Mineral and nutrient evaluation of horse feeds and fodder in South Africa.
Little information is available on the nutrient, and particularly the mineral provision of fodder and feed in the South African horse industry. Rational feeding models are not applied, and inadequacies in the ration are compensated for by increments in concentrate feed intake. This constitutes a violation of nutritional physiology in the hindgut fermenter, and consequences of high concentrate feeds are discussed. Nutrient provision from the fodder portion of the ration is not considered when feed formulation and raw material selection occur. Consequently, feed and fodder samples were collected from a variety of sources and subjected to mineral and nutrient analyses to elucidate the extent of the problem as it pertains to the meeting of requirements in horses of different life stages and work rates. 99 fodder samples were analysed and Principle Component Analyses (PCA) were conducted. Three statistically diverse groups of fodder were identified - kikuyu and lucerne contain high digestible energy and crude protein content which differentiates them from other grasses. Mineral provision from the three groups is diverse. There is justification for developing fodder specific feeds for horses based on these fodder types. 64 concentrate horse feeds were analysed by PCA to determine groups of similar nutrient content. Balancer and fibre feeds could be differentiated from other feeds based on their fibre and CP content. The balance of the feeds could not be segregated into their life stage or work purpose groups and statistically fell into the same feed group. Correlation matrices between advertised and actual nutrient content revealed inconsistencies between feed factories. Mineral provision in the feeds is a function of the factory they are produced in and not as a function of the life stage and work purpose of the feeds. Major mineral provision in horse feed is erratic and 15 out the 64 feeds exhibited inverse Ca:P ratios and very few have sufficient Mg to balance the Ca:Mg ratio required by horses. Horse feeds contain excess Fe and are often deficient in Cu and Zn while Mn provision is adequate. It is evident that brand or factory plays a more important role in mineral nutrition of horses, than life stage or work rate. Feed formulation strategies appear to be least cost based with little regard for horse requirements evident in the final feed products. Ration evaluation revealed that grasses are able to provide sufficient DE and CP for horses in light work while kikuyu and lucerne can support horses up to the moderate work category. All fodder types require mineral supplementation to provide absolute mineral levels and balance between minerals to horses. A comparison of five equine life stage reconstituted rations were then constructed and work ration scenarios demonstrated that DE and CP provision in most instances was sufficient, although CP overprovision did occur. Mineral levels were erratic and in the stud and race groups, feeds produced inverse Ca:P ratios. This could affect skeletal integrity and cause lameness – two issues often found in racehorses, leading to wasted training days and horse breakdowns. Major overprovision of Fe occurs in all the rations with concomitant deficiencies of Cu and Zn. This imbalance could have negative consequences in the horse in terms of immune and anti-oxidant systems. It is evident from the study that feeds are poorly formulated and feeding strategies currently employed in SA are flawed in their provision of health-promoting nutrition to horses. New strategies and feed formulation goals need to be investigated and the feeding of horses in SA needs to be restructured to respect the horse as a hindgut fermenter with an absolute requirement for fodder and to provide correct mineral balance in rations.
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