The objective of this experiment was to evaluate the effects of medium chain fatty acids (MCFA) on nursery pig performance in place of ZnO and carbadox. In this trial, 360 weanling pigs (DNA 200 x 400; 5.4 ± 0.07 kg BW) were fed for 35 days, with 6 pigs/pen and 10 replicate pens/treatment. Upon weaning, pigs were weighed and allotted to pens based on BW in a completely randomized design to one of 6 treatment diets: 1) Negative control (no added ZnO or carbadox); 2) Control + 3,000 ppm ZnO in phase 1 and 2,000 ppm ZnO in phase 2; 3) Control + 50 g/ton carbadox; 4) Control + C6:C8:C10 MCFA blend; 5) Control + Proprietary Oil Blend (Feed Energy Corp.); 6) Control + monolaurate blend (FORMI GML from ADDCON). Treatment diets were fed through two dietary phases and a common diet fed through phase three. Pigs and feeders were individually weighed on a weekly basis to determine average daily gain (ADG) and average daily feed intake (ADFI). From d 0 to 19, pigs being fed the ZnO or Carbadox diets had the greatest ADG. These pigs had significantly higher (P < 0.05) ADG than pigs fed the control or Feed Energy Proprietary Oil Blend, while pigs fed the C6:C8:C10 blend or FORMI GML diets had similar (P > 0.05) ADG compared to those fed carbadox. These effects were primarily driven by feed intake, which was greatest ( P < 0.05) in pigs fed ZnO and carbadox. Treatment diet had a marginally significant effect (P = 0.078) on G:F. Increased d 19 BW (P < 0.05) was observed for pigs fed ZnO and carbadox compared to the negative control, while other treatments were intermediate. Additionally, blood data and fecal scores were collected throughout the trial. On d 21, pigs fed ZnO or carbadox had higher (P < 0.0001) glucose values than those fed the Feed Energy Proprietary Oil Blend, with other diets being intermediate, showing potential health benefits of carbadox. While ZnO resulted in higher glucose values, it may also contribute to hepatic issues. While replacing ZnO and carbadox with MCFA did not result in significant changes in gut microflora, it did impact fecal consistency by softening the feces during the treatment period. Overall, these results show that ZnO and carbadox are valuable additives to help maximize growth performance in early stages of the nursery. Some MCFA products, like FORMI GML, may result in similar performance, while others restrict it. Thus, additional research is needed to study the effectiveness of MCFA to replace ZnO or feed-based antibiotics.

A total of 350 weanling pigs (DNA 400 × 200; initially, 5.67 ± 0.06 kg BW) were used in a 42-d study with 5 pigs per pen and 14 replicate pens per treatment. At weaning, pigs were allotted to pens in a completely randomized design and pens of pigs were randomly assigned to one of five dietary treatments: 1) negative control (CON; standard nursery diet containing only 150 ppm Zn from trace mineral premix and no acidifier); 2) control diet with 3,000 ppm added zinc from ZnO included in phase 1 and 2,000 ppm added zinc from ZnO included in phase 2 (ZnO); 3) control diet with 0.70% formic acid (FA; Amasil® NA; BASF, Florham, NJ); 4) control diet with 0.18% glycerol monolaurate (GML; Natural Biologics GML, Natural Biologics, Newfield, NY); and 5) control diet with a 1.0% blend of formic acid and glycerol monolaurate (FORMI; FORMI 3G, ADDCON GmbH, Bitterfeld-Wolfen, Germany). Pigs were fed treatment diets from d 0 to d 28 and were then fed a common diet from d 28 to d 42. From d 0 to d 7, pigs fed ZnO or FORMI had increased (P = 0.03) ADG compared to pigs fed CON, with no difference in feed intake (P > 0.05). Overall, pigs fed GML had reduced (P < 0.0001) ADG compared to those fed the CON, ZnO, or FORMI diets. Fecal DM was evaluated from d 7 to d 28 and there was a treatment × day interaction (P = 0.04). Pigs fed GML had a lower fecal DM % on d 7, but a higher fecal DM % on d 14 and 21; however, no differences in fecal DM were observed on d 28. Fresh fecal samples were collected from the same randomly selected pig on d 0 and d 14 (70 pigs total;14 pigs per treatment) for analysis of fecal microbial populations using 16S rDNA sequencing. Dietary treatment did not significantly impact fecal microbiota at the phyla level, but pigs fed ZnO had an increased relative abundance (P < 0.01) of the family Clostridiaceae. A blood sample was also collected from one pig per pen on d 0 and 14 for analysis of serum IgA, IgG, and TNF-α. There was no evidence that dietary treatment effected IgA, IgG, or TNF-α concentrations. The effect of sampling day was significant (P < 0.05), where circulating IgA and TNF-α was increased and IgG was decreased from d 0 to d 14. In summary, there is potential for a blend of formic acid and GML to improve growth performance immediately post-weaning without negatively impacting fecal consistency. Formic acid and GML alone or in combination did not impact fecal microbial populations or serum immune parameters.

A total of 360 weanling pigs (DNA 200 × 400; initially 9.7 ± 0.23 kg BW) were used in a 21-d experiment with 6 pigs/pen, 10 replicate pens/treatment, and 2 separate nursery rooms, each with 30 pens. Pigs were weighed and allotted to pens based on BW in a completely randomized block design to one of 6 treatment diets: 1) Negative control (no organic acids or antibiotics) and the control with 2) 0.25% Acidifier A; 3) 0.3% Acidifier B; 4) 0.5% Acidifier C); 5) 50 g/t Carbadox; 6) 400 g/t Chlortetracycline. Upon weaning, a common diet with no antibiotics or additives was fed for 21 d (phases 1 and 2; d -21 to d 0), followed by a 21 d experimental period (phase 3; d 0 to d 21) where treatment diets were fed. Pigs and feeders were individually weighed on a weekly basis to calculate average daily gain (ADG), average daily feed intake (ADFI) and feed efficiency (G:F). Data were analyzed using the PROC GLIMMIX procedure of SAS (v 9.4, SAS Inst., Cary, NC) with pen as the experimental unit, treatment as a fixed effect and room as a random effect. Dietary treatment had a significant impact (P < 0.05) on ADG, ADFI and G:F each week and for the overall experimental period (d 0 to 21). Specifically, from d 0 to 7, pigs fed CTC had increased (P = 0.001) ADG compared to those fed Acidifier B, Acidifier C and Carbadox, while pigs fed the negative control and Acidifier A diets were intermediate. Additionally, pigs fed the CTC diet had improved (P = 0.0002) ADFI when compared to all other treatments. From d 7 to 14 and d 14 to 21, pigs fed the Carbadox diet had decreased (P < 0.0001) ADG compared to all other treatments. During the overall period (d 0 to 21), pigs fed diets containing Carbadox had reduced ADG and ADFI (P < 0.0001), while pigs fed CTC had improved (P < 0.0001) ADG compared to all other treatments. Additionally, blood parameters, fecal consistency and fecal microbial populations were analyzed on a subset of pigs (n = 5 pigs/treatment). Dietary treatment significantly impacted (P < 0.05) concentrations of protein, globulin, phosphorus, alkaline phosphatase, and sorbitol dehydrogenase in the blood. Treatment also significantly impacted (P = 0.0005) fecal score but did not affect (P = 0.59) fecal microbial growth from d 0 to 21. In summary, CTC continues to be a valuable additive to improve performance in the nursery. Further investigation surrounding the efficacy of dietary acidifiers as antibiotic alternatives is warranted given inconclusive evidence in this study.

A total of 360 weanling pigs (DNA 200 x 400; initially 9.7 ± 0.23 kg BW) were used in a 21-d growth trial to evaluate the effects of commercial diet acidifiers in nursery diets. Upon weaning, pigs were weighed and allotted to pens (6 pigs/pen, 10 replicate pens/treatment, blocked by 2 separate nursery rooms) and pens were then randomly assigned to one of 6 treatment diets: 1) negative control (no antibiotics or acidifiers) and the control with 2) 0.25% Acidifier A (KEM-GEST™, Kemin Industries, Des Moines, IA); 3) 0.3% Acidifier B (ACITVATE® DA, Novus International, Saint Charles, MO); 4) 0.5% Acidifier C (OutPace®, PMI Additives, Arden Hills, MN); 5) 50 g/ton carbadox; 6) 400 g/ton chlortetracycline. Pigs were fed common phase 1 and phase 2 starter diets without antimicrobials for 21 days, then fed experimental diets for 21 days. Data were analyzed as a completely randomized block design with pen as the experimental unit. Dietary treatment significantly impacted (P < 0.05) all growth response criteria for each week of the experiment. Overall (d 0 to 21), ADG was the greatest (P < 0.0001) for pigs fed a diet containing CTC. Likewise, ADFI was increased (P < 0.0001) for pigs consuming CTC compared to those fed the negative control, acidifier A, acidifier B and carbadox diets, while those fed acidifier C were intermediate. Feed efficiency was poorest (P < 0.0001) in pigs fed a diet with carbadox. By the end of the experiment, pigs fed CTC were significantly heavier (P < 0.0001) than pigs fed all remaining treatments. In summary, feeding CTC improved nursery pig performance while carbadox unexpectedly reduced it. The addition of dietary acidifiers did not improve growth performance compared to a negative control.

A total of 80 crossbred, high-risk heifers (initially 250 ± 4.2 kg BW), were transported from an Oklahoma City, Oklahoma sale barn to the Kansas State University Beef Cattle Research Center. Cattle were unloaded and randomly placed into one of four receiving pens and provided ad libitum hay and water. Each pen was randomly assigned to one of four rest-times before processing: 1) immediately upon arrival (0); 2) after a 6-h rest period (6); 3) after a 24-h rest period (24); and 4) after a 48-h rest period (48). After all cattle were processed, heifers were allotted into individual pens with ad libitum access to a receiving ration and water. Heifers were weighed individually on d 0, 7, 14, 21, 28 and 35 to calculate average daily gain (ADG). Feed added and refusals were measured daily to determine dry matter intake (DMI). A fecal egg count reduction test and analysis of blood serum metabolites were also conducted. All data were analyzed using the GLIMMIX procedure of SAS (v. 9.4, Cary, NC) with individual animal as the experimental unit. Processing time did not impact (P > 0.05) heifer BW or ADG. From d 0 to 35, DMI decreased linearly (P = 0.027) as rest time increased. The number of days for heifers to reach a DMI of 2.5% BW was linearly increased (P = 0.023) as rest time increased. There was no evidence of differences (P ≥ 0.703) among rest times for feed efficiency. While morbidity did not differ between treatments (P > 0.10), mortality increased linearly (P = 0.026) as the time of rest increased. A significant processing time × day interaction (P < 0.0001) was observed for the prevalence of fecal parasites, where the percentage of positive samples was significantly lower 14-d after anthelmintic treatment, regardless of the processing time. Serum IBR titer for heifers processed at either 0 or 6-h upon arrival was significantly higher (P < 0.01) on d 35 compared to d 0. Heifers processed after a 48-h rest period had significantly higher glucose values (P < 0.01) on d 0 compared to heifers processed at 0, 6, or 24-h. In summary, rest time prior to processing did not impact receiving calf growth performance. A 6-h rest period upon arrival appeared to be most beneficial to DMI. Anthelmintic treatment at processing reduced the parasitic load in heifers processed at all times. Vaccine titer did not increase after initial processing in heifers processed 24- or 48-h after arrival, indicating the seroconversion of IBR antibodies during the longer rest period.

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Post-weaning diarrhea in pigs is often caused by the F4 or F18 strains of enterotoxigenic Escherichia coli (ETEC). To evaluate interventions for ETEC, experimental infection via a challenge model is critical. Others have reviewed ETEC challenge studies, but there is a lack of explanation for the variability in responses observed. Our objective was to quantitatively summarize the responses and variability among ETEC challenge studies and develop a tool for sample size calculation. The most widely evaluated response criteria across ETEC challenge studies consist of growth performance, fecal consistency, immunoglobulins, pro-inflammatory cytokines, and small intestinal morphology. However, there is variation in the responses seen following ETEC infection as well as the variability within each response criteria. Contributing factors include the type of ETEC studied, dose and timing of inoculation, and the number of replications. Generally, a reduction in average daily gain (ADG) and average daily feed intake (ADFI) are seen following ETEC challenge as well as a rapid increase in diarrhea. The magnitude of response in growth performance varies, and methodologies used to characterize fecal consistency are not standardized. Likewise, fecal bacterial shedding is a common indicator of ETEC infection, but the responses seen across the literature are not consistent due to differences in bacterial enumeration procedures. Emphasis should also be placed on the piglet’s immune response to ETEC, which is commonly assessed by quantifying levels of immunoglobulins and pro-inflammatory cytokines. Again, there is variability in these responses across published work due to differences in the timing of sample collection, dose of ETEC pigs are challenged with, and laboratory practices. Small intestinal morphology is drastically altered following infection with ETEC and appears to be a less variable response criterion to evaluate. For each of these outcome variables, we have provided quantitative estimates of the responses seen across the literature as well as the variability within them. While there is a large degree of variability across ETEC challenge experiments, we have provided a quantitative summary of these studies and a Microsoft Excel-based tool was created to calculate sample sizes for future studies that can aid researchers in designing future work.

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