Effects of restricted growth rate, elevated vitamin and mineral levels and aging on bone growth, histological integrity and biochemical composition of articular cartilage in boars
St. George, Roger L.
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The effect of restricting energy intake (ad libitim vs. 75% ad libitum) elevation of vitamin and mineral levels (150% NRC vs 100% NRC) and the effects of aging on bone growth, histological lesioning and biochemical composition of articular cartilage from growing boars was examined. Growth of the radius and tibia was characterized by radiography at eight equal time points from 110 to 330 d of age. Although ad libitum-fed boars had larger bones in most cases, calculation of weight corrected differences suggested that restriction of energy resulted in lover weight gain but that reduced energy intake slightly increased the rate of bone growth of the restrict-fed boars. Although elevation of vitamin and mineral levels resulted in a few scattered differences in bone size, no consistent trends were evident. Neither restriction of energy intake nor elevation of vitamins and minerals had any consistent effect on the reduction of histological lesion severity. Age, expressed as days on test, produced no definite trends toward increasing or decreasing frequency of histological lesions. The frequency and severity of gross lesions were unaffected by altered energy or vitamin-mineral levels, however, a sevenfold age-related increase in frequency of gross lesions was observed over time. Uronic acid content of the articular cartilage from the femur was greater for the restrict-fed boars, however, uronic acid content of cartilage from the humerus and radius tended to be greater for the ad libitum fed boars. Elevation of vitamins and minerals had no effect on uronic acid content of articular cartilage from the femur, humerus or radius. Uronic acid content of articular cartilage decreased consistently with age throughout the trial period. Galactose and hydroxyproline levels in cartilage samples from the femur, humerus and radius were generally unaffected by the imposed dietary treatments. Galactose levels were unaffected by age. Hydroxyproline content of cartilage from the radius and humerus increased with age, whereas, cartilage from the femur remained unchanged throughout the experimental period. No changes in percentage fat-free dry weight of articular cartilage samples from the femur, humerus, or radius due to treatment or age were evident. Articular cartilage from the radius had a higher percentage of fat-free dry weight than either the humerus or femur. Articular cartilage from the radius also contained less uronic acid than the femur or humerus. Galactose content of the radius was less than that of the humerus, however, galactose levels of the femur and radius did not differ. Hydroxyproline levels were similar among all areas sampled. In summary, skeletal growth rate was slightly greater for restrict-fed boars after weight correction, however, elevation of vitamins and minerals had no overall impact on any parameters measured. Age had a more pronounced, though inconsistent influence on lesion frequency, severity, and biochemical composition of the articular cartilage than the imposed dietary treatments.
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