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The effects of feeding narasin (Skycis) or virginiamycin (Stafac) on summer finishing pig performance
The purpose of this study was to determine the effects of narasin (NAR; Skycis®, Elanco Animal Health, Greenfield, IN) or virginiamycin (VIR; Stafac®, Phibro Animal Health, Teaneck, NJ) on the summer growth and harvest performance of grower-finisher pigs. Upon arrival (May 23, 2014), 360 barrows (Smithfield Premium Genetics, Rose Hill, NC) were weighed (initial BW 23.0 kg) and randomly allocated to one of three treatments: Control (CON), NAR 15 ppm, or VIR 11 ppm. Each treatment had 15 pens containing 8 pigs per pen (0.87 m2 per pig). Housing consisted of slatted flooring, mechanical ventilation and sprinklers activating at 28.9°C. Each treatment consisted of a sequence of 4 corn-soybean meal diets fed from d 0 to 90 and the CON diet fed to all treatments d 90 to harvest. Pigs were weighed on d 0, 28, 56, 77, 90, and harvest to determine start weight, phase weights, harvest weight, and ADG. Feed issuance and weigh backs were recorded in order to determine ADFI and G:F. At d 96, pigs were individually tattooed and transported to a commercial packer for harvest and collection of hot carcass weight. Data were analyzed in SAS using PROC GLM. Fixed effects included treatment and room. Pen was the experimental unit. From d 0 to 28, pigs fed NAR had greater (P<0.01) ADG than CON and VIR and greater (P<0.01) ADFI than CON and VIR. From d 28 to 56, pigs fed NAR had greater (P=0.01) ADG than CON and tended (P=0.07) to have greater ADG than VIR. Pigs fed NAR and VIR had greater (P<0.05) G:F from d 56 to 77 vs. their CON fed counterparts. Overall ADG was greater (P<0.05) for pigs fed NAR than for pigs fed the CON and VIR diets. Pigs fed NAR had greater (P<0.05) overall G:F than CON and numerically better G:F than pigs fed VIR. The percentage of pigs completing the study and mortality did not differ (P>0.05 between treatments. At harvest, pigs fed NAR had greater (P<0.01) carcass weight and yield than CON and VIR, while body weight CV was lower (P<0.05) for pigs fed NAR vs. CON and VIR diets. Results showed that supplementing diets with NAR during the summer significantly improved growth performance and carcass characteristics of finishing pigs.
Keywords: narasin, pig, virginiamycin