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 treatments 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 ppm) on growth performance, clinical pathology measurements, serum minerals, and enzymes, liver enzymes, and adrenal weights. Pigs (four/pen) were given ad libitum access to feed and water. Body weight and feed consumed 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 enzymes assays. Pigs housed with restricted floor space ate 21% less (P < .001) and grew 18% more slowly (P < .001) than pigs housed with adequate floor space, but their gain:feed ratio was 4% higher (P < .08). Growth 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 that more musculoskeletal bruising was observed for pigs housed with adequate floor space. This finding is supported by higher serum K concentration and creatine phosphokinase activity for pigs housed with adequate floor space. Corticosteroid activity and adrenal weights were similar for all treatments. Concentrations of blood Se and glutathione peroxidase were positively related to dietary Se levels, and serum Zn concentration 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 allowance were nonsignificant, which suggests that the main effects of Se, Zn and floor space were independent. Some hematologic values, serum metabolites, serum minerals, and serum and liver enzymes were decreased or increased, which is suggestive of stress of pigs housed with restricted 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.