By Hayden Williams, Jason Woodworth, Joel DeRouchey, Steve Dritz, Mike Tokach and Robert Goodband, Kansas State University
Since the emergence of porcine epidemic diarrhea virus in the United States, formaldehyde products have received attention as a potential method to reduce the risk of PEDV transmission due to the ability of feed to serve as a vector for the transmission of the disease. To reduce this risk, research using formaldehyde to reduce PEDV infectivity in contaminated feed and ingredients has been successful.
In addition, formaldehyde can be included in animal feed or ingredients to maintain Salmonella negative status for up to 21 days. However, formaldehyde is known to produce reactions with groups of amino acid residues of intact proteins, which has the potential to reduce availability and ultimately reduce growth performance and nutrient utilization. Therefore, the objective of this study was to evaluate the effects of dietary crystalline amino acid concentrations with or without formaldehyde treatment of diets on nursery pig growth performance, feed bacteria concentration and fecal microbial diversity.
To evaluate this hypothesis, treatments were arranged to test the effects of formaldehyde and crystalline amino acid inclusion (low versus high) plus a positive control diet. All treatment diets were formulated to be 80% of the standardized ileal digestible lysine of that contained in the positive control, which was also 90 to 95% of the requirement according to National Research Council (2012). A positive control was used in the experiment to represent diets that met the assumed standardized ileal digestible lysine requirement for maximum growth performance in this system. A total of 1,235 nursery pigs were randomly assigned to pens, and pens were subsequently assigned to dietary treatments beginning at approximately 27 pounds bodyweight. Treatment diets were fed for the full duration of the study and were fed in two dietary phases (27 to 39 pounds and 39 to 60 pounds bodyweight).
Overall (Day 0 to 28), a significant crystalline amino acid × formaldehyde interaction was observed for average daily feed intake and feed-to-gain ratio. The interaction for ADFI occurred because pigs fed diets with high crystalline amino acid inclusions and formaldehyde treatment had poorer ADFI compared to pigs fed diets without formaldehyde, but in the low crystalline amino acid diets, ADFI was the same. The interaction for F/G was observed because pigs fed low crystalline amino acid diets without formaldehyde had better F/G than with the formaldehyde treatment, but pigs fed high levels of crystalline amino acids had similar F/G regardless of formaldehyde inclusion. Despite the interaction, the application of formaldehyde to diets resulted in reduced ADG, ADFI, and ending body weight and poorer F/G compared to diets without the application of formaldehyde. Pigs fed the control diet had improved ADG, ending body weight, and F/G compared to those fed other diets containing reduced lysine. There was no evidence of difference between diets containing low and high levels of crystalline amino acids for any response criteria measured throughout the trial.
A crystalline amino acid × formaldehyde interaction was observed in analyzed diets for total lysine. This interaction occurred because formaldehyde inclusion in low crystalline amino acid diets reduced total lysine while there was no effect in high crystalline amino acid diets. There was no evidence of a difference between total lysine values with or without the inclusion of formaldehyde in high crystalline amino acid diets. The treatment of diets with formaldehyde decreased fecal bacterial abundance for Lactobacillaceae species. Formaldehyde treatment of diets increased Clostridiaceae species, with this increase being greater in high crystalline amino acid diets.
In summary, treatment of nursery diets with formaldehyde reduced ADG, ADFI, F/G and ending body weight compared to diets without the treatment of formaldehyde. Total lysine was reduced in the low crystalline amino acid diet with the treatment of formaldehyde, while treatment of diets with formaldehyde can alter the proportion of Lactobacillaceae and Clostridiaceae species within the bacterial community of the gut.