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Teat-order in groups of piglets reared on an artificial sow. I. Formation of teat-order and influence of milk yield on teat preference
Applied Animal Ethology, 8 (1982) 335-345 Elsevier Scientific Publishing Company, Amsterdam
-
Printed
in The Netherlands
335
TEAT-ORDER IN GROUPS OF PIGLETS REARED ON AN ARTIFICIAL SOW. I. FORMATION OF TEAT-ORDER AND INFLUENCE OF MILK YIELD ON TEAT PREFERENCE
LYNN E. JEPPESEN’ A.R.C.
Institute of Animal Physiology, Babraham,
‘Present Ashford,
address: Department of Agriculture, Kent TN25 5AH, Gt. Britain
(Accepted
for publication
9 March
Cambridge CB2 4AT (Gt. Britain)
Wye College
(University
of London),
1981)
ABSTRACT Jeppesen, L.E., 1982. Teat-order in groups of piglets reared on an artificial sow. I. Formation of teat-order and influence of milk yield on teat preference. Appl. Anim. Ethel., 8: 335-345. When eight groups of four piglets were reared on four-teat artificial sows (all teats yielding equal volumes of milk), each group formed a consistent teat-order. An artificial sow with a single row of fourteen teats was then constructed to rear groups of eight piglets, thus providing a greater choice of teat position. Development of teatorder was compared for the groups of 4 and 8 piglets. For the piglets reared on the fourteen-teat sows, preference for different sections of the udder was examined. The possible consequences of piglet social interactions and of early and rapid fixation on a small area of the udder are among features which require further research into the teat-order phenomenon. The position of the sow’s “voice” initially appeared to have a positive influence on the piglets’ activity at certain teat sites and there was preference for end teats. Two-thirds of the piglets finally fixed on a teat from the 3-teat area of the udder that they used most on Day 2. Large differences in piglet activity were observed on teats producing widely different volumes of milk. However, there was less association between activity and milk yield for teats with up to 30 ml difference in milk yield (the maximum milk-volume ranging between 50 and 120 ml).
INTRODUCTION
During the detailed observations of the feeding behaviour of groups of piglets being artificially reared on a dummy sow (Jeppesen, 1980), it was found that a teat-order rapidly developed and the opportunity was taken to investigate the factors influencing and maintaining the teat-order without the active contribution of a live sow. It is often difficult to observe the teat positions of piglets accurately on the real sow. Apart from the inconvenience of having to anticipate feeds to obtain a sufficient number of recordings, the udder is irregular and very
0304-3762/82/0000-0000/$02.75
o 1982 Elsevier
Scientific
Publishing
Company
336
flexible so that the bottom row and hind teats are frequently tucked out of view of the observer. The rapid movements of two rows of piglets in association with the teats are also difficult to record in detail. Thus, the artificial sow provided ideal conditions in which to observe the development of teat-order. Feeding times were controlled, contacts between piglets and teat were clearly visible and experimental alterations to certain features of the udder were possible. This paper describes how the dummy sow was used to investigate the influence of factors such as section of the udder and milk yield on piglets’ selection of, and competition for, teats. Most reports of observations on teat-order and competition agree that the anterior teats are the most popular (Donald, 1937a; Gill and Thomson, 1956; Hartsock et al., 1977). The most common theory to explain this observation is that the front teats usually produce the most milk and are therefore more attractive to piglets (Donald, 1937b). McBride et al. (1965) and Fraser and Jones (1975) found better growth-rates in piglets using the anterior teats. Gill and Thomson (1956) measured milk-intake by weighing piglets before and after feeds, and found that 15.3% more milk was produced by the front four teats than by the back four. There are various reports of the times taken to form a teat-order on the real sow. Donald (1937a) and McBride (1963) stated that teat preference clearly takes place within one week. Wesley (1967) was aware of considerable variation, and stated that, in general, piglets showed a more even distribution of sucking frequencies across the udder by Day 10. Donald (1937a) observed that teat-selection developed first on the front and rear teats and that more “errors” were made by piglets on the middle teats than by those at the ends. In the present study, the formation of a teat-order in groups of piglets reared on four-teat dummy sows was analysed, and as a result a further sow was constructed with a greater choice of teat position and a more clearly defined “head” and “tail” end. A comparison was made of the development of teat-preferences of piglets reared on the two types of udder. As an additional investigation into teat preference, the activities on teats producing consistently high or low yields of milk was examined. METHOD
1. Animals
and housing
Groups of 4 or 8 Large White piglets were taken from their mothers at 24 h of age and placed in small pens with the artificial sows at one end. The pens had been heated to around 28°C and lined with straw and sawdust. Creep lamps provided additional heat. After the first few days, the temperature was gradually lowered to around 23°C.
337
2. Artificial sow and feeding Figure 1 shows the parts of the sow exposed to the piglets. The dummy sow comprised a wood and wire-mesh framework. The udder was spongefilled and covered with thin sheet-rubber. The remaining “body” of the sow was covered with carpet underfelt and coconut matting. Projecting from the udder at regular intervals was a single row of rubber liners from milking-machine teat cup shells (Simplex Ltd.). A rubber teat (Maws) was inserted into the hollow of each inflation and fixed. The sections containing each teat were made as similar as possible in shape and “hang”. The piglets were fed a sow-milk replacer/whole cow’s milk mixture dispensed from aspirators through tubes and valves to the teats. Feedvolume and intervals between feeds were controlled, the latter, in general, being 1.5 h during the day and 3--4 h during the night. The piglets were alerted to each feed by means of a recorded sow lactation call played through a loud-speaker situated at one end of the dummy sow (“head-end”). The valves were controlled to open just after the peak in sow grunting, which is the time of milk let-down for the real sow (Whittemore and Fraser, 1974). There were at least 30 s for the piglets to adjust their teat positions before milk let-down. Each group was fed from the sow for at least 3 weeks.
Fig. 1. The fourteen-teat
artificial sow.
338 TAIL
HEAD /
I
1
2
3
4
5
6
7
6
9
10
11
12
13
14
00000000000000 ,4
\ Mtlk yield Teats
(ml)
10
*
*
h
*A
v
V-10
V-20
V-30
. .
. .
. .
. .
.
.
.
h 20
0
h> 0
h ”
V-10
. .
0 .
.
.
* 10
* 20
* Y-20
V-30
used Groups 9 10 11
.
.
. .
. Milk yield . I as above
.
0
Milk y&d equal from allteats except 7and 8
Fig. 2. Numbering and positions of teats on the 14-teat sow. The milk yield of each teat for Groups 9 and 10 is shown below. V was the maximum volume, which increased with the age of the piglets. The positions of teats finally fixed on by the eight Piglets in each of Groups 9, 10 and 11 are also shown.
For the 8 groups of 4 piglets (Groups l-8) a small, 4-teat dummy sow was used. All 4 teats yielded equal amounts of milk feed. For the 3 groups of 8 piglets (Groups 9-ll), a 14-teat sow was used as illustrated in Fig. 1. For two of these groups (9 and lo), milk yields from the teats were unequal. Eight teats yielded a fixed volume with respect to a maximum volume, V ml, which ranged between 50 and 120 ml (Fig. 2). This volume was increased with the age and capacity of the piglets. Four other teats yielded consistently low volumes of milk (10 or 20 ml), while the two central teats yielded no milk. For the third group (ll), 12 of the 14 teats yielded equal amounts of milk while the central pair were again “dry”. Since there were more teats than piglets on the 1Cteat sows, if milk was not removed from a particular teat during at least 2 days of feeding, that teat was no longer supplied with milk. This was an attempt to simulate the natural process of involution of an unused teat, as it occurs for the real sow. 3. Observations The teats on the artificial sow were numbered consecutively from 1 at the head-end to 14 at the tail-end. The piglets were each given a number from 1 to 4 or from 1 to 8, and this was marked on their backs with a felt pen for individual identification. The piglets were observed at as many feeds as possible, which was, on average, 12 or 13 feeds per day during the first 3 days and 7 or 8 feeds per day for the rest of the rearing period. The beginning of a feed was marked by the first grunt of the sow’s call and the end when the last piglet moved away from the sow. The number of “takes” each piglet made on each teat during each feed was recorded, a take indicating that the teat had been taken into the piglet’s mouth, or that he had stopped at the teat to nuzzle it. A new take on that teat by the same piglet was recorded when he returned to it from another teat or from leaving it to urinate or defaecate.
339
4. Analysis (a) The development of each piglet’s use of the teat it finally fixed on was measured by calculating the proportion of “takes” on this teat out of the total number of “takes” on all teats each day. The relative usage of ‘different teats by each piglet before and after the teat-order became fixed was examined, and the results were compared for the piglets as a group. (b) The relationship between the teat finally fixed on by a piglet and the teats most used by that piglet on Day 2, the first day of independent sucking, was examined for the 3 groups reared on the 1Cteat sows. The teat, the udder area consisting of 3 adjacent teat positions, and the sowhalf used most by that piglet on Day 2 were recorded. If two areas tied for the most activity, they were both included. The frequency of the teat finally fixed on coinciding with one of these areas was calculated. (c) Using the 14-teat artificial sows, the relationship between the total activity on a teat with its position on the udder on Day 2 was investigated. Out of the 24 piglets in Groups 9, 10 and 11, the teat (or teats) on which each piglet performed its greatest activity was scored within one of the following groups: (1) front teats (l-4); (2) centre teats with milk (5, 6, 9, 10); (3) back teats (11-14); (4) centre teats “dry” (7 and 8). The frequencies of the favoured teats being in each section were calculated. (d) Finally, the relationship between the total activity on a teat with its relative milk-yield was examined for different stages of development up to Day 13, when the teat-order was fixed for all groups. For Groups 9 and 10, Teats 1, 6, 11 and 12, yielding constant volumes of 10 or 20 ml milk, were termed “bad teats”. Teats 7 and 8 , yielding no milk, were “dry teats”, while the remaining teats yielding volumes related to V ml were referred to as “good teats”. RESULTS
1. Development
of a fixed teat-position
The piglets were usually feeding independently by the end of the first day of rearing on the artificial sow. Within a few hours, they learnt to recognise the new sow’s voice as a call to feed. Having orientated to the teats for a feed, they moved around each other trying each teat in turn. At first the groups on the 14-teat sows seemed to be trying teats at both ends of the sow, but soon each piglet was observed to head for one particular half of the udder. After a few days, at the sound of the lactation call, piglets in each group headed for a particular teat and the general movement during a feed was reduced. In groups 2-8, the proportion of activity of each piglet on the teat it finally fixed on, out of the 4 teats, rose above 25% during the first 2 or 3 days and by Day 8 had reached a maximum of between 70 and 100%.
340
Group 1 gave fluctuating values of activity at the final teat-position because they had digestive problems from the beginning of the artificial rearing-period which affected their feeding-regularity. The teat positions finally fixed on by each of Groups 9, 10 and 11 are shown in Fig. 2. It can be seen that not all the teats were used. For these 3 groups reared on the 14-teat sows, the values of activity on the teat finally used most by each piglet rose above 7% (1 out of 14 teats) by Day 4 for Groups 9 and 10 and by Day 9 for Group 11. The range of maximum values was obtained after 12 days for Groups 9 (80-100%) and 10 (65-100%) and by 16 days for Group 11 (45-100%). Some piglets in this latter group showed low values of activity on their final teat positions up to the last days of milk-feeding, indicating that they were frequently using more than one teat. It was observed that certain piglets in several of the groups used a second teat which they tried after finishing their own milk. This would occur even though this teat “belonged” to another piglet who had usually removed all the milk first. However, piglets would very rarely try a teat where the milk supply had been stopped. The teats were scored in descending order of use by each piglet, and the results for the piglets in a group were compared at different stages of development of the teat-order. The most consistent observation from this analysis was that two piglets rarely coincided in the particular teat they used most at any stage, and few piglets used more than one teat after the teat-order became fixed. Out of 11 groups, only in Groups 1 and 11 did two piglets coincide in the teat they used most for any length of time. In both of these cases, one of the piglets eventually had to fix on another teat when the teat-order was finally formed. TABLE
I
Mean number
of teats used after Day 8 by piglets reared
on 4-teat
sows
Group
Mean no. teats used per piglet
1
2
3
4
5
6
7
8
3.2
1.0
1.7
1.7
1.2
1.0
1.2
1.2 ._____-
TABLE
II
Mean number Group
9 10 11
of teats
used by piglets
Mean number
teats
Days 7-11
Days
3.6 2.9 4.9
1.0 1.2 1.9
used 12-21
reared
on 14-teat
sows
341 TABLE
III
% frequency of the teat finally fixed on being in a particular area of preference on Day 2 Area on which piglet was most active on Day 2 Group
Teat
Area (=3 adjacent teats)
Sow-half
10 11
25 12 50
62 75 62
62 100 87
Total %
29
67
a3
9
Table I shows the mean number of teats used after Day 8 by piglets reared on the 4-teat sows. Table II compares the mean number of teats used by piglets reared on the 14-teat sows during a 4-day period before Day 12 and during the period after Day 12 when the teat-order was more consistent. Table III shows the percentage frequency of the teat finally fixed on being in one of the favoured areas of a piglet on the first day of independent feeding for piglets in Groups 9, 10 and 11. Less than one-third of all the piglets remained on their initially-favoured teat, while two-thirds finally chose a teat from the initially-favoured udder-area. Only 17% of piglets chaged sow-half. 3. General preference
for a particular
area of the udder
The general frequencies of the teat on which each piglet was most active on Day 2 being in one of four areas of the udder are shown in Table IV, combined for the 3 groups 9, 10 and 11. Occasionally, more than one teat tied for the most activity and these were all included. It is clear that most piglets were more active on the front teats on Day 2. TABLE
IV
Frequency of the teats on which piglets in Groups 9-11 being in a particular udder area
were most active on Day 2
Section of udder
Teats
Actual frequency of favoured teats being in area
Front Centre with milk Back Centre “dry”
1, 2, 3, 4 5, 6, 9, 10 11, 12, 13, 14 7, 6
15 5 9 0
342
4. Association of activity on a teat with the teat’s milk yield Figure 3 compares the relative activities of Groups 9 and 10 (unequal yields) and 11 (equal yields) on each teat with the teat’s relative milk-yield. During Days 2-5 there appeared to be a relationship between activity and milk-yield for Groups 9 and 10, particularly with respect to the front teats. In comparison, the greatest proportion of the activity of Group 11 at this stage was on the back teats (13 and 14) as well as the front teats 1-4.
Fig. 3. Comparison of the activities of piglets on each teat, for each of Groups 9, 10 and 11, during three periods up to the fixation of a steady teat-order. The relative milk yields of each teat are shown in the top histograms. The results for Groups 9 and 10 are shown together in the diagrams as they received the same pattern of milk supply.
343
There was a distinct avoidance of the two “dry” teats by all groups from the beginning of observations while the “bad” teats, apart from Teat 1, declined in use during the period 6-9 days. Between Days 10 and 13 the “bad” teats, including Teat 1, were hardly used. Teats surplus to the demands of Group 11 were also discarded in the interval 10-13 days. DISCUSSION
It took longer for piglets to form a teat-order on the 1Cteat sow than on the 4-teat sow. In the former case, development of the teat-order was more comparable with the lo-day estimate of Wesley (1967). The combination of the preferences of twice as many piglets may have been as much a factor as having more teats from which to choose. Group 11 piglets, whose sow had more “good” teats than piglets, still rejected certain teats in the same time-interval as those piglets in Groups 9 and 10 whose choice was limited. There was no apparent reason for rejecting these particular teats, although the results for the areas of the udder on which most piglets were active on Day 2 suggested that the front four teats would be taken, and this was in fact the case. Observations during this study (Jeppesen, 1980) on the effect of the voice on the orientation of piglets to the artificial udder indicated that in the first few days it was the voice which attracted piglets to the head-end of the sow. McBride (1963) also reported the attraction of piglets to the source of the voice of the sow. This may provide a reason for the greater activity on the front four teats, since all the piglets would have tried these teats before moving further down the udder. Although more piglets were active on the front four teats on Day 2, it was also found that the final positioning of each piglet, when the piglets were spread out across the udder, was frequently related to the area, consisting of three adjacent teat-positions, favoured on Day 2. These results were consistent with those of Hemsworth et al. (1976), who observed live sows and litters. This introduces the interesting point that piglets removed for artificial rearing 24 h after birth may well have already chosen an area of their mother’s udder and yet were able to repeat the choice process on the artificial udder. Organisation at the udder appeared muddled before each piglet settled on one or two teats. However, analysis of the activities of each piglet on the teat finally fixed on during the first few days on the sow indicated that each piglet had already fixed on this teat, and this teat was different from those fixed on by litter-mates. This was apparent even though the piglets were still active on other teats at this time. Rigid stereotypy at the beginning of the development of the teat-order could be detrimental to a piglet reared on the real sow if, for example, the gland supplying his teat became infected, dried up, or was stolen by a less stereotyped piglet. Teats on the dummy sow were being chosen or rejected very early. Figure
344
3 shows that for Groups 9 and 10, the low volume of milk produced by Teat 1 had already influenced activity on this teat in the period 2-5 days, such that it was less than the activity on each of Teats 2, 3 and 4. In contrast, for Group 11 Teat 1 was as popular as the other front teats. The figure also shows the activity increasing on the positionally less-favoured teats, apart from the “bad” teats, and decreasing on the initially more favoured teats during the development of the teat-order. Movement of piglets away from an initially-preferred teat may be assumed to be caused by detection of a better teat in the preferred area, or superior defence of that teat or area by another piglet or piglets with the same preference. Relationships between the piglets may also influence the formation of teat-order and the particular neighbouring piglets may be important. Perhaps the “good” teat in the middle of the back-half of the udder was left by piglets in Group 11 because two piglets preferred not to feed together. However, McBride et al. (1965) could not find any correlation between social dominance and teat-position in front-to-rear order on the udder. Perhaps only the relative dominance of neighbours should be investigated. Where there were smaller differences in milk yield, that is between V ml and V-10,-20 and -30 ml, correlation between milk yield and activity was only found on the front half of the udder. It may be that attraction for the head-end was causing this trend or was reinforcing the response to different volumes of milk. However, the piglets on the front half of Group 11’s sow, which yielded an even distribution of milk, did not show a correlation of activity with closeness to the head. However, piglets on this sow showed a relatively high activity on each of the end teats, 13 and 14, during the period 2-5 days. It is possible that attraction for the end teats was opposing the correlation of activity with milk yield for teats in the back half of the sow. Since many piglets appeared to fix on a particular udder area as early as Day 2, it seems likely that they would only sample the milk yield of teats in that area. Thus, the 14-teat sow was unwittingly designed to provide ideal conditions for each piglet to find a “good” teat. There was an excess of teats for the piglets’ requirements, and if the udder can be thought of as divided into areas of three or more teats, each area containing “bad” teats would also have “good” teats available. Thus, if the piglets were sampling areas of three or more teats, they would always have found one of good yield. This would explain why so many piglets in Groups 9 and 10 changed their initially-favoured teat compared with the piglets in Group 11, but stayed in the same udder area. Under natural conditions, a piglet may choose or be forced to take an area of “bad” teats, or may be lucky enough to choose an area of “good” teats. Whilst much of the evidence suggests that the front teats are the most productive in the real sow’s udder, some researchers have indicated that a particular gland is not consistently a large or a small producer (Hartman et al., 1962; Hartsock et al., 1977). Thus, the importance of the observation that piglets may only sample the milk
345
yield of teats in a small, area cannot be shown until there is further regarding the milk production by individual glands of the sow.
evidence
REFERENCES Donald, H.P., 1937a. Suckling and suckling preferences in pigs, Emp. J. Exp. Agric., 5: 361-368. Donald, H.P., 1937b. The milk consumption and growth of suckling pigs. Emp. J. Exp. Agric., 5: 349-360. Fraser, D. and Jones, R.M., 1975. The ‘teat order’ of suckling pigs. I. Relation to birth weight and subsequent growth. J. Agric. Sci., Cambridge, 84: 387-391. Gill, J.C. and Thomson, W., 1956. Observations on the behaviour of suckling pigs. Br. J. Anim. Behav., 4: 46-51. Hartman, D.A., Ludwick, T.M. and Wilson, R.F., 1962. Certain aspects of lactation performance in sows. J. Anim. Sci., 21: 883-886. Hartsock, T.G., Graves, H.B. and Baumgardt, B.R., 1977. Agonistic behavior and the nursing order in suckling piglets: relationships with survival, growth and body composition. J. Anim. Sci., 44: 320-329. Hemsworth, P.H., Winfield, C.G. and Mullaney, P.D., 1976. A study of the development of the teat order in piglets. Appl. Anim. Ethol., 2: 225-233. Jeppesen, L.E., 1980. The behaviour of piglets reared on an artificial sow. Ph. D. Thesis, Cambridge University. McBride, G., 1963. The ‘teat order’ and communication in young pigs. Anim. Behav., 11: 53-56. McBride, G., James, J.W. and Wyeth, G.S.F., 1965. Social behaviour of domestic animals. VII. Variation in weaning weight in pigs. Anim. Prod., 7: 67-74. Wesley, F., 1967. Stereotypy and teat selection in pigs. Z. SPugetierkd., 5: 362-366. Whittemore, C.T. and Fraser, D., 1974. The nursing and suckling behaviour of pigs. II. Vocalization of the sow in relation to suckling behaviour and milk ejection. Br. Vet. J., 130: 346-356.
-
Printed
in The Netherlands
335
TEAT-ORDER IN GROUPS OF PIGLETS REARED ON AN ARTIFICIAL SOW. I. FORMATION OF TEAT-ORDER AND INFLUENCE OF MILK YIELD ON TEAT PREFERENCE
LYNN E. JEPPESEN’ A.R.C.
Institute of Animal Physiology, Babraham,
‘Present Ashford,
address: Department of Agriculture, Kent TN25 5AH, Gt. Britain
(Accepted
for publication
9 March
Cambridge CB2 4AT (Gt. Britain)
Wye College
(University
of London),
1981)
ABSTRACT Jeppesen, L.E., 1982. Teat-order in groups of piglets reared on an artificial sow. I. Formation of teat-order and influence of milk yield on teat preference. Appl. Anim. Ethel., 8: 335-345. When eight groups of four piglets were reared on four-teat artificial sows (all teats yielding equal volumes of milk), each group formed a consistent teat-order. An artificial sow with a single row of fourteen teats was then constructed to rear groups of eight piglets, thus providing a greater choice of teat position. Development of teatorder was compared for the groups of 4 and 8 piglets. For the piglets reared on the fourteen-teat sows, preference for different sections of the udder was examined. The possible consequences of piglet social interactions and of early and rapid fixation on a small area of the udder are among features which require further research into the teat-order phenomenon. The position of the sow’s “voice” initially appeared to have a positive influence on the piglets’ activity at certain teat sites and there was preference for end teats. Two-thirds of the piglets finally fixed on a teat from the 3-teat area of the udder that they used most on Day 2. Large differences in piglet activity were observed on teats producing widely different volumes of milk. However, there was less association between activity and milk yield for teats with up to 30 ml difference in milk yield (the maximum milk-volume ranging between 50 and 120 ml).
INTRODUCTION
During the detailed observations of the feeding behaviour of groups of piglets being artificially reared on a dummy sow (Jeppesen, 1980), it was found that a teat-order rapidly developed and the opportunity was taken to investigate the factors influencing and maintaining the teat-order without the active contribution of a live sow. It is often difficult to observe the teat positions of piglets accurately on the real sow. Apart from the inconvenience of having to anticipate feeds to obtain a sufficient number of recordings, the udder is irregular and very
0304-3762/82/0000-0000/$02.75
o 1982 Elsevier
Scientific
Publishing
Company
336
flexible so that the bottom row and hind teats are frequently tucked out of view of the observer. The rapid movements of two rows of piglets in association with the teats are also difficult to record in detail. Thus, the artificial sow provided ideal conditions in which to observe the development of teat-order. Feeding times were controlled, contacts between piglets and teat were clearly visible and experimental alterations to certain features of the udder were possible. This paper describes how the dummy sow was used to investigate the influence of factors such as section of the udder and milk yield on piglets’ selection of, and competition for, teats. Most reports of observations on teat-order and competition agree that the anterior teats are the most popular (Donald, 1937a; Gill and Thomson, 1956; Hartsock et al., 1977). The most common theory to explain this observation is that the front teats usually produce the most milk and are therefore more attractive to piglets (Donald, 1937b). McBride et al. (1965) and Fraser and Jones (1975) found better growth-rates in piglets using the anterior teats. Gill and Thomson (1956) measured milk-intake by weighing piglets before and after feeds, and found that 15.3% more milk was produced by the front four teats than by the back four. There are various reports of the times taken to form a teat-order on the real sow. Donald (1937a) and McBride (1963) stated that teat preference clearly takes place within one week. Wesley (1967) was aware of considerable variation, and stated that, in general, piglets showed a more even distribution of sucking frequencies across the udder by Day 10. Donald (1937a) observed that teat-selection developed first on the front and rear teats and that more “errors” were made by piglets on the middle teats than by those at the ends. In the present study, the formation of a teat-order in groups of piglets reared on four-teat dummy sows was analysed, and as a result a further sow was constructed with a greater choice of teat position and a more clearly defined “head” and “tail” end. A comparison was made of the development of teat-preferences of piglets reared on the two types of udder. As an additional investigation into teat preference, the activities on teats producing consistently high or low yields of milk was examined. METHOD
1. Animals
and housing
Groups of 4 or 8 Large White piglets were taken from their mothers at 24 h of age and placed in small pens with the artificial sows at one end. The pens had been heated to around 28°C and lined with straw and sawdust. Creep lamps provided additional heat. After the first few days, the temperature was gradually lowered to around 23°C.
337
2. Artificial sow and feeding Figure 1 shows the parts of the sow exposed to the piglets. The dummy sow comprised a wood and wire-mesh framework. The udder was spongefilled and covered with thin sheet-rubber. The remaining “body” of the sow was covered with carpet underfelt and coconut matting. Projecting from the udder at regular intervals was a single row of rubber liners from milking-machine teat cup shells (Simplex Ltd.). A rubber teat (Maws) was inserted into the hollow of each inflation and fixed. The sections containing each teat were made as similar as possible in shape and “hang”. The piglets were fed a sow-milk replacer/whole cow’s milk mixture dispensed from aspirators through tubes and valves to the teats. Feedvolume and intervals between feeds were controlled, the latter, in general, being 1.5 h during the day and 3--4 h during the night. The piglets were alerted to each feed by means of a recorded sow lactation call played through a loud-speaker situated at one end of the dummy sow (“head-end”). The valves were controlled to open just after the peak in sow grunting, which is the time of milk let-down for the real sow (Whittemore and Fraser, 1974). There were at least 30 s for the piglets to adjust their teat positions before milk let-down. Each group was fed from the sow for at least 3 weeks.
Fig. 1. The fourteen-teat
artificial sow.
338 TAIL
HEAD /
I
1
2
3
4
5
6
7
6
9
10
11
12
13
14
00000000000000 ,4
\ Mtlk yield Teats
(ml)
10
*
*
h
*A
v
V-10
V-20
V-30
. .
. .
. .
. .
.
.
.
h 20
0
h> 0
h ”
V-10
. .
0 .
.
.
* 10
* 20
* Y-20
V-30
used Groups 9 10 11
.
.
. .
. Milk yield . I as above
.
0
Milk y&d equal from allteats except 7and 8
Fig. 2. Numbering and positions of teats on the 14-teat sow. The milk yield of each teat for Groups 9 and 10 is shown below. V was the maximum volume, which increased with the age of the piglets. The positions of teats finally fixed on by the eight Piglets in each of Groups 9, 10 and 11 are also shown.
For the 8 groups of 4 piglets (Groups l-8) a small, 4-teat dummy sow was used. All 4 teats yielded equal amounts of milk feed. For the 3 groups of 8 piglets (Groups 9-ll), a 14-teat sow was used as illustrated in Fig. 1. For two of these groups (9 and lo), milk yields from the teats were unequal. Eight teats yielded a fixed volume with respect to a maximum volume, V ml, which ranged between 50 and 120 ml (Fig. 2). This volume was increased with the age and capacity of the piglets. Four other teats yielded consistently low volumes of milk (10 or 20 ml), while the two central teats yielded no milk. For the third group (ll), 12 of the 14 teats yielded equal amounts of milk while the central pair were again “dry”. Since there were more teats than piglets on the 1Cteat sows, if milk was not removed from a particular teat during at least 2 days of feeding, that teat was no longer supplied with milk. This was an attempt to simulate the natural process of involution of an unused teat, as it occurs for the real sow. 3. Observations The teats on the artificial sow were numbered consecutively from 1 at the head-end to 14 at the tail-end. The piglets were each given a number from 1 to 4 or from 1 to 8, and this was marked on their backs with a felt pen for individual identification. The piglets were observed at as many feeds as possible, which was, on average, 12 or 13 feeds per day during the first 3 days and 7 or 8 feeds per day for the rest of the rearing period. The beginning of a feed was marked by the first grunt of the sow’s call and the end when the last piglet moved away from the sow. The number of “takes” each piglet made on each teat during each feed was recorded, a take indicating that the teat had been taken into the piglet’s mouth, or that he had stopped at the teat to nuzzle it. A new take on that teat by the same piglet was recorded when he returned to it from another teat or from leaving it to urinate or defaecate.
339
4. Analysis (a) The development of each piglet’s use of the teat it finally fixed on was measured by calculating the proportion of “takes” on this teat out of the total number of “takes” on all teats each day. The relative usage of ‘different teats by each piglet before and after the teat-order became fixed was examined, and the results were compared for the piglets as a group. (b) The relationship between the teat finally fixed on by a piglet and the teats most used by that piglet on Day 2, the first day of independent sucking, was examined for the 3 groups reared on the 1Cteat sows. The teat, the udder area consisting of 3 adjacent teat positions, and the sowhalf used most by that piglet on Day 2 were recorded. If two areas tied for the most activity, they were both included. The frequency of the teat finally fixed on coinciding with one of these areas was calculated. (c) Using the 14-teat artificial sows, the relationship between the total activity on a teat with its position on the udder on Day 2 was investigated. Out of the 24 piglets in Groups 9, 10 and 11, the teat (or teats) on which each piglet performed its greatest activity was scored within one of the following groups: (1) front teats (l-4); (2) centre teats with milk (5, 6, 9, 10); (3) back teats (11-14); (4) centre teats “dry” (7 and 8). The frequencies of the favoured teats being in each section were calculated. (d) Finally, the relationship between the total activity on a teat with its relative milk-yield was examined for different stages of development up to Day 13, when the teat-order was fixed for all groups. For Groups 9 and 10, Teats 1, 6, 11 and 12, yielding constant volumes of 10 or 20 ml milk, were termed “bad teats”. Teats 7 and 8 , yielding no milk, were “dry teats”, while the remaining teats yielding volumes related to V ml were referred to as “good teats”. RESULTS
1. Development
of a fixed teat-position
The piglets were usually feeding independently by the end of the first day of rearing on the artificial sow. Within a few hours, they learnt to recognise the new sow’s voice as a call to feed. Having orientated to the teats for a feed, they moved around each other trying each teat in turn. At first the groups on the 14-teat sows seemed to be trying teats at both ends of the sow, but soon each piglet was observed to head for one particular half of the udder. After a few days, at the sound of the lactation call, piglets in each group headed for a particular teat and the general movement during a feed was reduced. In groups 2-8, the proportion of activity of each piglet on the teat it finally fixed on, out of the 4 teats, rose above 25% during the first 2 or 3 days and by Day 8 had reached a maximum of between 70 and 100%.
340
Group 1 gave fluctuating values of activity at the final teat-position because they had digestive problems from the beginning of the artificial rearing-period which affected their feeding-regularity. The teat positions finally fixed on by each of Groups 9, 10 and 11 are shown in Fig. 2. It can be seen that not all the teats were used. For these 3 groups reared on the 14-teat sows, the values of activity on the teat finally used most by each piglet rose above 7% (1 out of 14 teats) by Day 4 for Groups 9 and 10 and by Day 9 for Group 11. The range of maximum values was obtained after 12 days for Groups 9 (80-100%) and 10 (65-100%) and by 16 days for Group 11 (45-100%). Some piglets in this latter group showed low values of activity on their final teat positions up to the last days of milk-feeding, indicating that they were frequently using more than one teat. It was observed that certain piglets in several of the groups used a second teat which they tried after finishing their own milk. This would occur even though this teat “belonged” to another piglet who had usually removed all the milk first. However, piglets would very rarely try a teat where the milk supply had been stopped. The teats were scored in descending order of use by each piglet, and the results for the piglets in a group were compared at different stages of development of the teat-order. The most consistent observation from this analysis was that two piglets rarely coincided in the particular teat they used most at any stage, and few piglets used more than one teat after the teat-order became fixed. Out of 11 groups, only in Groups 1 and 11 did two piglets coincide in the teat they used most for any length of time. In both of these cases, one of the piglets eventually had to fix on another teat when the teat-order was finally formed. TABLE
I
Mean number
of teats used after Day 8 by piglets reared
on 4-teat
sows
Group
Mean no. teats used per piglet
1
2
3
4
5
6
7
8
3.2
1.0
1.7
1.7
1.2
1.0
1.2
1.2 ._____-
TABLE
II
Mean number Group
9 10 11
of teats
used by piglets
Mean number
teats
Days 7-11
Days
3.6 2.9 4.9
1.0 1.2 1.9
used 12-21
reared
on 14-teat
sows
341 TABLE
III
% frequency of the teat finally fixed on being in a particular area of preference on Day 2 Area on which piglet was most active on Day 2 Group
Teat
Area (=3 adjacent teats)
Sow-half
10 11
25 12 50
62 75 62
62 100 87
Total %
29
67
a3
9
Table I shows the mean number of teats used after Day 8 by piglets reared on the 4-teat sows. Table II compares the mean number of teats used by piglets reared on the 14-teat sows during a 4-day period before Day 12 and during the period after Day 12 when the teat-order was more consistent. Table III shows the percentage frequency of the teat finally fixed on being in one of the favoured areas of a piglet on the first day of independent feeding for piglets in Groups 9, 10 and 11. Less than one-third of all the piglets remained on their initially-favoured teat, while two-thirds finally chose a teat from the initially-favoured udder-area. Only 17% of piglets chaged sow-half. 3. General preference
for a particular
area of the udder
The general frequencies of the teat on which each piglet was most active on Day 2 being in one of four areas of the udder are shown in Table IV, combined for the 3 groups 9, 10 and 11. Occasionally, more than one teat tied for the most activity and these were all included. It is clear that most piglets were more active on the front teats on Day 2. TABLE
IV
Frequency of the teats on which piglets in Groups 9-11 being in a particular udder area
were most active on Day 2
Section of udder
Teats
Actual frequency of favoured teats being in area
Front Centre with milk Back Centre “dry”
1, 2, 3, 4 5, 6, 9, 10 11, 12, 13, 14 7, 6
15 5 9 0
342
4. Association of activity on a teat with the teat’s milk yield Figure 3 compares the relative activities of Groups 9 and 10 (unequal yields) and 11 (equal yields) on each teat with the teat’s relative milk-yield. During Days 2-5 there appeared to be a relationship between activity and milk-yield for Groups 9 and 10, particularly with respect to the front teats. In comparison, the greatest proportion of the activity of Group 11 at this stage was on the back teats (13 and 14) as well as the front teats 1-4.
Fig. 3. Comparison of the activities of piglets on each teat, for each of Groups 9, 10 and 11, during three periods up to the fixation of a steady teat-order. The relative milk yields of each teat are shown in the top histograms. The results for Groups 9 and 10 are shown together in the diagrams as they received the same pattern of milk supply.
343
There was a distinct avoidance of the two “dry” teats by all groups from the beginning of observations while the “bad” teats, apart from Teat 1, declined in use during the period 6-9 days. Between Days 10 and 13 the “bad” teats, including Teat 1, were hardly used. Teats surplus to the demands of Group 11 were also discarded in the interval 10-13 days. DISCUSSION
It took longer for piglets to form a teat-order on the 1Cteat sow than on the 4-teat sow. In the former case, development of the teat-order was more comparable with the lo-day estimate of Wesley (1967). The combination of the preferences of twice as many piglets may have been as much a factor as having more teats from which to choose. Group 11 piglets, whose sow had more “good” teats than piglets, still rejected certain teats in the same time-interval as those piglets in Groups 9 and 10 whose choice was limited. There was no apparent reason for rejecting these particular teats, although the results for the areas of the udder on which most piglets were active on Day 2 suggested that the front four teats would be taken, and this was in fact the case. Observations during this study (Jeppesen, 1980) on the effect of the voice on the orientation of piglets to the artificial udder indicated that in the first few days it was the voice which attracted piglets to the head-end of the sow. McBride (1963) also reported the attraction of piglets to the source of the voice of the sow. This may provide a reason for the greater activity on the front four teats, since all the piglets would have tried these teats before moving further down the udder. Although more piglets were active on the front four teats on Day 2, it was also found that the final positioning of each piglet, when the piglets were spread out across the udder, was frequently related to the area, consisting of three adjacent teat-positions, favoured on Day 2. These results were consistent with those of Hemsworth et al. (1976), who observed live sows and litters. This introduces the interesting point that piglets removed for artificial rearing 24 h after birth may well have already chosen an area of their mother’s udder and yet were able to repeat the choice process on the artificial udder. Organisation at the udder appeared muddled before each piglet settled on one or two teats. However, analysis of the activities of each piglet on the teat finally fixed on during the first few days on the sow indicated that each piglet had already fixed on this teat, and this teat was different from those fixed on by litter-mates. This was apparent even though the piglets were still active on other teats at this time. Rigid stereotypy at the beginning of the development of the teat-order could be detrimental to a piglet reared on the real sow if, for example, the gland supplying his teat became infected, dried up, or was stolen by a less stereotyped piglet. Teats on the dummy sow were being chosen or rejected very early. Figure
344
3 shows that for Groups 9 and 10, the low volume of milk produced by Teat 1 had already influenced activity on this teat in the period 2-5 days, such that it was less than the activity on each of Teats 2, 3 and 4. In contrast, for Group 11 Teat 1 was as popular as the other front teats. The figure also shows the activity increasing on the positionally less-favoured teats, apart from the “bad” teats, and decreasing on the initially more favoured teats during the development of the teat-order. Movement of piglets away from an initially-preferred teat may be assumed to be caused by detection of a better teat in the preferred area, or superior defence of that teat or area by another piglet or piglets with the same preference. Relationships between the piglets may also influence the formation of teat-order and the particular neighbouring piglets may be important. Perhaps the “good” teat in the middle of the back-half of the udder was left by piglets in Group 11 because two piglets preferred not to feed together. However, McBride et al. (1965) could not find any correlation between social dominance and teat-position in front-to-rear order on the udder. Perhaps only the relative dominance of neighbours should be investigated. Where there were smaller differences in milk yield, that is between V ml and V-10,-20 and -30 ml, correlation between milk yield and activity was only found on the front half of the udder. It may be that attraction for the head-end was causing this trend or was reinforcing the response to different volumes of milk. However, the piglets on the front half of Group 11’s sow, which yielded an even distribution of milk, did not show a correlation of activity with closeness to the head. However, piglets on this sow showed a relatively high activity on each of the end teats, 13 and 14, during the period 2-5 days. It is possible that attraction for the end teats was opposing the correlation of activity with milk yield for teats in the back half of the sow. Since many piglets appeared to fix on a particular udder area as early as Day 2, it seems likely that they would only sample the milk yield of teats in that area. Thus, the 14-teat sow was unwittingly designed to provide ideal conditions for each piglet to find a “good” teat. There was an excess of teats for the piglets’ requirements, and if the udder can be thought of as divided into areas of three or more teats, each area containing “bad” teats would also have “good” teats available. Thus, if the piglets were sampling areas of three or more teats, they would always have found one of good yield. This would explain why so many piglets in Groups 9 and 10 changed their initially-favoured teat compared with the piglets in Group 11, but stayed in the same udder area. Under natural conditions, a piglet may choose or be forced to take an area of “bad” teats, or may be lucky enough to choose an area of “good” teats. Whilst much of the evidence suggests that the front teats are the most productive in the real sow’s udder, some researchers have indicated that a particular gland is not consistently a large or a small producer (Hartman et al., 1962; Hartsock et al., 1977). Thus, the importance of the observation that piglets may only sample the milk
345
yield of teats in a small, area cannot be shown until there is further regarding the milk production by individual glands of the sow.
evidence
REFERENCES Donald, H.P., 1937a. Suckling and suckling preferences in pigs, Emp. J. Exp. Agric., 5: 361-368. Donald, H.P., 1937b. The milk consumption and growth of suckling pigs. Emp. J. Exp. Agric., 5: 349-360. Fraser, D. and Jones, R.M., 1975. The ‘teat order’ of suckling pigs. I. Relation to birth weight and subsequent growth. J. Agric. Sci., Cambridge, 84: 387-391. Gill, J.C. and Thomson, W., 1956. Observations on the behaviour of suckling pigs. Br. J. Anim. Behav., 4: 46-51. Hartman, D.A., Ludwick, T.M. and Wilson, R.F., 1962. Certain aspects of lactation performance in sows. J. Anim. Sci., 21: 883-886. Hartsock, T.G., Graves, H.B. and Baumgardt, B.R., 1977. Agonistic behavior and the nursing order in suckling piglets: relationships with survival, growth and body composition. J. Anim. Sci., 44: 320-329. Hemsworth, P.H., Winfield, C.G. and Mullaney, P.D., 1976. A study of the development of the teat order in piglets. Appl. Anim. Ethol., 2: 225-233. Jeppesen, L.E., 1980. The behaviour of piglets reared on an artificial sow. Ph. D. Thesis, Cambridge University. McBride, G., 1963. The ‘teat order’ and communication in young pigs. Anim. Behav., 11: 53-56. McBride, G., James, J.W. and Wyeth, G.S.F., 1965. Social behaviour of domestic animals. VII. Variation in weaning weight in pigs. Anim. Prod., 7: 67-74. Wesley, F., 1967. Stereotypy and teat selection in pigs. Z. SPugetierkd., 5: 362-366. Whittemore, C.T. and Fraser, D., 1974. The nursing and suckling behaviour of pigs. II. Vocalization of the sow in relation to suckling behaviour and milk ejection. Br. Vet. J., 130: 346-356.