The only thing more exciting than a positive pregnancy test, is the coming of spring and an impending foaling!
The nutrition of the late pregnant mare affects: the foal’s immunity against diseases, the risk of diarrhoea in the young foal, foal growth rate, and bone growth and the risk of bone and joint diseases (developmental orthopaedic disease - DOD) in the weanling and yearling — as well as size and weight at birth, we must be concerned about soundness.
DOD includes the debilitating bone diseases which afflict an increasing number of young horses: angular limb deformities – including bent and twisted legs; contracted tendons and club feet; epiphysitis and joint enlargements; bone cysts and OCD; thin and poor quality bone, and cartilage damage. The potential to develop DOD develops in late pregnancy and one factor is imbalanced diets.
The key nutrients for late pregnant mares are protein (including the amino acid levels in the protein), vitamins A and E, omega 3 oils and iodine, selenium, zinc, copper, in addition to usual requirement for vitamins and minerals.
Pregnancy increases the risk of laminitis and pregnant mares don’t need lots of energy – in fact, a high energy diet can be dangerous! The danger arises because mares become insulin-resistant during pregnancy – this means her muscles and liver resist the effects of insulin and don’t absorb much glucose from the blood – allowing the glucose to be diverted to the growing foal. Insulin-resistance puts mares at a much higher risk of laminitis (due to reduced glucose uptake by the laminae in the hooves) – compounded by the increasing body weight loaded onto the mares hooves, and if we make the mare fat on top of all this, we have primed her to develop laminitis. The bottom line is to avoid starch-energy-sugar-rich feeds and grains.
Added stress is placed on the hooves in wet weather – foot abscesses, white line disease, wall cracks and seedy toe increase in winter and spring when wet muddy conditions reduce the ability to exercise and create unhygienic conditions. To prevent weaknesses and subsequent pain, lameness and expense, it is essential to provide correct zinc, calcium, biotin and protein and to avoid excesses of selenium and vitamin A - both of which have been linked to hoof cracks and poor quality wall.
Pregnancy doesn’t increase energy needs – it does however increase the demand for protein to build the muscles, bone, red cells etc in the growing foal. High quality protein with the right amino acid balance is again important for cycling after foaling - mares on high quality protein diets had higher levels of reproductive hormones, began cycling sooner and ovulated 4-6 weeks earlier than mares on low quality protein diets.
As well as putting mares in danger of becoming overweight, unbalanced feeds also increase the risk of colic if the mare has to eat large amounts just to get the right amounts of trace minerals and protein. Digestive capacity is reduced as the growing foal occupies more of the mare’s abdomen. The incidence of abdominal rupture, colic, caecal impaction, torsions and ruptures, is higher in mares in the peri-foaling period than at any other time.
Being overweight also increases the risk of a higher than ideal foal size and birth weight - plus the risk of the mare ‘running milk’ and losing colostrum, and over-producing milk after foaling – increasing the chance of foal diarrhoea. Protection from diarrhoea and other diseases increases if mares are vaccinated against tetanus, Hendra and other viruses (check with your vet re the local disease risk) and brought to the foaling location at least one month before foaling. This allows her to confer some immunity to organisms in the foaling environment that cause joint ill, scours and septicaemia. The incidence of diarrhoea in foals is up to 63% higher in foals born to mares bought to new locations for foaling, than it is in foals of resident mares.
And, don’t forget worming! One of the wonders of nature is that just before foaling any adult worms carried by the mare, begin a rapid increase in egg production – ensuring maximum contamination of pasture and greatly increasing the chance of infection of the foal and survival of the parasites for another generation. In addition, the milk worm, strongyloides westeri, concentrates in the mammary gland, increasing chances of transmission to the next generation of horses and perpetuation of the next generation of worms.
Finally check paddocks for poisonous plants and processionary caterpillars – both of which can cause late-term abortions.
Look after your mares well as they enter the last months of pregnancy and wishing you all much success and joy with your new generation.
EQUINE CLINICAL NUTRITION
Dr Jennifer Stewart