INFLUENCE OF LEVEL OF ENERGY AND NUTRIENT INTAKE BY MARES ON REPRODUCTIVE PERFORMANCE AND ON BLOOD SERUM COMPOSITION OF THE MARES AND FOALS

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Abstract
An experiment, conducted at Olds College, involving seven pregnant and five open half-Arabian (half-sib) mares had the primary objective of evaluating the adequacy of National Academy of Sciences–National Research Council (NAS–NRC 1973) nutrient requirements of horses as they applied to mares receiving minimal shelter under central Alberta winter conditions. Mares were randomly assigned to two groups, the first receiving a diet formulated to meet NAS–NRC requirements and the second the same diet at a level of 85% of the former by weight. The dietary regimen was maintained from mid-gestation until 30-days post-partum. No significant (P < 0.05) differences were found for weight losses during pregnancy or for apparent digestibility of energy or nitrogen in mares, or for birth weight and 30-day weight of foals. Of the 12 blood serum constituents measured in both mares and foals, only three constituents varied significantly (P < 0.05) between groups. Blood urea nitrogen and cholesterol concentrations were higher for group 2 than for group 1 foals. Serum protein concentration was higher in group 1 than in group 2 mares. Colostrum and milk samples differed only in milk protein level which was higher (P < 0.05) for group 2 than for group 1 mares. During the phases of reproduction measured it was concluded that the lower level of energy and nutrient intake (85% of NAS–NRC recommended requirements) did not influence performance of pregnant mares and their foals.