Growth and carcass characteristics of lambs passively immunized with antibodies developed against ovine adipocyte plasma membranes

Polyclonal antisera were collected from a mare immunized with ovine adipocyte plasma membranes. Ten crossbred wether lambs received three consecutive daily intraperitoneal injections of horse antisheep adipocyte plasma membrane immunoglobulin (ASIg) or nonimmune serum immunoglobulin (NSIg). Each injection delivered 1.5 ml serum Ig protein equivalent to either 53.4 mg ASIg or 51.1 mg NSIg per kilogram of live body weight. Lambs were housed in individual metabolic crates during the 28-d experiment and given ad libitum access to a pelleted, high-concentrate diet. Daily feed consumption was monitored individually over the experimental period and N retention was determined. Blood was collected on d 0, 4, 7, 14 and 28 for determination of nonesterified fatty acid (NEFA), triacylglycerides (TG) and hematocrit. At the conclusion of the experiment, lambs were slaughtered and carcasses were evaluated. Passive immunization against sheep adipocyte plasma membrane reduced (P less than .05) perirenal adipose tissue weight and decreased ether extract content of both subcutaneous and perirenal fat. Treatment tended to reduce average backfat thickness (24%) and estimated kidney pelvic fat (16%). Treatment with ASIg reduced (P less than .05) blood plasma NEFA but did not alter blood TG or hematocrit values. Average daily weight gain was lower (P less than .01) in the ASIg-treated group. However, the efficiency of carcass production, measured as carcass weight, was not affected by ASIg treatment.