Distribution of fatty acids and effect of chemically treated ground, full-fat soybean supplements on tocopherols concentrations in crossbred (Dorset×Suffolk) lambs

Eighteen crossbred (Dorset×Suffolk) feeder lambs (35.0 kg BW) were used to determine the effect of chemically treated ground, full-fat soybeans on concentrations of vitamin E in fresh lambs, as well as to estimate the dependency of individual fatty acids depositions on sites of fat depots. Chemically treated soybeans were prepared with sodium hydroxide, water, and sodium caseinate along with acetaldehyde or diacetyl. Untreated, acetaldehyde-, or diacetyl-treated soybeans contained same levels of α-(20 mg/100 g lipid) and γ-(98 mg/100 g lipid) tocopherols and total lipid (17.3%, DM). Six lambs (three lambs/pen) in each treatment group were fed over 9 weeks with one of soybean supplements (600 g, DM) plus corn basal diet (3.0 kg, DM) and grass hay (1.08 kg, DM) by pen. Samples of the longissimus doris (LD) muscle, intermuscular, back, and kidney fat were obtained from each lamb carcass to determine tocopherols’ contents and fatty acid profiles. Lambs fed untreated soybean supplements had lower (P < 0.05) levels of α-tocopherol in back fat than did lambs fed treated supplements. No differences were found in concentrations of α- and γ- tocopherols in the LD muscle of lambs fed untreated and treated soybean supplements. However, levels of γ-tocopherol were higher (P < 0.05) in the LD muscle of lambs fed the diacetyl-treated supplements than in that of lambs fed the acetaldehyde-treated supplement. Kidney fat had the lowest (P < 0.05) amounts of monounsaturated and polyunsaturated fatty acids of all fat samples followed by the intermuscular and back fat sites. The LD nonpolar lipid had higher (P < 0.05) levels of the monounsaturated and polyunsaturated fatty acids than intermuscular and back fat sites, but lower (P < 0.05) levels than the LD muscle polar lipids. Based on the iodine values of five different fat depots sites, the fat sites could be ranked in increasing level of fat unsaturation as follows: kidney < back < intermuscular < LD nonpolar < LD polar. Results imply that compared with the untreated soybean supplements, the treated supplements protected tocopherols in soybeans from degradation in the rumen of the lambs and increased deposition in lamb tissues. © 2005 Elsevier B.V. All rights reserved.