, IBA, Milbury, MA). Pulsation ratio, pulsation rate, and vacuum were 55:45, 50 pulsations per min, and 44 Wa, respectively. Milking units were automatically detached when milk flow rate dropped below 200 g/min. During the five milkings between treatments, 5 cows entered the milking parlor at a time, and the milking units were attached immediately
after 20 s of prestripping and teat wiping. Cows were fed a total mixed ration throughout the experiment. Data were analyzed in a model including effects of stage, cow nested within stage, week, treatment, and interactions of stage x week and stage x treatment. Analysis was performed with either one observation per cow per week or an average per cow per week. An overview of cows and treatments for the different studies are in Table 1. Experiment 2
Eight of the cows that were in Experiment 1 continued in this study. Four cows were in early stage of lactation, 111 k 13 DIM, with an average daily milk yield of 36.4 f 4.9 kg, and 4 cows were in late stage of lactation, 311 f 22 DIM, with an average daily milk yield of 13.2 f 1.3 kg. Cows were subjected to four treatments in a Latin square design within stage of lactation. The duration of the experiment was 16 d; cows received a given treatment for four milkings, starting at a morning milking; and four milkings elapsed without treatment before cows were rotated to the next treatment. Treatments were a factorial design of 1) wipe each teat twice with a nearly dry cotton towel for 6 s or 2) wipe each teat five times and scrub each teat end for 20 s combined with prestrip one squirt from each teat or prestrip five powerful squirts from each teat. The attachment delay was 1.3 min. Residual milk was obtained from the fourth milking. Milk yield and time measurements
TABLE 1. Comparison of cows, treatments, and design in the four experiments.
Breed’
Cows
AH-1 AH-2 DH DJ
(no.) 12 8 12 78
Preparation
Attachment delay
-(s) 10 io4 10 10
30
Design3
(e) .5
304
30 30
Stage2
Milkings per treatment
.5 .5
1.3 1.3 1.3 1.3
3 .O
E, L
3.O 3 .O
E, L E, L EM,L
9 4 9 1
Lsq
LS¶ Lsq W S ¶
‘AH = American Holstein (Experiments 1 and 2); DH = Danish Holstein; DJ = Danish Jersey. %tage of lactation: E = early, M = mid, L = late. 3Experimental design: Lsq = Latin square, InLsq = incomplete Lsq. 4F’restripping and wiping of teats varied factorial from 10 to 30 s. Journal of Dairy Science Vol. 75. No. 8, 1992
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were recorded at every milking. Milking procedure and facilities were as outlined for Experiment 1. Period was used instead of week in the statistical model. Experiment 3
Twelve DH cows (with about 75% of genes from AH) from the Foulum Research Centre (Tjele, Denmark) herd were used. Four cows were in second lactation, 5 cows were in third lactation, 2 cows were in fourth lactation, and 1 cow was in seventh lactation. The early stage group was 47 f 6 DIM with an average daily milk yield of 33.7 f 3.8 kg, and the late stage group was 242 f 27 DIM with an average daily milk yield of 18.4 f 3.2 kg. Experimental design, treatments, recording of residual milk, and statistical procedure were as outlined for Experiment 1. Milk samples were analyzed for fat, protein, and lactose percentages with a Milkoscan 104 (Foss-Electric, Hillerod, Denmark). Machine-on time and the time until steady milk flow were recorded at every milking. Cows were milked at 0500 and 1600 h in a tie-stall barn in the same order at every milking. Cows were milked with a Uniflow claw (S. A. Christensen, Kolding, Denmark) and Stranko liners (3423005 Strange Hansen, Varde, Denmark). Pulsation ratio, pulsation rate, and vacuum were 60:40,60 pulsations per min, and 48 kPa, respectively. Pipelines were situated 190 cm above the floor. Milking units were automatically detached when milk flow rate dropped below 200 g/min. Between treatments, cows were milked by the standard milking routine (10). Cows were fed a total mixed ration throughout the experiment. Experlment 4
Seventy-eight DJ cows from a commercial herd were used (Table 2). The experiment included all cows in the herd. Cows showed no clinical signs of any disease during the experiment. Treatments were outlined as in Experiment 1. The experiment consisted of four evening milkings during 1 wk and three evening milkings during the following week. Cows were milked in a double-seven herringbone milking parlor. Treatments changed for every group of 7 cows (one side in the parlor), and Journal of Dairy Science Vol. 75, No. 8, 1992
TABLE 2. Number of Danish Jersey cows relative parity and stage of lactation.
to
First
Stage of lactation
DIM
lactation
Older
WlY Mid Late
250
13 16 4
21 15 9
every treatment was represented each evening and at a different time during each milking. Cows entered the milking parlor one at a time to synchronize possible conditioned stimuli with the onset of a treatment. Machine-on time, the time until steady milk flow, and milk yield were recorded at every evening milking, and milk samples were analyzed for fat, protein, and lactose percentages with a Milkoscan 104. Average flow rate was calculated by milk yield divided by machineon time. Cows were milked at 0500 and 1600 h with a HPl00 claw (Alfa-Laval, Vejle, Denmark) and Alfa-Lava1 liners (960018-83). Pulsation ratio, pulsation rate, and vacuum were 63:35, 60 pulsations per min and 42 kPa, respectively. Milking units were automatically detached when milk flow rate dropped below 200 g/min. Between treatments, 7 cows entered the milking parlor at the same time, and premilking teat preparation was applied for 10 s before the 7 units were attached. Cows were fed a mixed ration for ad libitum intake and concentrate according to milk yield throughout the experiment. Data were analyzed in a model including effects of stage, cow nested within stage, date, treatment, and the interaction stage x treatto 7.5, and >7.5 ment. Milk yield group (45, kg) and fat percentage group (<7, 7 to 8.5, and >8.5%) were analyzed in the model instead of stage. Analyses were performed for first lactation and older cows separately or combined. RESULTS
The effect of duration of premilking teat preparation and delay of attachment were analyzed within experiment and presented in the order of effect of number of milkings (AH-1, DH), influence on the time until steady milk flow, machine-on time, average milk flow, milk yield, milk composition, and residual milk yield (AH-1, AH-2, DH).
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TABLE 3. The influence. of duration of premillcing teat preparation and attachment delay on milking performance, milk yield, and milk composition in Experiment 1 with American Holsteins. Preparation
mini
5 2 min
.6 min
1.3 min 3.0 min
36
36
24
24
24
.33 6.78 1.78 11.0 11.0 4.05 3.60 2.13 16.1 9.48 30.4
.21 6.68 1.85 11.0 11.2 4.12 3.61 2.11 16.3 9.73 30.1
.42a 7.01a 1.77 11.0 11.2 4.13 3.56 2.14 15.8 9.37a 28.7a
.28a 6.64b 1.82 11.3 11.3 4.17 3.66 2.03 15.4 9.4Ia 28.4a
.12b 6.54b 1.86 10.7 10.7 3.95 3.60 2.19 17.4
.I8 Observations, no. Time to flow, min Machine-on time, min Average flow, kg/min Milk, kg 4% FCM, kg Fat, 8 Protein, 8 Residual milk, kg Residual milk, 8 Fat in residual milk, 8 Residual fat, %
Attachment delay
lO.0Sb 33.6b
SD
F?'
** *
.3 1 .62 .17 1.1 1.3 .33 .14 .62 4.5 .99 7.8
AD2
+
t t
* *
avbMeanswith different superscripts differ (P < .05). 'Observed times of preparation and attachment delay. 'Treatment effects of preparation (Pr) and attachment delay (AD). +P < .IO. *P < .05. **P < .01.
Experiment 1
duration of preparation; this was mainly due to an effect on milk flow rate. Except for the minor effects of number of Duration of preparation had no effect on milkings, time effect was not significant. Data milk yield, milk composition, or residual milk. in Table 3 are averages of the first and the Milk yield and fat and protein percentages ninth milking (least squares means). Fat con- were the highest, and amount of residual milk tent in the residual milk changed from lowest and percentage of residual milk were the after the attachment delay of 1.3 min at the lowest, following the attachment delay of 1.3 first milking to lowest after the short attach- min, but differences were insignificant (P > ment delay at the ninth milking. For both the .05). However, an increase in the attachment first and the ninth milkings, fat content in delay from 1.3 to 3.0 min significantly inresidual milk was highest after a 3.0-min at- creased the amount of residual fat in the udder. tachment delay. For cows in late lactation, fat An attachment delay of 3 min tended to content in normal milk was highest after the decrease milk yield, and this effect was most long preparation at the first milking but lowest pronounced in early lactation (Table 7). Percentage of fat retained in the udder decreased after the ninth milking. The time until steady milk flow decreased slightly in late lactation; the attachment delay with delayed attachment (P c .01) and with increased from .5 to 1.3 min and increased (P duration of preparation (P > .lo). Steady milk c .lo) when the attachment was delayed for flow was delayed in late lactation compared 3.0 min (data not shown). For cows in early with early lactation (Pc .001). In early lacta- lactation, residual fat in the percentage of total fat increased linearly with the length of the tion, milk flowed steadily within 10 s (Table attachment delay. Residual fat percentage was 7). In late lactation, time until steady milk flow the highest after the long preparation in early was greater than .5 min for the .5 min of lactation and highest in late lactation after a attachment delay, regardless of duration of short preparation (P c .Ol). These effects did preparation, and for the 1.3 min of attachment not follow tendencies of FCM (P > .lo), for delay following the short preparation. which highest milk yield was obtained after a Machine-on time decreased with delayed at- long preparation in early lactation and after a tachment but was only slightly influenced by short preparation in late lactation (Table 7). Journal of Dairy Science Vol. 75, No. 8, 1992
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TABLE 4. The influence of duration of premiUcing teat wiping and number of prestripping squirts on milking performance, milk yield, and milk composition in Experiment 2 with American Holsteins. Wiving of teats 5 s Observations, no. Time to flow, min Machine-on time, min Average flow, kg/min Milk, kg 4% FCM, kg Fat, % Protein, % Residual milk, kg Residual milk, % Fat in residual milk, % Residual fat, %
20 s
1'
5
.18 6.81 1.7Sa 11.5 11.7 4.32 3.68 2.23 17.7 9.26 30.5
8 .16 6.28 2.03b 10.8 10.9 4.23 3.64 2.26 17.9 9.26 31.6
8
1
8 .10 6.57 1.95ab 11.5 12.0 4.40 3.66 2.15 16.9 9.03 28.6
5
SD
.G9
.ll .48 .18 1.2
8
6.52 1 .89ab 11.5 12.0 4.39 3.68 2.03 15.7 9.33 27.5
1.1
.30 .10 .60 4.7 .66 7.2
&bMeans with different superscripts differ (P c .OS). 'Number of prestripping squirts. Experiment 2
Experiment 2 was designed to determine marginal effects of prestripping and wiping of teats in combination with the optimal attachment delay of 1.3 min found in Experiment 1. The time until steady milk flow decreased with duration of premilking teat preparation for cows in late lactation regardless of the kind of preparation (Table 4). The time until steady milk flow was not affected by preparation in early lactation. Five streams of milk, compared with one stream removed during prestripping, decreased machine-on time and increased average milk flow (P < .05) after a 5-s teat wiping procedure, whereas this effect failed to appear after a 204 teat wiping procedure. Milk yield, fat percentage, and residual milk followed the tendencies in Experiment 1. Milk yield and fat percentage were higher after 20 s than after 5 s of teat wiping, and prestripping in itself did not influence milk yield and milk composition. Corresponding to these observations, percentages of residual milk and fat were lowest after the 20 s of teat wiping, regardless of prestripping. Results from this experiment tend to support conclusions from the other experiments. Experiment 3
Number of first to ninth milkings was not significant, and data in Table 5 are averages of the treatment period (least squares means). Journal of Dairy Science Vol. 75. No. 8, 1992
The time until steady milk flow decreased with duration of preparation and with the length of the attachment delay. Steady milk flow occurred later in late lactation compared with flow in early lactation (P .OOl). In early lactation, milk flowed within 7 s, even after a short attachment delay (Table 7), but such small values were obtained only after a long attachment delay in late lactation. Milk flowed steadily within 11 s following a long preparation and attachment delay of 1.3 min in late lactation cows. Machine-on time decreased with time spent on preparation and with increase in the attachment delay from 1.3 to 3.0 min. In early lactation, machine-on time was shorter (P .01) after a long preparation than after a short preparation. Preparation had no effect on machine-on time in late lactation. Average milk flow rate increased with the length of the attachment delay, especially after a short preparation. Except for protein percentage in the milk, milk yield and composition were not affected by the treatments. However, fat percentage in the residual milk increased with the length of the attachment delay, indicating that milk yield and fat percentage should decrease simultaneously. In early lactation, the amount of residual milk was the highest after the long preparation (P .05). Milk yield was, for both stages of lactation, about the same as that in Experiment 1, and standard deviations were about the same magnitude or less; differences
2137
PREMILKING TEAT PREPARATION
TABLE 5. The influence of duration of premilking teat preparation and attachment delay on milking performance, milk, yield, and milk composition in Experiment 3 with Danish Holsteins.
Observations, no. Time to flow, min Machine-on time, min Average flow, kg/min Milk, kg 4% FCM, kg Fat, % Protein, % Lactose, % Residual milk, kg Residual milk, % Fat in residual milk, % Residual fat, %I
Preparation
Attachment delay
.17 min' 52 min
.6 min 1.3 min 3.0 min
36 .22 7.43 1.48 11.4 12.1 4.85 3.49a 4.73 2.61 19.4 10.07 32.7
24 .32a 7.41 1.48 11.4 11.8 4.85 3.47 4.73 2.84 20.6 9.66a 33.4
36 .15 7.27 1.51 11.4 12.1 4.82 3.46b 4.73 2.79 19.6 9.93 32.7
24 .16b 7.44 1.48 11.4 12.2 4.84 3.49 4.72 2.65 19.4 10.02& 32.6
24 .07c 7.21 1.54 11.5 12.2 4.81 3.48 4.73 2.62 18.6 10.32b 32.1
PrX
SD
P?
.15 .35 .10 .7 1.5 .36
t t
.06
.05 .65 4.0 .70 6.1
AD2
AD
a**
t t
*
*
* **
ab*cMeans with different superscripts differ ( P c .05). 'Observed times of preparation and attachment delay. 2Treatment effects of preparation (Pr) and attachment delay (AD).
tP <
.lo.
* P c .05. **P < .01.
***P< ,001.
(or lack of treatment effects) in this experiment were not due to greater variability among figures. Experiment 4
The time until steady milk flow decreased with time spent on preparation ( P < .05) and with increasing attachment delay ( P c .001) (Table 6). After a short preparation, the time until steady milk flow dropped steadily with delayed attachment, whereas, after a long preparation, increasing the attachment delay from .5 to 1.4 min caused a decline. Further attachment delay had marginal influence on the time until steady milk flow. In late lactation, milk flowed sooner after a short attachment delay with DJ cows than with the DH and AH cows (Table 7). For cows yielding less than 5 kg of milk per milking, milk flowed steadily within 10 s when the long preparation was followed by attachment delays of 1.4 and 3.0 min. After a short attachment delay, in combination with either short or long preparation, milk flowed within 25 and 20 s, respectively. The time until steady milk flow was unacceptably long (45 s)
following a short preparation and short attachment delay for cows with milk fat content higher than 8.5%. For this group of cows, the shortest time until steady milk flow (9 s) was obtained after a long preparation and attachment delay of 1.4 min. Long preparation compared with short preparation shortened the machine-on time by 10 s ( P c .lo), mainly through a higher average flow rate. The effect was independent of lactation number, stage, milk yield, and fat percentage in the milk. The attachment delay of 1.4 min resulted in the shortest machine-on time and the highest average flow rate. There was no interaction between preparation and attachment delay. For low yielding cows (4 kg of milk), machine-on time was 40 s shorter after the attachment delay of 1.4 min than after .5 min (data not shown). Longer attachment delay shortened machine-on time slightly. For high yielding cows, machine-on time decreased 19 s when attachment delay increased from .5 to 3.0 min. The decrease associated with attachment delay of 1.4 min compared with .5 min was due to a similar increase in average flow rate, whereas further reduction in machine-on Journal of Dairy Science Vol. 75, No. 8, 1992
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TABLE 6. The influence of duration of premilking teat preparation and attachment delay on milking performance, milk yield, and milk composition in Experiment 4 with Danish Jerseys. Reparation .16 min' .48 min Observations, no. Time to flow, min Machine-on time, min Average flow, kg/min Milk, kg 4% FCM, kg Fat, % Protein, % Lactose, %
254 .2@ 5.21 1.198 6.12 9.38 7.66' 4.23 4.72
267 .lSb 5.04
1.25b 6.10 9.49 7.81b 4.24 4.73
Attachment delay .5 min
1.4 min 3.1 min
177 176 168 .17b .1Y .22a 5.35a 4.96b 5.07b 1.26b 1.21' 1.18' 6.13ab 5.9Sb 6.23' 9.47' 9.06b 9.78' 7.74' 7.54b 7.93' 4.24 4.25 4.22 4.73 4.72 4.72
Pr x AD
SD
P?
AD2
.17 .87 .21 .81 1S O .77
*
*** ** * * ** ***
t
t
t
** *
.10
* *
.09
a*b7cMeanswith different superscripts differ (P < .05). 'Observed times of preparation and attachment delay. 2Treatment effects of preparation (Pr) and attachment delay (AD). +P < .lo. * P e .05. **P < .01. ***P < ,001.
time by increasing the attachment delay to 3.0 min was due to a drop in milk yield as well as in average flow rate. Preparation as a main effect had no influence on milk yield. Fat percentage increased
with time spent on preparation, whereas protein and lactose percentages were not influenced by preparation. Milk yield and fat percentage decreased with delayed attachment, whereas protein percentage increased slightly
TABLE 7. The influence of duration of premilking teat preparation and attachment delay on time until steady milk flow, machine-on time, and milk yield of the American Holsteins (AH-1, Experiment 1). Danish Holsteins (DH, Experiment 3), and Danish Jerseys (DJ, Experiment 4) in early and late lactation. Preparation .5 min'
Early lactation 1.3 min 3.0 min
.5 min
Late lactation 1.3 min 3.0 min
6) Steady milk flow, min AH- 1 10 30 DH 10 30 DJ 10 30 Machine-on time, min AH-1 10 30 DH 10 30 DJ 10 30 4% FCM, kg AH- 1 10 30 DH 10 30 10 DJ 30
.27 .ll .14 .08 .13 .12
.08 .06 .OS .05 .13 .09
.06 .05 .06 .05
7.58 7.06 8.65 8.02 5.89 5.64
7.12 7.18 8.64 8.42 5.23 5.32
14.9 15.8 15.4 15.9 11.1 11.1
'Attachment delay. Journal of Dairy Science Vol. 75, No. 8, 1992
15.3 15.9 16.3 16.0 10.4 11.1
.09
.57 .47 .28 .33
.61 .37 .35 .18 .32 .16
6.81 7.03 8.48 8.16 5.35 5.10
6.67 6.75 6.47 6.48 5.30 4.86
6.52 5.74 6.26 6.43 4.81 4.63
4.60
7.3 6.8 8.4 7.8 8.4 9.8
7.3 6.8 7.8 8.6 7.7 8.6
7.0 7.1 7.9 8.1 8.1 7.5
.12
14.0 14.6 16.7 15.9 10.4 10.2
.79 SO
.18 .20
.IO .08 .20 .15 5.99 6.33 6.07 6.13 5.09
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PREMILKING TEAT PREPARATION
namic movement of the liner stimulates older DJ cows more than 10 s of manual preparation does. However, when milk ejection is established, as by 30 s of preparation, any delay of attachment will decrease milk yield as well as fat percentage. For older cows in late lactation or cows yielding less than 5 kg of milk, milk yield and fat percentage were unaffected by increasing the attachment delay from .5 to 1.4 min after a long preparation, whereas further increase to 3.0 min decreased milk yield with more than 1 kg of FCM (data not shown). \ \
DISCUSSION
Premilking teat preparation affected milk yield of DJ cows only. The attachment delay influenced milk yield, milk composition, or 1 residual milk and fat of AH and DJ cows. \ \ Similarities in treatment effects within stages \ of lactation were striking for the two breeds, \ although differences in milk yield and fat percentage were large. The milk yield of DH cows did not respond to differences in preparation or attachment delay. These results contra.5 1.3 3 .O dict findings of Nielsen and Rasmussen (7) and Rasmussen et al. (10). For both short and Interval (min) long preparation, DH cows responded as did Figure 1. The influence of duration of premilking teat older DJ cows stimulated for a short time; Le., preparation (IO or 30 s) and machine attachment delay on there was no influence of attachment delay on milk yield on evening milkings for 1 ) first lactation and 2) milk yield, but the time until steady milk flow older Danish Jersey cows. decreased with increasing attachment delay. Consequently, stimulation through premilking teat preparation caused milk ejection of DH cows, but not to the extend that attachment (P c .lo). Lactose percentage was not infludelay became critical. enced by the attachment delay. Both AH and DJ cows were milked in Interactions (P < .05) between preparation, attachment delay, and lactation number were parlors, and treatments were conducted as significant for milk yield and kilograms of cows entered the milking parlor. No such synFCM (Figure 1). Applying a short preparation chronization occurred for DH cows in the tieto first lactation cows, the highest milk yield stall barn. By use of a standard milking routine for milking cows in the stalls, Rasmussen et al. was ObSeNed by attaching the milking unit (IO) imposed restricted conditions for milking after the .5-min delay, whereas 1.4 min of and increased lactation milk yield. In the light attachment delay was optimal following the of the DH results, but contrary to those of long preparation. Older cows decreased milk Nielsen and Rasmussen (7), the milk yield yield with increasing attachment delay follow- response using the standard milking routine ing a long preparation, whereas milk yield was likely arises as a synergetic effect between unaffected by the attachment delay following a adequate premilking teat preparation, short atshort preparation. This indicates that the need tachment delay (1.2 min), and conditioned for stimulation for DJ cows in the first lacta- stimulation. In the presence of synchronization tion is less than in later lactations and that (conditioned stimulation), 10 s of premilking attachment of the milking unit and the dy- teat preparation appears to be adequate for AH Journal of Dairy Science Vol. 75, No. 8, 1992
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cows to maximize milk yield, whereas more time is needed for DJ cows. Mayer et al. (4) point out that large volumes of cisternal milk, as for cows in early lactation, apparently may limit the complete ejection of alveolar milk. As a consequence, cisternal milk, or at least some of it, should be removed before milk ejection actually occurs. These findings agree with our observations on older DJ cows in early lactation; in those cows, milk yield decreased when machine attachment was delayed after sufficient stimulation (.5 min). The time from the beginning of preparation until intramammary pressure increased was 1.3 f .3 min in early and 1.7 f .4 min in late lactation (4), which shows why long attachment delays (>1.4 min) were not necessary for stimulated cows. Although not significant in every one of our studies, the time until steady milk flow decreased, and milk flow rate increased, with time spent on preparation. Gorewit and Gassman (2) observed similar trends. This indicates that elastic tissue or muscles surrounding milk lobes and inlets to cisterns and muscles in the streak canal may be more relaxed following a long preparation than a short one. The relaxation allows milk to flow more easily from the alveoli through the milk ducts and out of the teats (3). Experiment 2 indicates that the higher average flow rate and the shorter time until steady milk flow is not a matter of fatigue of the streak canal by intensive prestripping only, but rather an innervation of spinal nerves. Direct innervation of myoepithelial cells has not been evident (3). However, denervation of sympathetic nerves causes intramammary pressure to rise more quickly in response to oxytocin (3). Large fat droplets may pass relaxed lobes more easily, and fat percentage in the milk can increase, as observed in three of our four studies. Segregation of fat from the watery phase is less pronounced, and fat percentage in the last milk (stripping) or in the residual milk decreases, as observed by Svennersten et al. (13). The fat segregation might also contribute to a lower yield through fat depression when machine-on time is unnecessarily long. To avoid this fat segregation as much as possible, milk must be removed as it flows to the teat cisterns. The watery phase of the milk may drain out of the storage system more easily and Journal of Dairy Science Vol. 75. No. 8. 1992
quickly than the fat part because of differences in viscosity. Milk with more than 8.5% fat from DJ cows flowed steadily within 10 s when the unit was attached 1.4 min after the beginning of a 30-s preparation. Machine-on time for this group of cows was not affected differently by the treatments than for cows with less fat in the milk. This indicates that premilking teat preparation and time delay until attachment are more important for sufficient milk removal than viscosity of the milk. CONCLUSIONS
The milking machine should be attached shortly after premilking teat preparation if milk ejection is evoked. In early stage of lactation, the milking unit can be attached before milk ejection actually has occurred because more cisternal milk is available at this stage than later on, and, therefore, applying the milking machine when teats are not full is less likely to OCCUT.
If cows are not stimulated sufficiently (either manually or by conditioning), a time delay until attachment has no influence on milk yield, and an attachment delay of 3.0 min is preferable to minimize the time until steady milk flow occurs. ACKNOWLEDGMENTS
The sabbatical at Cornell University for M. D. Rasmussen was supported by the Danish Research Academy, Aarhus, Denmark. REFERENCES
1 Brandsma, S. 1978. The relation between milking, residual milk and milk yield. Page 47 in Roc. Int. Symp. Machine Milking. 17th Annu. Mtg. Natl. Mastitis Counc. Inc., Louisville, KY. Natl. Mastitis Counc., Arlington, VA. 2Gorewit, R. C., and K. B. Gassman. 1985. Effects of duration of udder stimulation on milking dynamics and oxytocin release. J. Dairy Sci. 68:1813. 3Lefcourt, A. M., and R. M. Akers. 1983. Is oxytocin really necessary for efficient milk removal in dairy cows7 J. Dairy Sci. 66:2251. 4Mayer, H., R. Bmckmaier, and D. Schams. 1991. Lactational changes in oxytocin release, intramammary pressure and milking characteristics in dairy cows. J. Dairy Res. 58:159. 5 Mein, G. A. 1990. Forces applied to the teat: conventional milking. Page 61 in Proc. Sem. Machine Milking Mastitis, Koldkaergaard, Aarhus. Natl. Inst. Anim. Sci. Foulum, DK.
PREMILKING TEAT PREPARATION 6 Menill, W. G., R. Sa@, L. G. Peterson. T.V. Bui, H. N. Erb, D. M. Galton, and R. Gates. 1987. Effects of predking stimulation on complete lactation milk yield and milking performance. J. Dairy Sci. 701676. 7 NielSen, s. M., and M.D. Rasmussen. 1987. Milking routines and equipment for tie-up cow sheds. Page 155 in Cattle prod. Res. Danish StatUS and Perspectives. Landhusholdnings=lskabets Forlag., Copenhagen, DK. 8 Phillips, D.S.M. 1984. Studies on pre-milking preparation2. The effect of delay pre-milking stirnulus and millcing. N.Z. J. Agric. Res. 27:31. 9 phillips, D.S.M. 1986. Studies on pre-dhg tion 8. A comparison of 10 and 45 seconds of wash and stimulus. N.Z. J. Agric. Res. 29:667. lORasmussen, M. D., E. S. Frimer, Z. Horvath, and N. E. Jensen. 1990. Comparison of a standardized and variable milking routine. J. Dairy Sci. 73:3472.
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11 Sagi, R., R. C. Gorewit, W. G. Merrill, and D. B. Wilson. 1980. Premikng stimulation effects on milking performance and oxytocin and prolactin release in cows. J. Dairy Sci. 63:800. 12 &hams, D., H. Mayer, A. prokopp, and H. Worstorff. 1984. oxytocin secretion during milking in cows with to the impofiance of a threshold level for milk J. ~ d o c f i n o l 102: , 337. 13 Svennersten, K., C. 0. Claesson, and L. Nelson. 1990. Effect of local stimulation of one quarter on milk production and milk components.J. Dairy Sci. 73:970. 14nompson, p. D., and R. L. Sieber. 1980. Milking machine effects on impacts and teat-end lesions. Page 61 in h c . Int. Workshop Machine Milking Mastitis, Moorepark, Ireland. Int. Dairy Fed., Brussels, Belgium.
Journal of Dairy Science Vol. 75, No. 8, 1992
RASMUSSEN and E. S. FRIMER
National Institute of Animal Science Department of Research in Cattle and Sheep Foulum, PO Box 39 DK-8830 Tjele, Denmark
D.
M. GALTON and L. G. PETERSSON Department of Animal Science Cornell University Ithaca, NY 14853
ABSTRACT
Premilking teat preparation and attachment delay were varied in four experiments conducted with American Holstein, Danish Holstein, and Danish Jersey cows. Premilking teat preparation varied from 10 to 30 s and consisted of wiping teats for 6 to 20 s and stripping one to five squirts of milk from each teat. Attachment delay from beginning of premilking teat preparation until machine attachment varied from .5 to 3.0 min. Longer preparation significantly increased milk yield for Danish Jersey cows, but not for American or Danish Holstein cows. Older Danish Jersey cows were more sensitive to premilking teat preparation than first lactation cows. Attachment delay influenced the milk yield in Danish Jersey cows, amount of residual fat in American Holsteins, and fat percentage in the residual milk of American and Danish Holstein cows. A 1.3-min delay can be generally recommended for the whole herd with only small or no milk loss for cows in early stage of lactation. Milk yield decreased for Danish Jersey cows and tended to decrease for American Holstein cows when machine attachment was delayed to 3.0 min, regardless of stage of lactation. The lack of treatment effects for Danish Holstein cows may be due to a lack of conditioned stimulation for cows
Received June 28, 1991. Accepted January 13, 1992. 1992 J Dairy Sci 75:2131-2141
milked in their tie stalls compared with the response of cows moved to milking parlors for milking. Added duration of teat wiping, vigorousness of teat stripping, and delay of machine attachment hastened steady milk flow. Conversely, advanced days in lactation delayed steady milk flow. The high fat content of Danish Jerseys did not delay the start of steady milk flow compared with the American and Danish Holsteins. In late stage of lactation, 30 s of teat preparation and 1.3 min of machine attachment delay minimized time until steady milk flow as well as 10 s of teat preparation and 3.0 min of attachment delay. (Key words: premilking teat preparation, milk yield, milking performance)
Abbreviation key: AH = American Holstein, DH = Danish Holstein, DJ = Danish Jersey. INTRODUCTION
The relative importance of stimulation obtained through premilking teat preparation, dynamic movement of the liner, emptying of the udder, and local intramammary regulatory mechanisms needs evaluation with respect to differences in breed, selection improvement, stage of lactation, milking management, and milking equipment. Through intensive selection and technology advancement, these factors have become dynamic and require periodic reevaluation. Phillips (9) demonstrated that Jersey cows required more stimuli for maximal milking management than did Holstein cows. More2131
2132
RASMUSSEN ET AL.
over, Phillips (9) proposed that selection against cows with high requirements for udder stimulus by applying little or no premilking teat preparation has, over time, reduced the threshold value for triggering the milk ejection reflex. In contrast, once oxytocin is released from the pituitary into the blood stream, transport time to the myoepithelial cells probably does not differ much between breeds and stages of lactation. The timing of oxytocin release might be of greater importance to milk removal than absolute concentrations of oxytocin released during milking (11, 12). In this context, both premilking teat preparation and machine attachment delay (defined as interval between start of preparation and attachment) need to be varied in order to check for interactions. Gorewit and Gassman (2) varied teat preparation from 0 to 120 s and attached the milking unit immediately after termination of preparation and thereby, according to the definition just given, confounded duration of teat preparation and attachment delay. Therefore, the influence on milking dynamics cannot be sorted into effects of preparation, attachment delay, or interactions between those factors. A time delay of 5 min, from preparation until attachment of the milking machine, increased residual milk and fat and decreased milk yield (l), although results from different studies are equivocal (7, 8, 10, 11). Finally, the existence in the udder of local regulatory mechanisms related to milk yield has been demonstrated (13). Previous stimulation studies (1, 2, 6, 7, 8, 9, 10, 11) focused on milk yield and composition, and this study is no exception. However, machine-on time decreases, and milk flow rate increases, with duration of premilking teat preparation (2, 6). These parameters and the time until steady milk flow might be more important for udder health and the practicability of a milking routine than recognized earlier. Machine milking of empty teats results in a higher compressive load applied from the liner on the teat surface ( 5 ) and in discomfort to the cow, which may result in cows kicking the milking unit. Moreover, automatic removers with a present neutral phase (phase at the beginning of the milking in which the unit does not detach, normally 1 to 2 min) detach the milking unit when milk flow fails to reach detachment flow rate within this phase; that is, milk ejection must occur Journal of Dairy Science Vol. 75, No. 8, 1992
within 1 to 2 min. Teat end erosions occur more often in herds with the milking unit attached immediately after preparation than with attachment 1 to 2 min after preparation (14). The objective of these studies was to evaluate the effects of premilking teat preparation and time delay until machine attachment on the time until steady milk flow, machine-on time, milk yield, and milk composition. MATERIALS AND METHODS
Four experiments were conducted in 1989. Cows used in Experiment 1 were American Holsteins (AH-I), as were cows in Experiment 2 (AH-2).Experiment 3 included Danish Holstein cows (DH),and Danish Jerseys (DJ) were used in Experiment 4. Experiment 1
Twelve AH cows from the Cornel1 University herd were used. Seven cows were in their second lactation, 2 cows were in their third lactation, and 3 cows were in their fourth lactation. Selection criteria were four functional quarters and no clinical signs of disease. Six cows were in early stage of lactation, 69 f 24 DIM, with an average daily milk yield of 36.0 f 4.5 kg, and 6 cows were in late stage of lactation, 266 f 17 DIM, with an average daily milk yield of 14.9 f 3.6 kg. Cows were subjected to six treatments in a Latin square design within stage of lactation. Duration of the experiment was 6 wk, and cows received a given treatment for nine consecutive milkings; the first milking started with an evening milking. Five milkings elapsed before cows were rotated to the next treatment. Treatments of premilking teat preparation (stimulation) were short (10 s) or long (30 s) and were combined with one of three attachment delays, .5, 1.3, or 3.0 min, measured from beginning of teat preparation until attachment of the milking machine. Short preparation included wiping of each teat twice with a nearly dry cotton towel and prestripping of one squirt of milk from each teat. Long preparation included wiping of each teat five times, scrubbing of each teat end with a nearly dry cotton towel, and powerful prestripping (full streams of milk entered the strip cup) of five to six squirts of milk from each teat.
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Residual milk was obtained immediately after the first and the ninth milkings by injection of 20 IU of oxytocin (Butler Co., Rochester, NY) into the milk vein and attachment of the milking unit 1 min thereafter. If present, stripping yield was included in the amount of residual milk. Milk samples were analyzed for milk fat and protein percentages at Northeast DHI Laboratory (Ithaca, NY).Milk yield was recorded at every milking. Time until steady milk flow (visual estimation of milk flow through the long milk hose) and machine-on time were recorded at two morning and two evening milkings between residual milk collections. Average flow rate was calculated by milk yield divided by machine-on time. Electronic milk flow recording was not possible in every study without interfering with the milking routine. Therefore, visual estimation of the milk flow was chosen. Milk was defined to flow steadily as soon as milk flowed continuously in every pulsation cycle. Cows were milked at 0600 and 1700 h in a double-five herringbone milking parlor. Cows entered the milking parlor one at a time to synchronize possible conditioned stimuli with the onset of a treatment. Cows were milked with an IBA Quarter Milker with IBA liners (S-6OO0, IBA, Milbury, MA). Pulsation ratio, pulsation rate, and vacuum were 55:45, 50 pulsations per min, and 44 Wa, respectively. Milking units were automatically detached when milk flow rate dropped below 200 g/min. During the five milkings between treatments, 5 cows entered the milking parlor at a time, and the milking units were attached immediately
after 20 s of prestripping and teat wiping. Cows were fed a total mixed ration throughout the experiment. Data were analyzed in a model including effects of stage, cow nested within stage, week, treatment, and interactions of stage x week and stage x treatment. Analysis was performed with either one observation per cow per week or an average per cow per week. An overview of cows and treatments for the different studies are in Table 1. Experiment 2
Eight of the cows that were in Experiment 1 continued in this study. Four cows were in early stage of lactation, 111 k 13 DIM, with an average daily milk yield of 36.4 f 4.9 kg, and 4 cows were in late stage of lactation, 311 f 22 DIM, with an average daily milk yield of 13.2 f 1.3 kg. Cows were subjected to four treatments in a Latin square design within stage of lactation. The duration of the experiment was 16 d; cows received a given treatment for four milkings, starting at a morning milking; and four milkings elapsed without treatment before cows were rotated to the next treatment. Treatments were a factorial design of 1) wipe each teat twice with a nearly dry cotton towel for 6 s or 2) wipe each teat five times and scrub each teat end for 20 s combined with prestrip one squirt from each teat or prestrip five powerful squirts from each teat. The attachment delay was 1.3 min. Residual milk was obtained from the fourth milking. Milk yield and time measurements
TABLE 1. Comparison of cows, treatments, and design in the four experiments.
Breed’
Cows
AH-1 AH-2 DH DJ
(no.) 12 8 12 78
Preparation
Attachment delay
-(s) 10 io4 10 10
30
Design3
(e) .5
304
30 30
Stage2
Milkings per treatment
.5 .5
1.3 1.3 1.3 1.3
3 .O
E, L
3.O 3 .O
E, L E, L EM,L
9 4 9 1
Lsq
LS¶ Lsq W S ¶
‘AH = American Holstein (Experiments 1 and 2); DH = Danish Holstein; DJ = Danish Jersey. %tage of lactation: E = early, M = mid, L = late. 3Experimental design: Lsq = Latin square, InLsq = incomplete Lsq. 4F’restripping and wiping of teats varied factorial from 10 to 30 s. Journal of Dairy Science Vol. 75. No. 8, 1992
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were recorded at every milking. Milking procedure and facilities were as outlined for Experiment 1. Period was used instead of week in the statistical model. Experiment 3
Twelve DH cows (with about 75% of genes from AH) from the Foulum Research Centre (Tjele, Denmark) herd were used. Four cows were in second lactation, 5 cows were in third lactation, 2 cows were in fourth lactation, and 1 cow was in seventh lactation. The early stage group was 47 f 6 DIM with an average daily milk yield of 33.7 f 3.8 kg, and the late stage group was 242 f 27 DIM with an average daily milk yield of 18.4 f 3.2 kg. Experimental design, treatments, recording of residual milk, and statistical procedure were as outlined for Experiment 1. Milk samples were analyzed for fat, protein, and lactose percentages with a Milkoscan 104 (Foss-Electric, Hillerod, Denmark). Machine-on time and the time until steady milk flow were recorded at every milking. Cows were milked at 0500 and 1600 h in a tie-stall barn in the same order at every milking. Cows were milked with a Uniflow claw (S. A. Christensen, Kolding, Denmark) and Stranko liners (3423005 Strange Hansen, Varde, Denmark). Pulsation ratio, pulsation rate, and vacuum were 60:40,60 pulsations per min, and 48 kPa, respectively. Pipelines were situated 190 cm above the floor. Milking units were automatically detached when milk flow rate dropped below 200 g/min. Between treatments, cows were milked by the standard milking routine (10). Cows were fed a total mixed ration throughout the experiment. Experlment 4
Seventy-eight DJ cows from a commercial herd were used (Table 2). The experiment included all cows in the herd. Cows showed no clinical signs of any disease during the experiment. Treatments were outlined as in Experiment 1. The experiment consisted of four evening milkings during 1 wk and three evening milkings during the following week. Cows were milked in a double-seven herringbone milking parlor. Treatments changed for every group of 7 cows (one side in the parlor), and Journal of Dairy Science Vol. 75, No. 8, 1992
TABLE 2. Number of Danish Jersey cows relative parity and stage of lactation.
to
First
Stage of lactation
DIM
lactation
Older
WlY Mid Late
13 16 4
21 15 9
every treatment was represented each evening and at a different time during each milking. Cows entered the milking parlor one at a time to synchronize possible conditioned stimuli with the onset of a treatment. Machine-on time, the time until steady milk flow, and milk yield were recorded at every evening milking, and milk samples were analyzed for fat, protein, and lactose percentages with a Milkoscan 104. Average flow rate was calculated by milk yield divided by machineon time. Cows were milked at 0500 and 1600 h with a HPl00 claw (Alfa-Laval, Vejle, Denmark) and Alfa-Lava1 liners (960018-83). Pulsation ratio, pulsation rate, and vacuum were 63:35, 60 pulsations per min and 42 kPa, respectively. Milking units were automatically detached when milk flow rate dropped below 200 g/min. Between treatments, 7 cows entered the milking parlor at the same time, and premilking teat preparation was applied for 10 s before the 7 units were attached. Cows were fed a mixed ration for ad libitum intake and concentrate according to milk yield throughout the experiment. Data were analyzed in a model including effects of stage, cow nested within stage, date, treatment, and the interaction stage x treatto 7.5, and >7.5 ment. Milk yield group (45, kg) and fat percentage group (<7, 7 to 8.5, and >8.5%) were analyzed in the model instead of stage. Analyses were performed for first lactation and older cows separately or combined. RESULTS
The effect of duration of premilking teat preparation and delay of attachment were analyzed within experiment and presented in the order of effect of number of milkings (AH-1, DH), influence on the time until steady milk flow, machine-on time, average milk flow, milk yield, milk composition, and residual milk yield (AH-1, AH-2, DH).
2135
PREMLKING TEAT PREPARATION
TABLE 3. The influence. of duration of premillcing teat preparation and attachment delay on milking performance, milk yield, and milk composition in Experiment 1 with American Holsteins. Preparation
mini
5 2 min
.6 min
1.3 min 3.0 min
36
36
24
24
24
.33 6.78 1.78 11.0 11.0 4.05 3.60 2.13 16.1 9.48 30.4
.21 6.68 1.85 11.0 11.2 4.12 3.61 2.11 16.3 9.73 30.1
.42a 7.01a 1.77 11.0 11.2 4.13 3.56 2.14 15.8 9.37a 28.7a
.28a 6.64b 1.82 11.3 11.3 4.17 3.66 2.03 15.4 9.4Ia 28.4a
.12b 6.54b 1.86 10.7 10.7 3.95 3.60 2.19 17.4
.I8 Observations, no. Time to flow, min Machine-on time, min Average flow, kg/min Milk, kg 4% FCM, kg Fat, 8 Protein, 8 Residual milk, kg Residual milk, 8 Fat in residual milk, 8 Residual fat, %
Attachment delay
lO.0Sb 33.6b
SD
F?'
** *
.3 1 .62 .17 1.1 1.3 .33 .14 .62 4.5 .99 7.8
AD2
+
t t
* *
avbMeanswith different superscripts differ (P < .05). 'Observed times of preparation and attachment delay. 'Treatment effects of preparation (Pr) and attachment delay (AD). +P < .IO. *P < .05. **P < .01.
Experiment 1
duration of preparation; this was mainly due to an effect on milk flow rate. Except for the minor effects of number of Duration of preparation had no effect on milkings, time effect was not significant. Data milk yield, milk composition, or residual milk. in Table 3 are averages of the first and the Milk yield and fat and protein percentages ninth milking (least squares means). Fat con- were the highest, and amount of residual milk tent in the residual milk changed from lowest and percentage of residual milk were the after the attachment delay of 1.3 min at the lowest, following the attachment delay of 1.3 first milking to lowest after the short attach- min, but differences were insignificant (P > ment delay at the ninth milking. For both the .05). However, an increase in the attachment first and the ninth milkings, fat content in delay from 1.3 to 3.0 min significantly inresidual milk was highest after a 3.0-min at- creased the amount of residual fat in the udder. tachment delay. For cows in late lactation, fat An attachment delay of 3 min tended to content in normal milk was highest after the decrease milk yield, and this effect was most long preparation at the first milking but lowest pronounced in early lactation (Table 7). Percentage of fat retained in the udder decreased after the ninth milking. The time until steady milk flow decreased slightly in late lactation; the attachment delay with delayed attachment (P c .01) and with increased from .5 to 1.3 min and increased (P duration of preparation (P > .lo). Steady milk c .lo) when the attachment was delayed for flow was delayed in late lactation compared 3.0 min (data not shown). For cows in early with early lactation (Pc .001). In early lacta- lactation, residual fat in the percentage of total fat increased linearly with the length of the tion, milk flowed steadily within 10 s (Table attachment delay. Residual fat percentage was 7). In late lactation, time until steady milk flow the highest after the long preparation in early was greater than .5 min for the .5 min of lactation and highest in late lactation after a attachment delay, regardless of duration of short preparation (P c .Ol). These effects did preparation, and for the 1.3 min of attachment not follow tendencies of FCM (P > .lo), for delay following the short preparation. which highest milk yield was obtained after a Machine-on time decreased with delayed at- long preparation in early lactation and after a tachment but was only slightly influenced by short preparation in late lactation (Table 7). Journal of Dairy Science Vol. 75, No. 8, 1992
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RASMUSSEN ET AL.
TABLE 4. The influence of duration of premiUcing teat wiping and number of prestripping squirts on milking performance, milk yield, and milk composition in Experiment 2 with American Holsteins. Wiving of teats 5 s Observations, no. Time to flow, min Machine-on time, min Average flow, kg/min Milk, kg 4% FCM, kg Fat, % Protein, % Residual milk, kg Residual milk, % Fat in residual milk, % Residual fat, %
20 s
1'
5
.18 6.81 1.7Sa 11.5 11.7 4.32 3.68 2.23 17.7 9.26 30.5
8 .16 6.28 2.03b 10.8 10.9 4.23 3.64 2.26 17.9 9.26 31.6
8
1
8 .10 6.57 1.95ab 11.5 12.0 4.40 3.66 2.15 16.9 9.03 28.6
5
SD
.G9
.ll .48 .18 1.2
8
6.52 1 .89ab 11.5 12.0 4.39 3.68 2.03 15.7 9.33 27.5
1.1
.30 .10 .60 4.7 .66 7.2
&bMeans with different superscripts differ (P c .OS). 'Number of prestripping squirts. Experiment 2
Experiment 2 was designed to determine marginal effects of prestripping and wiping of teats in combination with the optimal attachment delay of 1.3 min found in Experiment 1. The time until steady milk flow decreased with duration of premilking teat preparation for cows in late lactation regardless of the kind of preparation (Table 4). The time until steady milk flow was not affected by preparation in early lactation. Five streams of milk, compared with one stream removed during prestripping, decreased machine-on time and increased average milk flow (P < .05) after a 5-s teat wiping procedure, whereas this effect failed to appear after a 204 teat wiping procedure. Milk yield, fat percentage, and residual milk followed the tendencies in Experiment 1. Milk yield and fat percentage were higher after 20 s than after 5 s of teat wiping, and prestripping in itself did not influence milk yield and milk composition. Corresponding to these observations, percentages of residual milk and fat were lowest after the 20 s of teat wiping, regardless of prestripping. Results from this experiment tend to support conclusions from the other experiments. Experiment 3
Number of first to ninth milkings was not significant, and data in Table 5 are averages of the treatment period (least squares means). Journal of Dairy Science Vol. 75. No. 8, 1992
The time until steady milk flow decreased with duration of preparation and with the length of the attachment delay. Steady milk flow occurred later in late lactation compared with flow in early lactation (P .OOl). In early lactation, milk flowed within 7 s, even after a short attachment delay (Table 7), but such small values were obtained only after a long attachment delay in late lactation. Milk flowed steadily within 11 s following a long preparation and attachment delay of 1.3 min in late lactation cows. Machine-on time decreased with time spent on preparation and with increase in the attachment delay from 1.3 to 3.0 min. In early lactation, machine-on time was shorter (P .01) after a long preparation than after a short preparation. Preparation had no effect on machine-on time in late lactation. Average milk flow rate increased with the length of the attachment delay, especially after a short preparation. Except for protein percentage in the milk, milk yield and composition were not affected by the treatments. However, fat percentage in the residual milk increased with the length of the attachment delay, indicating that milk yield and fat percentage should decrease simultaneously. In early lactation, the amount of residual milk was the highest after the long preparation (P .05). Milk yield was, for both stages of lactation, about the same as that in Experiment 1, and standard deviations were about the same magnitude or less; differences
2137
PREMILKING TEAT PREPARATION
TABLE 5. The influence of duration of premilking teat preparation and attachment delay on milking performance, milk, yield, and milk composition in Experiment 3 with Danish Holsteins.
Observations, no. Time to flow, min Machine-on time, min Average flow, kg/min Milk, kg 4% FCM, kg Fat, % Protein, % Lactose, % Residual milk, kg Residual milk, % Fat in residual milk, % Residual fat, %I
Preparation
Attachment delay
.17 min' 52 min
.6 min 1.3 min 3.0 min
36 .22 7.43 1.48 11.4 12.1 4.85 3.49a 4.73 2.61 19.4 10.07 32.7
24 .32a 7.41 1.48 11.4 11.8 4.85 3.47 4.73 2.84 20.6 9.66a 33.4
36 .15 7.27 1.51 11.4 12.1 4.82 3.46b 4.73 2.79 19.6 9.93 32.7
24 .16b 7.44 1.48 11.4 12.2 4.84 3.49 4.72 2.65 19.4 10.02& 32.6
24 .07c 7.21 1.54 11.5 12.2 4.81 3.48 4.73 2.62 18.6 10.32b 32.1
PrX
SD
P?
.15 .35 .10 .7 1.5 .36
t t
.06
.05 .65 4.0 .70 6.1
AD2
AD
a**
t t
*
*
* **
ab*cMeans with different superscripts differ ( P c .05). 'Observed times of preparation and attachment delay. 2Treatment effects of preparation (Pr) and attachment delay (AD).
tP <
.lo.
* P c .05. **P < .01.
***P< ,001.
(or lack of treatment effects) in this experiment were not due to greater variability among figures. Experiment 4
The time until steady milk flow decreased with time spent on preparation ( P < .05) and with increasing attachment delay ( P c .001) (Table 6). After a short preparation, the time until steady milk flow dropped steadily with delayed attachment, whereas, after a long preparation, increasing the attachment delay from .5 to 1.4 min caused a decline. Further attachment delay had marginal influence on the time until steady milk flow. In late lactation, milk flowed sooner after a short attachment delay with DJ cows than with the DH and AH cows (Table 7). For cows yielding less than 5 kg of milk per milking, milk flowed steadily within 10 s when the long preparation was followed by attachment delays of 1.4 and 3.0 min. After a short attachment delay, in combination with either short or long preparation, milk flowed within 25 and 20 s, respectively. The time until steady milk flow was unacceptably long (45 s)
following a short preparation and short attachment delay for cows with milk fat content higher than 8.5%. For this group of cows, the shortest time until steady milk flow (9 s) was obtained after a long preparation and attachment delay of 1.4 min. Long preparation compared with short preparation shortened the machine-on time by 10 s ( P c .lo), mainly through a higher average flow rate. The effect was independent of lactation number, stage, milk yield, and fat percentage in the milk. The attachment delay of 1.4 min resulted in the shortest machine-on time and the highest average flow rate. There was no interaction between preparation and attachment delay. For low yielding cows (4 kg of milk), machine-on time was 40 s shorter after the attachment delay of 1.4 min than after .5 min (data not shown). Longer attachment delay shortened machine-on time slightly. For high yielding cows, machine-on time decreased 19 s when attachment delay increased from .5 to 3.0 min. The decrease associated with attachment delay of 1.4 min compared with .5 min was due to a similar increase in average flow rate, whereas further reduction in machine-on Journal of Dairy Science Vol. 75, No. 8, 1992
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TABLE 6. The influence of duration of premilking teat preparation and attachment delay on milking performance, milk yield, and milk composition in Experiment 4 with Danish Jerseys. Reparation .16 min' .48 min Observations, no. Time to flow, min Machine-on time, min Average flow, kg/min Milk, kg 4% FCM, kg Fat, % Protein, % Lactose, %
254 .2@ 5.21 1.198 6.12 9.38 7.66' 4.23 4.72
267 .lSb 5.04
1.25b 6.10 9.49 7.81b 4.24 4.73
Attachment delay .5 min
1.4 min 3.1 min
177 176 168 .17b .1Y .22a 5.35a 4.96b 5.07b 1.26b 1.21' 1.18' 6.13ab 5.9Sb 6.23' 9.47' 9.06b 9.78' 7.74' 7.54b 7.93' 4.24 4.25 4.22 4.73 4.72 4.72
Pr x AD
SD
P?
AD2
.17 .87 .21 .81 1S O .77
*
*** ** * * ** ***
t
t
t
** *
.10
* *
.09
a*b7cMeanswith different superscripts differ (P < .05). 'Observed times of preparation and attachment delay. 2Treatment effects of preparation (Pr) and attachment delay (AD). +P < .lo. * P e .05. **P < .01. ***P < ,001.
time by increasing the attachment delay to 3.0 min was due to a drop in milk yield as well as in average flow rate. Preparation as a main effect had no influence on milk yield. Fat percentage increased
with time spent on preparation, whereas protein and lactose percentages were not influenced by preparation. Milk yield and fat percentage decreased with delayed attachment, whereas protein percentage increased slightly
TABLE 7. The influence of duration of premilking teat preparation and attachment delay on time until steady milk flow, machine-on time, and milk yield of the American Holsteins (AH-1, Experiment 1). Danish Holsteins (DH, Experiment 3), and Danish Jerseys (DJ, Experiment 4) in early and late lactation. Preparation .5 min'
Early lactation 1.3 min 3.0 min
.5 min
Late lactation 1.3 min 3.0 min
6) Steady milk flow, min AH- 1 10 30 DH 10 30 DJ 10 30 Machine-on time, min AH-1 10 30 DH 10 30 DJ 10 30 4% FCM, kg AH- 1 10 30 DH 10 30 10 DJ 30
.27 .ll .14 .08 .13 .12
.08 .06 .OS .05 .13 .09
.06 .05 .06 .05
7.58 7.06 8.65 8.02 5.89 5.64
7.12 7.18 8.64 8.42 5.23 5.32
14.9 15.8 15.4 15.9 11.1 11.1
'Attachment delay. Journal of Dairy Science Vol. 75, No. 8, 1992
15.3 15.9 16.3 16.0 10.4 11.1
.09
.57 .47 .28 .33
.61 .37 .35 .18 .32 .16
6.81 7.03 8.48 8.16 5.35 5.10
6.67 6.75 6.47 6.48 5.30 4.86
6.52 5.74 6.26 6.43 4.81 4.63
4.60
7.3 6.8 8.4 7.8 8.4 9.8
7.3 6.8 7.8 8.6 7.7 8.6
7.0 7.1 7.9 8.1 8.1 7.5
.12
14.0 14.6 16.7 15.9 10.4 10.2
.79 SO
.18 .20
.IO .08 .20 .15 5.99 6.33 6.07 6.13 5.09
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PREMILKING TEAT PREPARATION
namic movement of the liner stimulates older DJ cows more than 10 s of manual preparation does. However, when milk ejection is established, as by 30 s of preparation, any delay of attachment will decrease milk yield as well as fat percentage. For older cows in late lactation or cows yielding less than 5 kg of milk, milk yield and fat percentage were unaffected by increasing the attachment delay from .5 to 1.4 min after a long preparation, whereas further increase to 3.0 min decreased milk yield with more than 1 kg of FCM (data not shown). \ \
DISCUSSION
Premilking teat preparation affected milk yield of DJ cows only. The attachment delay influenced milk yield, milk composition, or 1 residual milk and fat of AH and DJ cows. \ \ Similarities in treatment effects within stages \ of lactation were striking for the two breeds, \ although differences in milk yield and fat percentage were large. The milk yield of DH cows did not respond to differences in preparation or attachment delay. These results contra.5 1.3 3 .O dict findings of Nielsen and Rasmussen (7) and Rasmussen et al. (10). For both short and Interval (min) long preparation, DH cows responded as did Figure 1. The influence of duration of premilking teat older DJ cows stimulated for a short time; Le., preparation (IO or 30 s) and machine attachment delay on there was no influence of attachment delay on milk yield on evening milkings for 1 ) first lactation and 2) milk yield, but the time until steady milk flow older Danish Jersey cows. decreased with increasing attachment delay. Consequently, stimulation through premilking teat preparation caused milk ejection of DH cows, but not to the extend that attachment (P c .lo). Lactose percentage was not infludelay became critical. enced by the attachment delay. Both AH and DJ cows were milked in Interactions (P < .05) between preparation, attachment delay, and lactation number were parlors, and treatments were conducted as significant for milk yield and kilograms of cows entered the milking parlor. No such synFCM (Figure 1). Applying a short preparation chronization occurred for DH cows in the tieto first lactation cows, the highest milk yield stall barn. By use of a standard milking routine for milking cows in the stalls, Rasmussen et al. was ObSeNed by attaching the milking unit (IO) imposed restricted conditions for milking after the .5-min delay, whereas 1.4 min of and increased lactation milk yield. In the light attachment delay was optimal following the of the DH results, but contrary to those of long preparation. Older cows decreased milk Nielsen and Rasmussen (7), the milk yield yield with increasing attachment delay follow- response using the standard milking routine ing a long preparation, whereas milk yield was likely arises as a synergetic effect between unaffected by the attachment delay following a adequate premilking teat preparation, short atshort preparation. This indicates that the need tachment delay (1.2 min), and conditioned for stimulation for DJ cows in the first lacta- stimulation. In the presence of synchronization tion is less than in later lactations and that (conditioned stimulation), 10 s of premilking attachment of the milking unit and the dy- teat preparation appears to be adequate for AH Journal of Dairy Science Vol. 75, No. 8, 1992
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RASMUSSEN ET AL.
cows to maximize milk yield, whereas more time is needed for DJ cows. Mayer et al. (4) point out that large volumes of cisternal milk, as for cows in early lactation, apparently may limit the complete ejection of alveolar milk. As a consequence, cisternal milk, or at least some of it, should be removed before milk ejection actually occurs. These findings agree with our observations on older DJ cows in early lactation; in those cows, milk yield decreased when machine attachment was delayed after sufficient stimulation (.5 min). The time from the beginning of preparation until intramammary pressure increased was 1.3 f .3 min in early and 1.7 f .4 min in late lactation (4), which shows why long attachment delays (>1.4 min) were not necessary for stimulated cows. Although not significant in every one of our studies, the time until steady milk flow decreased, and milk flow rate increased, with time spent on preparation. Gorewit and Gassman (2) observed similar trends. This indicates that elastic tissue or muscles surrounding milk lobes and inlets to cisterns and muscles in the streak canal may be more relaxed following a long preparation than a short one. The relaxation allows milk to flow more easily from the alveoli through the milk ducts and out of the teats (3). Experiment 2 indicates that the higher average flow rate and the shorter time until steady milk flow is not a matter of fatigue of the streak canal by intensive prestripping only, but rather an innervation of spinal nerves. Direct innervation of myoepithelial cells has not been evident (3). However, denervation of sympathetic nerves causes intramammary pressure to rise more quickly in response to oxytocin (3). Large fat droplets may pass relaxed lobes more easily, and fat percentage in the milk can increase, as observed in three of our four studies. Segregation of fat from the watery phase is less pronounced, and fat percentage in the last milk (stripping) or in the residual milk decreases, as observed by Svennersten et al. (13). The fat segregation might also contribute to a lower yield through fat depression when machine-on time is unnecessarily long. To avoid this fat segregation as much as possible, milk must be removed as it flows to the teat cisterns. The watery phase of the milk may drain out of the storage system more easily and Journal of Dairy Science Vol. 75. No. 8. 1992
quickly than the fat part because of differences in viscosity. Milk with more than 8.5% fat from DJ cows flowed steadily within 10 s when the unit was attached 1.4 min after the beginning of a 30-s preparation. Machine-on time for this group of cows was not affected differently by the treatments than for cows with less fat in the milk. This indicates that premilking teat preparation and time delay until attachment are more important for sufficient milk removal than viscosity of the milk. CONCLUSIONS
The milking machine should be attached shortly after premilking teat preparation if milk ejection is evoked. In early stage of lactation, the milking unit can be attached before milk ejection actually has occurred because more cisternal milk is available at this stage than later on, and, therefore, applying the milking machine when teats are not full is less likely to OCCUT.
If cows are not stimulated sufficiently (either manually or by conditioning), a time delay until attachment has no influence on milk yield, and an attachment delay of 3.0 min is preferable to minimize the time until steady milk flow occurs. ACKNOWLEDGMENTS
The sabbatical at Cornell University for M. D. Rasmussen was supported by the Danish Research Academy, Aarhus, Denmark. REFERENCES
1 Brandsma, S. 1978. The relation between milking, residual milk and milk yield. Page 47 in Roc. Int. Symp. Machine Milking. 17th Annu. Mtg. Natl. Mastitis Counc. Inc., Louisville, KY. Natl. Mastitis Counc., Arlington, VA. 2Gorewit, R. C., and K. B. Gassman. 1985. Effects of duration of udder stimulation on milking dynamics and oxytocin release. J. Dairy Sci. 68:1813. 3Lefcourt, A. M., and R. M. Akers. 1983. Is oxytocin really necessary for efficient milk removal in dairy cows7 J. Dairy Sci. 66:2251. 4Mayer, H., R. Bmckmaier, and D. Schams. 1991. Lactational changes in oxytocin release, intramammary pressure and milking characteristics in dairy cows. J. Dairy Res. 58:159. 5 Mein, G. A. 1990. Forces applied to the teat: conventional milking. Page 61 in Proc. Sem. Machine Milking Mastitis, Koldkaergaard, Aarhus. Natl. Inst. Anim. Sci. Foulum, DK.
PREMILKING TEAT PREPARATION 6 Menill, W. G., R. Sa@, L. G. Peterson. T.V. Bui, H. N. Erb, D. M. Galton, and R. Gates. 1987. Effects of predking stimulation on complete lactation milk yield and milking performance. J. Dairy Sci. 701676. 7 NielSen, s. M., and M.D. Rasmussen. 1987. Milking routines and equipment for tie-up cow sheds. Page 155 in Cattle prod. Res. Danish StatUS and Perspectives. Landhusholdnings=lskabets Forlag., Copenhagen, DK. 8 Phillips, D.S.M. 1984. Studies on pre-milking preparation2. The effect of delay pre-milking stirnulus and millcing. N.Z. J. Agric. Res. 27:31. 9 phillips, D.S.M. 1986. Studies on pre-dhg tion 8. A comparison of 10 and 45 seconds of wash and stimulus. N.Z. J. Agric. Res. 29:667. lORasmussen, M. D., E. S. Frimer, Z. Horvath, and N. E. Jensen. 1990. Comparison of a standardized and variable milking routine. J. Dairy Sci. 73:3472.
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11 Sagi, R., R. C. Gorewit, W. G. Merrill, and D. B. Wilson. 1980. Premikng stimulation effects on milking performance and oxytocin and prolactin release in cows. J. Dairy Sci. 63:800. 12 &hams, D., H. Mayer, A. prokopp, and H. Worstorff. 1984. oxytocin secretion during milking in cows with to the impofiance of a threshold level for milk J. ~ d o c f i n o l 102: , 337. 13 Svennersten, K., C. 0. Claesson, and L. Nelson. 1990. Effect of local stimulation of one quarter on milk production and milk components.J. Dairy Sci. 73:970. 14nompson, p. D., and R. L. Sieber. 1980. Milking machine effects on impacts and teat-end lesions. Page 61 in h c . Int. Workshop Machine Milking Mastitis, Moorepark, Ireland. Int. Dairy Fed., Brussels, Belgium.
Journal of Dairy Science Vol. 75, No. 8, 1992