Pre-Slaughter Feed Acidification with Feed Grade Sodium Formate Reduces Microbial Abundance in Finishing Pigs

Forty-eight pigs were selected from a performance study looking at effect of different dosing regimens on animal performance in a commercial swine barn. As part of the performance trial, feed was treated with 0, 3, 6, or 9 g/kg of acidifier starting 2 weeks prior to first cuts (treatments 1, 2, 3, and 4). Fecal and cecal samples were collected 1 week prior to slaughter to ascertain the effect of feed acidification with feed grade sodium diformate (Amasil® NA) on microbial abundance. Digesta samples were analyzed for aerobic plate count (APC), Enterobacteriaceae, total coliforms, and E. coli by Eurofins Scientific (Des Moines, IA). Microbiology data (Log10 cfu/g) were analyzed by sampling site using JMP (13.1.0) according to a Generalized Linear Model, with a Poisson distribution and log link-function, with fixed effect of treatment. Single degree-of-freedom contrasts were used to compare each acidified treatment to the unacidified control (α = 0.05). Acidification with 3 and 6 g/kg tended to reduce cecal APC by 1.2 and 1.1 log10 cfu/g, respectively (P = 0.07). Total coliforms, E. coli, and Enterobacteriaceae counts were decreased by 1.2 to 1.6, 1.3 to 1.7, and 1.6 log10 cfu/g, respectively, relative to the control (P < 0.05). Feed acidification reduced colonic APC, total coliforms, E. coli and Enterobacteriaceae by between 1.3 to 1.9, 1.9 to 2.7, 3.0 to 3.9, and 1.8 to 2.6 log10 cfu/g, respectively, relative to the control (P < 0.01). Results indicate that acidification of finisher feed in the weeks immediately pre-slaughter can reduce microbial load of pigs.

Table 1. Microbiological analysis of digesta from finishing pigs fed Amasil® NA treated feed.
	Treatment				P-values
	1	2	3	4	1 vs 2	1 vs 3	1 vs 4
Cecum, log10 cfu/g
Aerobic Plate Count	4.77	3.70	3.54	3.70	0.07	0.07	0.68
Total Coliforms	3.28	1.73	2.13	1.87	0.02	0.02	0.03
E. coli	2.02	0.33	0.37	0.70	0.02	0.02	0.03
Enterobacteriaceae	3.82	2.18	2.19	2.20	0.02	0.02	0.02
Colon, log10 cfu/g
Aerobic Plate Count	5.76	4.48	3.88	4.05	<0.01	<0.01	<0.01
Total Coliforms	4.61	2.69	2.53	1.90	<0.01	<0.01	<0.01
E. coli	3.89	0.00	0.89	0.70	<0.01	<0.01	<0.01
Enterobacteriaceae	4.80	3.04	3.02	2.21	<0.01	<0.01	<0.01