Effect of confinement method on physiology and production of gestating gilts

Four replicates of 12 Dekalb crossbred gilts were blocked by breeding dates and randomly allotted to four treatments: tethers, crates, loose stalls and dirtlot. Ear vein cannulas were established and blood samples obtained from each gilt on d 2, 9 and 65 of treatment Blood cell counts, blood chemistry profile (12 items), triiodothyronine (T3), thyroxine (T4), basal cortisol and cortisol in response to administration of adrenocorticotrophic hormone (CR-ACTH) were determined. Tethered gilts had depressed CR-ACTH at d 2, probably related to their active struggles against the tethers during the initial period following restraint. Triiodothyronine was greatest in gilts housed loose with access to stalls, probably reflecting the fighting that often occurred among those gilts, and was lowest in gilts on dirtlot on d 2. Glutamic pyruvate transaminase was elevated in gilts on dirtlot at d 9 and 65, probably a result of their increased exercise. Behaviors indicative of "restlessness" were negatively correlated with CR-ACTH at d 9 and 65. Gilts were initially stressed when restrained in tethers, but their CR-ACTH became equivalent to that of gilts in other housing by 9 d. Housing had no effect on production.