Mature Merino ewes, either at pasture (paddock) or in a feedlot situation (penned), were given a serial challenge infection with the gastric nematode parasite, Haemonchus contortus, and compared with control animals for their behaviour in an arena test, their plasma cortisol concentration and haematological and immunological status. Very low levels of infection resulted and parasitic disease was not evident. There were, however, significant effects on behaviour of both the challenge infection and the feedlot situation. The parasitic treatment resulted in a reduced distance between the sheep and the person in the arena test and also an increase in locomotor activity in the case of penned sheep. Overall, the penned animals displayed twice as much locomotor activity as paddock sheep. Mechanisms whereby a infectious challenge could affect sheep behaviour require further investigation.

Two hundred and fifty Border Leicester x Merino ewes (40% heterozygous for the Booroola Fec B gene) were used in an experiment, replicated over 2 years, to examine the effects of cottonseed meal-based supplementation on lamb survival, birth, marking and weaning weight, as well as, liveweight and fleece characteristics of ewes. From 50 to 100 days of pregnancy, half of the ewes were supplemented with 80 g/head.day. The supplemented group was then split according to litter size and, until 30 days after lambing, were offered pellets at 80, 160 and 220 g/head .day, respectively, for ewes bearing single, twin and triplet (or more) lambs. Over the 2 years, ewes averaged 2.11 lambs per parturition and supplementation significantly increased lamb survival to weaning (73 v. 58%) with no interaction with litter size. Although supplementation had a positive effect on birth weight of all but twins, the effects of supplementation on survival were independent of birth weight effects. Significant effects of year, sire breed and litter size on lamb survival and birth weight were also noted. No effects of supplementation were apparent on lamb growth while ewe age, sire breed, sex and rearing rank all significantly influenced growth rates. Ewe weights, fleece weights and staple strength were significantly influenced by year, ewe age and litter size but not by supplementation. These findings indicate the benefits to lamb survival of providing a 'bypass' protein supplement to high fecundity flocks even when ewes are grazing good quality pastures.

The study demonstrated significant differences in some important immune components of the pig breeds studied. This may in turn indicate the variation in their immune competence or disease resistance. However, further investigation into the heritability and correlation with specific immune responses is required.

The effect of stress during pregnancy on fetal development has been demonstrated in studies such as the administration of glucocorticoids at 4 weeks of gestation which then 'programs' arterial blood pressure to be elevated during subsequent adult life (1). In the current experiment we have explored the effect of an acute stressful event applied to pregnant ewes at Day 2 and 3 of gestation. The morphology and cell counts of Day 2 and 3 embryos were evaluated following surgical collection from 15 superovulated ewes. Seven of these ewes were subjected on Days 2 and 3 after insemination to a 15 min period of shearing (partial), isolation and confinement adjacent to a working dog. These stresses were intended to produce a short-term cortisol peak at the time embryos were at the 4–8 cell stage. Embryos recovered from the 7 treated and 8 control ewes were graded according to IETS guidelines using a Nikon TE 300 inverted microscope. Cell counts were performed following staining of embryos with Hoechst 33342. Only embryos with >8 nuclei were included in the analysis to exclude embryos that were either unfertilised or died prior to the stressful events. Subjective grading showed no difference in grading embryos as transferable (stage of compact morula or later with quality grade of 1 or 2) between embryos derived from stressed and non-stressed ewes (45/63 v. 45/64). However cell counts were dramatically different as stressed ewes produced embryos with higher cell counts (74.7 � 32.0 v. 43.3 � 22.9; P�<�0.001 using one-way ANOVA). As it is presumed that cell counts are directly related to embryo quality, our results suggest that stress may be manipulated to increase embryo cell numbers and thus embryo quality. The apparently beneficial effect of stress is surprising as it is commonly stated that minimising stress during commercial animal embryo transfer programs results in improved results. We look forward to the opportunity to follow the in vivo development of embryos derived from ewes stressed at Day 2 and 3 of gestation. (1) Dodic M. et al. (1998) An early prenatal exposure to excess glucocorticoid leads to hypertensive offspring in sheep. Clin. Sci (Lond.) 94, 149–155.