Assessment of learning ability and behaviour in low birthweight lambs following intrauterine growth restriction

The present study used behavioural tasks to assess learning ability and beh aviour in postnatal lambs, and to examine the effects of low birthweight (L BW) and age on subsequent performance. It was hypothesized that intrauterin e growth restriction (IUGR) and LBW lead to learning and behavioural defici ts in the early postnatal period. IUGR and LBW were induced by umbilico-pla cental embolization from 120 days of gestational age (g.a.) to the onset of labour. Behavioural studies were performed on 6 LBW and 6 control lambs be tween 2 and 6 weeks after birth. LBW lambs were born at 139 +/- 1 days g.a. (2.4 +/- 0.2 kg) and control lambs were born at 149 +/- 1 days g.a. (4.5 /- 0.4 kg). Three tasks were used to assess the learning ability and behavi our of the lambs: a simple maze, an obstacle course, and a T-maze. LBW lamb s took longer to complete the simple maze at all ages, and made a greater n umber of errors at Week 1 of testing compared to control lambs; the total t rial duration and number of errors decreased with age for both groups. In t he obstacle course, the times taken to complete the first and third trials were used for analysis; a decrease in trial time and the number of errors f rom Trial 1 to Trial 3 were indications of the lamb's ability to learn how to negotiate the objects within the course. LBW lambs recorded longer trial durations for the first trial at Week 5 of testing, and for the third tria l at Week 4. LBW lambs made more errors for the first trial at Week 5 of te sting than control lambs. In the T-maze, there was no significant effect of treatment or age. It was concluded that differences between the groups may have been the result of LBW lambs being prematurely born. The value of the se tasks in the assessment of learning ability and behaviour in young lambs is discussed.