The aim of this study was to investigate the effects of graded levels of montmorillonite, a constituent of clay, on performance, hematological parameters and bone mineralization in weaned pigs. One hundred and twenty, 35-d-old crossbred pigs (Duroc×Large White×Landrace, 10.50±1.20 kg) were used in a 28-d experiment and fed either an unsupplemented corn-soybean meal basal diet or similar diets supplemented with 0.5, 1.0, 2.5 or 5.0% montmorillonite added at the expense of wheat bran. Each treatment was replicated six times with four pigs (two barrows and two gilts) per replicate. Feed intake declined (linear and quadratic effect, p< 0.01) with increasing level of montmorillonite while feed conversion was improved (linear and quadratic effect, p<0.01). Daily gain was unaffected by dietary treatment. Plasma myeloperoxidase declined linearly (p = 0.03) with increasing dietary level of montmorillonite. Plasma malondialdehyde and nitric oxide levels were quadratically affected (p<0.01) by montmorillonite with increases observed for pigs fed the 0.5 and 1.0% levels which then declined for pigs fed the 2.5 and 5.0% treatments. In bone, the content of potassium, sodium, copper, iron, manganese and magnesium were decreased (linear and quadratic effect, p<0.01) in response to an increase of dietary montmorillonite. These results suggest that dietary inclusion of montmorillonite at levels as high as 5.0% does not result in overt toxicity but could induce potential oxidative damage and reduce bone mineralization in pigs.

This study was conducted to investigate whether the free fatty acid (FFA) content of yellow grease would influence the performance and carcass characteristics of broiler chicks. A total of 432 one-day-old, male Arbor Acres broilers were randomly allotted to 1 of 4 treatments, with each treatment being applied to 6 pens of 18 chicks. The dietary treatments were based on corn and soybean meal and were supplemented with either soybean oil (2.86% FFA) or yellow grease with a low (2.74%), medium (12.59%), or high (19.05%) FFA content. The fat sources were supplemented at 1.5% of the diet during the starter phase (0 to 21 d) and at 3.0% of the diet during the grower phase (22 to 42 d). From d 0 to 42, the BW gains of chicks fed diets containing soybean oil and yellow grease with 2.74% FFA were similar. As the FFA level in the yellow grease increased, the BW gain of chicks decreased (P < 0.01). The reduction in BW gain appeared to be mediated by a reduction in feed intake. The dressing percentage and the percentage of breast muscle in the carcass were significantly (P < 0.01) lower for broilers fed any yellow grease diet compared with birds fed soybean oil. In contrast, abdominal fat was significantly increased in diets containing yellow grease. These results demonstrate that the performance of birds fed yellow grease with a low content of FFA was essentially equal to that of birds fed soybean oil. However, because yellow grease samples containing FFA levels greater than 2.74% negatively affected bird performance, producers should exercise caution with regard to feeding broilers yellow grease with an elevated FFA content. In 42-d-old broilers, serum total cholesterol and low-density lipoprotein cholesterol levels were elevated in birds fed yellow grease, regardless of the dietary level. In contrast, serum high-density lipoprotein cholesterol and triglyceride levels were unaffected by dietary treatment. Although dietary FFA may influence triglyceride-rich lipoprotein metabolism in broilers, an explanation for the observed effects remains elusive.