755
The evaluation of narasin in grow-finish swine diets
A total of 1,180 pigs were placed on study at approximately 27.0 ± 2.6 kg in a wean-to-finish barn to determine if feeding narasin improves feed conversion and average daily gain during the grow-finish period. Pigs were sorted by gender with the lower 10% being sorted off and the rest gate cut into a total of 48 test pens. Pens were randomly allocated to one of three treatments (control, narasin included at 15 ppm (S1), or narasin included at 20 ppm (S2). Treatments were randomly assigned within a block. Narasin was fed from d 0 to d 63. Diets consisted of 20% dried distillers grain with solubles (DDGS) from d 0 to 42, 20% DDGS from d 42 to 63, and then 0% DDGS from d 63 to market. Diets met or exceeded NRC (2012) recommendations. Pen weights and feed intake information were collected at each diet phase change to allow for calculation of ADFI and G:F by period. Data that were collected and analyzed included: wean-to-finish mortality (non-value pigs), full value pigs, non-full value pigs/culls (sub-standards at weaning and culls sold to secondary market), finishing ADG (pens), finishing ADFI (pens), G:F (pens), and days to 90 kg HCW. Data were analyzed as an incomplete block design using PROC Mixed, and starting average pig weight was used as a covariate. Data were reported as LSMEANS. The feeding of narasin resulted in no differences in ADG, ADFI, or G:F from d 0 to 21 of the study, regardless of inclusion rate. However, feeding narasin at both 15 and 20 ppm inclusion improved G:F from d 21 to 42 (0.431, 0.443 and 0.440, respectively; P < 0.003). Narasin inclusion improved G:F from d 0 to 63 (0.428, 0.435, 0.434, respectively; P < 0.01). Once narasin was removed from the diet at d 63 (approximately 89 kg BW), there were no differences in performance. After the removal of narasin from the diet, there were no further improvements or residual impacts on growth performance. Overall, from d 0 to 63, the feeding of narasin at either 15 or 20 ppm improved G:F when compared to control-fed pigs.
Keywords: grow-finish, narasin, pigs