The Relationship Between Immunopathology and Body Condition of Mixed‐Age Ewes

Ill thrift in ewes, characterised by less than desirable body condition, is a multifactorial condition often attributed to nutritional deficits, though immunopathological factors may also play a role. This study investigated associations between body condition scores (BCS) and immunopathological states in 120 mixed‐age ewes grazing pasture over 4 months from weaning to mating. Ewes were selected by BCS at weaning: <2.5 ( n = 60), 2.5–3.5 ( n = 32), and >3.5 ( n = 28). Samples were collected at four time points for haematology, biochemistry, pathogen‐specific antibody responses, salivary IgA to nematode antigens, and faecal egg and lungworm larval counts. Postmortem examinations were conducted on 21 ewes culled or euthanised during the study. Key findings included positive associations between BCS and haematocrit, red blood cell count, haemoglobin ( P ≤ 0.01), albumin, and anion gap ( P ≤ 0.02), while urea increased with decreasing BCS ( P < 0.03). Faecal egg counts, particularly later in the study, and lungworm larval counts were elevated in low‐BCS ewes ( P ≤ 0.04). Dental disease and attrition were common in postmortem findings. These results highlight complex immunopathological and physiological interactions associated with low BCS in mixed‐age ewes.