Kentucky Horse Breeders' Course Covers Reproduction, Deworming

The inaugural Kentucky Breeders' Short Course, hosted by the University of Kentucky Gluck Equine Research Center, drew more than 100 participants to Lexington's Fasig-Tipton Sales Pavilion in January. The two-day short course included participants who represented various breeds from Kentucky and about six other states.

Lecturers from the Gluck Center, other College of Agriculture faculty, and local veterinarians provided expertise on a variety of topics, including nutrition, stallion management, routine care, and pasture management. Some of the topics from the short course are recapped below.

Equine Parasites: A Long Way From Licorice

On the first day Gene Lyons, PhD, professor of classical parasitology in the Department of Veterinary Science, discussed the major types of parasites that affect the horse, including large strongyles, small strongyles, and ascarids.

Large strongyles are the most pathogenic (cause the most disease/damage) of the 100 species of worms affecting horses, often migrating outward from the gut and causing lesions in other organs. Small strongyles are less deadly, but more common, and they can drastically lower digestive efficiency. Ascarids are most problematic to young foals due to their naïve immune systems, and ascarid eggs can survive in pastures for years.

When the effects of worms were first noticed in horses, early scientists treated them with such therapies as licorice, poultry intestines, and their own blood. Fortunately, modern science developed deworming products in the 20th century, but now the result of long-term usage in horses is rearing its ugly head. Parasite resistance has become an area of concern for horse owners in recent years, particularly with regard to popular dewormers ivermectin and pyrantel pamoate.

According to Lyons, certain types of worms might have developed resistance to some medications, but these medications still work against others and should still be used along with a good pasture management program.

Genetic testing in horses

Another featured topic on the first day was genetic testing in horses by Kathryn Graves, PhD, of the UK College of Agriculture's Animal Genetic Testing & Research Laboratory. Since the equine genome was sequenced in 2007, a variety of genetic tests are now available to the public.

The Animal Genetic Testing and Research Laboratory can test for inherited diseases and traits from a hair sample. Horses have been test for common genetic diseases such as hyperkalemic periodic paralysis (HYPP) and severe combined immunodeficiency (SCID), in Quarter Horses and Arabians, respectively, in recent years, but lesser known disorders such as hereditary equine regional dermal asthenia (HERDA) and malignant hyperthermia (MH) are often forgotten.

Graves recommended that breeders and owners screen all breeding stock for genetic disorders common among their breed. She said a positive test should not automatically result in an animal's removal from the herd, since they might carry a recessive form of the gene, allowing the breeder to plan carefully to avoid inheritance of the trait.

Coat color testing is another scientific advantage born from the horse genome sequence. While scientists cannot tell breeders exactly what color their foal will be, they can give a list of possibilities based on samples from the stallion and mare. Color is now better understood than before the sequencing, and researchers even know what combination of genes produce unusual coats such as champagne, sabino, and tobiano.

For more information about genetic testing, contact the UK Animal Genetic Testing and Research Laboratory at 859/257-4757, ext. 81212.

Feeding the Broodmare

Laurie Lawrence, PhD, professor of equine nutrition in the UK's Department of Animal and Food Sciences, discussed the importance of tailoring a mare's diet to fit her various production stages and the time of year.

Before breeding, the mare's body condition score is linked to her fertility. Fleshier mares are more likely to get in foal and take fewer services to do so, which means managers should "let down" mares coming out of their athletic careers and allow their fat stores build up before breeding season.

Spring and fall pastures provide the mare extra nutrients during early and mid-gestation, but winter arrives as her nutrient requirements rise in late gestation. The fetus weight may make the broodmare less inclined to eat as much as she needs, so managers should build up her body condition score in the fall as much as possible (before her nutrient needs rise and while the fetus is lighter).

After foaling, nutritional needs increase with lactation. Young horses can drink up to three pounds of milk per day, which leads not only to energy store depletion in the mare, but also to bone demineralization. During weaning, managers should replenish broodmares' nutrient stores and maintain their body condition while on pasture.

Stallion Management

The second day of the short course was also filled with useful information for farm managers. The first presenter was Ed Squires, PhD, Dipl. ACT, executive director of the Gluck Equine Research Foundation and director of advancement and industry relations, who spoke about the management of stallions.

According to Squires, stallions should not be bred until they are at least 3 years old. Breeding earlier than age 3 can be a mistake because stallions can develop abnormal breeding behavior. Sexual maturity occurs at 5 to 6 years old.

Season is another important factor in the breeding of stallions. The stallion can produce sperm year-round, but he only produces half the amount of semen in the winter as he will in the spring. There is no change in the quality of semen as long as the stallion is ejaculated on a regular basis.

On average, a stallion has sufficient sperm to impregnate seven mares per day in a natural breeding program. Sex drive determines how often the stallion can be used whether it be one, two, or three times a day. A greater sex drive equals more frequent breeding.

Abnormal sexual behavior in both stallions with poor libido and those with excellent libido can include inability to attain an erection, dismounting at beginning of ejaculation, incomplete intromission or lack of pelvic thrust, or repeated intromission, but no ejaculation.

Other speakers at the short course included: Mats Troedsson, DVM, PhD, Dipl. ACT, chair of UK's Department of Veterinary Science and the Gluck Center; David Horohov, PhD, William Robert Mills Chair at the Gluck Center; Valerie Linse, DVM, MS, of Hagyard Equine Medical Institute; Kristina Lu, VMD, of Hagyard Equine Medical Institute; Peter Morresey, BVSc, Dipl. ACT, Dipl. ACVIM, of Rood & Riddle Equine Hospital; Mark Taylor, of Taylor Made Sales; Jill Stowe, PhD, assistant professor in the UK Department of Agricultural Economics; Ray Smith, MS, PhD, extension forage specialist in the UK Department of Plant and Soil Sciences; and Scott Morrison, DVM, of Rood & Riddle Equine Hospital.

The Gluck Center plans to make the Kentucky Breeders' Short Course an annual event. To be added to an e-mail list for information about upcoming equine educational events, contact Jenny Blandford at

Natalie Voss is a UK equine communications intern and undergraduate student in equine science. Alexandra Harper is a UK Equine Communications intern and undergraduate majoring in Communications.

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