NRC panel updates Nutrient Requirements for Horses - DVM
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NRC panel updates Nutrient Requirements for Horses


DVM360 MAGAZINE


The chapter on fats covers needs and research findings, along with the value of fats added to the horse's diet as oils, especially for exercise, and the benefit of the longer-chain fatty acids (omega-3, omega-6).

Omega-3's linolenic from linseed and flax, and DHA and EPA, the 20- and 22-carbon chain EFA's from fish oil, are now finding their way into horse diets via EFA supplements. According to the new NRC, "the data from studies in which horses were fed diets enriched with omega-3 (n-3) fatty acids (linseed, flaxseed or fish oils) have demonstrated modulation of inflammatory mediator synthesis by cells harvested from blood, peritoneal fluid or respiratory secretions.

However, the physiological importance of these findings is unclear and further research is needed to determine the effects of n-3 fatty acid supplementation in the treatment and prevention of inflammatory diseases in horses (e.g., recurrent airway obstruction)."

Protein

Chains of amino acids – proteins – are important constituents of tissues, enzymes, hormones and antibodies. The protein chapter discusses protein digestibility, bioavailability and the need for protein to maintain growth, pregnancy, lactation and exercise.

In summary, "total tract and prececal digestibility vary with protein source and protein concentration in the diet. It is important to consider amino acid profile and prececal digestibility of feedstuffs in addition to total crude protein, especially in rations fed to growing horses and those in high states of production."

Minerals and vitamins

The new volume states that "the horse obtains most of the necessary minerals from forages and concentrates. The mineral content of feeds and the availability of minerals vary with soil concentrations, plant species, stage of maturity and conditions of harvesting.

"The resulting variation in feed mineral content should be considered in assessing an animal's mineral status and formulating appropriate diets, as minerals are elements that cannot be created or destroyed under normal circumstances and must be provided in the ration."

Current information is provided on each mineral's (macro and micro) function, source and factors influencing absorption, signs of deficiency or excess and recommendations.

Besides minerals addressed in the past, new details are provided on special minerals – fluorine, chromium and silicon.

The vitamin requirements of horses "have been estimated using several response variables (e.g., prevention of specific deficiency symptoms, maximizing tissue stores, and optimization of various biological functions)."

The requirements for certain vitamins may change, depending on the response variable used.

For example, the vitamin E requirement to maintain erythrocyte stability in growing horses is different from the vitamin E requirement for an immunostimulatory effect in older horses.

Some vitamin needs – i.e., vitamins A, D, E, thiamin and riboflavin – have been estimated from substantial data, while the data on which the estimates for vitamin K, niacin, biotin, folate, vitamin B12, vitamin B6, pantothenic acid and vitamin C are insufficient for absolute certainty.

Upper limits for all the vitamins are given, defined as the "estimated (based on literature) upper range of vitamin intake that can be presumed to be safe, but not necessarily the maximum tolerance level of vitamin intake (NRC 1987)." For each vitamin discussed, its function, dietary sources, deficiency, toxicity and requirements are noted for maintenance, growth, breeding, gestation, lactation and work/exercise.

Water

Water, the horse's most essential nutrient – critical at a deficiency of 8 percent to 10 percent – is discussed, including its need and the horse's drinking habits.

"Water consumption by horses is episodic and circadian," states the NRC. "Drinking patterns are modified by water source, water availability and age of the horse. Each drinking episode is biphasic – a long draught is followed by sips of shorter duration."


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Source: DVM360 MAGAZINE,
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