No abstract

Piglets have difficulties with the abrupt changes at weaning associated with conventional pig production systems. Previously, it has been shown in rats that reward and announcement of reward counteracts impact of stress effects. In the present study, it was investigated if announcement of an environmental enrichment, more than enrichment alone, could facilitate play behaviour and reduce weaning-stress-induced behaviours such as increased aggression with subsequent increased injuries and increased social manipulative behaviours (i.e., tail biting, belly nosing, mounting). Twenty-four litters of conventional housed fattening piglets were kept under three different experimental conditions: sound cue (conditioned stimulus, CS) paired with an environmental enrichment (unconditioned stimulus, US) with a maximum delay between the CS and US of 30 s (CS-US paired) in which anticipatory behaviour develops; cue-environmental enrichment unpaired (CS-US unpaired) and no cue and no environmental enrichment (No CS-US). At two weeks of age the so-called 'anticipation procedure' started and ended two days after weaning. Growth, play, aggressive, social manipulative, eating and inactive behaviour, and injury rates were measured before and after weaning. Results of this study indicated that announcement of enrichment and not enrichment alone significantly increased play behaviour after weaning.

The present study investigated 1) the importance of the aromatization process during the perinatal period for the development of the sexually dimorphic nucleus in the preoptic area of the hypothalamus (SDN-POA) of male rats, and 2) the relationship between SDN-POA volume and parameters of masculinization in male rats that were treated perinatally with the aromatase-inhibitor ATD. Males were treated with ATD either prenatally or pre- and neonatally, or with the vehicle. Masculine sexual behavior and partner preference were investigated in adulthood. Thereafter, animals were sacrificed and SDN-POA volume was measured. The SDN-POA volume was reduced in both the prenatally and the pre- and neonatally treated group, with a larger reduction in the latter than in the former group. Combined pre- and neonatal ATD treatment resulted in reduced frequency of mounts, intromissions, and ejaculations, as well as a reduced preference for a female over a male. The SDN-POA size was significantly and positively correlated with frequency of masculine sexual behavior, as well as preference for a female over a male.

No abstract