The influence of piglet birth weight on physical and behavioural development in early life.

The objective of this study was to determine whether body weight at birth influences the physical and behavioural development of the neonatal pig. Sixteen sows and their litters were randomly allocated into four treatment groups. From the normal distribution curve of their birth weight, piglets were sub-divided into three groups: (1) low (<10th percentile) (2) normal (10-90th percentile) and (3) high (>90th percentile). To assess behavioural development, each litter was exposed to a ball placed in the creep area for a period of 1,800 s, and evaluated once over a 3-day period starting on either 5, 7, 14 or 21 days of postnatal life. Their response to, and interaction with, an object was used to calculate a numerical index of piglet behavioural development. Teat order was calculated following observations during consecutive suckling on days 11, 13 and 15 of life, and dominance hierarchy was assessed on day 12, 14 and 16. Individual body weight was recorded on days 0, 5, 7, 14 and 21 of postnatal life. Statistical differences between groups were analysed using general linear model, analysis of variance. Regression analyses were used to determine relationships between physical and behavioural development with teat order and dominance. There was a significant (p < 0.001) relationship between birth weight, growth performance and behavioural development. Behavioural developmental index (BDI) significantly improved (p < 0.001) with age and was also influenced by the day on which the ball was introduced (p < 0.01). Body weight on day 1 of the test was significantly (p < 0.001) correlated to BDI and age at test. Piglets demonstrating compensatory growth were more dominant and exhibited an improved behavioural developmental score than their slower growing littermates. In conclusion, compromised growth in utero can have a detrimental effect on the physical and behavioural development of the neonate. Animals with an enhanced developmental index in conjunction with a higher dominance value exhibited a improved neonatal growth performance. Copyright 2003 S. Karger AG, Basel