Introduction Like people, horses need the proper nutrition to be healthy and maintain a correct balance of the various chemicals, vitamins, minerals and nutrients in their bodies. This is especially important for both mares and stallions during the breeding season and during a mare's entire pregnancy. When certain imbalances and deficiencies exist, it can result in decreased fertility, reduced conception rates, and increased incidents of miscarriage.

General Equine Nutrition Providing optimal nutritional input will enhance reproductive performance. High quality protein intake concurrent with energy intake to maintain a body condition score (BCS) of 5.5 - 7.5 is critical for reproductive success. Due to increased nutrient requirements for breeding stallions and mares in late gestation, a high quality (nutrient dense) feeding program must be utilized to maintain an appropriate BCS. Supplementation should not be used to try to make a poor ration excellent. In addition to protein and energy needs, vitamin and mineral intake needs to be optimized. Mares in the last trimester of gestation need approximately 85% more calcium and phosphorus than in the first two trimesters.

For more information on equine nutrition, read the following articles:

Equine Therapeutic Nutrition I:
Nutritional Supplement Ingredients, The Good, The Bad and The Useless

Equine Therapeutic Nutrition II:
Customizing an Enteral Nutrition Program for the Critical Care Patient

Vitamins, Minerals & Trace Minerals Several vitamins and minerals are associated with increased reproductive performance in both males and females. The form that minerals are supplied in is critical. All of the minerals listed below have reported toxic effects on reproduction when exposure is to the inorganic forms and beneficial effects when exposure is from organic forms.

BIOTIN has been heavily researched in many species with respect to its effect on female reproductive performance parameters and gamete development. The most well documented effects are on sow conception rates and return to estrus post parturition. Many effects of biotin on prenatal development have also been established.

BORON is a good example of a nutrient that is beneficial to the spermatogenic cycle, embryonic, and fetal development when provided in an organic form. However, with exposure to an inorganic form, testicular damage & mutagenic effects are common. Boron is involved in the production of many sex hormones.

CHROMIUM deficiency can cause a decrease in sperm count, but exposure to inorganic forms can cause severe testicular damage, improper testicular development, or neoplasia. Many positive effects on female reproduc-tive efficiencies and lactation improvements have been found.

FOLIC ACID plays critical roles in the normal reproduction of cells. A deficiency of folate has been associated with defects in pre-implantation embryos and the neural, skeletal, digestive and urinary tracts of developing fetuses.

MANGANESE plays a large part in attachment and conception. Exposure to inorganic Mn causes reduced male fertility.

THIAMINE is crucial to the viability and motility of sperm. Normal development in the uterus depends on the presence of thiamine.

ZINC deficiency has negative effects on testosterone levels and sperm development. Exposure to inorganic zinc causes harm to reproductive tissues.

The Benefits of Glucosamine Sulphate Glucosamine is a very small "building block" type nutrient that is found ubiquitously in mammalian tissues. It is actively concentrated in some tissues such as connective tissues and all mucosal linings. Many important reproductive cells and structures contain large concentrations of glucosamine. Simply identifying a basic nutrient that is heavily involved with several stages of reproduction does not make it a good supplement. Most of the glucosamine containing structures mentioned contain the acetylated form of glucosamine linked together by sulphur bonds. However, this form has been shown to be highly utilized in the digestive tract, with little being absorbed. Any absorption of this form occurs via passive diffusion. Glucosamine Sulphate is, however, absorbed actively from the digestive tract using a glucose transporter. This active absorption has been documented to be over 90% efficient within 30 minutes in at least 3 species. The acetylation of Glucosamine Sulphate as well as its conversion to galactosamine is readily performed in most tissues.

Beware of Certain Forms of Supplementation There are several basic molecules that are present in many different reproductive cells and tissues. Most of these are not available in a purified, supplemental form. Others that may be available are either not economical or are not absorbed efficiently. Supplying large amounts of a purified nutrient may not positively affect the desired systems and can have negative effects. There are some anecdotal accounts of both Chondroitin Sulfate and injectable PSGAG's causing a decrease in stallion reproductive performance. No verification of these theories is in the literature, but a reaction to these larger molecules by some individual stallions may explain these reports.