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Sow behaviour during parturition in relation to the observed and the genetic merit for weaning survival
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Applied Animal Behaviour Science 114 (2008) 86–92 www.elsevier.com/locate/applanim
Sow behaviour during parturition in relation to the observed and the genetic merit for weaning survival Koen Anton Uitdehaag a,*, Dinand Ekkel b, Egbert Kanis a, Egbert Knol c a
Animal Breeding and Genomics Centre, Wageningen University, P.O. Box 338, 6700 AH Wageningen, The Netherlands b Professional Agricultural University, De Drieslag 1, 8251 JZ Dronten, The Netherlands c IPG, Institute for Pig Genetics B.V., Schoenaker 6, 6641 SZ Beuningen, The Netherlands Accepted 14 January 2008 Available online 20 February 2008
Abstract The sow’s breeding value for mothering ability (EBVma) can be estimated as the genetic effect of the foster sow on piglet survival at weaning. Sows with a high EBVma have litters with a short average interval from birth until first colostrum intake. In the present study, it was investigated whether sows with a high EBVma show differences in maternal behaviour during parturition. It was hypothesized that during parturition, sows with a high EBVma and/or weaning survival were less active (increased durations of lying laterally and lying ventrally, decreased durations of standing and sitting and less postural transitions) than sows with a low EBVma. These behaviours were observed from birth of first piglet until birth of last piglet using 25 sows with known EBVma. It was found that during parturition sows with high weaning survival showed longer durations of sitting and shorter durations of standing than sows with low weaning survival. These results indicate that maternal behaviour during parturition has an effect on piglet survival at weaning. No effect of EBVma on maternal behaviour during parturition was found. In conclusion, EBVma of sows did not show a relationship with their maternal behaviour during parturition. This would suggest that the previously found difference in interval until first colostrum intake of piglets from sows with varying EBVma, is not related to differences in maternal behaviour during parturition, although this should be specifically tested in future experiments. The results from this study can be used as a starting point for future research to eventually provide breeding companies with tools to select sows for pre-weaning survival of piglets. # 2008 Elsevier B.V. All rights reserved. Keywords: Sow; Maternal behaviour; Piglet survival; Genetics
* Corresponding author. Tel.: +31 317 482207; fax: +31 317 483929. E-mail address: [email protected] (K.A. Uitdehaag). 0168-1591/$ – see front matter # 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.applanim.2008.01.005
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1. Introduction Genetic merit for mothering ability (EBVma) of sows can be estimated as the maternal genetic effect of the foster sow on piglet survival until weaning. Weaning survival (WSURV) can be calculated as follows (as proportion): WSURV ¼
number of piglets alive at weaning number of live born piglets cross fostered piglets
EBVma is expressed as deviation from the population mean (population mean is a number between 0 and 100). From a study carried out by Knol et al. (2002), it was concluded that the sow’s EBVma, rather than her piglets’ genetic merit for vitality, is related to the litter average time interval between piglet expulsion and first colostrum intake. A short interval is essential for survival of piglets. Piglets born from a group of sows with a high EBVma had a shorter mean interval from birth until first colostrum intake than piglets born from sows with lower EBVma (40 min versus 100 min). The difference in EBVma between both groups of sows was 9.18% (minimum: 4.92%, maximum: +4.26; overall mean = 0.79). Knol et al. (2002) also showed that the difference in interval from birth until first colostrum intake between sows with different EBVma is not related to differences in udder and teat morphology. Possibly, differences in maternal behaviour during parturition between sows with different EBVma may explain the difference in length of this interval (Fig. 1). Several studies have already contributed to the understanding of optimal sow behaviour during parturition. Pedersen et al. (2003) concluded that during parturition, the most important factor for piglet survival is udder accessibility. Consequently, optimal sow behaviour during
Fig. 1. Schematic representation of the (expected) relations between the genetic merit for mothering ability, sow behaviour during parturition, piglet interval from birth until first colostrum intake and weaning survival. The dashed arrow indicates the main objective of this study: investigation of the relation between the genetic merit for mothering ability and sow behaviour during parturition.
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parturition is to remain in lateral recumbence. Furthermore, Jarvis et al. (1999) stated that, during parturition, increased duration of lying laterally enhances suckling opportunity, but also reduces the risk of crushing piglets. Considering all available facts, it was hypothesized that during parturition, sows with a higher EBVma spend more time lying laterally, spend less time standing and have fewer postural transitions than sows with a low EBVma. The objectives of this study were to test these hypotheses and to investigate the relationship between other during behaviours parturition and weaning survival. 2. Material and methods 2.1. Animals In this experiment, maternal behaviour during parturition of 25 crated sows from a pure-bred dam-line (Dutch Landrace origin) was recorded from birth of first piglet until birth of last piglet on a nucleus farm in Rio Verde, Goias (Brazil). Selection of sows for this experiment was based on their EBVma (percent points; mean 0.65, range: 3.72 to +2.38) and on parity (parity 4). Behavioural recordings were done in the farrowing house, where 14 crated sows were housed. Sows entered approximately 1 week before parturition and were fed a commercial lactation diet twice daily at 04:00 and 16:00 h. 2.2. Behavioural observations Continuous focal sampling was used to manually record (pen, paper and stopwatch) sow behaviour during 6 h starting from birth of the first piglet. This was set as the upper limit for duration of parturition. Observations were done by one and the same person who was positioned on the rear end of the farrowing crate facing the back of the sow. During these recordings, sows were not fed and parturition was not interfered with for birth assistance and managerial activities. No medication was used that could affect the process of parturition. For the recordings, an ethogram was compiled based on the objectives of this study and sow postures were taken as main point of interest (Table 1). 2.3. Other variables Additional data was collected to account for possible effects of other factors (i.e. sow-, reproduction-, weight- and time-related variables) in the analysis. Next to their EBVma’s, it was recorded whether sows were either primiparous or multiparous. During the behavioural observations, the total number of piglets born, the total number of piglets born alive and the number of stillborn piglets were recorded. Piglets were weaned 3 weeks after parturition and weaning survival was calculated at this time, as the number of piglets alive at weaning divide by number of live born piglets cross-fostered piglets. All sows (including Table 1 Ethogram used for the behavioural observations during parturition Posture
Definition a
Standing Kneeling Sitting Lying ventrally Lying laterally Postural transitions a
Upright position with four feet on the ground Knees of the forelegs on the ground, feet of hind legs on the ground Feet of forelegs on the ground, hind legs in lying position One or both forelegs stretched in front of sow Legs stretched next to animal Change of posture
At each moment a sow’s posture was recorded from which frequency and duration were calculated; for postural transitions only the frequency was recorded.
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non-experimental sows) in the farrowing house could be used for cross fostering, which took place according to litter size and piglet birth weight after the behavioural observations. For parturitions that ended during the day (between 07:00 and 17:00 h), individual piglet weights were collected immediately after the behavioural observations and for parturitions that ended during the night (between 17:00 and 07:00 h), these weights were collected immediately after 07:00 h the next morning. From individual piglet weights, litter birth weight (kg), mean piglet birth weight (kg) and standard deviation of mean piglet birth weight (kg) were calculated. Time-related variables were time of day at which parturition took place, duration of parturition (h), mean inter-piglet interval (min) and standard deviation of mean inter-piglet interval (min). 2.4. Statistical analysis Sow behaviour until birth of last piglet (=total duration of parturition) was analysed. Before the analyses, frequencies of postures were SQRT-transformed, whereas durations (expressed as ratio of total duration of parturition) and weaning survival were ARCSIN (SQRT)-transformed. Sow postures were related to EBVma as dependent variables in the following model: posture ¼ m þ bI EBVma þ bcov COV þ e
ðmodel IÞ;
and to weaning survival as independent variables in the following model: WSURV ¼ m þ bII posture þ bcov COV þ e
ðmodel IIÞ;
where in both models only one posture could be included at the time. The regression coefficient estimates bI and bII were of our main interest. Untransformed postures were included as independent variables in model II. Using a stepwise selection procedure, EBVma (model I) and posture (model II) were included in the analyses by default. Other, independent variables could enter the model if they had an F statistic with P 0.05. After adding a new variable to the model, significance levels of other variables already included in the model had to remain 0.05, otherwise they were deleted from the model. No other variables (COV) were eventually included in model 1, whereas in model 2, mean piglet birth weight was always included and duration of parturition was only included in the analysis of duration of sitting.
3. Results The 25 sows gave birth to 265 piglets (251 born alive and 14 stillborn). Average litter size was 10.04 (2.84) piglets born alive (standard deviation between brackets) and on average + 0.4 crossfostered piglets were added per litter. Mean weaning survival was 90% (14). The average litter birth weight was 15.6 kg (3.5) and mean piglet birth weight 1.55 kg (0.33). All piglets were born within the 6 h observational period and the average duration of parturition was 2.41 h (1.43). The mean interval between two subsequently born piglets was 14.8 min (7.64). During parturition, sows spent on average 83% lying laterally, 5% lying ventrally, 6% sitting and 6% standing (Table 2). 3.1. EBVma, weaning survival and sow postures Two postures were found to be significantly related to weaning survival (Table 2; model II); a 1% increase in duration of standing lead to 0.6% decrease in weaning survival (bII = 0.60 0.11, F 1,22 = 7.94; P = 0.01) and a 1% increase in duration of sitting lead to 0.55% increase in weaning survival (bII = 0.55 0.28, F 1,21 = 9.18; P = 0.01). In model II, the effect of mean piglet birth weight on weaning survival was always significant, irrespective of the posture that was included. A 100 g increase in mean piglet weight lead to an
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Table 2 Means (standard deviations between brackets) of postures and regression coefficients of weaning survival on these postures (bII standard error) and on mean piglet weight (bcov standard error) in model II Posture
Mean (standard deviation)
bII standard errora
bcov standard error 0.14 0.09* 0.12 0.06*
Standing Frequencyb Durationc
1.48 (2.04) 0.06 (0.16)
0.00 0.01 0.60 0.11***
Sitting Frequency Duration
3.36 (3.89) 0.06 (0.10)
0.01 0.01 0.55 0.28**
0.39 0.13** 0.21 0.08**, 0.03 0.02*,d
Lying ventrally Frequency Duration
3.12 (4.44) 0.05 (0.07)
0.01 0.01 0.28 0.41
0.16 0.08* 0.14 0.08*
Lying laterally Frequency Duration
4.56 (3.88) 0.83 (0.20)
0.01 0.01 0.29 0.13
0.15 0.08* 0.12 0.08*
11.52 (11.73)
0.00 0.00
0.16 0.08**
Postural transitions Frequency
a Presented regression coefficients are based on untransformed data and their significance levels are based on transformed data. b Frequency is the number of times that particular behaviour was observed until birth of last piglet. c Duration is expressed as a proportion of duration of parturition. d Regression coefficient of weaning survival on duration of parturition. * P < 0.05. ** P < 0.01. *** P < 0.001.
increase in weaning survival varying from 0.12% (bcov = 0.12 0.06, F 1,22 = 6.88; P = 0.02, for the model including duration of standing) to 0.39% (bcov = 0.39 0.13, F 1,22 = 8.93; P = 0.01, for the model including frequency of sitting), depending on the posture involved. In the analysis of duration of sitting, a 1 h prolonged parturition lead to an increase in weaning survival of 3% (bcov = 0.03 0.02, F 1,21 = 5.25; P = 0.03). Postures during parturition were not affected by a sow’s EBVma (model I), nor was EBVma correlated to weaning survival (0.00 1.00; Pearson correlation coefficient). 4. Discussion The objective of this study was to evaluate the effect of EBVma on duration and frequency of sow postures during parturition (model I). Variation between sows in these postures during parturition could possibly explain the previously found short mean intervals from birth to first colostrum intake of piglets from sows with high EBVma (Knol et al., 2002), although these intervals were not measured in the present study. It was hypothesized that sows with higher EBVma would spend more time lying laterally, spend less time standing, and have fewer number of postural transitions than sows with a low EBVma. Based on the positive regression of weaning survival on EBVma (0.94) as found by Knol et al. (2002), weaning survival and EBVma were expected to be similarly related to during parturition behaviour. It was found that EBVma was not related to during parturition behaviour or to weaning survival. Not finding a relation between EBVma and weaning survival is probably due to the small number of sows (n = 25). Selection of
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sows with either extreme low or extreme high EBVma’s was expected to create a behavioural contrast between both groups. EBVma’s in this study (3.72 to +2.38) were not as extreme as in the study by Knol et al. (2002; 4.92 to +4.26), which may have contributed to the absence of an effect of EBVma on behaviour during parturition. Weaning survival decreased with a longer duration of standing and increased with a longer duration of sitting. Several studies have shown that behaviour before and during parturition is strongly affected by the farrowing environment (Pedersen et al., 2003; Ho¨tzel et al., 2004; Jarvis et al., 2004). Increased duration of sitting positively affected weaning survival, but has also been found to be increased in crated nesting gilts as compared with other housing systems (Cronin et al., 1993; Jarvis et al., 1997). Jarvis et al. (2004) suggested that, both in the nesting and parturient gilt, increased sitting might be the result of a motivational conflict: strong motivation to interact with piglets and to investigate piglets is thwarted by environmental restrictions. Considering the results from the present study in a crate environment, postures resulting from this motivational conflict (either sitting or standing) may have determined the success of maternal care measured as weaning survival. Supporting this hypothesis, Weary et al. (1998) found that of 39 crushed piglets (out of 98 litters) from pen housed sows during the first 48 h after parturition, 21 crushes occurred after a standing to lying event and only one crush occurred after a sitting to lying event. In a crate environment, however, Weary et al. (1996) and Edwards and Malkin (1986) did not find any relation between sow postural transitions and piglet mortality. In the present study with a crate environment, increased weaning survival for sows with longer duration of sitting and shorter duration of standing therefore does not seem related to a decreased risk of piglets getting crushed. Estimation of EBVma includes information from relatives in different farrowing environments and possible effects of these environments are adjusted for. Because behaviour during parturition depends on the farrowing environment (Pedersen et al., 2003; Ho¨tzel et al., 2004; Jarvis et al., 2004), sows with high EBVma may have characteristics that are less dependent on these farrowing environments. Morrow-Tesch and McGlone (1990), for example, investigated the effect of manipulating both the piglet’s sensory system and odours from the sow’s ventrum on piglet nipple attachment. Deprivation of the piglet’s olfactory system totally prevented nipple attachment, indicating the important role of the piglets’ olfactory system to proceed in successful suckling after birth. Grandinson et al. (2002) estimated a strong negative, genetic correlation between a sow’s reaction to a screaming piglet and the number of piglet deaths due to crushing at day 4 after farrowing. Although these measurements also include observations after parturition, they do suggest that interaction between the sow and her piglets cued by olfactory and auditory stimuli are involved in piglet survival. In identifying characteristics of sows with high EBVma, future research should focus on sow characteristics cued by olfactory and auditory stimuli tested in different farrowing environments. 5. Conclusion Sow maternal behaviour during parturition was not affected by their EBVma, which suggests that the previously found short interval until first colostrum intake of litters from sows with high EBVma may not be caused by particular sow behavioural characteristics, although this should be specifically tested in future experiments. When housed in a farrowing crate, a decreased duration of standing and an increased duration of sitting seem to positively affect piglet survival at weaning.
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Acknowledgements The authors would like to thank the people of IPG for kindly providing data used in this experiment. We would also like to thank the staff of TOPIGS Brazil and the staff at the nucleus farm in Rio Verde for their help with the observations and for taking care of the experimental animals. References Cronin, G.M., Schirmer, B.N., McCallum, T.H., Smith, J.A., Butler, K.L., 1993. The effects of providing sawdust to preparturient sows in farrowing crates on sow behaviour, the duration of parturition and the occurrence of intra-partum stillborn piglets. Appl. Anim. Behav. Sci. 36, 301–315. Edwards, A., Malkin, S.J., 1986. An analysis of piglet mortality with behavioural observations. Anim. Prod. 42, 470. Grandinson, K., Rydhmer, L., Strandberg, E., Thodberg, K., 2002. Genetic analysis of sows’ reaction to a screaming piglet, and its relation to piglet mortality and growth. In: Proceedings of the 7th World Congress on Genetics Applied to Livestock Production, Montpellier, pp. 51–53. Ho¨tzel, M.J., Pinheiro Machado, F.L.C., Wolf, F.M., Dalla Costa, O.A., 2004. Behaviour of sows and piglets reared in intensive outdoor or indoor systems. Appl. Anim. Behav. Sci. 86, 27–39. Jarvis, S., Reed, B.T., Lawrence, A.B., Calvert, S.K., Stevenson, J., 2004. Peri-natal environmental effects on maternal behaviour, pituitary and adrenal activation, and the progress of parturition in the primiparous sow. Anim. Welf. 13, 171–181. Jarvis, S., Lawrence, A.B., McLean, K.A., Deans, L.A., Chirnside, J., Calvert, S.K., 1997. The effect of environment on behavioural activity, ACTH, b-endorphin and cortisol in pre-farrowing gilts. Anim. Sci. 65, 465–472. Jarvis, S., McLean, K.A., Calvert, S.K., Deans, L.A., Chirnside, J., Lawrence, A.B., 1999. The responsiveness of sows to their piglets in relation to the length of parturition and the involvement of endogenous opioids. Appl. Anim. Behav. Sci. 63, 195–207. Knol, E.F., Verheijen, C., Leenhouwers, J.I., Lende, T.v.d., 2002. Genetic and biological aspects of mothering ability in sows. In: Proceedings of the 7th World Congress on Genetics Applied to Livestock Production, Montpellier, pp. 35–38. Morrow-Tesch, J., McGlone, J.J., 1990. Sensory systems and nipple attachment behavior in neonatal pigs. Physiol. Behav. 47, 1–4. Pedersen, L.J., Damm, B.I., Marchant-Forde, J.N., Jensen, K.H., 2003. Effects of feed-back from the nest on maternal responsiveness and postural changes in primiparous sows during the first 24 h after farrowing onset. Appl. Anim. Behav. Sci. 83, 109–124. Weary, D.M., Pajor, E.A., Fraser, D., Honkanen, A.-M., 1996. Sow body movements that crush piglets: a comparison between two types of farrowing accommodation. Appl. Anim. Behav. Sci. 49, 149–158. Weary, D.M., Phillips, P.A., Pajor, E.A., Fraser, D., Thompson, B.K., 1998. Crushing of piglets by sows: effects of litter features, pen features and sow behaviour. Appl. Anim. Behav. Sci. 61, 103–111.
Applied Animal Behaviour Science 114 (2008) 86–92 www.elsevier.com/locate/applanim
Sow behaviour during parturition in relation to the observed and the genetic merit for weaning survival Koen Anton Uitdehaag a,*, Dinand Ekkel b, Egbert Kanis a, Egbert Knol c a
Animal Breeding and Genomics Centre, Wageningen University, P.O. Box 338, 6700 AH Wageningen, The Netherlands b Professional Agricultural University, De Drieslag 1, 8251 JZ Dronten, The Netherlands c IPG, Institute for Pig Genetics B.V., Schoenaker 6, 6641 SZ Beuningen, The Netherlands Accepted 14 January 2008 Available online 20 February 2008
Abstract The sow’s breeding value for mothering ability (EBVma) can be estimated as the genetic effect of the foster sow on piglet survival at weaning. Sows with a high EBVma have litters with a short average interval from birth until first colostrum intake. In the present study, it was investigated whether sows with a high EBVma show differences in maternal behaviour during parturition. It was hypothesized that during parturition, sows with a high EBVma and/or weaning survival were less active (increased durations of lying laterally and lying ventrally, decreased durations of standing and sitting and less postural transitions) than sows with a low EBVma. These behaviours were observed from birth of first piglet until birth of last piglet using 25 sows with known EBVma. It was found that during parturition sows with high weaning survival showed longer durations of sitting and shorter durations of standing than sows with low weaning survival. These results indicate that maternal behaviour during parturition has an effect on piglet survival at weaning. No effect of EBVma on maternal behaviour during parturition was found. In conclusion, EBVma of sows did not show a relationship with their maternal behaviour during parturition. This would suggest that the previously found difference in interval until first colostrum intake of piglets from sows with varying EBVma, is not related to differences in maternal behaviour during parturition, although this should be specifically tested in future experiments. The results from this study can be used as a starting point for future research to eventually provide breeding companies with tools to select sows for pre-weaning survival of piglets. # 2008 Elsevier B.V. All rights reserved. Keywords: Sow; Maternal behaviour; Piglet survival; Genetics
* Corresponding author. Tel.: +31 317 482207; fax: +31 317 483929. E-mail address: [email protected] (K.A. Uitdehaag). 0168-1591/$ – see front matter # 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.applanim.2008.01.005
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87
1. Introduction Genetic merit for mothering ability (EBVma) of sows can be estimated as the maternal genetic effect of the foster sow on piglet survival until weaning. Weaning survival (WSURV) can be calculated as follows (as proportion): WSURV ¼
number of piglets alive at weaning number of live born piglets cross fostered piglets
EBVma is expressed as deviation from the population mean (population mean is a number between 0 and 100). From a study carried out by Knol et al. (2002), it was concluded that the sow’s EBVma, rather than her piglets’ genetic merit for vitality, is related to the litter average time interval between piglet expulsion and first colostrum intake. A short interval is essential for survival of piglets. Piglets born from a group of sows with a high EBVma had a shorter mean interval from birth until first colostrum intake than piglets born from sows with lower EBVma (40 min versus 100 min). The difference in EBVma between both groups of sows was 9.18% (minimum: 4.92%, maximum: +4.26; overall mean = 0.79). Knol et al. (2002) also showed that the difference in interval from birth until first colostrum intake between sows with different EBVma is not related to differences in udder and teat morphology. Possibly, differences in maternal behaviour during parturition between sows with different EBVma may explain the difference in length of this interval (Fig. 1). Several studies have already contributed to the understanding of optimal sow behaviour during parturition. Pedersen et al. (2003) concluded that during parturition, the most important factor for piglet survival is udder accessibility. Consequently, optimal sow behaviour during
Fig. 1. Schematic representation of the (expected) relations between the genetic merit for mothering ability, sow behaviour during parturition, piglet interval from birth until first colostrum intake and weaning survival. The dashed arrow indicates the main objective of this study: investigation of the relation between the genetic merit for mothering ability and sow behaviour during parturition.
88
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parturition is to remain in lateral recumbence. Furthermore, Jarvis et al. (1999) stated that, during parturition, increased duration of lying laterally enhances suckling opportunity, but also reduces the risk of crushing piglets. Considering all available facts, it was hypothesized that during parturition, sows with a higher EBVma spend more time lying laterally, spend less time standing and have fewer postural transitions than sows with a low EBVma. The objectives of this study were to test these hypotheses and to investigate the relationship between other during behaviours parturition and weaning survival. 2. Material and methods 2.1. Animals In this experiment, maternal behaviour during parturition of 25 crated sows from a pure-bred dam-line (Dutch Landrace origin) was recorded from birth of first piglet until birth of last piglet on a nucleus farm in Rio Verde, Goias (Brazil). Selection of sows for this experiment was based on their EBVma (percent points; mean 0.65, range: 3.72 to +2.38) and on parity (parity 4). Behavioural recordings were done in the farrowing house, where 14 crated sows were housed. Sows entered approximately 1 week before parturition and were fed a commercial lactation diet twice daily at 04:00 and 16:00 h. 2.2. Behavioural observations Continuous focal sampling was used to manually record (pen, paper and stopwatch) sow behaviour during 6 h starting from birth of the first piglet. This was set as the upper limit for duration of parturition. Observations were done by one and the same person who was positioned on the rear end of the farrowing crate facing the back of the sow. During these recordings, sows were not fed and parturition was not interfered with for birth assistance and managerial activities. No medication was used that could affect the process of parturition. For the recordings, an ethogram was compiled based on the objectives of this study and sow postures were taken as main point of interest (Table 1). 2.3. Other variables Additional data was collected to account for possible effects of other factors (i.e. sow-, reproduction-, weight- and time-related variables) in the analysis. Next to their EBVma’s, it was recorded whether sows were either primiparous or multiparous. During the behavioural observations, the total number of piglets born, the total number of piglets born alive and the number of stillborn piglets were recorded. Piglets were weaned 3 weeks after parturition and weaning survival was calculated at this time, as the number of piglets alive at weaning divide by number of live born piglets cross-fostered piglets. All sows (including Table 1 Ethogram used for the behavioural observations during parturition Posture
Definition a
Standing Kneeling Sitting Lying ventrally Lying laterally Postural transitions a
Upright position with four feet on the ground Knees of the forelegs on the ground, feet of hind legs on the ground Feet of forelegs on the ground, hind legs in lying position One or both forelegs stretched in front of sow Legs stretched next to animal Change of posture
At each moment a sow’s posture was recorded from which frequency and duration were calculated; for postural transitions only the frequency was recorded.
K.A. Uitdehaag et al. / Applied Animal Behaviour Science 114 (2008) 86–92
89
non-experimental sows) in the farrowing house could be used for cross fostering, which took place according to litter size and piglet birth weight after the behavioural observations. For parturitions that ended during the day (between 07:00 and 17:00 h), individual piglet weights were collected immediately after the behavioural observations and for parturitions that ended during the night (between 17:00 and 07:00 h), these weights were collected immediately after 07:00 h the next morning. From individual piglet weights, litter birth weight (kg), mean piglet birth weight (kg) and standard deviation of mean piglet birth weight (kg) were calculated. Time-related variables were time of day at which parturition took place, duration of parturition (h), mean inter-piglet interval (min) and standard deviation of mean inter-piglet interval (min). 2.4. Statistical analysis Sow behaviour until birth of last piglet (=total duration of parturition) was analysed. Before the analyses, frequencies of postures were SQRT-transformed, whereas durations (expressed as ratio of total duration of parturition) and weaning survival were ARCSIN (SQRT)-transformed. Sow postures were related to EBVma as dependent variables in the following model: posture ¼ m þ bI EBVma þ bcov COV þ e
ðmodel IÞ;
and to weaning survival as independent variables in the following model: WSURV ¼ m þ bII posture þ bcov COV þ e
ðmodel IIÞ;
where in both models only one posture could be included at the time. The regression coefficient estimates bI and bII were of our main interest. Untransformed postures were included as independent variables in model II. Using a stepwise selection procedure, EBVma (model I) and posture (model II) were included in the analyses by default. Other, independent variables could enter the model if they had an F statistic with P 0.05. After adding a new variable to the model, significance levels of other variables already included in the model had to remain 0.05, otherwise they were deleted from the model. No other variables (COV) were eventually included in model 1, whereas in model 2, mean piglet birth weight was always included and duration of parturition was only included in the analysis of duration of sitting.
3. Results The 25 sows gave birth to 265 piglets (251 born alive and 14 stillborn). Average litter size was 10.04 (2.84) piglets born alive (standard deviation between brackets) and on average + 0.4 crossfostered piglets were added per litter. Mean weaning survival was 90% (14). The average litter birth weight was 15.6 kg (3.5) and mean piglet birth weight 1.55 kg (0.33). All piglets were born within the 6 h observational period and the average duration of parturition was 2.41 h (1.43). The mean interval between two subsequently born piglets was 14.8 min (7.64). During parturition, sows spent on average 83% lying laterally, 5% lying ventrally, 6% sitting and 6% standing (Table 2). 3.1. EBVma, weaning survival and sow postures Two postures were found to be significantly related to weaning survival (Table 2; model II); a 1% increase in duration of standing lead to 0.6% decrease in weaning survival (bII = 0.60 0.11, F 1,22 = 7.94; P = 0.01) and a 1% increase in duration of sitting lead to 0.55% increase in weaning survival (bII = 0.55 0.28, F 1,21 = 9.18; P = 0.01). In model II, the effect of mean piglet birth weight on weaning survival was always significant, irrespective of the posture that was included. A 100 g increase in mean piglet weight lead to an
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Table 2 Means (standard deviations between brackets) of postures and regression coefficients of weaning survival on these postures (bII standard error) and on mean piglet weight (bcov standard error) in model II Posture
Mean (standard deviation)
bII standard errora
bcov standard error 0.14 0.09* 0.12 0.06*
Standing Frequencyb Durationc
1.48 (2.04) 0.06 (0.16)
0.00 0.01 0.60 0.11***
Sitting Frequency Duration
3.36 (3.89) 0.06 (0.10)
0.01 0.01 0.55 0.28**
0.39 0.13** 0.21 0.08**, 0.03 0.02*,d
Lying ventrally Frequency Duration
3.12 (4.44) 0.05 (0.07)
0.01 0.01 0.28 0.41
0.16 0.08* 0.14 0.08*
Lying laterally Frequency Duration
4.56 (3.88) 0.83 (0.20)
0.01 0.01 0.29 0.13
0.15 0.08* 0.12 0.08*
11.52 (11.73)
0.00 0.00
0.16 0.08**
Postural transitions Frequency
a Presented regression coefficients are based on untransformed data and their significance levels are based on transformed data. b Frequency is the number of times that particular behaviour was observed until birth of last piglet. c Duration is expressed as a proportion of duration of parturition. d Regression coefficient of weaning survival on duration of parturition. * P < 0.05. ** P < 0.01. *** P < 0.001.
increase in weaning survival varying from 0.12% (bcov = 0.12 0.06, F 1,22 = 6.88; P = 0.02, for the model including duration of standing) to 0.39% (bcov = 0.39 0.13, F 1,22 = 8.93; P = 0.01, for the model including frequency of sitting), depending on the posture involved. In the analysis of duration of sitting, a 1 h prolonged parturition lead to an increase in weaning survival of 3% (bcov = 0.03 0.02, F 1,21 = 5.25; P = 0.03). Postures during parturition were not affected by a sow’s EBVma (model I), nor was EBVma correlated to weaning survival (0.00 1.00; Pearson correlation coefficient). 4. Discussion The objective of this study was to evaluate the effect of EBVma on duration and frequency of sow postures during parturition (model I). Variation between sows in these postures during parturition could possibly explain the previously found short mean intervals from birth to first colostrum intake of piglets from sows with high EBVma (Knol et al., 2002), although these intervals were not measured in the present study. It was hypothesized that sows with higher EBVma would spend more time lying laterally, spend less time standing, and have fewer number of postural transitions than sows with a low EBVma. Based on the positive regression of weaning survival on EBVma (0.94) as found by Knol et al. (2002), weaning survival and EBVma were expected to be similarly related to during parturition behaviour. It was found that EBVma was not related to during parturition behaviour or to weaning survival. Not finding a relation between EBVma and weaning survival is probably due to the small number of sows (n = 25). Selection of
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sows with either extreme low or extreme high EBVma’s was expected to create a behavioural contrast between both groups. EBVma’s in this study (3.72 to +2.38) were not as extreme as in the study by Knol et al. (2002; 4.92 to +4.26), which may have contributed to the absence of an effect of EBVma on behaviour during parturition. Weaning survival decreased with a longer duration of standing and increased with a longer duration of sitting. Several studies have shown that behaviour before and during parturition is strongly affected by the farrowing environment (Pedersen et al., 2003; Ho¨tzel et al., 2004; Jarvis et al., 2004). Increased duration of sitting positively affected weaning survival, but has also been found to be increased in crated nesting gilts as compared with other housing systems (Cronin et al., 1993; Jarvis et al., 1997). Jarvis et al. (2004) suggested that, both in the nesting and parturient gilt, increased sitting might be the result of a motivational conflict: strong motivation to interact with piglets and to investigate piglets is thwarted by environmental restrictions. Considering the results from the present study in a crate environment, postures resulting from this motivational conflict (either sitting or standing) may have determined the success of maternal care measured as weaning survival. Supporting this hypothesis, Weary et al. (1998) found that of 39 crushed piglets (out of 98 litters) from pen housed sows during the first 48 h after parturition, 21 crushes occurred after a standing to lying event and only one crush occurred after a sitting to lying event. In a crate environment, however, Weary et al. (1996) and Edwards and Malkin (1986) did not find any relation between sow postural transitions and piglet mortality. In the present study with a crate environment, increased weaning survival for sows with longer duration of sitting and shorter duration of standing therefore does not seem related to a decreased risk of piglets getting crushed. Estimation of EBVma includes information from relatives in different farrowing environments and possible effects of these environments are adjusted for. Because behaviour during parturition depends on the farrowing environment (Pedersen et al., 2003; Ho¨tzel et al., 2004; Jarvis et al., 2004), sows with high EBVma may have characteristics that are less dependent on these farrowing environments. Morrow-Tesch and McGlone (1990), for example, investigated the effect of manipulating both the piglet’s sensory system and odours from the sow’s ventrum on piglet nipple attachment. Deprivation of the piglet’s olfactory system totally prevented nipple attachment, indicating the important role of the piglets’ olfactory system to proceed in successful suckling after birth. Grandinson et al. (2002) estimated a strong negative, genetic correlation between a sow’s reaction to a screaming piglet and the number of piglet deaths due to crushing at day 4 after farrowing. Although these measurements also include observations after parturition, they do suggest that interaction between the sow and her piglets cued by olfactory and auditory stimuli are involved in piglet survival. In identifying characteristics of sows with high EBVma, future research should focus on sow characteristics cued by olfactory and auditory stimuli tested in different farrowing environments. 5. Conclusion Sow maternal behaviour during parturition was not affected by their EBVma, which suggests that the previously found short interval until first colostrum intake of litters from sows with high EBVma may not be caused by particular sow behavioural characteristics, although this should be specifically tested in future experiments. When housed in a farrowing crate, a decreased duration of standing and an increased duration of sitting seem to positively affect piglet survival at weaning.
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