J. T. Gebhardt

Evaluation of the Effects of Flushing Feed Manufacturing Equipment with Chemically- Treated Rice Hulls on Porcine Epidemic Diarrhea Virus Cross Contamination During Feed Manufacturing

Various strategies have been proposed to mitigate potential risk of porcine epidemic diarrhea virus (PEDV) transmission via feed and feed ingredients. Wet disinfection has been found to be the most effective decontamination of feed mill surfaces; however, this is not practical on a commercial feed production scale. Another potential mitigation strategy would be using chemically treated rice hulls flushed through the feed manufacturing equipment. Therefore, the objective of this study was to determine the effects of medium-chain fatty acids (MCFA) or formaldehyde-treated rice hull flush batches as potential chemical mitigation strategies for PEDV during feed manufacturing. Feed without evidence of PEDV RNA contamination was inoculated with PEDV. Based on polymerase chain reaction analysis, this feed had a cycle threshold (Ct) = 30.2 and was confirmed infective in bioassay. After manufacturing the PEDV-positive feed, untreated rice hulls, formaldehyde-treated rice hulls, 2% MCFA(a 1:1:1 blend of hexanoic, octanoic, and decanoic acid) treated rice hulls, or 10% MCFA-treated rice hulls were flushed through laboratory scale mixers. For the untreated rice hulls, 3 of 6 samples had detectable PEDV RNA, whereas 1 of 6 formaldehyde-treated rice hull flush samples and 2 of 6 of the 2% MCFA rice hull flush samples had detectable PEDV RNA. However, PEDV RNA was not detected in any of the 10% MCFA rice hull flush samples. Then, rice hulls treated with 10% MCFA were mixed and discharged through a production scale mixer and bucket elevator following PEDV-positive feed. No rice hull flush or feed samples from the mixer following chemically treated rice hull flush had detectible PEDV RNA. However, one 10% MCFA rice hull sample collected from the bucket elevator discharge spout had detectible PEDV RNA. Dust collected following mixing of PEDV contaminated feed had detectable PEDV RNA (Ct = 29.4) and was infectious. However, dust collected immediately after the 10% MCFA rice hull flush batch had a reduced quantity of PEDV RNA (Ct = 33.7) and did not cause infection. Overall, the use of rice hull flushes effectively reduced the quantity of detectible RNA present after mixing a batch of PEDV-positive feed. Chemical treatment of rice hulls with formaldehyde or 10% MCFA provided additional reduction in detectible RNA. Finally, dust collected after manufacturing PEDV-inoculated feed has the potential to serve as a vector for PEDV transmission.

Determining the impact of commercial feed additives as potential porcine epidemic diarrhea virus mitigation strategies as determined by polymerase chain reaction analysis and bioassay1

Abstract Mitigation of porcine epidemic diarrhea virus (PEDV) was assessed using two feed additives (0.5% inclusion of a benzoic acid [BA] product and 0.02% inclusion of an essential oil [EO] product; DSM Nutritional Products Inc., Parsippany, NJ), and combination of both products (0.5% BA and 0.02% EO) in spray-dried porcine plasma (SDPP) and a swine gestation diet (FEED) as determined by real-time quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) and bioassay. Viral RNA quantification was performed at 7 sampling days post-laboratory inoculation (d 0, 1, 3, 7, 14, 21, and 42) and infectivity was assessed via bioassay with 10-d-old pigs. There was a tendency for treatment × feed matrix × day interaction (P = 0.094), in which the cycle threshold (Ct) value increased over time in FEED when treated with both feed additives, whereas there was no increase over time observed in SDPP treated with both feed additives. There was a feed matrix × day interaction (P < 0.001) in which Ct increased over time in FEED, whereas very little increase over time was observed in SDPP. A tendency for a treatment × feed matrix effect (P = 0.085) was observed where FEED treated with the combination of EO and BA had a greater (P < 0.05) PEDV Ct value than other FEED treatments, and all SDPP treatments had the lower PEDV Ct values compared to FEED treatments (P < 0.05). Overall, the combination of both feed additives was most effective at reducing the quantity of genetic material as detected by qRT-PCR (P < 0.001) compared to either additive alone or no feed additive. Virus shedding was observed in the d 7 postinoculation SDPP treatment that was treated with both feed additives, as well as d 0 untreated FEED and d 0 FEED treated with both feed additives. No other treatment bioassay room had detectible RNA shed and detected in fecal swabs or cecal contents. In summary, the combination of EO and BA enhanced the degradation of PEDV RNA in feed but had little impact on RNA degradation in SDPP. Both untreated feed and feed treated with the combination of EO and BA resulted in infection at d 0 post-laboratory inoculation; however, neither set of samples was infective at d 1 postinoculation. In addition, SDPP harbored greater levels of quantifiable RNA for a longer duration of time compared to FEED, and these viral particles remained viable for a longer duration of time indicating differences in viral stability exist between different feed matrices.

Influence of chromium propionate dose and feeding regimen on growth performance and carcass composition of pigs housed in a commercial environment1,2

Abstract Although chromium (Cr) feeding study results have been variable, our hypothesis was feeding a regimen that changed dosage over time would result in a larger positive response in growth performance and carcass characteristics. In Exp. 1, a total of 1,206 pigs (PIC 337 × 1050, initial BW 28.7 kg) were used with 27 pigs per pen and 9 pens per treatment. Diets were corn–soybean meal-dried distillers grains with solubles based and were fed in a five-phase feeding program. Treatments were arranged as a 2 × 2 + 1 factorial with a control diet containing no added Cr propionate (Kemin Industries Inc., Des Moines, IA), or diets with either 100 or 200 µg/kg added Cr during the grower (dietary phases 1 and 2) and/or finisher (dietary phases 3, 4, and 5) periods. During the grower period, ADG and G:F were similar among pigs fed the control or 100 µg/kg added Cr diets, but decreased in pigs fed 200 µg/kg Cr (quadratic, P ≤ 0.001). During the finisher period, pigs supplemented with 200 µg/kg added Cr had the greatest ADG and G:F (quadratic, P ≤ 0.019). Overall, increasing Cr had no effect on ADG or ADFI; but G:F was greatest (quadratic, P = 0.020) when pigs were fed 100 µg/kg of added Cr throughout. Carcass characteristics were not influenced by Cr dosage or feeding regimen. In Exp. 2, a total of 1,206 pigs (PIC 359 × 1050, initial BW 48.9 kg) were used with 27 pigs per pen and 15 pens per treatment. Diets were corn–soybean meal, dried distillers grains with solubles based and were fed in four phases. There were three dietary treatments: a diet with no added Cr for both grower (dietary phase 1 and 2) and finisher (dietary phase 3 and 4) periods, a diet with 200 µg/kg added Cr during the grower and 100 µg/kg added Cr during the finisher periods, or a diet with 200 µg/kg added Cr for both periods. Addition of 200 µg/kg Cr in both periods marginally increased (P < 0.10) ADG compared with pigs fed no added Cr. There was no evidence (P ≥ 0.523) of added Cr influencing overall ADFI and G:F. Percentage carcass yield was reduced (P = 0.018) when Cr was added at 200 µg/kg for both periods, with no evidence of differences (P ≥ 0.206) in other carcass characteristics. In summary, overall G:F was improved in Exp. 1, and ADG in Exp. 2, by added Cr, but there was no evidence that different feeding regimens will consistently result in improved performance. However, these data are consistent with the literature in that added Cr in growing-finishing pigs diets improves, albeit small, ADG or G:F.

Effect of roller mill configuration on growth performance of nursery and finishing pigs and milling characteristics1

Three experiments were conducted to evaluate the effects of roller mill configuration on growth performance of nursery and finishing pigs, feed preference, and feed mill throughput. The four experimental treatments included corn ground through a roller mill using two, three, four sets of rolls in a fine-grind configuration, or four sets of rolls in a coarse grind configuration. The same roller mill was used for all configurations with the appropriate lower rolls completely open when using the two or three roll pair configurations. Across all studies, mean particle size averaged approximately 540, 435, 270, and 385 µm for the four roller mill configurations, respectively. In Exp. 1, 320 pigs (DNA 400 × 200, initially 10.7 ± 0.27 kg BW) were randomly allotted to treatments with five pigs per pen and 16 pens per treatment in a 21-d growth trial. While there were no evidence of differences observed for ADG or ADFI, pigs fed corn ground using the 4-high coarse configuration had a marginally significant (P = 0.091) improvement in G:F compared with those fed with the 2-high configuration, with others intermediate. In Exp. 2, 90 pigs (PIC 327 × 1050, initially 12.1 ± 0.25 kg BW) were randomly allotted to one of three diet comparisons to determine feed preference between the 2-high, 4-high fine, and 4-high coarse configurations. When given a choice, pigs consumed more (P < 0.05) of the diet containing corn ground through the 2-high roller mill (67%) or 4-high coarse configuration (63%) compared with corn ground through the 4-high fine configuration. In Exp. 3, 922 finishing pigs (PIC TR4 × [FAST Large white × PIC Line 2], initially 40.1 ± 0.36 kg BW) were used in a 97-d experiment with pens of pigs randomly allotted by initial BW to the same experimental treatments used in Exp. 1. There were 21 pigs per pen and 11 pens per treatment. Pigs fed corn ground with the 2-high configuration had greater (P < 0.05) ADG compared with those fed corn ground using the 3-high configuration. Pigs fed corn ground with the 4-high fine configuration had the poorest (P < 0.05) ADG. No differences were observed in G:F. Grinding rate (tonne/h) was greatest (P < 0.05) for the 4-high coarse configuration, while net electricity consumption (kWh/tonne) was lowest (P < 0.05) for the 2-high configuration and greatest for the 4-high fine configuration. In summary, nursery pig G:F tended to be greatest using the 4-high coarse configuration, and finishing pig ADG was maximized using the 2- and 4-high coarse configurations.

105 Young Scholar Presentation: A Review of Medium Chain Fatty Acids and Their Recent Role in Feed Safety.

Medium chain fatty acids (MCFA), have been researched extensively to reduce the likelihood of animal feed being contaminated by biological pathogens, including bacteria and viruses. Medium chain fatty acids have shown to be bactericidal and bacteriostatic by incorporating themselves into the lipid membrane of bacteria, which alters the cell membrane permeability leading to cell death. However, the effectiveness can be dependent upon the MCFA chain length and species of bacteria. Most research completed prior to 2013 focused on the antimicrobial properties of MCFA. However, with the emergence of Porcine Epidemic Diarrhea Virus (PEDV), MCFA began to gain more attention for their potential uses in feed safety and swine nutrition as a potential antiviral additive. Medium chain fatty acids have shown repeated success against PEDV in vivo and in vitro. Notably, 2% MCFA [1:1:1 blend of caproic, caprylic, and capric] was equally successful at mitigating PEDV as commercially-available formaldehyde products in complete swine feed (P>0.05). However, the effectiveness varies within feed matrix, as MCFA was not as effective as formaldehyde at mitigation in spray dried animal plasma and meat and bone meal (P<0.05). A lower concentration of the MCFA blend (1%), as well as the individual addition of 0.66% caproic, 0.66% caprylic, or 0.66% capric acids also enhanced the RNA degradation of PEDV in complete swine feed (P<0.05). Other research has evaluated the same 2% MCFA blend in a transboundary based study, replicating the time and environmental condition that feed ingredients undertake during a trip from China to the United States. Again, the MCFA treated ingredients were deemed to be negative throughout the simulated transboundary trip (P<0.05). Medium chain fatty acids have also been evaluated as a surface decontaminate and as a potential feed mill flush step. However, the overall effectiveness was not as substantial as the results observed in the feed ingredient studies. Currently, it is not known what the exact mode of action of the MCFA is against PEDV, but it is hypothesize that the MCFA are interacting with the lipid bilayer envelope of the virus and altering the envelope in a way in which it cannot bind with the host receptors. This mode of action would be similar to that of the bacteria as both outer membranes consist of a lipid bilayer. Future research is now focused on the use of MCFA against other enveloped and non-enveloped swine viruses as well as an antibiotic alternative in swine production.

Evaluation of the effects of flushing feed manufacturing equipment with chemically treated rice hulls on porcine epidemic diarrhea virus cross-contamination during feed manufacturing1

Abstract Various strategies have been proposed to mitigate potential risk of porcine epidemic diarrhea virus (PEDV) transmission via feed and feed ingredients. Wet disinfection has been found to be the most effective decontamination of feed mill surfaces; however, this is not practical on a commercial feed production scale. Another potential mitigation strategy would be using chemically treated rice hulls flushed through the feed manufacturing equipment. Therefore, the objective of this study was to determine the effects of medium-chain fatty acids (MCFA) or formaldehyde-treated rice hull flush batches as potential chemical mitigation strategies for PEDV during feed manufacturing. Feed without evidence of PEDV RNA contamination was inoculated with PEDV. Based on polymerase chain reaction analysis, this feed had a cycle threshold (Ct) = 30.2 and was confirmed infective in bioassay. After manufacturing the PEDV-positive feed, untreated rice hulls, formaldehyde-treated rice hulls, 2% MCFA- (a 1:1:1 blend of hexanoic, octanoic, and decanoic acid) treated rice hulls, or 10% MCFA-treated rice hulls were flushed through laboratory scale mixers. For the untreated rice hulls, 3 of 6 samples had detectable PEDV RNA, whereas 1 of 6 formaldehyde-treated rice hull flush samples and 2 of 6 of the 2% MCFA rice hull flush samples had detectable PEDV RNA. However, PEDV RNA was not detected in any of the 10% MCFA rice hull flush samples. Then, rice hulls treated with 10% MCFA were mixed and discharged through a production scale mixer and bucket elevator following PEDV-positive feed. No rice hull flush or feed samples from the mixer following chemically treated rice hull flush had detectible PEDV RNA. However, one 10% MCFA rice hull sample collected from the bucket elevator discharge spout had detectible PEDV RNA. Dust collected following mixing of PEDV contaminated feed had detectable PEDV RNA (Ct = 29.4) and was infectious. However, dust collected immediately after the 10% MCFA rice hull flush batch had a reduced quantity of PEDV RNA (Ct = 33.7) and did not cause infection. Overall, the use of rice hull flushes effectively reduced the quantity of detectible RNA present after mixing a batch of PEDV-positive feed. Chemical treatment of rice hulls with formaldehyde or 10% MCFA provided additional reduction in detectible RNA. Finally, dust collected after manufacturing PEDV-inoculated feed has the potential to serve as a vector for PEDV transmission.

Feed batch sequencing to decrease the risk of porcine epidemic diarrhea virus (PEDV) cross-contamination during feed manufacturing

Abstract Feed has been identified as a vector of transmission for porcine epidemic diarrhea virus (PEDV). The objective of this study was to determine if feed batch sequencing methods could minimize PEDV cross-contamination. Porcine epidemic diarrhea virus-free swine feed was manufactured to represent the negative control. A 50 kg feed batch was mixed in a pilot scale feed mill for 5 min, sampled, then discharged for 10 min into a bucket elevator and sampled again upon exit. Next, a pathogenic PEDV isolate was used to inoculate 49.5 kg of PEDV-free feed to form the positive control. The positive control was mixed, conveyed and sampled similar to the negative control. Subsequently, 4 sequence batches (sequence 1 to 4) were formed by adding a 50 kg batch of PEDV-negative feed to the mixer after the prior batch was mixed and conveyed; all sequences were mixed, conveyed, and sampled similar to the negative and positive control batches. None of the equipment was cleaned between batches within a replicate. This entire process was replicated 3 times with cleaning the feed mill between replicates. Feed was then analyzed for PEDV RNA by real-time reverse transcriptase semiquantitative polymerase chain reaction (rRT-PCR) as measured by cycle threshold (Ct) and for infectivity by bioassay. Sequence 1 feed had higher (P ˂ 0.05) rRT-PCR Ct values than the positive batch and sequence 2 feed had higher (P ˂ 0.05) Ct values than sequence 1, regardless of sampled location. Feed sampled from the mixer from sequence 2, 3, and 4 was rRT-PCR negative whereas feed sampled from the bucket elevator was rRT-PCR negative from sequence 3 and 4. Bioassay was conducted using 66 mixed sex 10-d-old pigs confirmed negative for PEDV allocated to 22 different rooms. Pigs were initially 10-d old. Control pigs remained PEDV negative for the study. All pigs from the mixer positive batch (9/9) and bucket elevator positive batch (3/3) were rRT-PCR positive on fecal swabs by the end of the study. One replicate of pigs from mixer sequence 1 was rRT-PCR positive (3/3) by 7 dpi. One replicate of mixer pigs from sequence 2 was rRT-PCR positive (3/3) by 7 dpi although no detectable PEDV RNA was found in the feed. The results demonstrate sequenced batches had reduced quantities of PEDV RNA although sequenced feed without detectible PEDV RNA by rRT-PCR can be infectious. Therefore, a sequencing protocol can reduce but not eliminate the risk of producing infectious PEDV carryover from the first sequenced batch of feed.

Quantifying Medium Chain Fatty Acid Mitigation Activity Over Time against Porcine Epidemic Diarrhea Virus in Nursery Pig Diets

Medium chain fatty acids (MCFA) are six to twelve carbon length molecules that have shown significant promise as potential mitigants of biological hazards in feed and feed ingredients. The use of residual duration of activity approaches, such as MCFA, have significant advantages compared to point-in-time mitigation strategies. The primary advantage of MCFA is the ability to mitigate the risks generated by post-processing contamination; however, the duration of mitigation activity has not been established. Therefore, the objective of this experiment was to characterize the mitigation properties of MCFA-treated swine feed 40 d following feed manufacturing. Treatments (n = 8) consisted of a dose response including 0, 0.25, 0.50, 1.0, and 1.5% dietary inclusion of a MCFA blend (1:1:1 ratio C6, C8, and C10) as well as 0.5% C6 alone, 0.5% C8 alone, or 0.5% C10 alone. Following feed manufacturing, feed was stored in bags at barn temperature and humidity for 40 d (June to July 2017). Following sampling after storage, subsamples were placed in separate high-density polyethylene bottles and inoculated with Porcine Epidemic Diarrhea Virus (PEDV) to achieve a final titer of 104 TCID50/g. Separate sample bottles were analyzed on d 0 and 3 post-inoculation. A significant treatment × day interaction (P < 0.001) was observed, where the cycle threshold (Ct) numerically increased over time in select treatments, and was numerically reduced in others. Means separation, adjusted to control experiment-wise error rate, did not indicate evidence of a difference within treatment among days of analysis (P > 0.05) for any of the eight treatments. When evaluating increasing inclusion of MCFA blend, an inclusion level × day interaction was observed (quadratic, P = 0.023), where PEDV Ct values increased (quadratic, P = 0.001) on d 0 with increasing levels of MCFA blend inclusion also increased on d 3 (linear, P < 0.001). On d 0 postinoculation, the addition of C6, C8, or C10 alone resulted in significantly greater Ct values compared to no supplemented MCFA (P < 0.05). The addition of 0.5% C6 and 0.5% C8 did not change Ct value (P > 0.05) compared to 0.5% MCFA blend; however, adding 0.5% C10 resulted in a lower Ct value (P < 0.05) compared to 0.5% MCFA blend. On d 3 post-inoculation, the addition of 0.5% C6 or 0.5% C10 resulted in greater Ct values compared to control (P < 0.05), whereas, no improvement was observed with 0.5% C8 compared to control (P > 0.05). The addition of 0.5% MCFA blend resulted in insufficient evidence of difference in Ct values compared to adding individual MCFA (P > 0.05). In summary, treatment of feed with medium chain fatty acids retains mitigation properties for a significant period of time following feed manufacturing. Although we did not assess infectivity through bioassay, the data herein suggest a residual duration mitigation potential for MCFA well beyond feed manufacturing. Additional research characterizing the duration of activity beyond one point in time following feed manufacturing is warranted.

Further Investigation Evaluating the Effect of Dietary Chromium Propionate and Yucca schidigera Supplementation in Finishing Pig Diets

A total of 2,430 pigs (PIC 359 × 1050; initial BW = 64.6 lb) were used to evaluate the effects of dietary chromium propionate (Cr; KemTRACE Cr, Kemin Industries, Des Moines, IA) and a Yucca schidigera-based extract (Micro-Aid; DPI Global, Porterville, CA) on growth performance of finishing pigs housed in commercial conditions. Pigs were placed in balanced, mixed-gender pens (27 pigs per pen), blocked by average pen BW, and randomly assigned to treatment. Diets were corn-soybean meal-based and were formulated in 5 dietary phases to meet or exceed NRC6 requirement estimates. Dietary treatments were fed for the full duration of the study and were arranged in a 2 × 3 factorial with 14 pens per treatment. Main effects included chromium (0 or 200 ppb added Cr), and Yucca schidigera extract (0, 62.5, or 125 ppm active ingredient). For the overall study, a marginally significant (linear; P ≤ 0.072) Cr × Yucca schidigera interaction was observed for ADG and ADFI. Pigs fed Yucca schidigera without added Cr had similar ADG and ADFI; however, pigs fed added Cr had increased ADG and ADFI as Yucca schidigera increased from 62.5 to 125 ppm. Added Cr had no effect on F/G (P > 0.05). Increasing Yucca schidigera resulted in a marginally significant poorer (quadratic; P = 0.057) F/G. The main effect of added Yucca schidigera on final BW (quadratic; P = 0.012) resulted in pens which were supplemented with 62.5 ppm having the lowest final BW. Carcass characteristics, including HCW, loin depth, backfat, percentage lean, and percentage yield, were not influenced by added Cr (P ≥ 0.278). Added Yucca schidigera did not influence loin depth, backfat, percentage lean, or percentage yield (P ≥ 0.152). In summary, adding Cr propionate along with Yucca schidigera led to modest changes in performance, with the greatest benefit observed with 200 ppb Cr and 125 ppm (active ingredient) Yucca schidigera.

Effect of Chromium Propionate Level and Feeding Regimen on Finishing Pig Growth Performance and Carcass Characteristics

A total of 1,206 pigs (PIC 359 × 1050; initial BW = 107.9 lb) were used in an 84-d study to evaluate the effects of added dietary chromium (Cr; KemTRACE chromium propionate, Kemin Industries Inc., Des Moines, IA) and feeding regimen on growth performance of finishing pigs housed under commercial conditions. Pigs were placed in mixed-gender pens (27 pigs per pen), blocked by BW, and randomly assigned to 1 of 3 dietary treatments (15 pens per treatment). Diets were corn-soybean meal-based with added dried distillers gains with solubles, and were fed in 4 phases. Treatments were: 1) control, no Cr in grower or finisher formulas; 2) 200 ppb of Cr fed in both grower and finisher; and 3) 200 ppb of Cr fed in grower and 100 ppb fed in finisher. The grower phase was from 108 to 202 lb and the finisher phase was 202 to 273 lb. There was no evidence (P ≥ 0.197) of treatment differences in the grower period. In the finishing period, added Cr resulted in a marginally significant increase (linear; P = 0.061) in ADG (2.03, 2.02, 2.08 ± 0.022 lb/d; 0, 100, 200 ppb added Cr, respectively) with no evidence of an effect (P ≥ 0.148) on ADFI and F/G. For the overall period, there was marginal significance that at least one treatment differed from another (P = 0.086) for ADG. When compared directly, addition of 200 ppb Cr in both grower and finisher increased (P = 0.037) ADG, compared to control with pigs fed 200 ppb added Cr fed in grower, followed by 100 ppb fed in finisher intermediate (1.97, 1.98, and 2.01 ± 0.013 lb/d; 0, 200/100, and 200/ 200 ppb added Cr, respectively). There was no evidence (P ≥ 0.526) of differences in overall ADFI and F/ G. Percentage carcass yield was reduced (P = 0.018) in pigs fed 200 ppb added Cr for both the grower and finishing periods compared to other treatments. There was no evidence of differences (P ≥ 0.206) in HCW, loin depth, backfat, or percentage lean between treatments. In summary, adding 200 ppb of Cr in both grower and finisher formulas increased finishing ADG, led to a marginally significant improvement in overall ADG, but reduced carcass yield.