Abstract

The Miniature horse population is a rapidly expanding sector of the New Zealand (NZ) equine population. It is estimated that there have been 6,052 Miniature horses registered in NZ, with 677 new registrations in 2004. The lay literature implies that the Miniature horse breed has a high level of reproductive and congenital defects. To obtain reference data on the reproductive and congenital disorders of the NZ Miniature horse breed a face-to-face survey was conducted with 22 breeders located in the lower North Island of NZ. The 22 breeders were the owners of 421 horses (246 mares, 52 stallions, 88 foals and 35 geldings). The mean number of Miniature horses on the property was 19 horses (range 4-60), 11 broodmares (range 2-30) and 2 stallions (range 0 ¨C 8). Most horses (75%) were registered with the NZ Miniature horse Association or the American Miniature Horse Society (23%). Most Miniature horses were type A, being ≤86cm in height at the withers (72%). The average foal crop per breeder was 7 foals, which were conceived with hand serving (61.4%) or a combination of hand serving and having the stallion run with the mare (31.8%).Confirmation of pregnancy was by blood test (49.2%), ultrasound verification (19%), combination of blood test and ultrasound (6%), or non return to oestrus (23.4%). Seventeen breeders had mares that were covered by the stallion during the season but did not return a positive pregnancy (23.4% of mares covered in the season). There was a lower percentage of apparent fetal loss on farms that used blood tests or ultrasound to verify pregnancy compared to farm relying on non return to oestrus(10.38% ± 2.49% vs. 20.79% ± 4.59%, p=0.06).The incidence of fetal abortion (<300 days gestation) was 1.75% (CI 0.5-3.03), and 5.2% (CI 2.6 -7.8%) of mares suffered from dystocia. The incidence for premature placental separation was 0.82% (CI 0.26-1.39%) and the incidence of retained placenta was 1.4% (CI 0 -3.6%). The incidence of dwarfism was 0.7% (CI 0.11-1.28%), with 11 breeders reporting foals that had excluded from the studbook due to dwarfism. The incidence of parrot and sow mouth was 1.22% (CI 0 -2.43%) and 0.45% (CI 0- 0.84%), respectively. The incidence of respiratory disorders (including signs indicative of collapsed trachea and cleft palate) was 2.2% (CI 0.7 -3.7%). The data collected indicate that the incidence of reproductive and congenital disorders in the New Zealand Miniature horse population is lower than expected.

CW, Rogers, EK Gee, E Hangoor, and EC Firth

Proceedings of the New Zealand Society of Animal Production, Volume 66, Napier, 274-278, 2006