Genetic analysis of emotional reactivity in sheep: effects of the genotypes of the lambs and of their dams.

A total of 1347 weaned lambs from eight genotypes were tested over five consecutive years: Romanov (ROM) and Lacaune (LAC) pure breeds, the two F1 crossbreeds (RL and LR) and the offspring of ewes from these four genotypes sired with Berrichon-du-Cher rams (BCF). The lambs were individually exposed to three challenging tests involving novelty, human contact and social isolation. Ten synthetic variables were used to express social reactivity (i.e., active vs. passive strategy), exploratory activity and reactivity to humans. BCF crossbreds were more active (i.e., high bleats, locomotion and attempts to escape) than purebreds and F1. In contrast, ROM expressed more passive responses (i.e., low bleats and vigilance postures) than LAC and BCF crossbreds. In addition, ROM approached a motionless human less and had longer flight distances to an approaching human than did LAC and BCF crossbreds. When restrained, ROM, and to a lesser extent B x ROM and B x LR, avoided human contact more than did LAC, RL and B x LAC. Most of these differences were explained by direct additive genetic effects while maternal influences or heterosis effects were rarely significant. The highest heritability was for high bleats (h2 = 0.48). Females were more active and avoided human contact more than did males.

Biochemical and chemical supports for a transnatal olfactory continuity through sow maternal fluids.

Recognition of the mother is of major importance for the survival of mammalian neonates. This recognition is based, immediately after birth, on the detection of odours that have been learned by the fetus in utero. If the ethological basis of a transnatal olfactory continuity is well established, little is known on the nature of its olfactory cues, and nothing about the presence of potential carrier proteins in the maternal fluids such as amniotic fluid, colostrum and milk. We have identified the components of the pig putative maternal pheromone in these fluids of the sow. We also used a ligand-oriented approach to functionally characterize carrier proteins for these compounds in the maternal fluids. Six proteins were identified, using binding assay, immunodetection and peptide mapping by mass spectrometry. These proteins are known to transport hydrophobic ligands in biological fluids. Among them, alpha-1 acid glycoprotein (AGP) and odorant-binding protein (OBP) have been described in the oral sphere of piglets as being involved in the detection of pig putative maternal pheromone components. These are the first chemical and biochemical data supporting a transnatal olfactory continuity between the fetal and the postnatal environments.

Transnatal olfactory continuity in the rabbit: behavioral evidence and short-term consequence of its disruption.

This study investigates the role of prenatal odor learning on postnatal adaptive orientation responses in the newborn rabbit. Preference tests revealed that pups are equally attracted to the odors of placentae and colostrum (Experiments 1-4), suggesting that an odor continuity may exist between the fetal and neonatal environments. To test some predictions derived from this hypothesis, we manipulated the odor of the diet of pregnant-lactating does to control the chemical niches of their perinates. Fetuses exposed in this way to the odor of cumin (C) were selectively attracted as neonates to the odor of pure C (Experiment 6). Prenatal exposure to C also was followed, to a certain extent, by enhanced attraction to C odor in the placenta or colostrum from females which had consumed it (Experiments 5 & 7). Finally, the functional implications of perinatal odor continuity were tested by disrupting it. The odor component of the feto-neonatal transitional environment revealed indeed to affect the ability of certain pups to gain colostrum and milk at the very first sucking opportunities (Experiment 8).