Piglets born with a high degree of meconium staining display altered behaviour throughout lactation

Piglets may experience asphyxia during parturition. In some, this results in anoxia and the piglet is still born. For others, the degree of asphyxia is less severe and the piglets are born alive, but may suffer organ damage. The brain is particularly susceptible to hypoxia, and induced asphyxia at birth has been shown to alter cognitive ability in guinea pigs (Becker and Donnell 1952). Hence, hypoxic piglets may display behavioural deficiencies. In the present study it was hypothesised that piglets exposed to birth hypoxia would be more anxious than normoxic piglets.

Piglets were identified as normoxic or hypoxic by assessing the meconium stain score (Mota-Rojas et al. 2002) following birth [score 0 (n = 18) and 3 (n = 17) respectively]. On d 11 and 21 of age, each piglet was placed inside a holding box for 1 min, and then a door was removed revealing an open arena. Emergence time from the holding box, and then behaviours (listed in Table 1) were recorded via real time observations and video camera during the arena test. Non-normally distributed data were natural-logarithmically transformed and when this occurred, the back-transformed means are presented in parenthesis. Data were analysed using a general linear model (ASReml, 3rd Edition; UK).

Table 1.  The effect of hypoxia (as indicated by meconium score) on piglet behaviour. Values are mean ± SEM

There was no significant effect of the interaction between level of hypoxia and day, so only main effects are reported in Table 1. There was a strong trend for piglets with a meconium stain score of 3 to take longer to emerge from the holding box (P = 0.059) than pigs with a meconium stain score of 0 (Table 1). Piglets with a meconium stain score of 3 displayed fewer squeals (P < 0.05) and fewer grunts (P < 0.05) than piglets with a meconium stain score of 0.

Whilst effects of hypoxia on peri-natal behaviour appear commonly in the literature (Herpin et al. 1996), the present data support the notion that piglets born with a high degree of meconium staining display altered behaviour for at least 21 d during lactation. The increase in emergence time and reduction in low pitched grunts in high meconium stained piglets may represent a decreased willingness to interact with a new environment. This supports the hypothesis in part and, in turn, warrants the need for further research into the long term effects of hypoxia on pig behaviour.