Original article

Comparison of different machine milking clusterson dairy ewes with large size teats

N Fernández R Requena, MC Beltran, C Peris,M Rodríguez, P Molina, A Torres

Department of Animal Science, Polytechnical University of Valencia,Cnmino de Vera 14, 46071 Valencia, Spain

(Received 12 March 1996; accepted 20 November 1996)

Summary — Sixty-five Manchega ewes were milked with three different commercial clusters withdifferent teatcup and claw characteristics. Clusters with a lip mouthpiece deflection close to 20mm/kg (vs 8 mm/kg) increased the amount of machine milk (7.6-11.5%) and reduced the handstripped milk (22.7!t0.5%) and residual milk volumes (9.7-14.9%). They also improved the milk fat(2.3-2.5%), lactose (1.0- 1.4%) and dry matter (1.8%) composition, thereby potentially simplifyingthe machine milking routine. Milk flow was improved by large claws (91-140 mL vs 48 mL) in a milk-ing parlour where the pipeline was placed above the platforms. Teatcup falls were related to a linermouthpiece with a bore greater than 17 mm and to a heavy shell + liner + short milk and pulse tubes(224 g vs 156-168 g). The combined low weight of these permitted a reduction in vacuum level, thusdecreasing the risk of mastitis. The claw’s weight (89-201 g) had no influence on teatcup fallsbecause it hung from a band. The final conclusion was that teat size determined the optimal type ofliner. Thus, a mouthpiece bore of 17 mm was better for teats up to 45 mm long or 20 mm wide,while a bore of 19 mm was preferable for bigger teats.

machine milking / ewe / cluster / milking efficiency

Résumé — Comparaison de différents faisceaux-trayeurs dans la traite mécanique de brebis avecde grands trayons. À l’origine, les machines à traire furent conçues pour la brebis Lacaune, dont letrayon est plus étroit que celui de la plupart des races ovines européennes. Une adaptation de lamachine aux caractéristiques de certaines races pourrait donc se révéler nécessaire. Dans ce travail,65 brebis de race Manchega ont été divisées en trois groupes et soumises à la traite avec trois faisceaux-trayeurs de marques commerciales différentes, pendant 6 semaines, en utilisant un schéma en carrélatin (3 x 3). Les faisceaux-trayeurs différaient par les caractéristiques du corps du manchon (longueur,pression de flambage) et de l’embouchure (diamètre, souplesse des lèvres) mais aussi par le poids dufaisceau-trayeur, la taille et le dessin de la griffe. Une souplesse des lèvres de près de 20 mm/kg (vs8 mm/kg) augmente le lait machine (8-1 1 %) et réduit la repasse (23-41 %) ainsi que le lait rési-

* Correspondence and reprints

duel (1(>-15%n). Elle améliore la composition du lait, augmente le taux butyreux (2,3-2,5°l0), la teneuren lactose (1,0-1,4%) et en matière sèche ( 1,8 %), et fait entrevoir la possibilité d’une traite simpli-fiée (sans repasse). L’emploi de griffes de grande taille (91-140 vs 48 mL) facilite le transfert du laitvers le récipient de contrôle (lactoduc en ligne haute). Le décrochage des faisceaux-trayeurs est plusaisé lorsque le diamètre de l’embouchure est supérieur à 17 mm, et lorsque le poids de l’ensemble gobe-let + manchon + courts tuyaux à lait et de pulsation est élevé (224 vs 156-168 g). Un poids inférieurà cet ensemble permettrait de réduire le degré de vide de traite et, par là, le risque de mammite. Enrevanche, le poids de la griffe (89-201 g) ne semble pas avoir d’influence, car elle est suspendue àune courroie qui en réduit l’effet. En conclusion, la taille du trayon détermine le modèle optimal dumanchon, et il apparaît qu’un diamètre d’embouchure de 17 mm s’adapte mieux aux trayons ayantmoins de 45 mm de long et/ou 20 mm de large, tandis qu’une embouchure de 19 mm est préférablepour de plus grands trayons.

traite mécanique / brebis / faisceau-trayeur / efficacité de la traite

INTRODUCTION

In comparison with dairy cattle, there aremany more dairy sheep breeds used in com-mercial milk production. The sheep breedsdiffer in udder conformation and this makesthe development of optimal mechanicalmilking equipment more difficult.

With machine milked sheep, a relativelylarge proportion of the yield is obtained asstripping milk (Labussi!re, 1988) and inmilking parlours this can result in a 42°l0reduction in the number of animals milked

per hour (Ferndndez et al, 1989). ).Some machine milking problems are

actually due to the fact that the design isbased on Lacaune breed characteristics. Thisbreed has narrower ( I 5 mm) teats thanChurra (16 mm), Karagouniko (21 mm),Manchega (19 9 mm), Sarda ( 17 mm), Serrada Estrela ( 17 mm) and Tsigay ( 17 mm)breeds (Labussière, 1988). Such et al ( 1989)showed that ewes with bigger teats producedgreater quantities of stripping milk than theothers.

One of the factors affecting milking per-formance is the liner design, and differentauthors have demonstrated this by chang-ing the liner mouthpiece characteristics (LeDu, 1978; Such et al, 1989), using linersmade with different materials (Le Du, 1982),comparing old and new liners (Le Du andTaverna, 1989a) or by varying the roughinner barrel (Le Du and Taverna, 1989b).

Similarly, Peris et al (1989) demonstratedthe influence of liner mouthpiece design onthe volume of the different fractions of milkobtained in machine milking, although someof the models which reduced stripping frac-tions through a wider mouthpiece borecaused an increase in teatcup falls.

The present work studied the effective-ness of new commercial clusters, whosedesign takes into account some of the detailswhich could improve the milking of eweswith large teats.

MATERIALS AND METHODS

Ewes

Sixty-five Manchega ewes, from the Polytech-nical University of Valencia (Spain), were sub-jected to a suckling + milking (morning) systemfor a period of 5 weeks after lambing, followedby exclusive milking (morning + evening milk-ings) until the end of the lactation. They wereclassified, by lactation number and yield to lac-tation day 55, into three groups (table I). ).

After the experiment, the ewes were classi-fied according to their teat length and width(table V).

Milking

The ewes were milked in a n ulking parlour withsix clusters and the milk pipeline and recordingcontainer entrance were I .0 m and 0.9 m. respec-

tively, above the platforms . The recording con-tainers were located between the long milk tubesand the milk pipeline throughout the experi-ment. The vacuum level was 42 kPa, the pulsa-tion rate 120/min and the pulsator ratio 50%.Three different types of commercial clusters weretested and their major characteristics are pre-sented in table II and figures I and 2. Most ofthe barrel measurements were taken from plas-ter moulds (JL Ponce de Le6n, personal com-

munication). The lip mouthpiece deflection cor-responded to the descending value of the lip whena 0.5 kg weight was applied to a stopper closingthe mouthpiece bore (O’Shea et al, 1983). Barrelrigidity was determined from the minimum nec-essary vacuum, applied to the liner end, neededto close the barrel within the shell (Le Du et al,1978). The liners from the A and C clusters wereintegral (the liner and short milk tube formed asingle element).

At each milking, separate measurements weremade of the milk yield obtained by the milkingmachine unaided (MM), the yields of machinestrippings when there was vigorous udder mas-sage (MS), and finally the hand strippings whichstarted 1 min after the teatcups were detachedand any milk left in the udder removed (HS). ).

Experimental design

Each group was milked with each cluster for a

period of 2 weeks, following a Latin squaredesign (3 x 3) for 6 weeks, starting the 9th weekafter lambing, when all the animals had becomeaccustomed to machine milking (4th week afterweaning).

Twice a week (Tuesdays and Thursdays)morning and evening milk yields (MM + MS +HS) and composition, milk fractioning (MM,MS, HS), somatic cell count and the incidence offalls were recorded. Milk composition (fat, totalprotein, true protein, lactose and dry matter con-tent) was measured using an infra-red analyser(D400 Bran+Luebbe, Werkstrasse 4, 22844 Ham-burg, Germany), and the somatic cell count witha Fossomatic 90 (Foss Electric; DK-3400Hillerod, Denmark). Teatcup falls were recordedas follows: no falls, 0; I, fall produced by theliner slipping (passive falls); 2, due to an unex-pected movement by the ewe (active falls). OnThursdays, after the evening milking, the resid-ual milk (RM) was obtained manually afterinjecting 2 IU oxytocin into the jugular.

Morphology of the udder

Before starting the experiment the udder char-acteristics (L, teat length; WI’ teat width at thebase; W,, teat width at the central section; a,implantation angle; N, teat position) were mea-sured independently (Labussiere, 1984) by twoassistants. The average values of these measure-ments are presented in table I.

Kinetic milk emission

Kinetic milk emission was used to evaluate theeffect of the claw and cluster on milking time,milk extraction and evacuation to the recordingcontainers placed above the platforms. Records

of kinetic milk emission of the machine milking(Labussiere, 1984) were taken from a group of 24ewes belonging to the two peak class once theexperiment had finished. A manual method ofmeasuring was used; a strip of graph paper wasattached to the outside of the recording containerand the milk levels were recorded every 5 s. Thekinetic characteristics were taken from theserecords: V 1, volume of the first peak; V2, volumeof the second peak; MFI, maximum milk flow ofthe first peak; MF2, maximum milk flow of thesecond peak; Fm, average flow of both first andsecond peaks; D, time lapsed before the secondpeak appeared; time for the maximum flow ofthe first peak; time for the maximum flow of thesecond peak; T, total time. Every day a differ-ent cluster (A, B or C) was utilized and, in addi-tion, a kinetic was also taken from a combina-tion of liner A and claws B (A+B) or C (A+C) inorder to determine the significance of claw sizeon milk flow.

Statistical analysis

The statistical model employed was as follows:

where: Y;!klm - variable studied (total milk pro-duction, milk fractioning, milk composition,kinetic of emission and the log of the somaticcell count); ,u, general mean; a., effect of theewe; /3 , effect of the period; yk (!), effect of theday, within the period; 6,, effect of the milkingcluster and Eijklm’ residual.

Total milk production and milk fractioningdata were also analysed after classifying the ewesinto three groups, according to their teat lengths.This analysis was repeated after reclassifying theewes into three groups according to their teatwidth. To analyse the statistical significance ofthe interaction between teat size group x milkingcluster the model was:

where: Y¡jklm’ variable studied (total milk pro-duction and milk fractioning); !(, general mean;X. effect of the teat size group (length or width); );

Œ. (/I,), effect of the ewe, within the teat sizegroup; 1B, effect of the period; y (0k), effect of theday, within the period; 8¡, effect of the milkingcluster; Aj x 8¡, interaction between teat size groupand milking cluster and Eijklm’ residual.

The general linear model (GLM) procedure(SAS, 1989) was used with results expressed asleast squares means. Student’s t-test was utilizedto assess differences between means. The fre-

quence of teatcup falls was analysed comparing,two by two, the three clusters, with the chi-squared analysis. The relationship between vari-ables of udder morphology and milking fractionswas carried out following the SAS Corr proce-dure.

RESULTS

Milk yield and milk fractioning

The results presented in table III indicatethat the average daily milk production(DMP) and machine stripping milk (MS)did not vary significantly between clusters.Nevertheless, the machine milk (MM) vol-ume was higher and the hand stripping (HS)volume lower for cluster C than for clustersB and A. With respect to cluster A, the useof clusters C and B increased the MM by11.5% and 7.6%, reduced the HS by 40.5%and 22.7%, and also reduced the residualmilk by 14.9% and 9.7%, respectively.

Relationship between morphologyof the udder and milk fractioning

The relationship between udder morphol-ogy and milk fractions for all the ewes andall the clusters was studied using correla-tion coefficients.

The most important relationships estab-lished were between the different parametersof the udder (table IV). Thus, longer (L)teats tend to be wider (W) and had a lowerimplantation angle (a), with a tendency topresent a lower position index (N). Teatswith higher a had a higher N.

Ewes with longer and wider teats gaveboth a higher daily milk and hand strippingmilk production.

Interactions between cluster and teat

length groups, and cluster and teat widthgroups were significant for MM (P < 0.05)and HS (P < 0.01 and 0.005, respectively),but not for daily milk production, MS orRM.

Machine milk production increased(table V) with the use of cluster C comparedto either cluster B or cluster A. This was true

for both very long teats (L > 45 mm) or very

wide teats (W > 20 mm). With cluster C,less HS milk was obtained than with clus-ter B and with B less than with A in the case

of ewes with very long, very wide, or evenmedium (L = 35-45 mm; W = 18-20 mm),or small sized teats (L < 35 mm).

Milk composition

The results of milk composition are pre-sented in table VI. The results only differedwith respect to the cluster used for the fat,lactose and dry matter contents. These val-ues were similar for clusters B and C, andlower for cluster A.

Kinetic milk emission

Of all the parameters that defined kineticmilk emission, only the time when the milkflow reached its first peak, the maximumflow at the first peak (MF1) and the aver-age flow (Fm) were different depending onthe cluster used (table VII). Cluster A had

the slowest flow, although the combinationof liner A and claws B or C increased bothMF1 and Fm.

There were no significant correlationsbetween teat size (L or W) and milk flow.

Teatcup falls

The frequency of teatcup falls is shown intable VIII. Cluster B had the lowest inci-dence of both active and passive falls, whilecluster A gave the greatest number of pas-sive falls.

DISCUSSION

Daily milk production was similar with allthe tested clusters because the routine

employed included hand stripping, althoughcluster A had a poorer milk fractioning(lower MM and higher HS) than the others.The HS had a compensatory effect on thetotal production. The use of clusters B or Cwould simplify the routine (ie without HS)which could increase milking parlour yield.

Machine stripping yields (MS) were alsosimilar between clusters. This fraction

depended on the udder characteristics(Labussière and Ricordeau, 1970). In thisexperiment they were the same.A wide and/or flexible liner mouthpiece

increases the duration of the communica-

tion between both the udder and the teat cis-terns and decreases the stripping fractions(Le Du and Bondiguel, 1979; Peris et al,1989). Lip mouthpiece deflection must havebeen important in the improvement of milkfractioning of cluster B with respect to clus-ter A, because B had a narrower bore. The

improved results from cluster C as com-pared with cluster B could be due to itswider bore. Its higher lip mouthpiece deflec-tion might explain its improved results overcluster A. These facts demonstrated that lipmouthpiece deflection was more importantthan the bore size for milk fractioning.Moreover, the higher volume of the cavity ofliner C could have reduced the stripping vol-ume, as O’Shea et al (1983) have demon-strated in cows.

The fact that the difference between clus-ters was greater with the increase in teat sizeconfirmed the importance of the linermouthpiece design on milk fractioning, andit also appeared that the length of the teatwas more restrictive than its width. The dif-ferences in HS were significant betweenclusters even in the case of the shortest teat

(table V). Similar results were observed bySuch et al (1989).

Mein ( 1992), however, indicates that cowteats become longer by 40-50% duringmilking. In this experiment this would re-present an average length of 60 mm afterelongation. Given that the length of the liner(9 + 5 in fig 1 ) was between 102-108 mm,

what could have happened in the case oflargest teats is that the liner did not closecompletely and thus resulted in a poorerfractioning. A longer barrel might improvethis. Mein (1992) also suggests that the boreof the barrel should be I to 2 mm narrowerthan the teat; this was not the case with anyof the liners used in this experiment.

The fact that the milk fat content waslower for cluster A was to be expected,because clusters B and C emptied the udderto a greater extent (lower values of RM;table III). It is known (Labussiere, 1969;Torres et al, 1985) that milk fractions havea greater fat content when they are locatedhigher up in the udder and thus are last to bemilked.

As many cluster design factors wereimplicated, it is difficult to explain the dif-ferences in the time taken to reach the maxi-mum flow of the first peak. The fact thatcharacteristics of the second peak were inde-pendent of the cluster used could be relatedto the alveolar origin of the milk. Milk prob-ably descends from the upper part of theudder little by little and clusters with poorresults, such as cluster A, are acceptable.The low flows MFl and Fm of cluster Acould be due to poor milking results and/orto the claw, because after combining liner Aand claws from B or C the flow increased.The claws from clusters B and C had an

opening and closing vacuum system whichwas less operative than cluster A (fig 2).This was particularly true in the case of clus-ter C, which was designed in such a waythat the closing of the vacuum was difficultduring the change of teatcups. Not closingthe vacuum could increase the risk of mas-titis in flocks due to brusque removal of theteatcups.

The passive teatcup falls (slipping falls)could be related to cluster design. Passivefalls could be caused by very high flow dur-ing milking, both a wide bore and/or adeflection of the liner lip mouthpiece or theweight of the cluster. The flow of milk was

similar in all the cases so it could not be

responsible for the differences in falls. Dif-ferences in passive falls were greater in clus-ters A and C than in cluster B, and were alsogreater in cluster A than in cluster C. Clus-ters A and C had the largest mouthpiecebore, the narrowest bore at the end of theliner but a very different lip mouthpiecedeflection, suggesting that this factor wasless important than the others. The weight ofthe claw had no effect because, in milkingparlours for sheep, it hangs from a bandwhich reduces its effect. Nevertheless, theweight of shell + liner + short milk and pulsetubes had a direct influence on passive fallsbecause they hang from the udder. Theseweights were 224, 168 and 156 g for clustersA, B and C, respectively, which might jus-tify the greater number of passive falls ofcluster A compared with C. In the case oflow passive falls it would be possible toreduce the vacuum level in the cluster andwith it, the risk of mastitis.

In summary, it seems that the ideal linerwas related to the teat size, when the teatswere 45 mm long or 20 mm wide, or less,liner type B was optimum, but for longer orwider teats type C was the most optimal.

ACKNOWLEDGMENTS

The authors are grateful to Alfa-Laval Agri SAand Westfalia Separator for the equipment, andalso Prof Barraclough and Donnellan for check-ing the English. This work forms part of the pro-ject AGF95-0634, financed by the SpanishComisi6n Interministerial de Ciencia y Tec-

nologia.

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