Researchers at the Maxwell H. Gluck Equine Research Center at the University of Kentucky explored the causes of death of 259 foals among the 1294 foetal, neonatal, and juvenile horse cases presented at the Livestock Disease Diagnostic Center from September 2004 to August 2005.

Those cases included only those that resulted from a live birth and where death occurred under 180 days.

Most of the deaths occurred by 30 days of age (174 of the 259 cases, or 67%), the researchers wrote in Equine Disease Quarterly.

Of these 174 cases, the top five causes of death included septicemia, or blood poisoning (44 foals, or 25% of cases), musculoskeletal issues other than rib fractures (29 foals, 17%), pneumonia (25 foals, 14%), gastrointestinal problems (19 foals, 11%), and rib fractures (18 foals, 10%).

All deaths from rib fractures occurred in this age bracket. (Rib fractures can result from multiple factors, including dystocia and trauma.)

Among all foals up to 180 days of age, of the 259 cases, septicaemia was the predominant killer, causing 21% of all deaths (54 of the 259 foals). Of these, Escherichia coli (17 out of 54, or 31.5%) was the primary single organism grown from cultures obtained from septic animals. However, mixed cultures (17 out of 54 animals, or 31.5%) were equally significant.

Deaths from musculoskeletal problems accounted for 51 (20%) of the 259 cases, with 33 cases attributed to fractures. Trauma, other than those resulting in fractures, accounted for an additional nine cases of mortality.

When gastrointestinal problems (42 cases, or 16%) were identified as the cause of death, ulcers (9 out of 42, or 21.5%) and colitis (8 out of 42, or 19%) were the top two diagnoses.

Of the 15% of cases attributed to pneumonia (40 of 259), cultures failed to yield growth in 40% (16 of 40) of the cases. This could be attributed to treatment with antibiotics or to a viral or fungal etiology. Rhodococcus equi was cultured from 13 of the 40 (33%) pneumonia cases.

Researchers Dr Tracy Sturgill and Dr Craig Carter said while the majority of the musculoskeletal causes cannot be prevented, improvements in orthopedic therapy allow for better outcomes.

"Prevention may be the best option for reducing deaths due to infectious etiologies, as foals are uniquely susceptible to infectious diseases," they wrote.

"Therefore, it becomes imperative that veterinarians continue to educate horse owners and farm managers about vaccination, hygiene, and early recognition of clinical signs. More inclusive studies are currently being investigated on foal mortality."