David Miller

This study aimed to determine whether dietary manipulation of starch and fat could affect fertility in breeding ewe lambs. The hypothesis tested was that a high starch (insulin promoting) diet would increase the rate of onset of oestrous activity and conception compared to high fat (insulin suppressing) diet. Two diets, a high starch and a high fat diet, were fed to ewe lambs (n=102 per treatment) for a continuous 60-day period, (30 days prior to and after joining with the ram), and a sub-sample of 39 ewes per treatment were blood sampled for insulin analysis. Joining body mass pre-joining growth rate did not differ between the treatment groups. There was no overall effect nutrition on plasma insulin concentrations, though concentrations in the high starch group increased by day 18 compared to day O (P<0.005). Irrespective of nutritional treatment, joining plasma insulin concentration had no effect on conception rates. There was no effect of nutrition on the proportion of ewes cycling or the number of twin pregnancies. There was an increase in the conception rate of the cycling ewes in the high starch group (P<0.05). Higher body mass at joining, irrespective of diet, increased cycling rate (P<0.01), conception rate (P<0.05) and twinning rate (P<001). These findings indicate that manipulation of starch and fat in the diet of breeding ewe lambs does not affect their fertility, and that achieving a target body mass, pre-joining, is a more effective strategy to increase conception rates.

Traditionally, the main focus in behavioural studies of group-housed sows has been how aggression changes over time, with little attention paid to other (not necessarily negative) aspects of behaviour. For example, it has been established that, compared with open group pens, the presence of partial feeding stalls results in reduced levels of aggression over the first 90 min of mixing (Barnett et al, 1992), but there are few data regarding other behaviour. Behaviour is dynamic and negative interactions are not the only welfare-relevant actions, and therefore other behaviour such as investigation (sniffing/interacting with pen or another animal), time spent walking, standing (in the group or stalls) or lying should also be quantified to provide a more holistic picture of sow activity at mixing into groups. There are also limited studies on sows mixed at 5 d post-mating. We predicted that behaviour of sows changes over the 90 min post-mixing and that the expression of aggression is transient as the animals establish their social structure.

Administering oxytocin to neonatal rats has positive long-term effects on growth and development (Uvnas-Moberg and Petersson, 2005). These effects include a reduction in the stress response to weaning, increased post-weaning feed intake and alterations in the expression of gastrointestinal (GI) hormones regulating feed intake (Uvnas-Moberg et al., 1998; Sohlstrom et al., 1999). Two GI hormones of importance in regulating feed intake are ghrelin and leptin, which have antagonistic actions. Ghrelin expression is increased in response to fasting and leptin expression increases rapidly in response to feed intake. Since weaning the piglet is associated with stress and growth restriction, this study examined whether oxytocin given to young pigs could reduce the extent of the post-weaning growth check, along with any associated changes in ghrelin and leptin expression.