EFFECTS OF RATION AND INSIDE VERSUS OUTSIDE HOUSING ON PLASMA LEVELS OF ASCORBIC ACID, LACTIC ACID, GLUCOSE AND CHOLESTEROL IN HEREFORD STEERS WINTERED UNDER PRACTICAL CONDITIONS

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Abstract
The relationship between housing and blood plasma concentrations of ascorbic acid, lactic acid, glucose, and cholesterol were studied with 60 yearling Hereford steers. One half of the steers were wintered (November–April) inside a barn and the other half in an open yard. Each group was subdivided into two treatments and fed hay or hay plus cracked barley. During a pre-experimental period (July–October) all steers were on pasture. The steers fed hay + grain gained approximately twice as much as the steers fed hay only. However, the steers housed inside gained only slightly more than those kept outside. There were only small differences in feed intakes between the inside and outside steers. Levels of all measured metabolites fluctuated during the pre-experimental period (July–October) when all steers were on pasture. During November–January, animals wintered inside showed a larger decrease in plasma glucose and increase in plasma ascorbic acid than did those wintered outside. Plasma lactic acid and cholesterol levels also decreased during this time but the differences between rations were larger than those between types of housing; the levels were lower in animals fed hay plus barley than in those fed hay only. No direct correlation between plasma levels of lactic acid, glucose, and cholesterol and cold stress were established. However, some changes in plasma levels of ascorbic acid might have been associated with cold exposure.