Social instability increases aggression in groups of dairy goats, but with minor consequences for the goats’ growth, kid production and development

The aim of the present study was to study the effects of social instability (regrouping) during the second trimester (7 weeks) of pregnancy on aggression, cortisol concentrations and growth in goats and its consequences for survival, growth and some aspects of behavioural development in the kids. Six weeks after mating, 32 goats were distributed into eight groups. In four of the groups, randomly chosen pairs of goats were rotated between groups every Monday morning (around 08:30 h) for 7 weeks (unstable groups), starting 6 weeks into gestation (second trimester). The remaining four groups were kept stable throughout the entire pregnancy (stable groups). The adult goats were video recorded for 6 h twice a week for the first, second, fourth and seventh regrouping and for the 2 last weeks before expected birth. Blood samples of the adult goats were collected in a period from 1 week before the start of the first regrouping and until 1 week before expected birth. Blood samples from a maximum of two kids from each litter were collected at 3 weeks of age. Two kids from each litter were subjected to two types of behavioural tests: a ‘social test’ at the age of 1 and 7 weeks and a ‘novel object test’ at the age of 5 weeks. Except for the higher aggression level in the unstable groups, social instability did not have any other significant effects on factors such as growth, cortisol level or kid production in the goats. There were only minor effects on the behavioural development in the goat kids. However, kids from the unstable groups showed more escape attempts in the first trial of a ‘social test’, spent more time in contact with a novel object and unfamiliar kids, and showed less fear (escape attempts) after they were given one exposure to the social test situation. Furthermore, kids from unstable groups had a lower basal cortisol level than kids from stable groups.