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1、RESEARCHOpen Access Feed additives decrease survival of delta coronavirus in nursery pig diets Katie M. Cottingim1, Harsha Verma2, Pedro E. Urriola1, Fernando Sampedro2, Gerald C. Shurson1 and Sagar M. Goyal2* Abstract Background: Feed contaminated with feces from infected pigs is believed to be a p
2、otential route of transmission of porcine delta coronavirus (PDCoV). The objective of this study was to determine if the addition of commercial feed additives (e.i., acids, salt and sugar) to swine feed can be an effective strategy to inactive PDCoV. Results: Six commercial feed acids (UltraAcid P,
3、Activate DA, KEMGEST, Acid Booster, Luprosil, and Amasil), salt, and sugar were evaluated. The acids were added at the recommended concentrations to 5 g aliquots of complete feed, which were also inoculated with 1 mL of PDCoV and incubated for 0, 7, 14, 21, 28, and 35 days. In another experiment, do
4、uble the recommended concentrations of these additives were also added to the feed samples and incubated for 0, 1, 3, 7, and 10 days. All samples were stored at room temperature (25 C) followed by removal of aliquots at 0, 7, 14, 21, 28, and 35 days. Any surviving virus was eluted in a buffer soluti
5、on and then titrated in swine testicular cells. Feed samples without any additive were used as controls. Both Weibull and log-linear kinetic models were used to analyze virus survival curves. The presence of a tail in the virus inactivation curves indicated deviations from the linear behavior and he
6、nce, the Weibull model was chosen for characterizing the inactivation responses due to the better fit. At recommended concentrations, delta values (days to decrease virus concentration by 1 log) ranged from 0.621.72 days, but there were no differences on virus survival among feed samples with or wit
7、hout additives at the manufacturers recommended concentrations. Doubling the concentration of the additives reduced the delta value to0.28 days (P1, the curve is convex (it forms a shoulder-shaped response), if n 1, the curve is concave (it forms a tail-shaped response), and if n=1, the curve is a s
8、traight line and can be described by a lin- ear model. Statistical analysis Three replicates per treatment were used to determine how well the model fit the experimental data by calculat- ing the Adj. R2defined as follows: Adj: R21 m1 1 SSQregression SSQtotal ? m j 2 4 3 5 4 Table 1 Commercial name
9、of feed additives, active ingredients, concentration when mixed with complete feed at the manufacturers recommended doses (1) and twice the manufacturers recommended doses (2) along with pH of the diet and additive mixture Feed additive (Manufacturer); (Active ingredients)AmountpH1 1212 Complete fee
10、d005.82c0.025.82c0.02 UltraAcid P (Nutriad, Dendermonde, Belgium); (orthophosphoric, citric, fumaric, and malic acids) 150 mg300 mg5.84c0.035.78c0.02 Acid Booster (Agri-Nutrition, DeForest, WI); (phosphoric, citric, and lactic acids) 10 mg20 mg5.84c0.025.84cg0.05 KEMGEST (Kemin Agrifoods, Des Moines
11、, IA); (phosphoric, fumaric, lactic, and citric acid) 10 mg20 mg4.20e0.033.98e0.03 Activate DA (Novus International, St. Charles, MO); (fumaric, benzoic, and 2-hydroxy-4-methylthiobutanoic acids) 20 mg40 mg5.50b0.035.11b0.02 Luprosil (Propionic acid, BASF, Florham Park, NJ); (99.5% propionic acid) 5
12、6 l112 l5.74d0.035.67d0.03 Amasil (Formic Acid, BASF, Florham Park, NJ); (61% formic acid, 20.5% sodium formate, 18.5% water) 46 l92 l5.88c0.035.88gh0.01 Sugar (Shoppers Value, Eden Prairie, MN); (sucrose)20 mg40 mg3.22f0.042.93f0.02 Salt (Essential Every-day, Eden Prairie, MN); (sodium chloride)20
13、mg40 mg4.93a0.054.39a0.03 1Results shown are means of three replications; different superscripts differ at (P 0.05) Cottingim et al. Porcine Health Management (2017) 3:5 Page 3 of 7 where m is the number of observations, j is the number of model parameters, and SSQ is the sum of squares. The effect
14、of different additives on the kinetic parame- ters and survival of virus was assessed by using a mixed model (SAS, v9.3; SAS Inst. Inc., Cary, NC) that in- cluded the effect of additives and time as fixed effects and replicate/batch as random effects. Each vial was considered as the experimental uni
15、t. Data were analyzed for outliers and the presence of a normal distribution using the UNIVARIATE procedure of SAS that calls for calculations of sample moments, measurements of loca- tion and variability, standard deviation, test for nor- mality, robust estimates on scale, missing values among othe
16、rs. The LSMEANS statement in SAS was used to calculate treatment means adjusted for model effects, while Tukeys test was used to determine differences among treatments. For this study, significance was con- sidered when P 0.05. Results Effect of additives on the survival of PDCoV in feed at their recommended concentrations The goodness of model fit was analyzed by comparing the Adj. R2values from the log-linear and Weibull models. The Adj. R2values for the log-linear model (0.480.57) we
