METACARPAL AND METATARSAL DIMENSIONAL, MECHANICAL AND MINERAL CHARACTERISTICS OF CROSSBRED BOARS AS INFLUENCED BY NUTRITION AND AGE

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Abstract
Crossbred boars (35 days of age) were assigned in a 2 × 2 factorial arrangement to dietary energy (ad libitum and 75% of ad libitum) and mineral-vitamin (100 and 150% of National Academy of Sciences-National Research Council (NAS-NRC 1979) recommendation) intakes to determine the effects on metacarpal and metatarsal dimensional and mechanical characteristics and chemical composition. The third and fourth metacarpal and metatarsal were removed from boars necropsied at 15-day intervals from 85 to 295 days on test. Bone weight, length, shaft diameter and wall thickness increased with age, while bone ether extract decreased and ash content increased. As age increased, percentage Ca content of bone ash increased, P content remained unchanged and Mg, Cu, Zn, Fe and Mn content decreased. At an equal age, bone weight, length, shaft diameters and mechanical characteristics were greater for ad libitum-fed boars; however, weight-correction produced trends in favor of the limit-fed boars. Although mineral-vitamin level had no effect on the weight, length or diameter of bones, the 150% NAS-NRC mineral-vitamin level increased bone wall thickness and bone mechanical properties, with these effects more prominent in the metatarsals than the metacarpals. Metatarsals were heavier and longer than metacarpals. Percentage of ether extract was higher for ad libitum-fed boars. The 150% NAS-NRC mineral-vitamin level increased percentage bone ash and bone ash Ca level, while dietary energy or mineral-vitamin levels failed to affect content of any of the other bone ash minerals examined. The results of this study indicate that changes in bone characteristics resulting from ad libitum feeding are due to a larger body size at a given age, while higher values for mechanical characteristics can be obtained by elevation of dietary mineral-vitamin levels. Key words: Boars, energy intake, minerals, vitamins, bone characteristics, bone mineral composition