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Impact of narasin (Skycis) on live performance and carcass traits of pigs sold in a three-phase marketing system
The objective was to evaluate the effect of feeding narasin (Skycis, Elanco Animal Health, Greenfield, IN) on growth performance, efficiency, and carcass characteristics of finishing pigs sold in a 3-phase marketing system. Pigs (N=1,232) were housed in 56 single sex pens, divided into two even blocks based on age. Within each block, 14 pens were fed either 0 ppm narasin (control) or 15 ppm narasin for the final 85 days of finishing (initiated at an average of 52.95 kg BW). In each pen, 18% of pigs were sold in the 1st marketing group (day 64 of dietary treatment), 50% were sold in the 2nd marketing group (day 78), and 32% were sold in the 3rd marketing group (day 85). Data were analyzed as a randomized complete block design with pen as the experimental unit. The model included fixed effects of diet, sex, and their interaction. Block and replicate nested within block were random variables. Carcass data from marketing group 3, block 2 was not collected due to inclement weather. Narasin had no effect on growth performance traits (P>0.05) in phases 1 (days 1-28) or 2 (days 28-56). Regardless of sex, pigs fed narasin tended to have a 1% greater overall ADG than pigs fed the control diet (P=0.07; 0.99 v. 0.98 kg) and had a 1.2% greater G:F than pigs fed the control diet (P=0.03; 0.347 vs. 0.343). In the 1st marketing group barrows fed narasin had greater ADFI than gilts fed the same diet (P=0.03). Overall pooled effects of feeding narasin tended to reduce (P=0.08) loin depth by 1.1% (60.00 v. 60.66 mm), however no effects of narasin on carcass weight, yield, or leanness were observed in marketing groups 1 and 2 (P≥0.21). In marketing group 3, barrows fed narasin had a 0.9 percentage unit reduced estimated lean compared with barrows fed control (P=0.04; 51.1 v. 52.0%). Regardless of sex, estimated lean of pigs from the 3rd marketing group fed narasin was 0.55 percentage units (P<0.01; 52.19 v. 52.74) less than controls. This is likely due to narasin pigs from the 3 marketing group being 0.98 mm fatter (P=0.03) than controls (21.72 v. 22.70). Feeding narasin for up to 85 days had little impact on growth performance within marketing group, but did increase overall ADG. Although differences were observed within marketing group, overall pooled results suggest feeding narasin did not change carcass characteristics of finishing pigs.
Keywords: carcass, growth, narasin