Effects of sex and periconceptional ewe nutrition on offspring behavioural and physiological response to isolation

  • Mr Carlos Hernandez, Liggins Institute, National Research Centre for Growth and Development, University of Auckland and AgResearch Ruakura, New Zealand
  • Dr Lindsay Matthews, Animal Behaviour and Welfare, AgResearch, Ruakura Research Centre, New Zealand
  • Dr Mark Oliver, Liggins Institute and National Research Centre for Growth and Development, University of Auckland, New Zealand
  • Dr Frank Bloomfield, Liggins Institute and National Research Centre for Growth and Development, University of Auckland, New Zealand
  • Dr Jane Harding, Liggins Institute and National Research Centre for Growth and Development, University of Auckland, New Zealand

    • In pastoral sheep production, conception often occurs when nutrient reserves are poor and food availability is low. The aim of this study was to assess effects of ewe periconceptional undernutrition (food restriction to achieve 10-15% weight reduction) on offspring behavioural and physiological responses to isolation at 4 (n=130) and 18 (n=79) months of age. We studied four nutritional treatments: control ewes well nourished throughout pregnancy (n=39) or undernourished (UN) from -60 to +30d from mating (n=36), -2 to +30d (n=20) or -60 to 0d (n=26). Animals were isolated in a 4x2.5m enclosure for 5min and number of vocalizations, occasions standing against enclosure walls, jumps, and activity (number of times animals crossed lines dividing the enclosure into quadrants) were recorded. Blood withdrawn from jugular catheters immediately before, 10 and 60 min after isolation was analysed for cortisol concentrations. Data were compared using Fisher's exact test or REML analysis, including nutritional group, singleton/twin, sex, year and ewe as random effects, with Tukey HSD adjustment for multiple comparisons. Data are mean±SEM. Four-month females had a higher cortisol area under the curve (AUC) than males (360.4±23.6 vs 299.2±19.1 ng.min/ml, p=0.05) and vocalized more (51.1±2.5 vs 37.8±2.3, p=0.0001). Fewer UN-2+30 animals stood against walls (17.7% vs 50% controls and 56% UN-60-0, p=0.05), and fewer UN-60-0 animals jumped (0% vs 22% controls p=0.05). Eighteen-month females had higher cortisol AUC than males (606.1±78.1 vs 294±28.6 ng.min/ml, p<0.0001), vocalized more (22.1±3.9 vs 2.2±1.4, p=0.0001) and were more active (44.7±4.6 vs 31.2±2.8 quadrants crossed, p=0.01). UN-60+30 animals had lower cortisol AUC than controls (357.8±28.4 vs 477.7±37.9 ng.min/ml, p=0.05). We conclude that females have a stronger behavioural and physiological response to isolation than males before and after puberty. Furthermore, maternal periconceptional undernutrition suppresses pre-puberty stress behavioural reactions and post-puberty cortisol secretion in response to isolation-stress in the offspring.