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The effects of providing sawdust to pre-parturient sows in farrowing crates on sow behaviour, the duration of parturition and the occurrence of intra-partum stillborn piglets
Applied Animal Behaviour Science, 36 ( 1993 ) 301-315
301
Elsevier Science Publishers B.V., Amsterdam
The effects of providing sawdust to pre-parturient sows in farrowing crates on sow behaviour, the duration of parturition and the occurrence of intra-partum stillborn piglets G.M. Cronin, B.N. Schirmer, T.H. McCallum, J.A. Smith and K.L. Butler Victorian Institute of Animal Science, Sneydes Road, Werribee, Vic. 3030, Australia (Accepted 18 December 1992 ) ABSTRACT Cronin, G.M., Schirmer, B.N., McCallum, T.H., Smith, J.A. and Butler, K.L., 1993. The effects of providing sawdust to pre-parturient sows in farrowing crates on sow behaviour, the duration of parturition and the occurrence ofintra-partum stillborn piglets. Appl. Anim. Behav. Sci., 36: 301315. The behaviour of 174 sows (parities 1-10) in commercial farrowing crates was recorded at 10-m in intervals around parturition. Approximately half of the sows received regular applications of sawdust on the floor of their crate during the pre-partum period (SD treatment). Control treatment (Con) sows did not receive sawdust. Younger sows (parities 1-3 ) in the SD treatment spent less (P< 0.01 ) time belly lying from 24 to 16 h pre-partum, were more (P<0.05) active in the last 8 h pre-partum and less (P<0.05) active during parturition than in the Con treatment. More root/nose/paw behaviour occurred during 24 to 16 h (P< 0.01 ) and the last 8 h ( P < 0.005 ) pre-partum, and more (P< 0.03 ) feeder-directed behaviour occurred in the last 8 h pre-partum, in the SD than Con treatment. Sows in the SD treatment compared with sows in the Con treatment had a shorter ( P < 0.05 ) mean duration of parturition ( 159 and 201 min per sow) and a lower (P < 0.01 ) incidence of piglets that were overlayed during parturition and the subsequent 6 h (2.4% and 21.1% of sows, respectively). While there were no differences in the proportion of litters of younger sows that contained stillborn piglets of the class intra-partum death (IPD: 26.1 and 31.6% of sows), there was a difference (P< 0.02 ) in the ratio of litters containing 0, l or multiple IPD per litter: (SD:73%, 27% and 0% vs. Con:68%, 16% and 16% of litters, respectively). As a consequence of the lower occurrence of IPD, litter size born alive was greater (P< 0.03 ) in the SD than Con treatment ( l 0.5 and l 0.0 piglets). Older sows (parities 4 and above) in the SD treatment spent less time sitting (P< 0.05 ) and more time side lying (P<0.06), and performed less (P<0.01) bar biting during the last 8 h pre-partum than older sows in the Con treatment. In conclusion, the application of sawdust during the pre-partum period appeared to stimulate prepartum activity in younger sows, including root/nose/paw behaviour, which may, in turn, positively affect the process of parturition and reduce overlaying of piglets, both of which are relevant to increasing piglet survival, The differing results for older sows suggest that experience with sawdust (for nesting material ) is an important determinant of subsequent responses of farrowing sows to this material. Keywords: Pig; Parturition; Housing
Correspondence to: G.M. Cronin, Victorian Institute of Animal Science, Sneydes Road, Werribee, Vic. 3030, Australia. © 1993 Elsevier Science Publishers B.V. All rights reserved 0168-1591/93/$06.00
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INTRODUCTION
Over the last 30 years there have been major changes to the design of farrowing accommodation used by the pig industry. Whereas sows once predominantly farrowed in yards or large pens with straw, modern farrowing crates have no bedding material and are designed to control movement by the sow to improve piglet survival. Concern has been expressed over the welfare of sows in farrowing crates because of the 'inability' of sows to perform the full repertoire of species-specific farrowing behaviours, in particular nesting behaviour (Baxter, 1982), or to build a farrowing nest consistent with the requirement for a safe, private and comfortable environment. It has consistently been reported that, during the 24 h prior to parturition, sows in farrowing crates or pens without nesting material appear highly motivated to perform behaviours such as rooting, nosing and pawing. These behaviours are assumed to be 'nesting behaviour' (Vestergaard and Hansen, 1984; Lammers and de Lange, 1986; Widowski and Curtis, 1990) in spite of the fact that the sows are unable to construct a farrowing nest. One interpretation of this is that 'nesting behaviour' has a function for the sow other than simply the construction of a farrowing nest. Recent evidence suggests that it is the performance of nesting behaviour per se, rather than the availability of a constructed nest, that is important for sows (Widowski and Curtis, 1990). Furthermore, Arey et al. (1991 ) found an increased performance of nesting behaviour by sows provided with a preformed nest compared with sows that constructed their own nest. Cronin and Van Amerongen (1991) reported that primiparous sows, that farrowed in crates covered by a large hessian bag and with straw bedding on the floor (to simulate a completed farrowing nest), tended to perform more nesting behaviour prior to parturition than sows in crates without the cover or straw, and this was associated with increased responsiveness by sows towards the distress calls of their piglets and less savaging and overlaying. The aim of this experiment was to investigate the effects of providing sawdust, as a substitute for bedding material, for pre-parturient sows in commercial farrowing crates on the performance of farrowing behaviour, the duration of parturition as a measure of'ease of parturition' and the incidence of piglet deaths during parturition. The third parameter was included since it is known that prolonged parturition increases intra-partum stillbirths (Sprecher et al., 1975). ANIMALS, MATERIALS AND METHODS
The experiment was performed over three visits (replicates) to a large commercial pig farm in southeastern Australia during the late autumn and winter. From the piggery records it was known that the majority of sows far-
SAWDUST PROVISION AND THE EFFECTS ON PRE-PARTURIENT SOWS
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rowed on Thursday and Friday each week. Each replicate of the experiment began on Wednesday (Day 1 ). The sows observed in the experiment were Large Whites (LW) that had been mated to LW boars. The experiment was performed in three different, but similar, farrowing sheds at the farm, which were staffed by the same team of stockpeople. Shed temperature was thermostatically controlled at 21 °C. Each shed contained 184 total confinement farrowing crates arranged in four rows. The crates measured 1.8 m wide X 2.1 m long within which was a 0.6-m-wide sow-stall. The floor of the crate was solid concrete except for two areas of plastic-coated, woven metal mesh across the entire width of the front (0.2 m ) and the rear (0.75 m ) of the crate. A gas heater was suspended above the concrete floor, 0.7 m from the front of the crate, between every second farrowing crate and was designed to heat the creep areas of two adjacent farrowing crates.
Experimental procedure At about 13:00 h on Day 1 six observers entered the farrowing shed to commence setting up the experiment (e.g. identifying experimental sows with numbered cards, etc. ). Any sows that had already farrowed or commenced to farrow by 14:00 h were excluded. Individual sows were randomly allotted to sawdust (SD) and control (Con) treatments using a random number list (Rohlf and Sokal, 1981 ). The experiment c o m m e n c e d at 14:00 h on Day 1 and concluded at 14:00 h on Day 3. Observers worked in pairs during 8-h shifts and there were two separate routines, concurrently conducted, which the observers performed alternately on an hourly basis.
Routine 1 The observer walked through the farrowing shed along the aisle in front of the sows and, for each sow in the experiment, recorded her posture and activity. This procedure was repeated at 10-min intervals throughout the experiment. Observations on each sow continued until either 6 h had elapsed after the birth of the sow's last piglet or 14:00 h on Day 3. The postures recorded were standing, sitting, lying on belly and lying on side. For sows in the last category, the observer also recorded whether the sow's udder was towards or away from the creep heater. Seven activities were recorded: inactive/asleep, feeder-directed behaviour, drinker-directed behaviour, r o o t / n o s e / p a w behaviour ('nesting'), bar biting, changing posture from either standing to lying, or sitting to lying, or the reverse, and any other activity. For greater detail of the description of these postures and activities see Cronin and Smith ( 1992 ). Routine 2 The observer walked along the aisle behind the sows to monitor the course of parturition. Once a sow had delivered her first piglet, the observer recorded
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on a prepared card the sow's identity, parity number, the date and time of c o m m e n c e m e n t of farrowing and the status of the piglet: piglets were classified at birth as being alive or as having died intra-partum or pre-partum (see below). The time of birth of each individual piglet in the litter and the status of the piglet were recorded within 1-2 min of the piglet's delivery. Any interference to sows by the piggery staff (e.g. injection with oxytocin or manual assistance to remove piglets from sows, etc. ) was recorded on the sow's card, as was the occurrence of sows that overlaid/stood on, or savaged, or attempted to savage piglets during the period of parturition and the subsequent 6 h. The observer also administered sawdust to treatment sows as described later.
Identifying stillbirths Stillbirths were classified as either pre-partum or intra-partum deaths (Randall and Penny, 1967; Bille et al.., 1974). In the former category, deaths occur late in gestation and were therefore not expected to be affected by the farrowing treatments. Similarly the occurrence of m u m m i f i e d piglets was not expected to be affected by farrowing treatment and thus in the present experiment m u m m i f i e d piglets were included in the pre-partum death category ( P P D & M ) . On the other hand, intra-partum deaths (IPD) occur during parturition and may be influenced by the imposition of farrowing treatment. Therefore, the data for these two distinct classes of stillborn piglet were analysed separately in this experiment.
Treatments There were two treatments: ( 1 ) SD m sows were provided with 1 1 of sawdust on the front third of the concrete floor of the farrowing crate at about 13:30 h on Day 1. Thereafter, sows received one or two handfuls every 30-60 min as an observer walked past the front of the farrowing crate, until either the sow c o m m e n c e d farrowing or 06:00 h on Day 3. The observer applied sawdust by gently dropping it on the solid floor adjacent to the sow's head. Sawdust was added at regular intervals to maintain a supply of sawdust as the sow could push the sawdust out of reach under the side bars of the crate or through the perforated floor. Prior to this experiment the sows had had no previous experience with bedding material in the pre-partum period. (2) Con - - sows did not receive sawdust.
Statistical analysis Regression analysis (Genstat, 1984 version; Lawes Agricultural Trust, Rothamsted Experimental Station, U K ) was used to determine the effects of
SAWDUST PROVISION AND THE EFFECTS ON PRE-PARTURIENT SOWS
305
treatment, parity number of the sow (parity numbers 6 and above were combined) and replication on the total number of piglets born and the number born alive per sow. Owing to insufficient numbers in some of the older parity groups, the data were combined a posteriori to provide two groups; these were parities 1-3 (younger sows ) and parities 4 and above (older sows ). Analysis of variance and co-variance (Genstat, 1984) were used to test for treatment effects within the two parity classes on the total number of piglets born and the number born alive per sow (adjusted for total born ), the duration of parturition (after log~ transformation ), the time from the start of the experiment (i.e. from 14:00 h Day l ) to the birth of the first piglet in the litter and the proportion of observations that noted sows occupying the four different postures and their activity (after angular transformation). Sow behaviour data were analysed within five time periods: 24-16 h pre-partum, 16-8 h pre-partum, 8-0 h pre-partum, the period of parturition (i.e. time from the first- to the last-born piglet in the litter) and the first 6 h post-partum (i.e. recorded from the time of the last-born piglet's delivery). No record was made of the time sows expelled foetal membranes. The data for most of the different behaviours that together accounted for total activity could not be normalised by the angular transformation and were analysed for treatment effects by the Mann-Whitney U-test, corrected for tied values to compute the statistic z (Siegel, 1956 ) in the five time periods. Within treatments and time periods, differences in the preference of sows for lying with the udder towards or away from the piglet heater were analysed by the Student's t-test. Within parity classes, the effects of treatment on the incidence of IPD and PPD&M were examined by the Chi-squared test, based on the size of the litters, divided by the number of IPD or PPD&M contained in the litter. Similarly, the Chi-squared test was used to examine the effects of treatment on the incidence of sows that received assistance at farrowing, that savaged or attempted to savage piglets and sows that overlaid or stood on piglets during parturition and the subsequent 6 h. RESULTS A total of 288 pro-parturient sows were observed during the three visits to the farm: the numbers of sows observed per visit were 100, 72 and 116, respectively. Of the 116 sows in Visit 3, 71 were observed under Routines 1 and 2, since their mating dates suggested that they were close to farrowing while the remaining 45 were only monitored in Routine 2 (i.e. duration of parturition and status of individual births). On the three visits to the farm, the percentages of sows observed in Routines 1 and 2 that completed parturition before the end of the observation period (14:00 h Day 3) were 69, 75 and 61%, respectively. Only 13% of the 45 sows in Visit 3 observed only in Routine 2 completed parturition during the allotted period. The 174 sows that
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completed parturition during the observation time on the three visits to the piggery, gave birth to a total of 2000 piglets: 1829 were born alive, 118 were IPD and 53 were P P D & M (31 were pre-partum deaths and 22 were m u m mified). The treatments did not affect ( P > 0.05 ) the incidence of parturition in which sows were assisted (oxytocin was administered to 11.6% of sows and manual assistance was given to 11.0% of sows in both treatments combined) or the occurrence of savaging. Three sows savaged or attempted to savage piglets: there was one sow from each parity, 2, 3 and 4, and one piglet died from savaging. The sows observed ranged from parity 1 (gilts) to parity 10. The majority of sows, however, were in the parity range 1-5. The data for one sow were omitted since she gave birth to a 12th piglet about 39 h after the 1 lth was born and it was not possible to determine the stillbirth class of the piglet. Within parity groups there were no effects ( P > 0.05 ) of treatment on the mean time interval from c o m m e n c e m e n t of observations ( 14:00 h Day 1 ) to c o m m e n c e m e n t of parturition (Table 1 ).
Piglets born per sow There were no effects ( P > 0.05 ) of treatment or replicate (visit to the farm) on the total number of piglets born (alive + IPD + PPD&M ) per sow. As expected, there were effects of parity number of the sow on the total number of piglets born and the n u m b e r born alive per sow. From the regression analyses, there was a linear and a quadratic relationship, respectively, between the total n u m b e r born ( Y~) and n u m b e r born alive (Y2) and parity number of the sow
(x). Within the younger and older parity groups there were no effects ( P > 0.05 ) of treatment on the total n u m b e r of piglets born per sow (Table 1 ). The total number of piglets born per sow ranged from four to 19 for young sows and from five to 21 for old sows. After adjusting for total born, the SD treatment had more liveborn piglets per sow than the Con treatment for the younger ( P < 0 . 0 3 ) , but not for the older ( P > 0 . 0 5 ) parity sows (Table 1 ).
Stillborn piglets The proportion of piglets born in the SD and Con treatments that were classed as P P D & M are shown in Table 1. The n u m b e r of P P D & M per litter ranged from zero to four piglets amongst litters of younger sows and from zero to five piglets per litter for older sows; the distribution curves for the n u m b e r of P P D & M per litter did not differ ( P > 0.05) between the SD and Con treatments for the younger (X2 = 2 . 2 0 ) and the older sows ()C32=2.23). There were no effects ( P > 0.05 ) of treatment on the proportion of litters that
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contained piglet(s) of this class (younger sows: 7/42 litters and 10/57 litters, X12=0.01; older sows: 12/44 litters and 7/31 litters, X2 =0.21, respectively, for the SD and Con treatments). The occurrence of IPD piglets in the two treatments was expressed as a proportion of piglets born alive plus IPD (Table 1 ). The number of IPD per litter ranged from zero to five piglets amongst litters of younger sows and from zero to seven per litter for older sows; the distribution curves for the number of IPD per litter differed ( P < 0.05 ) between the SD and Con treatments for younger sows (X2 = 13.11 ), but not ( P > 0.05 ) for the older sows (X2 = 4.74). While there were no differences ( P > 0.05 ) owing to the SD and Con treatments in the proportion of litters that contained IPD (younger sows: 26% and 32% of litters, respectively; X~ = 0.34; older sows: 50% and 45% of litters, respectively; X~ = 0.17), there was an effect ( P < 0.02 ) of treatment on the ratio of litters of younger sows that contained nil, one or multiple IPD, respectively: SD, 74%, 26% and 0% of litters; Con, 68%, 16% and 16% of litters; X~ = 7.97, but not ( P > 0.05) for the older sows: SD, 50%, 18% and 32% of litters: Con, 45%, 32% and 23% of litters; X~ =2.14.
Duration of parturition After adjusting for the total number of piglets born in the litter, younger SD-treatment sows had a shorter ( P < 0.05) mean duration of parturition than Con-treatment sows (Table 1 ); the duration of parturition ranged from 24 min for a litter of eight piglets to 845 min for a litter of 15 piglets. Amongst the older sows there was a trend ( P < 0.08) for a longer duration of parturition in the SD treatment (Table 1 ); the duration of parturition ranged from 55 min for a litter of 13 piglets to 1020 min for a litter often piglets.
Occurrence of overlaying The proportion of younger sows that overlaid or stood on piglets during parturition and the subsequent 6 h was lower ( P < 0.01 ) for the SD than Con treatment ( 1/41 vs. 12/57 sows, respectively, X2 = 7.18 ). For older sows, while the incidence was lower for the SD than Con treatment, the difference was not significant (3/44 vs. 5/31 sows, respectively, X2 = 1.65, P > 0.05 ).
Sow behaviour observations Postures For the younger sows the only significant postural difference ( P < 0.01 ), owing to treatment, occurred for belly lying during 24-16 h pre-partum (Table 2; untransformed means 19.0% and 28.3% of observations, respectively, for the SD and Con treatments). As shown in Fig. 1, the predominant
SAWDUSTPROVISION AND THE EFFECTS ON PRE-PARTURIENTSOWS
309
TABLE 2 Posture and activity parameters where there were differences caused by treatment effects in the five time periods around parturition Parity group
Parameter
Time period
SD
Con
LSD(e=o.os)
P-value
Young sows Old sows Young sows Young sows
Lie on belly ~ Sit ~ Total activity ~ Total activity I
24-16 h pre-partum 8-0 h pre-partum 8-0 h pre-partum parturition
24.1 17.1 31.9 10.1
31.5 22.8 26.0 16.0
5.65 5.53 5.31 5.67
< 0.01 < 0.04 < 0.03 < 0.04
z-value Young sows Young sows Young sows Young sows Young sows Old sows
Feeder-directed 2 Drinker-directed 2 Root/nose/paw 2 Root/nose/paw 2 Other behaviour 2 Bar bite 2
8-0 h pre-partum 16-8 h pre-partum 24-16 h pre-partum 8-0 h pre-partum parturition 8-0 h pre-partum
2 2 2 5 0 0
0 0 0 2 3 2
2.22 1.84 2.56 2.83 2.30 2.63
< 0.03 < 0.07 < 0.01 < 0.005 < 0.02 < 0.01
Values shown are ~angular transformed means, expressed as degrees, for parameters analysed by ANOVA and 2median values for parameters analysed by the M a n n - W h i t n e y U-test (two-tailed).
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SD Con
SD Con
SD Con
SD Con
24 to 16h
16 to 8h
8 to Oh
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Pre-partu m
SD Con 0 to 6h Post-partu m
Fig. 1. T h e p r o p o r t i o n o f t i m e t h a t young sows (parities 1 - 3 ) in the SD a n d Con t r e a t m e n t s occupied the different postures during observations. T h e r e was a significant t r e a t m e n t effect ( P < 0.01 ) o n the t i m e spent belly lying d u r i n g the 8-h period 2 4 - 1 6 h pre-partum.
posture was lying. Both parity groups spent a similar proportion of time in each of the four postures. For the older sows, within time periods the only significant effect ( P < 0.04) of treatment was on the time sows spent sitting in the period 8-0 h pre-partum (Table 2; untransformed means 11.4% and 18.1% of observations, respectively, for the SD and Con treatments). For both
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G . M . C R O N I N E T AL.
the younger and older parity sows, there was no clear preference ( P > 0.05 ) for side lying with the udder towards the piglet heater. Activities For younger parity sows there were effects of treatment on total activity during 8-0 h pre-partum (Table 2; untransformed means 29.7% and 22.8% of observations, respectively, for the SD and Con treatments) and during parturition (Table 2; untransformed means 6.5% and 12.0% of observations, respectively, for the SD and Con treatments). Figure 2 shows the proportion of observations in which younger sows were recorded to perform the different activities that accounted for total activity. The application of sawdust increased the time younger parity sows performed feeder-directed behaviour in the 8-0 h pre-partum period (Table 2; mean values 2.6% and 1.4% of observations, respectively, for the SD and Con treatments) and drinker-directed behaviour in the 16-8 h pre-partum period (Table 2; mean values 3.7% and 2.3% of observations, respectively, for the SD and Con treatments). Also, more root/nose/paw behaviour was recorded for younger sows in the SD than in the Con treatment during 24-16 h pre-partum (Table 2; mean values 2.5% and 0.9% of observations, respectively, for the SD and Con treatments) and 8-0 h pre-partum (Table 2; mean values 6.0% and 3.8% of observations, respectively, for the SD and Con treatments). In the SD compared with Con treatment, there was less ( P < 0.02) occurrence of'other' behaviour by younger sows during parturition (Table 2; mean values 3.4% and 8.0% of observations, respectively, for the SD and Con treatments).
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SAWDUST PROVISION AND THE EFFECTS ON PRE-PARTURIENT SOWS
31 1
Amongst the older parity sows, there was an effect ( P < 0.01 ) of treatment on the performance of bar-biting behaviour in the 8-0 h pre-partum period (Table 2; mean values 1.0% and 3.7% of observations, respectively, for the SD and Con treatments). From the commencement of observations on Day 1, the percentage of younger parity sows that were recorded to be active was higher during the first hour (35% of sows, both treatments combined) than during the subsequent 3-h period ( 16% of sows). Root/nose/paw behaviour was performed by a larger percentage of SD compared with Con treatment sows in the first hour (7% and 2% of sows, respectively), but during the next 3-h period the incidence was constant at about 2% of sows in both treatments. The initial response by the older parity sows was similar to that of the younger sows. DISCUSSION
The regular application of sawdust to young sows in commercial farrowing crates increased their level of activity and performance of root/nose/paw behaviour during the 24-h period pre-farrowing and reduced the mean duration of parturition, compared with sows that did not receive sawdust. Further, the SD-treatment sows had proportionately fewer intra-partum deaths which, according to Sprecher et al. ( 1975 ), would be expected since the duration of parturition affects the incidence of intra-partum stillbirths. Similar responses to the application of sawdust were not found in older sows and although the results for the older sows were not significant, the trends were generally in the opposite direction to those of the younger sows. As previously reported by Vestergaard and Hansen (1984), Lammers and de Lange (1986), and Widowski and Curtis (1990) sows display a peak of activity during the 24-h period pre-partum, including an increase in the performance of root/nose/paw behaviour, which has been interpreted to be 'nesting behaviour'. While a similar finding is apparent in this experiment, sows that received sawdust directed their behaviour at the material potentially contributing to the increase in pre-partum activity. Alternatively, the disturbance associated with the regular application of sawdust may have simply stimulated the increased activity, the consequence of which would be a proportionate increase in all the individual behaviours. Interestingly, the Contreatment sows were more active during parturition than the SD-treatment sows (sawdust applications had stopped), a factor which may have contributed to the higher incidence of piglet overlays at that time for the Con treatment. In practical terms the shorter parturition time of young sows in the SD treatment led to more liveborn pigs. There are a number of processes that can affect piglet survival, including the duration of parturition, the access of piglets to the udder, the availability ofcolostrum and milk, the posture changing
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of the sow when piglets are beneath the sow, and savaging by the sow (English and Morrison, 1984; Svendsen et al., 1986a,b; Fraser, 1990). In the present experiment, it was clear that sawdust application affected some of these parameters, although not all were measured. In particular, differences occurred in the duration of parturition and the incidence of sows overlaying piglets around parturition. The apparent access of piglets to the udder was not affected by treatment (as determined by time sows spent side lying) and the incidence of savaging of piglets by sows was rare and did not occur for primiparous sows as has previously been found (Spicer et al., 1986 ). The results for young sows suggest that the level of activity and/or the performance of certain pre-partum behaviours (e.g. root/nose/paw), may be associated with the duration of parturition. Since the duration of parturition in sows is reported to affect piglet survival, either directly or indirectly, it would therefore seem important to determine those factors which promote shorter parturition. From surveys, the mean duration of parturition is in the order of 2.3-2.9 h (Jones, 1966; Randall, 1972; Fahmy and Flipot, 1981 ) and Jackson ( 1976 ) quotes 2.5 h as 'normal' for the sow, although longer farrowing times have also been reported (e.g. Friend et al., 1962, 5.1 h; Olsson and Svendsen, 1989, 4.3 h). A number of experimental treatments have been found to affect the duration of parturition in sows. For example, parturition was longer for sows in crates than pens (Svendsen and Andr6asson, 1980, 7.2 h vs. 4.6 h, respectively), for sows in tethers than loose-housed (Vestergaard and Hansen, 1984, 5.6 h vs. 3.9 h, respectively) and for non-exercised than exercised sows (Ferket and Hacker, 1985, I 1.4 h vs. 4.3 h, respectively). It could be argued that the duration of farrowing was excessively long in all these experiments and thus the positive response to treatments merely brought the observed duration closer to 'normal' values. The experiment most similar in design to the present experiment is that of Edwards and Furniss ( 1988 ). These authors video-recorded the farrowing of 20 multiparous sows in crates, half of which were provided with chopped straw bedding, and found no effect on the duration of parturition (3.3 h vs. 5 2 h, respectively, for sows without and with straw bedding). Although Edwards and Furniss (1988) do not state whether the sows in their experiment farrowed previously in the presence or absence of straw, it is likely that they used sows with no previous experience of straw at farrowing, and that a reasonable proportion of the sows were older parity animals. For the sows farrowing with chopped straw, the slightly longer duration of parturition was similar to the finding for older sows in the present experiment that the sawdust treatment slightly delayed the duration of parturition (2.4 h vs. 3.2 h, respectively). It is a reasonable assumption that older sows may have adapted to farrowing in crates without bedding and that the application of straw or sawdust may interfere with, rather than promote, the process of parturition leading to slower farrowing times and subsequent higher levels of intra-partum stillbirths. The older sows, which lacked experience of sawdust (bedding) at farrowing, may
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have perceived the sawdust as a novel stimulus and in this context were either distracted or responded inappropriately compared with the young sows. Recent work by Lawrence et al. ( 1992 ) showed that environmental disturbance can disrupt parturition in the pig. Further research is clearly warranted on the effects of the experience of nesting material on the subsequent responses of farrowing sows. In the present experiment the mean duration of parturition for the younger parity sows was 2.2 h and 2.8 h, respectively, for the SD and Con treatments. While these values are both close to the expected mean for 'normal' farrowing (2.5 h), a reduction in farrowing time by a fifth occurred in response to sawdust application. Although a cause and effect relationship has not been proven, the shorter farrowing time may have resulted in a reduced incidence of intrapartum deaths, specifically via a reduction in the proportion of litters which contained multiple intra-partum deaths. The occurrence of stillbirths in the present experiment (8.6% of piglets born including mummified pigs; 7.5% without mummified pigs) was higher than most reports for sows in the literature (e.g. Randall and Penny, 1970, 6.3%; Randall, 1972, 6.5%; Bille et al., 1974, 5.9%; Glastonbury, 1976, 5.8%; Spicer et al., 1986, 8.3%; Dyck and Swierstra, 1987, 5.3% ), but this may have been an artefact of the high proportion of older parity sows in the experiment a n d / o r the large litter sizes, especially amongst the older parity sows. As expected, intra-partum compared with pre-partum stillbirths accounted for the majority of stillbirths (79%). In conclusion, the results of this experiment showed that the application of sawdust to younger parity sows increased the level of pre-partum activity and a number of other behaviours such as root/nose/paw behaviour, reduced the duration of parturition, and reduced the incidences of intra-partum stillbirths and overlays around parturition. The fact that older sows did not respond in a similar manner to younger sows may indicate that experience with nesting material may affect subsequent responses to sawdust. The results also suggest that the performance of pre-farrowing nesting behaviour (root/nose/paw) may influence the process of parturition and overlaying, which in turn may lead to improved piglet survival in the peri-partum period. ACKNOWLEDGEMENTS
We thank Drs. John Barnett and Paul Hemsworth and Mr Chris Winfield for their advice on aspects of this research and for their critical comments on the manuscript, and Tim Payne, Madeline Toner, Maree Cox, Samantha Urmston, Ross Anderson, Debbie Sage and Heleen van de Weerd for their help with the observations. We also gratefully acknowledge Bunge Meat Industries for their generous assistance in providing the facilities for the research, and for the co-operation of Wayne Mills and piggery staff at Corowa.
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This experiment was supported by a grant from the Australian Pig Research and Development Corporation.
REFERENCES Arey, D.S., Petchey, A.M. and Fowler, V.R., 1991. The preparturient behaviour of sows in enriched pens and the effect of pre-formed nests. Appl. Anim. Behav. Sci., 31: 61-68. Baxter, M.R., 1982. The nesting behaviour of sows and its disturbance by confinement at farrowing. In: W. Bessei (Editor), Disturbed Behaviour in Farm Animals. Eugen Ulmer, Hohenheim, pp. 101-114. Bille, N., Nielsen, N.C., Larsen, J.L. and Svendsen, J., 1974. Preweaning mortality in pigs. 2. The perinatal period. Nord. Vet., 26:294-313. Cronin, G.M. and van Amerongen, G., 1991. The effect of modifying the farrowing environment on sow behaviour and survival and growth of piglets. Appl. Anim. Behav. Sci., 30: 287298. Cronin, G.M. and Smith, J.A., 1992. Effects of accommodation type and straw bedding around parturition and during lactation on the behaviour of primiparous sows and survival and growth of piglets to weaning. Appl. Anim. Behav. Sci., 33" 191-208. Dyck, G.W. and Swierstra, E.E., 1987. Causes of piglet death from birth to weaning. Can. J. Anim. Sci., 67: 543-547. Edwards, S.A. and Furniss, S.J., 1988. The effects of straw in crated farrowing systems on peripartat behaviour of sows and piglets. Br. Vet. J., 144: 139-146. English, P.R. and Morrison, V., 1984. Causes and prevention of piglet mortality. Pig News Inf., 5: 369-376. Fahmy, M.H. and Flipot, P., 1981. Duration of farrowing and birth and nursing order in relation to piglet growth and survival. World Rev. Anim. Prod., 17: 3, 5, 17-24. Ferket, S.L. and Hacker, R.R., 1985. Effect of forced exercise during gestation on reproductive performance of sows. Can. J. Anim. Sci., 65: 851-859. Fraser, D., 1990. Behavioural perspectives on piglet survival. J. Reprod. Fert., 40:355-370 (suppl.). Friend, D.W., Cunningham, H.M. and Nicholson, J.W.G., 1962. The duration of farrowing in relation to the reproductive performance of Yorkshire sows. Can. J. Comparative Med. Vet. Sci., 26: 127-130. Glastonbury, J.R.W., 1976. A survey of preweaning mortality in the pig. Aust. Vet. J., 52: 272276. Jackson, P., 1976. When things go wrong at farrowing. Pig Farming, 24 ( 1 ): 43-47. Jones, J.E.T., 1966. Observations on parturition in the sow: Part II: The parturient and postparturient phases. Br. Vet. J., 122:471-478. Lammers, G.J. and de Lange, A., 1986. Pre- and post-farrowing behaviour in primiparous domesticated pigs. Appl. Anim. Behav. Sci., 15:31-43. Lawrence, A.B., Petherick, J.C., Mclean, K. and Gilbert, C., 1992. Mediation of stress-induced inhibition of oxytocin in farrowing sows by endogenous opioids. Proc. Br. Soc. Anim. Prod., Winter Meeting, 1992, Paper No. 56. Anim. Prod., 54: 463. Olsson, A.C. and Svendsen, J., 1989. Observations at farrowing and mother-offspring interactions in different housing systems. Swedish University of Agricultural Sciences, Lund, Sweden, Report 65, 84 pp. Randall, G.C.B., 1972. Observations on parturition in the sow. I. Factors associated with the delivery of the piglets and their subsequent behaviour. Vet. Rec., 90:178-182.
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Randall, G.C.B. and Penny, R.H.C., 1967. Stillbirths in pigs: The possible role of anoxia. Br. Vet. J., 81: 359-361. Randall, G.C.B. and Penny, R.H.C., 1970. Stillbirth in the pig: An analysis of the breeding records of five herds. Br. Vet. J., 126: 593-603. Rohlf, F.J. and Sokal, R.R., 1981. Statistical Tables. 2nd Edn. W.H. Freeman, San Francisco, CA, 219 pp. Siegel, S., 1956. Nonparametric Statistics for the Behavioural Sciences. McGraw-Hill, New York, 312 pp. Spicer, E.M., Driesen, S.J., Fahy, V.A., Horton, B J., Sims, L.D., Jones, R.T., Cutler, R.S. and Prime, R.W., 1986. Causes of preweaning mortality on a large intensive piggery. Aust. Vet. J., 63:71-75. Sprecher, D.J., Leman, A.D. and Carlisle, S., 1975. Effects of parasympathomimetics on porcine stillbirth. American Journal of Veterinary Research, 36:1331-1333. Svendsen, J. and Andrrasson, B., 1980. Perinatal mortality in pigs: Influence of housing. In: N.C. Nielsen, P. Hogh and N. Bille (Editors), Proc. Int. Pig Vet. Soc. Congr., 30 June-3 July 1980, Campus of Natural Sciences, University of Copenhagen, Int. Pig Vet. Soc., Ames, IA. p. 3. Svendsen, J., Svendsen, L.S. and Bengtsson, A.Ch., 1986a. Reducing perinatal mortality in pigs. In: A.D. Leman, B. Straw, R.D. Glock, W.L. Mengeling, R.C.H. Penny and E. Scholl (Editors), Diseases of Swine (6th Edn.). Iowa State University Press, Ames, IA, pp. 813-825. Svendsen, J., Bengtsson, A.Ch. and Svendsen, L.S., 1986b. Occurrence and causes of traumatic injuries in neonatal pigs. Pig News Inf., 7:159-170. Vestergaard, K. and Hansen, L.L., 1984. Tethered versus loose sows: Ethological observations and measures of productivity. I. Ethological observations during pregnancy and farrowing. Ann. Rech. Vrt., 15: 245-256. Widowski, T.M. and Curtis, S.E., 1990. The influence of straw, cloth tassel, or both on the prepartum behavior of sows. Appl. Anim. Behav. Sci., 27:53-71.
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The effects of providing sawdust to pre-parturient sows in farrowing crates on sow behaviour, the duration of parturition and the occurrence of intra-partum stillborn piglets G.M. Cronin, B.N. Schirmer, T.H. McCallum, J.A. Smith and K.L. Butler Victorian Institute of Animal Science, Sneydes Road, Werribee, Vic. 3030, Australia (Accepted 18 December 1992 ) ABSTRACT Cronin, G.M., Schirmer, B.N., McCallum, T.H., Smith, J.A. and Butler, K.L., 1993. The effects of providing sawdust to pre-parturient sows in farrowing crates on sow behaviour, the duration of parturition and the occurrence ofintra-partum stillborn piglets. Appl. Anim. Behav. Sci., 36: 301315. The behaviour of 174 sows (parities 1-10) in commercial farrowing crates was recorded at 10-m in intervals around parturition. Approximately half of the sows received regular applications of sawdust on the floor of their crate during the pre-partum period (SD treatment). Control treatment (Con) sows did not receive sawdust. Younger sows (parities 1-3 ) in the SD treatment spent less (P< 0.01 ) time belly lying from 24 to 16 h pre-partum, were more (P<0.05) active in the last 8 h pre-partum and less (P<0.05) active during parturition than in the Con treatment. More root/nose/paw behaviour occurred during 24 to 16 h (P< 0.01 ) and the last 8 h ( P < 0.005 ) pre-partum, and more (P< 0.03 ) feeder-directed behaviour occurred in the last 8 h pre-partum, in the SD than Con treatment. Sows in the SD treatment compared with sows in the Con treatment had a shorter ( P < 0.05 ) mean duration of parturition ( 159 and 201 min per sow) and a lower (P < 0.01 ) incidence of piglets that were overlayed during parturition and the subsequent 6 h (2.4% and 21.1% of sows, respectively). While there were no differences in the proportion of litters of younger sows that contained stillborn piglets of the class intra-partum death (IPD: 26.1 and 31.6% of sows), there was a difference (P< 0.02 ) in the ratio of litters containing 0, l or multiple IPD per litter: (SD:73%, 27% and 0% vs. Con:68%, 16% and 16% of litters, respectively). As a consequence of the lower occurrence of IPD, litter size born alive was greater (P< 0.03 ) in the SD than Con treatment ( l 0.5 and l 0.0 piglets). Older sows (parities 4 and above) in the SD treatment spent less time sitting (P< 0.05 ) and more time side lying (P<0.06), and performed less (P<0.01) bar biting during the last 8 h pre-partum than older sows in the Con treatment. In conclusion, the application of sawdust during the pre-partum period appeared to stimulate prepartum activity in younger sows, including root/nose/paw behaviour, which may, in turn, positively affect the process of parturition and reduce overlaying of piglets, both of which are relevant to increasing piglet survival, The differing results for older sows suggest that experience with sawdust (for nesting material ) is an important determinant of subsequent responses of farrowing sows to this material. Keywords: Pig; Parturition; Housing
Correspondence to: G.M. Cronin, Victorian Institute of Animal Science, Sneydes Road, Werribee, Vic. 3030, Australia. © 1993 Elsevier Science Publishers B.V. All rights reserved 0168-1591/93/$06.00
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INTRODUCTION
Over the last 30 years there have been major changes to the design of farrowing accommodation used by the pig industry. Whereas sows once predominantly farrowed in yards or large pens with straw, modern farrowing crates have no bedding material and are designed to control movement by the sow to improve piglet survival. Concern has been expressed over the welfare of sows in farrowing crates because of the 'inability' of sows to perform the full repertoire of species-specific farrowing behaviours, in particular nesting behaviour (Baxter, 1982), or to build a farrowing nest consistent with the requirement for a safe, private and comfortable environment. It has consistently been reported that, during the 24 h prior to parturition, sows in farrowing crates or pens without nesting material appear highly motivated to perform behaviours such as rooting, nosing and pawing. These behaviours are assumed to be 'nesting behaviour' (Vestergaard and Hansen, 1984; Lammers and de Lange, 1986; Widowski and Curtis, 1990) in spite of the fact that the sows are unable to construct a farrowing nest. One interpretation of this is that 'nesting behaviour' has a function for the sow other than simply the construction of a farrowing nest. Recent evidence suggests that it is the performance of nesting behaviour per se, rather than the availability of a constructed nest, that is important for sows (Widowski and Curtis, 1990). Furthermore, Arey et al. (1991 ) found an increased performance of nesting behaviour by sows provided with a preformed nest compared with sows that constructed their own nest. Cronin and Van Amerongen (1991) reported that primiparous sows, that farrowed in crates covered by a large hessian bag and with straw bedding on the floor (to simulate a completed farrowing nest), tended to perform more nesting behaviour prior to parturition than sows in crates without the cover or straw, and this was associated with increased responsiveness by sows towards the distress calls of their piglets and less savaging and overlaying. The aim of this experiment was to investigate the effects of providing sawdust, as a substitute for bedding material, for pre-parturient sows in commercial farrowing crates on the performance of farrowing behaviour, the duration of parturition as a measure of'ease of parturition' and the incidence of piglet deaths during parturition. The third parameter was included since it is known that prolonged parturition increases intra-partum stillbirths (Sprecher et al., 1975). ANIMALS, MATERIALS AND METHODS
The experiment was performed over three visits (replicates) to a large commercial pig farm in southeastern Australia during the late autumn and winter. From the piggery records it was known that the majority of sows far-
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rowed on Thursday and Friday each week. Each replicate of the experiment began on Wednesday (Day 1 ). The sows observed in the experiment were Large Whites (LW) that had been mated to LW boars. The experiment was performed in three different, but similar, farrowing sheds at the farm, which were staffed by the same team of stockpeople. Shed temperature was thermostatically controlled at 21 °C. Each shed contained 184 total confinement farrowing crates arranged in four rows. The crates measured 1.8 m wide X 2.1 m long within which was a 0.6-m-wide sow-stall. The floor of the crate was solid concrete except for two areas of plastic-coated, woven metal mesh across the entire width of the front (0.2 m ) and the rear (0.75 m ) of the crate. A gas heater was suspended above the concrete floor, 0.7 m from the front of the crate, between every second farrowing crate and was designed to heat the creep areas of two adjacent farrowing crates.
Experimental procedure At about 13:00 h on Day 1 six observers entered the farrowing shed to commence setting up the experiment (e.g. identifying experimental sows with numbered cards, etc. ). Any sows that had already farrowed or commenced to farrow by 14:00 h were excluded. Individual sows were randomly allotted to sawdust (SD) and control (Con) treatments using a random number list (Rohlf and Sokal, 1981 ). The experiment c o m m e n c e d at 14:00 h on Day 1 and concluded at 14:00 h on Day 3. Observers worked in pairs during 8-h shifts and there were two separate routines, concurrently conducted, which the observers performed alternately on an hourly basis.
Routine 1 The observer walked through the farrowing shed along the aisle in front of the sows and, for each sow in the experiment, recorded her posture and activity. This procedure was repeated at 10-min intervals throughout the experiment. Observations on each sow continued until either 6 h had elapsed after the birth of the sow's last piglet or 14:00 h on Day 3. The postures recorded were standing, sitting, lying on belly and lying on side. For sows in the last category, the observer also recorded whether the sow's udder was towards or away from the creep heater. Seven activities were recorded: inactive/asleep, feeder-directed behaviour, drinker-directed behaviour, r o o t / n o s e / p a w behaviour ('nesting'), bar biting, changing posture from either standing to lying, or sitting to lying, or the reverse, and any other activity. For greater detail of the description of these postures and activities see Cronin and Smith ( 1992 ). Routine 2 The observer walked along the aisle behind the sows to monitor the course of parturition. Once a sow had delivered her first piglet, the observer recorded
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on a prepared card the sow's identity, parity number, the date and time of c o m m e n c e m e n t of farrowing and the status of the piglet: piglets were classified at birth as being alive or as having died intra-partum or pre-partum (see below). The time of birth of each individual piglet in the litter and the status of the piglet were recorded within 1-2 min of the piglet's delivery. Any interference to sows by the piggery staff (e.g. injection with oxytocin or manual assistance to remove piglets from sows, etc. ) was recorded on the sow's card, as was the occurrence of sows that overlaid/stood on, or savaged, or attempted to savage piglets during the period of parturition and the subsequent 6 h. The observer also administered sawdust to treatment sows as described later.
Identifying stillbirths Stillbirths were classified as either pre-partum or intra-partum deaths (Randall and Penny, 1967; Bille et al.., 1974). In the former category, deaths occur late in gestation and were therefore not expected to be affected by the farrowing treatments. Similarly the occurrence of m u m m i f i e d piglets was not expected to be affected by farrowing treatment and thus in the present experiment m u m m i f i e d piglets were included in the pre-partum death category ( P P D & M ) . On the other hand, intra-partum deaths (IPD) occur during parturition and may be influenced by the imposition of farrowing treatment. Therefore, the data for these two distinct classes of stillborn piglet were analysed separately in this experiment.
Treatments There were two treatments: ( 1 ) SD m sows were provided with 1 1 of sawdust on the front third of the concrete floor of the farrowing crate at about 13:30 h on Day 1. Thereafter, sows received one or two handfuls every 30-60 min as an observer walked past the front of the farrowing crate, until either the sow c o m m e n c e d farrowing or 06:00 h on Day 3. The observer applied sawdust by gently dropping it on the solid floor adjacent to the sow's head. Sawdust was added at regular intervals to maintain a supply of sawdust as the sow could push the sawdust out of reach under the side bars of the crate or through the perforated floor. Prior to this experiment the sows had had no previous experience with bedding material in the pre-partum period. (2) Con - - sows did not receive sawdust.
Statistical analysis Regression analysis (Genstat, 1984 version; Lawes Agricultural Trust, Rothamsted Experimental Station, U K ) was used to determine the effects of
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treatment, parity number of the sow (parity numbers 6 and above were combined) and replication on the total number of piglets born and the number born alive per sow. Owing to insufficient numbers in some of the older parity groups, the data were combined a posteriori to provide two groups; these were parities 1-3 (younger sows ) and parities 4 and above (older sows ). Analysis of variance and co-variance (Genstat, 1984) were used to test for treatment effects within the two parity classes on the total number of piglets born and the number born alive per sow (adjusted for total born ), the duration of parturition (after log~ transformation ), the time from the start of the experiment (i.e. from 14:00 h Day l ) to the birth of the first piglet in the litter and the proportion of observations that noted sows occupying the four different postures and their activity (after angular transformation). Sow behaviour data were analysed within five time periods: 24-16 h pre-partum, 16-8 h pre-partum, 8-0 h pre-partum, the period of parturition (i.e. time from the first- to the last-born piglet in the litter) and the first 6 h post-partum (i.e. recorded from the time of the last-born piglet's delivery). No record was made of the time sows expelled foetal membranes. The data for most of the different behaviours that together accounted for total activity could not be normalised by the angular transformation and were analysed for treatment effects by the Mann-Whitney U-test, corrected for tied values to compute the statistic z (Siegel, 1956 ) in the five time periods. Within treatments and time periods, differences in the preference of sows for lying with the udder towards or away from the piglet heater were analysed by the Student's t-test. Within parity classes, the effects of treatment on the incidence of IPD and PPD&M were examined by the Chi-squared test, based on the size of the litters, divided by the number of IPD or PPD&M contained in the litter. Similarly, the Chi-squared test was used to examine the effects of treatment on the incidence of sows that received assistance at farrowing, that savaged or attempted to savage piglets and sows that overlaid or stood on piglets during parturition and the subsequent 6 h. RESULTS A total of 288 pro-parturient sows were observed during the three visits to the farm: the numbers of sows observed per visit were 100, 72 and 116, respectively. Of the 116 sows in Visit 3, 71 were observed under Routines 1 and 2, since their mating dates suggested that they were close to farrowing while the remaining 45 were only monitored in Routine 2 (i.e. duration of parturition and status of individual births). On the three visits to the farm, the percentages of sows observed in Routines 1 and 2 that completed parturition before the end of the observation period (14:00 h Day 3) were 69, 75 and 61%, respectively. Only 13% of the 45 sows in Visit 3 observed only in Routine 2 completed parturition during the allotted period. The 174 sows that
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completed parturition during the observation time on the three visits to the piggery, gave birth to a total of 2000 piglets: 1829 were born alive, 118 were IPD and 53 were P P D & M (31 were pre-partum deaths and 22 were m u m mified). The treatments did not affect ( P > 0.05 ) the incidence of parturition in which sows were assisted (oxytocin was administered to 11.6% of sows and manual assistance was given to 11.0% of sows in both treatments combined) or the occurrence of savaging. Three sows savaged or attempted to savage piglets: there was one sow from each parity, 2, 3 and 4, and one piglet died from savaging. The sows observed ranged from parity 1 (gilts) to parity 10. The majority of sows, however, were in the parity range 1-5. The data for one sow were omitted since she gave birth to a 12th piglet about 39 h after the 1 lth was born and it was not possible to determine the stillbirth class of the piglet. Within parity groups there were no effects ( P > 0.05 ) of treatment on the mean time interval from c o m m e n c e m e n t of observations ( 14:00 h Day 1 ) to c o m m e n c e m e n t of parturition (Table 1 ).
Piglets born per sow There were no effects ( P > 0.05 ) of treatment or replicate (visit to the farm) on the total number of piglets born (alive + IPD + PPD&M ) per sow. As expected, there were effects of parity number of the sow on the total number of piglets born and the n u m b e r born alive per sow. From the regression analyses, there was a linear and a quadratic relationship, respectively, between the total n u m b e r born ( Y~) and n u m b e r born alive (Y2) and parity number of the sow
(x). Within the younger and older parity groups there were no effects ( P > 0.05 ) of treatment on the total n u m b e r of piglets born per sow (Table 1 ). The total number of piglets born per sow ranged from four to 19 for young sows and from five to 21 for old sows. After adjusting for total born, the SD treatment had more liveborn piglets per sow than the Con treatment for the younger ( P < 0 . 0 3 ) , but not for the older ( P > 0 . 0 5 ) parity sows (Table 1 ).
Stillborn piglets The proportion of piglets born in the SD and Con treatments that were classed as P P D & M are shown in Table 1. The n u m b e r of P P D & M per litter ranged from zero to four piglets amongst litters of younger sows and from zero to five piglets per litter for older sows; the distribution curves for the n u m b e r of P P D & M per litter did not differ ( P > 0.05) between the SD and Con treatments for the younger (X2 = 2 . 2 0 ) and the older sows ()C32=2.23). There were no effects ( P > 0.05 ) of treatment on the proportion of litters that
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G.M. CRONIN ET A L
contained piglet(s) of this class (younger sows: 7/42 litters and 10/57 litters, X12=0.01; older sows: 12/44 litters and 7/31 litters, X2 =0.21, respectively, for the SD and Con treatments). The occurrence of IPD piglets in the two treatments was expressed as a proportion of piglets born alive plus IPD (Table 1 ). The number of IPD per litter ranged from zero to five piglets amongst litters of younger sows and from zero to seven per litter for older sows; the distribution curves for the number of IPD per litter differed ( P < 0.05 ) between the SD and Con treatments for younger sows (X2 = 13.11 ), but not ( P > 0.05 ) for the older sows (X2 = 4.74). While there were no differences ( P > 0.05 ) owing to the SD and Con treatments in the proportion of litters that contained IPD (younger sows: 26% and 32% of litters, respectively; X~ = 0.34; older sows: 50% and 45% of litters, respectively; X~ = 0.17), there was an effect ( P < 0.02 ) of treatment on the ratio of litters of younger sows that contained nil, one or multiple IPD, respectively: SD, 74%, 26% and 0% of litters; Con, 68%, 16% and 16% of litters; X~ = 7.97, but not ( P > 0.05) for the older sows: SD, 50%, 18% and 32% of litters: Con, 45%, 32% and 23% of litters; X~ =2.14.
Duration of parturition After adjusting for the total number of piglets born in the litter, younger SD-treatment sows had a shorter ( P < 0.05) mean duration of parturition than Con-treatment sows (Table 1 ); the duration of parturition ranged from 24 min for a litter of eight piglets to 845 min for a litter of 15 piglets. Amongst the older sows there was a trend ( P < 0.08) for a longer duration of parturition in the SD treatment (Table 1 ); the duration of parturition ranged from 55 min for a litter of 13 piglets to 1020 min for a litter often piglets.
Occurrence of overlaying The proportion of younger sows that overlaid or stood on piglets during parturition and the subsequent 6 h was lower ( P < 0.01 ) for the SD than Con treatment ( 1/41 vs. 12/57 sows, respectively, X2 = 7.18 ). For older sows, while the incidence was lower for the SD than Con treatment, the difference was not significant (3/44 vs. 5/31 sows, respectively, X2 = 1.65, P > 0.05 ).
Sow behaviour observations Postures For the younger sows the only significant postural difference ( P < 0.01 ), owing to treatment, occurred for belly lying during 24-16 h pre-partum (Table 2; untransformed means 19.0% and 28.3% of observations, respectively, for the SD and Con treatments). As shown in Fig. 1, the predominant
SAWDUSTPROVISION AND THE EFFECTS ON PRE-PARTURIENTSOWS
309
TABLE 2 Posture and activity parameters where there were differences caused by treatment effects in the five time periods around parturition Parity group
Parameter
Time period
SD
Con
LSD(e=o.os)
P-value
Young sows Old sows Young sows Young sows
Lie on belly ~ Sit ~ Total activity ~ Total activity I
24-16 h pre-partum 8-0 h pre-partum 8-0 h pre-partum parturition
24.1 17.1 31.9 10.1
31.5 22.8 26.0 16.0
5.65 5.53 5.31 5.67
< 0.01 < 0.04 < 0.03 < 0.04
z-value Young sows Young sows Young sows Young sows Young sows Old sows
Feeder-directed 2 Drinker-directed 2 Root/nose/paw 2 Root/nose/paw 2 Other behaviour 2 Bar bite 2
8-0 h pre-partum 16-8 h pre-partum 24-16 h pre-partum 8-0 h pre-partum parturition 8-0 h pre-partum
2 2 2 5 0 0
0 0 0 2 3 2
2.22 1.84 2.56 2.83 2.30 2.63
< 0.03 < 0.07 < 0.01 < 0.005 < 0.02 < 0.01
Values shown are ~angular transformed means, expressed as degrees, for parameters analysed by ANOVA and 2median values for parameters analysed by the M a n n - W h i t n e y U-test (two-tailed).
100 .,.-L Key
~.
80
Stand/kneel
o
Sit
60,
l l e on belly
O
"5
,.o
l l e on side; udder towards heater l i e on s~de; udder away from beater
40.
"t::
g
o
20.
Q.
Treatment Time period
0-
SD Con
SD Con
SD Con
SD Con
24 to 16h
16 to 8h
8 to Oh
Partum
Pre-partu m
SD Con 0 to 6h Post-partu m
Fig. 1. T h e p r o p o r t i o n o f t i m e t h a t young sows (parities 1 - 3 ) in the SD a n d Con t r e a t m e n t s occupied the different postures during observations. T h e r e was a significant t r e a t m e n t effect ( P < 0.01 ) o n the t i m e spent belly lying d u r i n g the 8-h period 2 4 - 1 6 h pre-partum.
posture was lying. Both parity groups spent a similar proportion of time in each of the four postures. For the older sows, within time periods the only significant effect ( P < 0.04) of treatment was on the time sows spent sitting in the period 8-0 h pre-partum (Table 2; untransformed means 11.4% and 18.1% of observations, respectively, for the SD and Con treatments). For both
310
G . M . C R O N I N E T AL.
the younger and older parity sows, there was no clear preference ( P > 0.05 ) for side lying with the udder towards the piglet heater. Activities For younger parity sows there were effects of treatment on total activity during 8-0 h pre-partum (Table 2; untransformed means 29.7% and 22.8% of observations, respectively, for the SD and Con treatments) and during parturition (Table 2; untransformed means 6.5% and 12.0% of observations, respectively, for the SD and Con treatments). Figure 2 shows the proportion of observations in which younger sows were recorded to perform the different activities that accounted for total activity. The application of sawdust increased the time younger parity sows performed feeder-directed behaviour in the 8-0 h pre-partum period (Table 2; mean values 2.6% and 1.4% of observations, respectively, for the SD and Con treatments) and drinker-directed behaviour in the 16-8 h pre-partum period (Table 2; mean values 3.7% and 2.3% of observations, respectively, for the SD and Con treatments). Also, more root/nose/paw behaviour was recorded for younger sows in the SD than in the Con treatment during 24-16 h pre-partum (Table 2; mean values 2.5% and 0.9% of observations, respectively, for the SD and Con treatments) and 8-0 h pre-partum (Table 2; mean values 6.0% and 3.8% of observations, respectively, for the SD and Con treatments). In the SD compared with Con treatment, there was less ( P < 0.02) occurrence of'other' behaviour by younger sows during parturition (Table 2; mean values 3.4% and 8.0% of observations, respectively, for the SD and Con treatments).
,~
KEY 40_ [~
~
~ ~
30_
g,
~11 Ik
• 20.
Feeder
r ~ Drinker ~1~Nesting ~Bar biting ~ l Changing posture I I Other
o
~itH
flll//
t.i o Q. o a.
Treatment
i
SD Con 24to16h
SD Con 16toSh
Pre-partum
SD Con
SD Con
SD Con
8to0h
Partum
0to6h Post-partum
Fig. 2. The proportion of time that young sows (parities 1-3) in the SD and Con treatments performed the different behaviours that together constituted total activity. * above paired columns indicates significant effect of treatment on total activity (P< 0.05 ).
SAWDUST PROVISION AND THE EFFECTS ON PRE-PARTURIENT SOWS
31 1
Amongst the older parity sows, there was an effect ( P < 0.01 ) of treatment on the performance of bar-biting behaviour in the 8-0 h pre-partum period (Table 2; mean values 1.0% and 3.7% of observations, respectively, for the SD and Con treatments). From the commencement of observations on Day 1, the percentage of younger parity sows that were recorded to be active was higher during the first hour (35% of sows, both treatments combined) than during the subsequent 3-h period ( 16% of sows). Root/nose/paw behaviour was performed by a larger percentage of SD compared with Con treatment sows in the first hour (7% and 2% of sows, respectively), but during the next 3-h period the incidence was constant at about 2% of sows in both treatments. The initial response by the older parity sows was similar to that of the younger sows. DISCUSSION
The regular application of sawdust to young sows in commercial farrowing crates increased their level of activity and performance of root/nose/paw behaviour during the 24-h period pre-farrowing and reduced the mean duration of parturition, compared with sows that did not receive sawdust. Further, the SD-treatment sows had proportionately fewer intra-partum deaths which, according to Sprecher et al. ( 1975 ), would be expected since the duration of parturition affects the incidence of intra-partum stillbirths. Similar responses to the application of sawdust were not found in older sows and although the results for the older sows were not significant, the trends were generally in the opposite direction to those of the younger sows. As previously reported by Vestergaard and Hansen (1984), Lammers and de Lange (1986), and Widowski and Curtis (1990) sows display a peak of activity during the 24-h period pre-partum, including an increase in the performance of root/nose/paw behaviour, which has been interpreted to be 'nesting behaviour'. While a similar finding is apparent in this experiment, sows that received sawdust directed their behaviour at the material potentially contributing to the increase in pre-partum activity. Alternatively, the disturbance associated with the regular application of sawdust may have simply stimulated the increased activity, the consequence of which would be a proportionate increase in all the individual behaviours. Interestingly, the Contreatment sows were more active during parturition than the SD-treatment sows (sawdust applications had stopped), a factor which may have contributed to the higher incidence of piglet overlays at that time for the Con treatment. In practical terms the shorter parturition time of young sows in the SD treatment led to more liveborn pigs. There are a number of processes that can affect piglet survival, including the duration of parturition, the access of piglets to the udder, the availability ofcolostrum and milk, the posture changing
312
G.M. CRONIN ET AL.
of the sow when piglets are beneath the sow, and savaging by the sow (English and Morrison, 1984; Svendsen et al., 1986a,b; Fraser, 1990). In the present experiment, it was clear that sawdust application affected some of these parameters, although not all were measured. In particular, differences occurred in the duration of parturition and the incidence of sows overlaying piglets around parturition. The apparent access of piglets to the udder was not affected by treatment (as determined by time sows spent side lying) and the incidence of savaging of piglets by sows was rare and did not occur for primiparous sows as has previously been found (Spicer et al., 1986 ). The results for young sows suggest that the level of activity and/or the performance of certain pre-partum behaviours (e.g. root/nose/paw), may be associated with the duration of parturition. Since the duration of parturition in sows is reported to affect piglet survival, either directly or indirectly, it would therefore seem important to determine those factors which promote shorter parturition. From surveys, the mean duration of parturition is in the order of 2.3-2.9 h (Jones, 1966; Randall, 1972; Fahmy and Flipot, 1981 ) and Jackson ( 1976 ) quotes 2.5 h as 'normal' for the sow, although longer farrowing times have also been reported (e.g. Friend et al., 1962, 5.1 h; Olsson and Svendsen, 1989, 4.3 h). A number of experimental treatments have been found to affect the duration of parturition in sows. For example, parturition was longer for sows in crates than pens (Svendsen and Andr6asson, 1980, 7.2 h vs. 4.6 h, respectively), for sows in tethers than loose-housed (Vestergaard and Hansen, 1984, 5.6 h vs. 3.9 h, respectively) and for non-exercised than exercised sows (Ferket and Hacker, 1985, I 1.4 h vs. 4.3 h, respectively). It could be argued that the duration of farrowing was excessively long in all these experiments and thus the positive response to treatments merely brought the observed duration closer to 'normal' values. The experiment most similar in design to the present experiment is that of Edwards and Furniss ( 1988 ). These authors video-recorded the farrowing of 20 multiparous sows in crates, half of which were provided with chopped straw bedding, and found no effect on the duration of parturition (3.3 h vs. 5 2 h, respectively, for sows without and with straw bedding). Although Edwards and Furniss (1988) do not state whether the sows in their experiment farrowed previously in the presence or absence of straw, it is likely that they used sows with no previous experience of straw at farrowing, and that a reasonable proportion of the sows were older parity animals. For the sows farrowing with chopped straw, the slightly longer duration of parturition was similar to the finding for older sows in the present experiment that the sawdust treatment slightly delayed the duration of parturition (2.4 h vs. 3.2 h, respectively). It is a reasonable assumption that older sows may have adapted to farrowing in crates without bedding and that the application of straw or sawdust may interfere with, rather than promote, the process of parturition leading to slower farrowing times and subsequent higher levels of intra-partum stillbirths. The older sows, which lacked experience of sawdust (bedding) at farrowing, may
SAWDUST PROVISION AND THE EFFECTS ON PRE-PARTURIENT SOWS
313
have perceived the sawdust as a novel stimulus and in this context were either distracted or responded inappropriately compared with the young sows. Recent work by Lawrence et al. ( 1992 ) showed that environmental disturbance can disrupt parturition in the pig. Further research is clearly warranted on the effects of the experience of nesting material on the subsequent responses of farrowing sows. In the present experiment the mean duration of parturition for the younger parity sows was 2.2 h and 2.8 h, respectively, for the SD and Con treatments. While these values are both close to the expected mean for 'normal' farrowing (2.5 h), a reduction in farrowing time by a fifth occurred in response to sawdust application. Although a cause and effect relationship has not been proven, the shorter farrowing time may have resulted in a reduced incidence of intrapartum deaths, specifically via a reduction in the proportion of litters which contained multiple intra-partum deaths. The occurrence of stillbirths in the present experiment (8.6% of piglets born including mummified pigs; 7.5% without mummified pigs) was higher than most reports for sows in the literature (e.g. Randall and Penny, 1970, 6.3%; Randall, 1972, 6.5%; Bille et al., 1974, 5.9%; Glastonbury, 1976, 5.8%; Spicer et al., 1986, 8.3%; Dyck and Swierstra, 1987, 5.3% ), but this may have been an artefact of the high proportion of older parity sows in the experiment a n d / o r the large litter sizes, especially amongst the older parity sows. As expected, intra-partum compared with pre-partum stillbirths accounted for the majority of stillbirths (79%). In conclusion, the results of this experiment showed that the application of sawdust to younger parity sows increased the level of pre-partum activity and a number of other behaviours such as root/nose/paw behaviour, reduced the duration of parturition, and reduced the incidences of intra-partum stillbirths and overlays around parturition. The fact that older sows did not respond in a similar manner to younger sows may indicate that experience with nesting material may affect subsequent responses to sawdust. The results also suggest that the performance of pre-farrowing nesting behaviour (root/nose/paw) may influence the process of parturition and overlaying, which in turn may lead to improved piglet survival in the peri-partum period. ACKNOWLEDGEMENTS
We thank Drs. John Barnett and Paul Hemsworth and Mr Chris Winfield for their advice on aspects of this research and for their critical comments on the manuscript, and Tim Payne, Madeline Toner, Maree Cox, Samantha Urmston, Ross Anderson, Debbie Sage and Heleen van de Weerd for their help with the observations. We also gratefully acknowledge Bunge Meat Industries for their generous assistance in providing the facilities for the research, and for the co-operation of Wayne Mills and piggery staff at Corowa.
314
G.M.CRONINETAL.
This experiment was supported by a grant from the Australian Pig Research and Development Corporation.
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