The effect of narasin on apparent nitrogen digestibility and large intestine volatile fatty acid concentrations in finishing swine.

The effect of narasin on apparent nitrogen and dry matter digestibilities and large intestine VFA concentrations in finishing swine was investigated. The study used 21 crossbred barrows averaging 72 kg. Seven blocks were formed on the basis of pretreatment dry matter digestibility, and barrows were randomly assigned to three treatments in each block. Treatments consisted of a control (C) and narasin (N15 and N30) applied at 15 and 30 ppm, respectively. Fecal and urine samples were collected. Upon the completion of the digestibility work, intestinal samples were taken from three locations, and VFA concentrations for each animal were measured. Weight gains for the N15 and N30 treatments were increased 3.0 and 6.0% (not significant), respectively, over control. Fecal nitrogen was decreased (P < .05) in the narasin-fed barrows, and apparent nitrogen digestibility was increased (P < .05). Neither nitrogen retention nor urinary nitrogen excretion was altered (P > .05) due to narasin. There were no increases (P > .05) in apparent dry matter digestibility due to narasin. Analysis of pooled colon samples showed an increase (P < .05) in the concentration of propionic acid in relation to acetic and butyric in the narasin-fed barrows. Butyric acid was reduced (P < .05) in the transverse colon of narasin-fed barrows. In summary, narasin administration to finishing barrows resulted in improved apparent nitrogen digestibility, thus decreasing fecal nitrogen, and increased relative concentrations of propionic acid in the large intestine.