Is belly nosing redirected suckling behaviour?

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Abstract

Through two experiments, we examined whether individual piglets’ behaviour on the sow during nursing is related to post-weaning oral and ingestive behaviour. Specifically, we wanted to determine whether piglets with high suckling motivation during the nursing period are predisposed to developing belly nosing after weaning. An additional aim was to determine how piglets’ growth relates to pre- and post-weaning behaviour. In Experiment 1, 95 individual piglets from 16 litters were observed before weaning for the occurrence of suckling behaviour during and between nursing bouts on three separate days. These piglets were mixed with unfamiliar conspecifics at weaning (15 days of age) and housed with either a nipple or a push-lever bowl drinker. The occurrence of belly nosing and related oral–nasal behaviour patterns was quantified from video recordings. Piglets were weighed at birth, weaning and at days 7, 14 and 19 after weaning. There was a negative relationship between pre-weaning suckling behaviour and post-weaning belly nosing when pigs were housed with a bowl drinker (P < 0.10) and between suckling and penmate-directed behaviour when pigs were housed with a nipple drinker (P < 0.05). Belly nosing tended to be negatively correlated with post-weaning average daily gain (P < 0.10). In Experiment 2, other post-weaning ingestive behaviour patterns were included in a principal components analysis (PCA) for a more in-depth look at the relationships among pre-weaning suckling and post-weaning behaviour patterns. Sixty-six piglets from seven litters were observed before weaning on three separate days and weaned at 21 days. Belly nosing, penmate and object nosing, along with maintenance behaviour patterns were observed from video recordings. Piglets were weighed at birth, weaning and at days 7, 14 and 21 after weaning. Piglets that belly nosed also performed penmate nosing. These piglets tended to be smaller at birth (P < 0.10) and weaning (P < .10) and grew slower after weaning than their littermates (P < 0.01). They also performed less suckling behaviour during nursing bouts. Piglets that spent more time at the feeder after weaning also performed more object-directed nosing. These piglets grew faster before (P < 0.01) and after weaning (P < 0.10) and were heavier at weaning than their littermates (P < 0.01). Results from both experiments indicate that belly nosing is not predicted by pig pre-weaning suckling behaviour. However, belly nosing may be similar to the final massage of suckling behaviour in the sense that the behaviour represents the piglets’ nutritional need.

Introduction

Belly nosing is a common abnormal oral–nasal behaviour pattern in young pigs that involves one pig performing a distinctive, rhythmic rubbing of its snout on the belly of another pig (Fraser, 1978). This behaviour pattern occurs most often when piglets are weaned at young ages into confinement systems. Although the behaviour is repetitive and appears to have no obvious function, and therefore could be considered a stereotypy (Mason, 1991), it is generally not considered one because it is most often transient in nature. The behaviour usually develops four to seven days after weaning, peaks at around two weeks, and then wanes, although it may become a fixation for some individuals, as it is occasionally observed in the grower-finisher stage (Gonyou et al., 1998) and in group housed adult sows (personal observation).

When belly nosing is performed persistently, it can result in skin lesions on the belly and flank of the receiver (Bøe, 1993, Worobec et al., 1999, Straw and Bartlett, 2001) and may ultimately lead to ulceration (Allison, 1976). While it is generally accepted that early weaning plays the biggest role in the occurrence of belly nosing, other factors that may be important to the motivational system of this behaviour, such as the interaction of feeding and drinking motivational systems, are still being investigated. Suckling behaviour in piglets involves a period of udder massage prior to milk ejection, slow and fast sucking during milk ejection, and a second period of udder massage following milk let-down (Fraser, 1980). Because belly nosing resembles piglets’ massaging of the sow's udder, researchers have hypothesized that the behaviour is caused, in part, by a piglet's motivation to suckle (Fraser, 1978, Blackshaw, 1981, Metz and Gonyou, 1990, Gonyou et al., 1998, Weary et al., 1999). This is supported by evidence that accommodating suckling through the provision of blind teats for non-nutritive (Rau, 2002) or nutritive sucking (Widowski et al., 2005) reduces belly nosing.

Within litters or mixed groups of piglets, there is immense variation in the performance of belly nosing, with 50–80% of piglets exhibiting belly nosing in any given circumstance (Straw and Bartlett, 2001, Li and Gonyou, 2002). Previous studies have identified piglets that perform the most belly nosing, or “nosers”; these piglets will spend upwards of 8% of their time belly nosing (Li and Gonyou, 2002), have slower growth rates after weaning (Bøe, 1993, Straw and Bartlett, 2001) and are more active than non-nosers (Gonyou et al., 1998, Li and Gonyou, 2002). These piglets may also be belly nosing at the expense of feeding, since time spent belly nosing is negatively correlated with time spent at the feeder in individual piglets (Li and Gonyou, 2002, Bruni, 2004). The role of hunger in the development of belly nosing is equivocal, since belly nosing does not occur when piglets are experiencing the most severe nutrient deficiency within the first couple of days after weaning (Gonyou et al., 1998), and attempts to stimulate the behaviour by altering intake via diet quality (Gardner et al., 2001) or feed restriction (Bruni, 2004) have had mixed results.

Although it has been suggested that belly nosing is related to pre-weaning suckling behaviour (Fraser, 1978, Metz and Gonyou, 1990), the relationship between suckling motivation and belly nosing has not been explored. It is possible that piglets with the highest suckling motivation, presumably those that spend the most time suckling during and between nursing bouts, are the ones most affected by abrupt weaning and therefore become “nosers”. In a longitudinal study examining pre-weaning suckling and post-weaning behaviour in horses, Nicol and Badnell-Waters (2005) found that foals that performed the most suckling and nuzzling before weaning developed abnormal oral behaviour over the four years after weaning. Similarly, dairy calves that perform the most intersucking (sucking at the udder of herd-members) before weaning were most likely to intersuck after weaning and into adulthood (Keil and Langhans, 2001). While no equivalent study has been done in piglets, Mason et al. (2003) examined individual piglet behaviour prior to weaning and correlated it to short-term post-weaning behaviour and growth. In this study, the authors found no relationship between teat preference or teat consistency and belly nosing, nor any relationship between belly nosing and growth parameters. However, their study focused mainly on the short-term emotional responses to weaning and therefore only followed piglets through two days after weaning. Therefore, there is still a gap in the knowledge of individual pre-weaning behavioural characteristics that may be related to the development of abnormal oral behaviour after weaning. The goal of the current study was to discern whether individual piglets’ behaviour on the sow during nursing is related to post-weaning oral and ingestive behaviour. Specifically, we wanted to determine whether piglets with high suckling motivation during the nursing period are predisposed to developing belly nosing after weaning. An additional aim was to determine how piglets’ growth relates to pre- and post-weaning behaviour. These relationships were examined in two separate experiments using slightly different approaches. In Experiment 1, we investigated the relationship between pre-weaning suckling and post-weaning oral behaviour patterns in early-weaned piglets that were mixed at weaning into pens that contained one of two different styles of drinkers, drinkers that we previously found to differentially influence belly nosing (Torrey and Widowski, 2004). In Experiment 2, entire litters were maintained intact post-weaning to explore the intralitter differences in piglet suckling behaviour and their relationship to post-weaning behaviour and growth.

Section snippets

Materials and methods

All procedures used in these experiments were reviewed and approved by the University of Guelph Animal Care Committee in accordance with the Canadian Council on Animal Care.

Time budgets

The percentage of scans at which any piglet performed suckling behaviour during nursing bouts ranged from 40.43 to 100%. On average, piglets performed suckling behaviour during nursing bouts 80.48 ± 1.23% of the scans. Between nursing bouts, values for individual piglets ranged from 0 to 34.26% of the scans. Piglets spent an average of 7.56 ± 1.98% of the scans performing suckling behaviour between nursing bouts. There was no difference in suckling behaviour between piglets that were allotted to

Discussion

Abnormal sucking and nosing in piglets is a little-understood phenomena. While there are some definitive growth characteristics related to piglets that perform more belly nosing and pen-mate nosing and chewing after weaning (Gonyou et al., 1998, Gardner et al., 2001, Straw and Bartlett, 2001), why some piglets develop the behaviour while others do not under identical housing and management is unclear. Our experiments were designed specifically to examine the relationships among pre-weaning

Conclusions

It has often been suggested that belly nosing is redirected suckling behaviour performed when piglets are weaned at young ages into confinement housing systems. The lack of correspondence between suckling behaviour and belly nosing indicates that belly nosing is not determined by some general predisposition to suck. Rather it may represent redirected suckling behaviour in the sense that, like the final massage of suckling, belly nosing reflects the pig's nutritional need.

Acknowledgements

We thank Dr. Margaret Quinton for assistance with statistical analysis, the staff at Arkell Swine Research Center for their cooperation and assistance, and Emily Toth and Lindsay Tippin for their technical assistance. This research was funded by grants from the Natural Sciences and Engineering Research Council of Canada, the National Pork Board of the United States and the Ontario Ministry of Agriculture and Food.

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