INFLUENCE OF FLOOR SPACE ALLOWANCE AND DIETARY SELENIUM AND ZINC ON GROWTH-PERFORMANCE, CLINICAL PATHOLOGY MEASUREMENTS AND LIVER-ENZYMES, AND ADRENAL WEIGHTS OF WEANLING PIGS

Crossbred weanling pigs (n = 96, average initial weight, 8.4 kg) were used in a 6-wk trial using a 2 x 2 x 3 factorial arrangement of treatm ents to determine the effects of floor space allowance (.28 and .14 m2 /pig), dietary Se (40 and 200 ppb), and dietary Zn (30, 80, and 250 pp m) on growth performance, clinical pathology measurements, serum miner als, and enzymes, liver enzymes, and adrenal weights. Pigs (four/pen) were given ad libitum access to feed and water. Body weight and feed c onsumed were recorded weekly, and heparinized blood samples were taken for the various assays. Three pigs per pen were killed at the end of the trial for gross examination of organs and tissues and for liver en zymes assays. Pigs housed with restricted floor space ate 21% less (P < .001) and grew 18% more slowly (P < .001) than pigs housed with adeq uate floor space, but their gain:feed ratio was 4% higher (P < .08). G rowth performance was not influenced by dietary Se and Zn treatments. There was no mortality in any of the treatments, and no visible gross abnormalities in organs and tissues at necropsy examination, except th at more musculoskeletal bruising was observed for pigs housed with ade quate floor space. This finding is supported by higher serum K concent ration and creatine phosphokinase activity for pigs housed with adequa te floor space. Corticosteroid activity and adrenal weights were simil ar for all treatments. Concentrations of blood Se and glutathione peri oxidase were positively related to dietary Se levels, and serum Zn con centration was related to dietary Zn levels. Other effects of dietary Se and Zn on clinical pathology measurements were minimal and usually unexplained. Most two-way interactions of Se and Zn with floor space a llowance were nonsignificant, which suggests that the main effects of Se, Zn, and floor space were independent. Some hematologic values, ser um metabolites, serum minerals, and serum and liver enzymes were decre ased or increased, which is suggestive of stress of pigs housed with r estricted floor space. However, most values were unchanged, and a few changed in the direction to suggest benefits of restricting space; all values were within an expected normal range.