Thoroughbred broodmares in New Zealand are at greater odds of exposure to Leptospira than racehorses, possibly as a result of aspects of the on-farm pasture-based management. To identify biologically plausible risk factors cohorts of broodmares were prospectively followed on four Thoroughbred stud farms for a five-week period during the 2017-2018 season. Up to three cohorts of mares within each group of mares identified at the start of the study as empty (not in foal), in-foal, or mares having just foaled (with foal at foot) were followed on each farm and measurements made of pasture dry matter (DM) on offer, paddock location, mare cohort structure and farm management. The farm with stallions had a greater number of changes in mare cohort membership (2 (1-2) vs. 0 (0-1), P=0.001). The total pasture DM on offer was least for empty mares compared to in-foal mares, and mares with foals at foot (1483 (1157-2380) vs. 2070 (1499-2534) vs. 2299 (1390-3196) kg DM/ha, P=0.009). Pregnant mares had the greatest stocking density 4 (2 -6) mares/ha, due to use of small foaling paddocks. The low pasture DM on offer and high stocking rate for empty mares may provide a mechanism for exposure to environmental sources of Leptospira.

J, Bengtsson, CW Rogers, PJ Back, U Emanuelson, J Roca, EK Gee, and CF Bolwell

Proceedings of the New Zealand Society of Animal Production, Volume 78, Lincoln, 88-91, 2018
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